diff --git a/app/api/auth/token/route.ts b/app/api/auth/token/route.ts
index 3e6a90667..ba2d3d9ee 100644
--- a/app/api/auth/token/route.ts
+++ b/app/api/auth/token/route.ts
@@ -273,21 +273,29 @@ export async function PUT(request: NextRequest) {
     // The refresh token may have been minted by the password+TOTP login route,
     // which works without a configured OAuth client by falling back to the
     // default client id - refreshing must fall back the same way (#873).
+    // Discovery or the token endpoint out of reach is an outage: the client
+    // waits it out. A 500 here would count toward signing the user out.
+    let tokenResponse: Response;
     const upstream = IS_DESKTOP_BUILD ? await readCustomUpstream(cookieStore, slot) : null;
-    const tokenEndpoint = await getTokenEndpoint(serverId, upstream ? { upstream } : { fallbackClientId: DEFAULT_CLIENT_ID });
+    try {
+      const tokenEndpoint = await getTokenEndpoint(serverId, upstream ? { upstream } : { fallbackClientId: DEFAULT_CLIENT_ID });
 
-    const params = buildOAuthParams({
-      grant_type: 'refresh_token',
-      refresh_token: refreshToken,
-    }, serverId, await defaultClientOptions(serverId, upstream));
+      const params = buildOAuthParams({
+        grant_type: 'refresh_token',
+        refresh_token: refreshToken,
+      }, serverId, await defaultClientOptions(serverId, upstream));
 
-    const tokenResponse = await observeUpstream('oauth', () => fetch(tokenEndpoint, {
-      method: 'POST',
-      headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
-      body: params.toString(),
-      // See revokeRefreshToken: the body holds the refresh token.
-      redirect: 'error',
-    }));
+      tokenResponse = await observeUpstream('oauth', () => fetch(tokenEndpoint, {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
+        body: params.toString(),
+        // See revokeRefreshToken: the body holds the refresh token.
+        redirect: 'error',
+      }));
+    } catch (error) {
+      logger.warn('Token refresh: provider unreachable', { error: error instanceof Error ? error.message : 'Unknown error' });
+      return NextResponse.json({ error: 'Token endpoint unavailable' }, { status: 503 });
+    }
 
     if (!tokenResponse.ok) {
       const errorText = await tokenResponse.text();
@@ -302,7 +310,10 @@ export async function PUT(request: NextRequest) {
         cookieStore.delete(accessTokenCookieName(slot));
         clearCustomUpstream(cookieStore, slot);
         clearIdToken(cookieStore, slot, request.nextUrl.basePath);
-        return NextResponse.json({ error: 'Refresh failed' }, { status: 401 });
+        // Only invalid_grant says the login itself is over. invalid_client, or
+        // a provider refusing an early refresh (#552), says nothing about it,
+        // and the client keeps the account's local data for those.
+        return NextResponse.json({ error: oauthErrorCode(errorText) === 'invalid_grant' ? 'invalid_grant' : 'Refresh failed' }, { status: 401 });
       }
       return NextResponse.json({ error: 'Token endpoint unavailable' }, { status: 503 });
     }
@@ -350,6 +361,15 @@ export async function PUT(request: NextRequest) {
   }
 }
 
+function oauthErrorCode(body: string): string | null {
+  try {
+    const code = (JSON.parse(body) as { error?: unknown }).error;
+    return typeof code === 'string' ? code : null;
+  } catch {
+    return null;
+  }
+}
+
 /**
  * Revoke a slot's refresh token and clear its token cookies. With
  * `endSession`, also returns the URL that ends the provider's session, or null
diff --git a/app/api/offline/shell/route.ts b/app/api/offline/shell/route.ts
index 43a88d3ec..ac0fc757a 100644
--- a/app/api/offline/shell/route.ts
+++ b/app/api/offline/shell/route.ts
@@ -7,8 +7,10 @@ export const dynamic = 'force-dynamic';
 const BASE_PATH = (process.env.NEXT_PUBLIC_BASE_PATH ?? '').replace(/\/+$/, '');
 /** Files a page can load: scripts, styles, fonts and the images they name. */
 const SHELL_FILE = /\.(js|css|woff2?|svg|png|webp)$/;
+/** The local store's engine in public/. */
+const ENGINE_FILE = /\.(mjs|wasm)$/;
 
-async function listFiles(dir: string, prefix: string, out: string[]): Promise<void> {
+async function listFiles(dir: string, prefix: string, out: string[], wanted: RegExp = SHELL_FILE): Promise<void> {
   let entries;
   try {
     entries = await readdir(dir, { withFileTypes: true });
@@ -16,8 +18,8 @@ async function listFiles(dir: string, prefix: string, out: string[]): Promise<vo
     return;
   }
   for (const entry of entries) {
-    if (entry.isDirectory()) await listFiles(join(dir, entry.name), `${prefix}${entry.name}/`, out);
-    else if (SHELL_FILE.test(entry.name)) out.push(`${prefix}${entry.name}`);
+    if (entry.isDirectory()) await listFiles(join(dir, entry.name), `${prefix}${entry.name}/`, out, wanted);
+    else if (wanted.test(entry.name)) out.push(`${prefix}${entry.name}`);
   }
 }
 
@@ -26,12 +28,18 @@ async function listFiles(dir: string, prefix: string, out: string[]): Promise<vo
  * /_next/static/, which is the same for every user and content-hashed. A
  * tab with offline mode on hands the list to the service worker, which keeps
  * the files in this build's cache so the app also starts without a network.
+ * The local store's worker and its database engine come along: without them
+ * the store can't start offline. The worker's address carries the build id, as
+ * the page asks for it (lib/store/client/api.ts).
  */
 export async function GET() {
   const files: string[] = [];
   await listFiles(join(process.cwd(), '.next', 'static'), `${BASE_PATH}/_next/static/`, files);
+  await listFiles(join(process.cwd(), 'public', 'sqlite3mc'), `${BASE_PATH}/sqlite3mc/`, files, ENGINE_FILE);
+  const buildId = process.env.NEXT_PUBLIC_BUILD_ID ?? '';
+  files.push(`${BASE_PATH}/store-worker.js${buildId ? `?v=${encodeURIComponent(buildId)}` : ''}`);
   return NextResponse.json(
-    { buildId: process.env.NEXT_PUBLIC_BUILD_ID ?? '', files },
+    { buildId, files },
     { headers: { 'Cache-Control': 'no-store' } },
   );
 }
diff --git a/components/email/email-composer.tsx b/components/email/email-composer.tsx
index d4ff3a9a8..06ce32889 100644
--- a/components/email/email-composer.tsx
+++ b/components/email/email-composer.tsx
@@ -3,6 +3,7 @@
 import React, { useState, useEffect, useRef, useCallback, useMemo } from "react";
 import { useMvComposeWindow } from "@/components/email/mv-compose-context";
 import { useLocale, useTranslations } from "next-intl";
+import { isServerOutage } from "@/lib/jmap/offline-hooks";
 import { Button, TOUCH_HIT_AREA } from "@/components/ui/button";
 import { ConfirmDialog } from "@/components/ui/confirm-dialog";
 import { Dialog } from "@/components/ui/dialog";
@@ -560,6 +561,7 @@ export function EmailComposer({
   const tClassification = useTranslations('classification');
   const tProofreading = useTranslations('proofreading');
   const tOffline = useTranslations('offline');
+  const tOfflineNotes = useTranslations('offlineConflicts');
   const tSendGuards = useTranslations('send_guards');
   const timeFormat = useSettingsStore((state) => state.timeFormat);
   const plainTextModeDefault = useSettingsStore((state) => state.plainTextMode);
@@ -4213,6 +4215,8 @@ export function EmailComposer({
       } else if (err instanceof SubmissionQuotaError) {
         // At a full submission quota only an administrator can help.
         toast.error(sendFailureMessage(err, t));
+      } else if (isServerOutage(err)) {
+        toast.error(t('send_failed'), { message: tOfflineNotes('server_not_answering') });
       } else if (err instanceof Error && OFFLINE_SEND_ERRORS[err.name]) {
         // Offline mode (#523) refused to keep it: says why, in the user's language.
         toast.error(t('send_failed'), { message: tOffline(OFFLINE_SEND_ERRORS[err.name]) });
diff --git a/components/offline/__tests__/offline-host.test.tsx b/components/offline/__tests__/offline-host.test.tsx
new file mode 100644
index 000000000..1cceb0a23
--- /dev/null
+++ b/components/offline/__tests__/offline-host.test.tsx
@@ -0,0 +1,55 @@
+import 'fake-indexeddb/auto';
+import { cleanup, fireEvent, render, screen } from '@testing-library/react';
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { OfflineHost } from '../offline-host';
+import { queueSend } from '@/lib/offline/queue';
+import { useOfflineStore, writeEnabled } from '@/lib/offline/state';
+import { passSignOutGates } from '@/lib/sign-out-cleanup';
+import { setStoreBackend } from '@/lib/store/client/api';
+import { InProcessStore } from '@/lib/store/__tests__/helpers/in-process-store';
+import { wipeEverything } from '@/lib/offline/offline-mode';
+import { useAccountStore } from '@/stores/account-store';
+
+let store: InProcessStore;
+
+beforeEach(() => {
+  store = new InProcessStore();
+  setStoreBackend(store);
+  localStorage.clear();
+  useOfflineStore.setState({ outbox: [], pendingChanges: 0, conflicts: [] });
+  useAccountStore.setState({ accounts: [{ id: 'acc' }] as never });
+  writeEnabled(['acc']);
+});
+
+afterEach(async () => {
+  cleanup();
+  await wipeEverything();
+  setStoreBackend(null);
+});
+
+describe('the question before a sign-out', () => {
+  it('counts what the queue holds, though the screen has seen none of it', async () => {
+    await queueSend('acc', { subject: 'Hello', to: [] }, { kind: 'email', args: [] });
+    useOfflineStore.setState({ outbox: [] });
+    render(<OfflineHost />);
+    const answer = passSignOutGates('acc');
+    fireEvent.click(await screen.findByRole('button', { name: /signout\.confirm/ }));
+    expect(await answer).toBe(true);
+  });
+
+  it('asks about a change that hasn\'t reached the server, on its own', async () => {
+    await store.ensureOpen('acc');
+    store.dbs.get('acc')!.run("INSERT INTO calendar_pending (jmap, record_id, kind, patch, queued_at) VALUES ('j1', 'ev', 'update', '{}', 1)");
+    render(<OfflineHost />);
+    const answer = passSignOutGates('acc');
+    expect(await screen.findByText(/signout_changes_title/)).toBeTruthy();
+    fireEvent.click(await screen.findByRole('button', { name: /signout\.confirm/ }));
+    expect(await answer).toBe(true);
+  });
+
+  it('asks nothing with nothing waiting', async () => {
+    render(<OfflineHost />);
+    expect(await passSignOutGates('acc')).toBe(true);
+    expect(screen.queryByRole('button', { name: /signout\.confirm/ })).toBeNull();
+  });
+});
diff --git a/components/offline/__tests__/offline-settings.test.tsx b/components/offline/__tests__/offline-settings.test.tsx
index 7cace4d96..5a9e35962 100644
--- a/components/offline/__tests__/offline-settings.test.tsx
+++ b/components/offline/__tests__/offline-settings.test.tsx
@@ -14,6 +14,7 @@ import { useOfflineStore } from '@/lib/offline/state';
 import { useAuthStore } from '@/stores/auth-store';
 import { usePolicyStore } from '@/stores/policy-store';
 import { DEFAULT_ORGANISATION_POLICY } from '@/lib/admin/organisation-policy';
+import { setStoreBackend, type StoreBackend } from '@/lib/store/client/api';
 
 function setNoOffline(noOffline: boolean) {
   usePolicyStore.setState({
@@ -24,6 +25,8 @@ function setNoOffline(noOffline: boolean) {
 }
 
 beforeEach(() => {
+  // jsdom has no OPFS: the store's page side says it's there, as a browser would.
+  setStoreBackend({ supported: () => true } as unknown as StoreBackend);
   offline.enableOffline.mockClear();
   offline.disableOffline.mockClear();
   useAuthStore.setState({ activeAccountId: 'acc' });
@@ -32,6 +35,17 @@ beforeEach(() => {
 });
 
 describe('Settings > Offline', () => {
+  it('says so in a private window, with no switch to turn on', () => {
+    useOfflineStore.setState({ storageBlocked: true });
+    try {
+      render(<OfflineSettings />);
+      expect(screen.getByTestId('offline-private')).toBeTruthy();
+      expect(screen.queryByTestId('offline-switch')).toBeNull();
+    } finally {
+      useOfflineStore.setState({ storageBlocked: false });
+    }
+  });
+
   it('is off until the user turns it on in this browser', () => {
     render(<OfflineSettings />);
     const toggle = screen.getByTestId('offline-switch');
diff --git a/components/offline/__tests__/outbox-conflicts.test.tsx b/components/offline/__tests__/outbox-conflicts.test.tsx
new file mode 100644
index 000000000..871b77cbf
--- /dev/null
+++ b/components/offline/__tests__/outbox-conflicts.test.tsx
@@ -0,0 +1,68 @@
+import 'fake-indexeddb/auto';
+import { act, fireEvent, render, screen } from '@testing-library/react';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { setStoreBackend, type StoreBackend } from '@/lib/store/client/api';
+import { useOfflineStore } from '@/lib/offline/state';
+import { useAuthStore } from '@/stores/auth-store';
+import { OutboxList } from '../outbox-list';
+import { OfflineBanner } from '../offline-banner';
+
+const conflict = (id: number, reason: 'changed' | 'gone' | 'refused', op: 'update' | 'destroy' = 'update', detail?: string) => ({
+  id,
+  account: 'acc',
+  recordId: `m${id}`,
+  createdAt: Date.UTC(2026, 10, 3),
+  summary: { subject: `Subject ${id}`, op, reason, ...(detail ? { detail } : {}) },
+});
+
+let area: ReturnType<typeof vi.fn>;
+
+beforeEach(() => {
+  area = vi.fn(async (_account: string, name: string) => (name === 'outbox.read' ? { patches: 0, entries: [], conflicts: [] } : undefined));
+  setStoreBackend({ supported: () => true, area } as unknown as StoreBackend);
+  useAuthStore.setState({ activeAccountId: 'acc' });
+  useOfflineStore.setState({ enabled: ['acc'], outbox: [], pendingChanges: 0, conflicts: [], browserOffline: false, downServers: [], startedOffline: false });
+});
+
+afterEach(() => {
+  setStoreBackend(null);
+  useOfflineStore.setState({ enabled: [], conflicts: [] });
+});
+
+describe('changes that did not go through', () => {
+  it('lists each with what happened to it', () => {
+    useOfflineStore.setState({ conflicts: [conflict(1, 'changed'), conflict(2, 'changed', 'destroy'), conflict(3, 'gone'), conflict(4, 'refused', 'update', 'Read only')] });
+    render(<OutboxList />);
+    const rows = screen.getAllByTestId('offline-conflict-row');
+    expect(rows.map((row) => row.getAttribute('data-reason'))).toEqual(['changed', 'changed', 'gone', 'refused']);
+    expect(rows[0].textContent).toContain('Subject 1');
+    expect(rows[0].textContent).toContain('changed');
+    expect(rows[1].textContent).toContain('changed_delete');
+    expect(rows[2].textContent).toContain('gone');
+    expect(rows[3].textContent).toContain('refused');
+  });
+
+  it('shows nothing when there are none', () => {
+    render(<OutboxList />);
+    expect(screen.queryByTestId('offline-conflicts')).toBeNull();
+  });
+
+  it('dismisses one in the store and reads the queue again', async () => {
+    useOfflineStore.setState({ conflicts: [conflict(7, 'changed')] });
+    render(<OutboxList />);
+    await act(async () => {
+      fireEvent.click(screen.getByRole('button', { name: 'dismiss_label' }));
+    });
+    expect(area).toHaveBeenCalledWith('acc', 'outbox.dismissConflict', { id: 7 });
+    expect(area).toHaveBeenCalledWith('acc', 'outbox.read');
+    expect(useOfflineStore.getState().conflicts).toEqual([]);
+  });
+
+  it('the banner points to them while online, with nothing else to say', () => {
+    useOfflineStore.setState({ conflicts: [conflict(1, 'changed')] });
+    render(<OfflineBanner />);
+    expect(screen.getByTestId('offline-banner-conflicts')).toBeTruthy();
+    fireEvent.click(screen.getByTestId('offline-banner-conflicts'));
+    expect(screen.getByTestId('offline-conflict-row')).toBeTruthy();
+  });
+});
diff --git a/components/offline/offline-banner.tsx b/components/offline/offline-banner.tsx
index c04def228..dc179e362 100644
--- a/components/offline/offline-banner.tsx
+++ b/components/offline/offline-banner.tsx
@@ -24,9 +24,11 @@ export function OfflineBanner() {
   const browserOffline = useOfflineStore((s) => s.browserOffline || s.startedOffline);
   const serverDown = useOfflineStore((s) => !!server && s.downServers.includes(serverKey(server)));
   const waiting = useOfflineStore((s) => s.outbox.length);
+  const conflicts = useOfflineStore((s) => s.conflicts.length);
+  const tConflicts = useTranslations('offlineConflicts');
   const [open, setOpen] = useState(false);
   const offline = browserOffline || serverDown;
-  if (IS_LITE || !active || (!offline && waiting === 0 && !open)) return null;
+  if (IS_LITE || !active || (!offline && waiting === 0 && conflicts === 0 && !open)) return null;
   return (
     <>
       <div
@@ -50,6 +52,17 @@ export function OfflineBanner() {
             {t('banner.outbox', { count: waiting })}
           </button>
         )}
+        {conflicts > 0 && (
+          <button
+            type="button"
+            data-testid="offline-banner-conflicts"
+            aria-haspopup="dialog"
+            onClick={() => setOpen(true)}
+            className="min-h-11 rounded-md px-1 font-medium underline underline-offset-2 hover:bg-foreground/5 sm:min-h-0"
+          >
+            {tConflicts('banner', { count: conflicts })}
+          </button>
+        )}
       </div>
       <Dialog isOpen={open} onClose={() => setOpen(false)} title={t('outbox.title')} testId="offline-outbox-dialog">
         <OutboxList heading={false} />
diff --git a/components/offline/offline-host.tsx b/components/offline/offline-host.tsx
index 63e797918..0ddb51046 100644
--- a/components/offline/offline-host.tsx
+++ b/components/offline/offline-host.tsx
@@ -6,8 +6,7 @@ import { ConfirmDialog } from '@/components/ui/confirm-dialog';
 import { useConfirmDialog } from '@/hooks/use-confirm-dialog';
 import { addSignOutGate } from '@/lib/sign-out-cleanup';
 import { reloadToNewBuild } from '@/lib/app-update';
-import { confirmLoss, setOfflineNotifier, startOfflineMode, type OfflineNotice } from '@/lib/offline/offline-mode';
-import { useOfflineStore } from '@/lib/offline/state';
+import { confirmLoss, setOfflineNotifier, startOfflineMode, unsentCount, type OfflineNotice } from '@/lib/offline/offline-mode';
 import { toast } from '@/stores/toast-store';
 
 /**
@@ -20,6 +19,9 @@ export function OfflineHost() {
   const t = useTranslations('offline');
   const tRef = useRef(t);
   tRef.current = t;
+  const tConflicts = useTranslations('offlineConflicts');
+  const tConflictsRef = useRef(tConflicts);
+  tConflictsRef.current = tConflicts;
   const { dialogProps, confirm } = useConfirmDialog();
   const confirmRef = useRef(confirm);
   confirmRef.current = confirm;
@@ -45,6 +47,21 @@ export function OfflineHost() {
         case 'lost':
           toast.warning(tr('toast.lost', { subjects: notice.subjects.map((s) => s || tr('outbox.no_subject')).join(', ') }), { duration: 0 });
           break;
+        case 'conflict':
+          toast.warning(tConflictsRef.current('toast', { count: notice.count }));
+          break;
+        case 'storage-failed':
+          toast.warning(tConflictsRef.current('storage_failed'), { duration: 0 });
+          break;
+        case 'legacy-stranded':
+          toast.warning(tConflictsRef.current('legacy_stranded'), { duration: 0 });
+          break;
+        case 'store-reset':
+          toast.warning(tConflictsRef.current('store_reset'), { duration: 0 });
+          break;
+        case 'store-unavailable':
+          toast.warning(tConflictsRef.current('store_unavailable'), { duration: 0 });
+          break;
         case 'refused-delete':
           toast.warning(tr('toast.refused_delete'));
           break;
@@ -66,12 +83,16 @@ export function OfflineHost() {
     const stop = startOfflineMode();
     // Messages that would be lost: ask before a sign-out the user started.
     const removeGate = addSignOutGate(async (accountId) => {
-      const unsent = useOfflineStore.getState().outbox.filter((row) => accountId === 'all' || row.account === accountId).length;
-      if (unsent === 0) return true;
+      const { messages, changes } = await unsentCount(accountId);
+      if (messages === 0 && changes === 0) return true;
       const tr = tRef.current;
+      const trConflicts = tConflictsRef.current;
       const ok = await confirmRef.current({
-        title: tr('signout.title'),
-        message: tr('signout.message', { count: unsent }),
+        title: messages > 0 ? tr('signout.title') : trConflicts('signout_changes_title'),
+        message: [
+          ...(messages > 0 ? [tr('signout.message', { count: messages })] : []),
+          ...(changes > 0 ? [trConflicts('signout_changes', { count: changes })] : []),
+        ].join(' '),
         confirmText: tr('signout.confirm'),
         variant: 'destructive',
       });
diff --git a/components/offline/offline-settings.tsx b/components/offline/offline-settings.tsx
index 013e37ecb..d8c1a0439 100644
--- a/components/offline/offline-settings.tsx
+++ b/components/offline/offline-settings.tsx
@@ -30,6 +30,8 @@ export function OfflineSettings() {
   const syncing = useOfflineStore((s) => !!account && s.syncing.includes(account));
   const lastSynced = useOfflineStore((s) => (account ? s.lastSyncedAt[account] : undefined));
   const unsent = useOfflineStore((s) => s.outbox.filter((row) => row.account === account).length);
+  const blocked = useOfflineStore((s) => s.storageBlocked);
+  const tNotes = useTranslations('offlineConflicts');
   const [confirmOff, setConfirmOff] = useState(false);
 
   if (IS_LITE) return null;
@@ -42,7 +44,9 @@ export function OfflineSettings() {
 
   return (
     <SettingsSection id="offline" title={t('title')} description={t('description')}>
-      {!offlineSupported() ? (
+      {blocked ? (
+        <p className="text-sm text-muted-foreground" data-testid="offline-private">{tNotes('store_private')}</p>
+      ) : !offlineSupported() ? (
         <p className="text-sm text-muted-foreground" data-testid="offline-unsupported">{t('unsupported')}</p>
       ) : !allowed ? (
         <div className="py-3" data-testid="offline-forbidden">
diff --git a/components/offline/outbox-list.tsx b/components/offline/outbox-list.tsx
index 54745baf3..7e8c3a864 100644
--- a/components/offline/outbox-list.tsx
+++ b/components/offline/outbox-list.tsx
@@ -6,6 +6,7 @@ import { Button } from '@/components/ui/button';
 import { ConfirmDialog } from '@/components/ui/confirm-dialog';
 import { deleteOutboxEntry, retryOutboxEntry } from '@/lib/offline/flush';
 import { refreshQueueState, scheduleFlushAll } from '@/lib/offline/offline-mode';
+import { dismissConflict, type ConflictEntry } from '@/lib/offline/queue';
 import { isOfflineNow, useOfflineStore, type OutboxRow } from '@/lib/offline/state';
 import { useAccountStore } from '@/stores/account-store';
 
@@ -15,13 +16,16 @@ import { useAccountStore } from '@/stores/account-store';
  * be sent again or deleted; one whose connection broke on the way is never
  * sent again on its own (it may have gone out); one held because the
  * organisation's rules changed can only be deleted (and written again).
+ * Changes that didn't go through ("changed on another device") are listed too.
  */
 export function OutboxList({ heading = true }: { heading?: boolean }) {
   const t = useTranslations('offline.outbox');
   const tErrors = useTranslations('offline.errors');
+  const tConflicts = useTranslations('offlineConflicts');
   const format = useFormatter();
   const rows = useOfflineStore((s) => s.outbox);
   const changes = useOfflineStore((s) => s.pendingChanges);
+  const conflicts = useOfflineStore((s) => s.conflicts);
   const accounts = useAccountStore((s) => s.accounts);
   const [deleting, setDeleting] = useState<OutboxRow | null>(null);
   const several = new Set(rows.map((r) => r.account)).size > 1 || accounts.length > 1;
@@ -37,11 +41,22 @@ export function OutboxList({ heading = true }: { heading?: boolean }) {
   };
 
   const retry = async (row: OutboxRow) => {
-    await retryOutboxEntry(row.id);
+    await retryOutboxEntry(row.account, row.id);
     await refreshQueueState();
     if (!isOfflineNow()) scheduleFlushAll(0);
   };
 
+  const conflictText = (conflict: ConflictEntry) => {
+    if (conflict.summary.reason === 'refused') return tConflicts('refused', { reason: conflict.summary.detail ?? '' });
+    if (conflict.summary.reason === 'gone') return tConflicts('gone');
+    return tConflicts(conflict.summary.op === 'destroy' ? 'changed_delete' : 'changed');
+  };
+
+  const dismiss = async (conflict: ConflictEntry) => {
+    await dismissConflict(conflict.account, conflict.id);
+    await refreshQueueState();
+  };
+
   return (
     <div className={heading ? 'pt-2' : undefined} data-testid="offline-outbox">
       {heading && <h4 className="text-sm font-medium text-foreground">{t('title')}</h4>}
@@ -51,7 +66,7 @@ export function OutboxList({ heading = true }: { heading?: boolean }) {
       ) : (
         <ul className="mt-3 divide-y divide-border rounded-md border border-border" aria-label={t('title')}>
           {rows.map((row) => (
-            <li key={row.id} className="flex flex-col gap-2 px-3 py-2.5 sm:flex-row sm:items-start sm:justify-between" data-testid="offline-outbox-row" data-status={row.status}>
+            <li key={`${row.account}:${row.id}`} className="flex flex-col gap-2 px-3 py-2.5 sm:flex-row sm:items-start sm:justify-between" data-testid="offline-outbox-row" data-status={row.status}>
               <div className="min-w-0 flex-1">
                 <p className="truncate text-sm font-medium text-foreground">{row.subject || t('no_subject')}</p>
                 <p className="truncate text-xs text-muted-foreground">
@@ -77,13 +92,33 @@ export function OutboxList({ heading = true }: { heading?: boolean }) {
       {changes > 0 && (
         <p className="mt-2 text-xs text-muted-foreground" data-testid="offline-pending-changes">{t('changes', { count: changes })}</p>
       )}
+      {conflicts.length > 0 && (
+        <div className="mt-3" data-testid="offline-conflicts">
+          <p className="text-xs text-muted-foreground">{tConflicts('description')}</p>
+          <ul className="mt-2 divide-y divide-border rounded-md border border-border" aria-label={tConflicts('title')}>
+            {conflicts.map((conflict) => (
+              <li key={`${conflict.account}:${conflict.id}`} className="flex flex-col gap-2 px-3 py-2.5 sm:flex-row sm:items-start sm:justify-between" data-testid="offline-conflict-row" data-reason={conflict.summary.reason}>
+                <div className="min-w-0 flex-1">
+                  <p className="truncate text-sm font-medium text-foreground">{conflict.summary.subject || t('no_subject')}</p>
+                  <p className="text-xs text-destructive [overflow-wrap:anywhere]">
+                    {conflictText(conflict)} · {format.dateTime(conflict.createdAt, { dateStyle: 'short', timeStyle: 'short' })}
+                  </p>
+                </div>
+                <div className="flex shrink-0 gap-2">
+                  <Button variant="outline" size="sm" aria-label={tConflicts('dismiss_label', { subject: conflict.summary.subject || t('no_subject') })} onClick={() => void dismiss(conflict)}>{tConflicts('dismiss')}</Button>
+                </div>
+              </li>
+            ))}
+          </ul>
+        </div>
+      )}
       <ConfirmDialog
         isOpen={!!deleting}
         onClose={() => setDeleting(null)}
         onConfirm={() => {
           const row = deleting;
           setDeleting(null);
-          if (row) void deleteOutboxEntry(row.id).then(refreshQueueState);
+          if (row) void deleteOutboxEntry(row.account, row.id).then(refreshQueueState);
         }}
         title={t('delete_confirm_title')}
         message={t('delete_confirm_message')}
diff --git a/integration/tests/22-ent-offline.spec.ts b/integration/tests/22-ent-offline.spec.ts
index 0491db978..3a32f0af6 100644
--- a/integration/tests/22-ent-offline.spec.ts
+++ b/integration/tests/22-ent-offline.spec.ts
@@ -24,6 +24,9 @@ import { JMAP_URL } from './helpers/config';
  * - a mail written offline waits in the outbox; the required classification
  *   label still stops it; once online it goes out with SIO-Label;
  * - read, flag and delete to Trash made offline reach the server;
+ * - a change the server can no longer take shows as changed on another device;
+ * - the Trash emptied offline is emptied on the server after;
+ * - a send whose response got lost is looked up and goes out once;
  * - a sign-out the user starts asks first when unsent mail would be lost,
  *   then wipes the device; the idle sign-out wipes it and the login page
  *   names the lost message;
@@ -148,24 +151,69 @@ async function send(page: Page): Promise<void> {
   await page.keyboard.press('Control+Enter');
 }
 
-/** Whether the offline database exists, without opening it (opening would create it). */
+/** Whether anything of the local store is left, without opening it (opening would create it). */
 async function offlineDatabaseExists(page: Page): Promise<boolean> {
-  return page.evaluate(async () => (await indexedDB.databases()).some((d) => d.name === 'bulwark-offline'));
+  return page.evaluate(async () => {
+    if ((await indexedDB.databases()).some((d) => d.name === 'bulwark-store' || d.name === 'bulwark-offline')) return true;
+    const root = await navigator.storage.getDirectory();
+    return root.getDirectoryHandle('.bulwark-store').then(() => true, () => false);
+  });
 }
 
-async function offlineDatabase(page: Page): Promise<{ exists: boolean; emails: number }> {
+/**
+ * The store's files as bytes, with no worker holding them: which of `needles`
+ * occur in them. Goes to a same-origin file without scripts first, so that
+ * leaving the app ends the owner.
+ */
+async function rawStoreFiles(page: Page, needles: string[]): Promise<{ bytes: number; found: string[] }> {
+  await page.goto(new URL('/sw.js', page.url()).href);
+  return page.evaluate(async (wanted) => {
+    const read = async (dir: FileSystemDirectoryHandle): Promise<string[]> => {
+      const parts: string[] = [];
+      for await (const handle of (dir as unknown as { values(): AsyncIterable<FileSystemHandle> }).values()) {
+        if (handle.kind === 'directory') parts.push(...await read(handle as FileSystemDirectoryHandle));
+        else parts.push(new TextDecoder('latin1').decode(await (await (handle as FileSystemFileHandle).getFile()).arrayBuffer()));
+      }
+      return parts;
+    };
+    const root = await navigator.storage.getDirectory();
+    const files = await read(await root.getDirectoryHandle('.bulwark-store'));
+    return {
+      bytes: files.reduce((sum, file) => sum + file.length, 0),
+      found: wanted.filter((needle) => files.some((file) => file.includes(needle))),
+    };
+  }, needles);
+}
+
+/** The file of the account's store, from the key database. */
+async function storeFileName(page: Page): Promise<string> {
+  return page.evaluate(() => new Promise<string>((resolve, reject) => {
+    const open = indexedDB.open('bulwark-store');
+    open.onerror = () => reject(open.error);
+    open.onsuccess = () => {
+      const all = open.result.transaction('accounts').objectStore('accounts').getAll();
+      all.onsuccess = () => {
+        open.result.close();
+        resolve((all.result as Array<{ file: string }>)[0].file);
+      };
+    };
+  }));
+}
+
+/** The accounts the local store holds a key for. Their mail is in encrypted files nothing here can read. */
+async function offlineDatabase(page: Page): Promise<{ exists: boolean; accounts: number }> {
   return page.evaluate(async () => {
     const dbs = await indexedDB.databases();
-    if (!dbs.some((d) => d.name === 'bulwark-offline')) return { exists: false, emails: 0 };
-    return new Promise<{ exists: boolean; emails: number }>((resolve) => {
-      const req = indexedDB.open('bulwark-offline');
+    if (!dbs.some((d) => d.name === 'bulwark-store')) return { exists: false, accounts: 0 };
+    return new Promise<{ exists: boolean; accounts: number }>((resolve) => {
+      const req = indexedDB.open('bulwark-store');
       req.onsuccess = () => {
         const db = req.result;
-        if (!db.objectStoreNames.contains('emails')) { db.close(); resolve({ exists: true, emails: 0 }); return; }
-        const count = db.transaction('emails').objectStore('emails').count();
-        count.onsuccess = () => { db.close(); resolve({ exists: true, emails: count.result }); };
+        if (!db.objectStoreNames.contains('accounts')) { db.close(); resolve({ exists: true, accounts: 0 }); return; }
+        const count = db.transaction('accounts').objectStore('accounts').count();
+        count.onsuccess = () => { db.close(); resolve({ exists: true, accounts: count.result }); };
       };
-      req.onerror = () => resolve({ exists: false, emails: 0 });
+      req.onerror = () => resolve({ exists: false, accounts: 0 });
     });
   });
 }
@@ -230,6 +278,45 @@ test('with the browser offline, kept mail opens, also after a reload without a n
   await page.context().close();
 });
 
+test('the files on the device hold no readable mail, and a store whose key went starts over', async ({ browser }) => {
+  const subject = `Offline encrypted ${RUN}`;
+  const secret = `Secret body ${RUN}`;
+  await deliverAndWait(subject, secret);
+  const page = await userPage(browser, ENT.alice);
+  await enableOffline(page);
+  await toMail(page);
+  await expect.poll(async () => (await offlineDatabase(page)).accounts, { timeout: 30_000 }).toBeGreaterThan(0);
+  await openMessage(page, subject);
+  await expect(body(page)).toContainText(secret, { timeout: 20_000 });
+  // Long enough for the store to have the message and its text on disk.
+  await page.waitForTimeout(5_000);
+  const file = await storeFileName(page);
+
+  const raw = await rawStoreFiles(page, [subject, secret, 'SQLite format 3', file]);
+  expect(raw.bytes).toBeGreaterThan(100_000);
+  // The name of the file is the one thing here in the clear: the search works.
+  expect(raw.found).toEqual([file]);
+
+  // The browser clears the key database and leaves the files.
+  await page.evaluate(() => new Promise<void>((resolve) => {
+    const request = indexedDB.deleteDatabase('bulwark-store');
+    request.onsuccess = () => resolve();
+    request.onerror = () => resolve();
+    request.onblocked = () => resolve();
+  }));
+  await page.goto(new URL('/', page.url()).href);
+  // Once on screen and once for screen readers.
+  await expect(page.locator('p', { hasText: "couldn't be read" }).first()).toBeVisible({ timeout: 60_000 });
+  await toMail(page);
+  await expect(page.locator('[data-testid="email-list-item"]', { hasText: subject }).first()).toBeVisible({ timeout: 60_000 });
+  await expect.poll(async () => (await offlineDatabase(page)).accounts, { timeout: 30_000 }).toBeGreaterThan(0);
+  const newFile = await storeFileName(page);
+  expect(newFile).not.toBe(file);
+  const after = await rawStoreFiles(page, [file, newFile]);
+  expect(after.found).toEqual([newFile]);
+  await page.context().close();
+});
+
 test('a mail written offline waits in the outbox, the required label still stops it, and it goes out labelled when back online', async ({ browser }) => {
   const subject = `Outbox label ${RUN}`;
   await setPolicy(browser, { organisation: { labels: { list: LABELS, defaultId: '', required: true, extraHeader: '' } } });
@@ -332,6 +419,111 @@ test('read, flag and delete to Trash made offline reach the server once back onl
   await page.context().close();
 });
 
+test('a change the server can no longer take is shown as changed on another device', async ({ browser }) => {
+  const subject = `Offline conflict ${RUN}`;
+  await deliverAndWait(subject, 'Moved twice');
+  const page = await userPage(browser, ENT.alice);
+  await enableOffline(page);
+  await toMail(page);
+  await page.context().setOffline(true);
+
+  await openMessage(page, subject);
+  await page.keyboard.press('Delete');
+  await expect(page.locator('[data-testid="email-list-item"]', { hasText: subject })).toHaveCount(0, { timeout: 15_000 });
+
+  // Meanwhile another device files it elsewhere.
+  const other = await jmapAs(ENT.alice);
+  const junk = (await other.mailboxByRole('junk'))!.id;
+  const id = (await waitForMessage(ENT.alice, (m) => m.subject === subject)).id;
+  await other.request([['Email/set', { accountId: other.accountId, update: { [id]: { mailboxIds: { [junk]: true } } } }, '0']]);
+
+  await page.context().setOffline(false);
+  await page.getByTestId('offline-banner-conflicts').click({ timeout: 90_000 });
+  const row = page.getByTestId('offline-conflict-row').filter({ hasText: subject });
+  await expect(row).toHaveAttribute('data-reason', 'changed');
+  await expect(row).toContainText('Changed on another device');
+  // The other device's move stands.
+  expect(Object.keys((await waitForMessage(ENT.alice, (m) => m.subject === subject)).mailboxIds)).toEqual([junk]);
+  await shot(page, 'f-offline-conflict');
+  await row.getByRole('button', { name: /^Dismiss/ }).click();
+  await expect(page.getByTestId('offline-conflict-row').filter({ hasText: subject })).toHaveCount(0);
+  await page.context().close();
+});
+
+test('emptying the Trash offline shows at once and reaches the server once back online', async ({ browser }) => {
+  const subject = `Offline empty trash ${RUN}`;
+  await deliverAndWait(subject, 'Gone for good');
+  const client = await jmapAs(ENT.alice);
+  const trash = (await client.mailboxByRole('trash'))!.id;
+  const id = (await waitForMessage(ENT.alice, (m) => m.subject === subject)).id;
+  await client.request([['Email/set', { accountId: client.accountId, update: { [id]: { mailboxIds: { [trash]: true } } } }, '0']]);
+  const page = await userPage(browser, ENT.alice);
+  await enableOffline(page);
+  await toMail(page);
+  await page.context().setOffline(true);
+
+  await page.getByText('Trash', { exact: true }).first().click();
+  await expect(page.locator('[data-testid="email-list-item"]', { hasText: subject }).first()).toBeVisible({ timeout: 30_000 });
+  await page.getByRole('button', { name: 'Empty folder' }).first().click();
+  await page.getByRole('alertdialog').getByRole('button', { name: 'Empty folder' }).click();
+  await expect(page.locator('[data-testid="email-list-item"]', { hasText: subject })).toHaveCount(0, { timeout: 15_000 });
+  // Nothing reached the server yet.
+  expect((await messages(ENT.alice, RUN)).some((m) => m.subject === subject)).toBe(true);
+
+  await page.context().setOffline(false);
+  await expect.poll(async () => (await messages(ENT.alice, RUN)).some((m) => m.subject === subject), { timeout: 90_000 }).toBe(false);
+  await page.context().close();
+});
+
+/** A send taken from the outbox gets no answer. `arrives` is what reached the server of it. */
+async function loseResponse(browser: Browser, subject: string, arrives: (body: { methodCalls: Array<[string, unknown, string]> }) => void) {
+  const page = await userPage(browser, ENT.alice);
+  await enableOffline(page);
+  await toMail(page);
+  const context = page.context();
+  await blockMailServer(context);
+  await waitUntilOffline(page);
+  await compose(page, ENT.bob, subject, 'Only one copy');
+  await send(page);
+  await expect(page.getByTestId('offline-banner-outbox')).toHaveText('1 message in the outbox', { timeout: 30_000 });
+
+  // The server comes back, and takes the send, but its answer never arrives.
+  const origin = `${new URL(JMAP_URL).origin}/**`;
+  let lost = 0;
+  await context.unroute(origin);
+  await context.route(origin, async (route) => {
+    const sent = route.request().postData() ?? '';
+    if (lost === 0 && sent.includes('EmailSubmission/set')) {
+      lost += 1;
+      const body = JSON.parse(sent);
+      arrives(body);
+      await route.fetch({ postData: JSON.stringify(body) });
+      await route.abort('connectionreset');
+      return;
+    }
+    await route.continue();
+  });
+
+  await expect.poll(() => lost, { timeout: 120_000 }).toBe(1);
+  // Looked up, found in Sent, done: the row goes without another submission.
+  await expect(page.getByTestId('offline-banner-outbox')).toHaveCount(0, { timeout: 120_000 });
+  await waitForMessage(ENT.bob, (m) => m.subject === subject);
+  const copies = (await messages(ENT.alice, RUN)).filter((m) => m.subject === subject);
+  expect(copies).toHaveLength(1);
+  expect(copies[0].keywords.$draft).toBeFalsy();
+  await context.close();
+}
+
+test('a send whose response got lost goes out once', async ({ browser }) => {
+  await loseResponse(browser, `Offline lost response ${RUN}`, () => {});
+});
+
+test('a send of which only the draft arrived is submitted, and goes out once', async ({ browser }) => {
+  await loseResponse(browser, `Offline lost submission ${RUN}`, (body) => {
+    body.methodCalls = body.methodCalls.filter(([name]) => name === 'Email/set');
+  });
+});
+
 test('signing out asks first when unsent mail would be lost, then wipes the device', async ({ browser }) => {
   const subject = `Unsent at sign-out ${RUN}`;
   const page = await userPage(browser, ENT.alice);
@@ -342,7 +534,7 @@ test('signing out asks first when unsent mail would be lost, then wipes the devi
   await compose(page, ENT.bob, subject, 'Never sent');
   await send(page);
   await expect(page.getByTestId('offline-banner-outbox')).toHaveText('1 message in the outbox', { timeout: 30_000 });
-  expect((await offlineDatabase(page)).emails).toBeGreaterThan(0);
+  expect((await offlineDatabase(page)).accounts).toBeGreaterThan(0);
 
   // Sign out from the account menu: asked first, and Cancel keeps everything.
   await accountSwitcher(page).click();
@@ -417,17 +609,20 @@ test('forbidding offline mode wipes the device at the next policy fetch and hide
   await enableOffline(carol);
   await toMail(alice);
   const loadedAt = Date.now();
-  expect((await offlineDatabase(alice)).emails).toBeGreaterThan(0);
+  expect((await offlineDatabase(alice)).accounts).toBeGreaterThan(0);
 
+  // Waiting starts now: the app may fetch the policy again at any time, not
+  // only on focus, and the notice doesn't stay.
+  const notice = alice.getByText('Your organisation turned off offline mode', { exact: false }).first().waitFor({ state: 'visible', timeout: 180_000 });
   // ent-team (alice, not carol) may no longer keep mail on devices.
   await setPolicy(browser, {
     scopes: [{ id: 'no-offline', label: 'No offline', match: { groups: [ENT.team] }, policy: { organisation: { devices: { noOffline: true } } } }],
   });
   // The open tab fetches the policy again when it gets focus (at most once a minute).
   await alice.waitForTimeout(Math.max(0, 62_000 - (Date.now() - loadedAt)));
-  await alice.evaluate(() => window.dispatchEvent(new Event('focus')));
-  await expect(alice.getByText('Your organisation turned off offline mode', { exact: false }).first()).toBeVisible({ timeout: 30_000 });
-  await expect.poll(async () => (await offlineDatabase(alice)).emails, { timeout: 20_000 }).toBe(0);
+  await alice.evaluate(() => window.dispatchEvent(new Event('focus'))).catch(() => {});
+  await notice;
+  await expect.poll(async () => (await offlineDatabase(alice)).accounts, { timeout: 20_000 }).toBe(0);
   await alice.goto('/settings/backup/offline');
   await expect(alice.getByTestId('offline-forbidden')).toBeVisible({ timeout: 30_000 });
   await expect(alice.getByTestId('offline-switch')).toHaveCount(0);
@@ -436,7 +631,7 @@ test('forbidding offline mode wipes the device at the next policy fetch and hide
   // carol is outside the scope: her switch and her mail stay.
   await carol.reload();
   await expect(carol.getByTestId('offline-switch')).toHaveAttribute('aria-checked', 'true', { timeout: 30_000 });
-  expect((await offlineDatabase(carol)).emails).toBeGreaterThan(0);
+  expect((await offlineDatabase(carol)).accounts).toBeGreaterThan(0);
   await alice.context().close();
   await carol.context().close();
   await setPolicy(browser, {});
diff --git a/lib/__tests__/lite-scripts.test.ts b/lib/__tests__/lite-scripts.test.ts
index 5bf2edb5d..2b7e49d95 100644
--- a/lib/__tests__/lite-scripts.test.ts
+++ b/lib/__tests__/lite-scripts.test.ts
@@ -59,6 +59,8 @@ import {
   stalwartPrefixProblems,
   stalwartRewriteIndex,
   stalwartZipEntryProblems,
+  unexpectedEngineFiles,
+  LITE_REMOVED_PATHS,
   unexpectedApiStrings,
   withScriptHashCsp,
 } from '../../scripts/lite/lib.mjs';
@@ -343,6 +345,33 @@ describe('lite build helpers', () => {
   });
 });
 
+describe('the local store in an export', () => {
+  it('finds every engine file, and nothing else', () => {
+    expect(unexpectedEngineFiles([
+      'store-worker.js',
+      'sqlite3mc/2.6.1-3.54.0/sqlite3.mjs',
+      'sqlite3mc\\2.6.1-3.54.0\\sqlite3.wasm',
+      '_next/static/media/sqlite3.wasm',
+      'pst-worker.js',
+      'en/mail/index.html',
+      '_next/static/chunks/app.js',
+    ])).toEqual([
+      'store-worker.js',
+      'sqlite3mc/2.6.1-3.54.0/sqlite3.mjs',
+      'sqlite3mc/2.6.1-3.54.0/sqlite3.wasm',
+      '_next/static/media/sqlite3.wasm',
+    ]);
+  });
+
+  it('removes what a dev checkout holds before a build, and offline mode never starts in Lite', () => {
+    expect(LITE_REMOVED_PATHS).toEqual(expect.arrayContaining(['public/store-worker.js', 'public/sqlite3mc']));
+    const offlineMode = readFileSync(join(process.cwd(), 'lib/offline/offline-mode.ts'), 'utf8');
+    expect(offlineMode).toMatch(/if \(IS_LITE \|\| !hasIndexedDb\(\)\) return false;/);
+    const build = readFileSync(join(process.cwd(), 'scripts/lite/build.mjs'), 'utf8');
+    expect(build).not.toMatch(/build-store-worker/);
+  });
+});
+
 describe('prepare / postbuild / verify against a fake checkout', () => {
   it('plans the server-only trees and every test file, skipping node_modules, repos and scripts', () => {
     const root = makeRepo();
diff --git a/lib/__tests__/oauth-token-route.test.ts b/lib/__tests__/oauth-token-route.test.ts
index c12d8185a..0170c197b 100644
--- a/lib/__tests__/oauth-token-route.test.ts
+++ b/lib/__tests__/oauth-token-route.test.ts
@@ -166,7 +166,39 @@ describe('oauth token route - access token cache (#552)', () => {
 
     const { status } = await callPut();
 
-    expect(status).toBe(500);
+    expect(status).toBe(503);
+    expect(cookieStore.get('jmap_rt')).toBeTruthy();
+  });
+
+  it('names a real invalid_grant, and only that, for the client to wipe on', async () => {
+    const refuse = (status: number, body: string) => fetchMock.mockResolvedValueOnce(new Response(body, { status }));
+    cookieStore.set('jmap_rt', 'refresh-token');
+    refuse(400, JSON.stringify({ error: 'invalid_grant' }));
+    expect(await callPut({ force: 'true' })).toMatchObject({ status: 401, body: { error: 'invalid_grant' } });
+
+    for (const body of [JSON.stringify({ error: 'invalid_client' }), JSON.stringify({ error: 'invalid_request', error_description: 'Token is not valid yet' }), '<html>Forbidden</html>']) {
+      cookieStore.set('jmap_rt', 'refresh-token');
+      refuse(403, body);
+      const { status, body: answer } = await callPut({ force: 'true' });
+      expect(status).toBe(401);
+      expect(answer.error).not.toBe('invalid_grant');
+    }
+  });
+
+  it('answers 503 when the token endpoint is out of reach, which the client waits out', async () => {
+    cookieStore.set('jmap_rt', 'refresh-token');
+    fetchMock.mockRejectedValue(new TypeError('fetch failed'));
+    const { status } = await callPut({ force: 'true' });
+    expect(status).toBe(503);
+    expect(cookieStore.get('jmap_rt')).toBeTruthy();
+  });
+
+  it('answers 503 when discovery fails, also for a server it has no config for', async () => {
+    cookieStore.set('jmap_rt', 'refresh-token');
+    getTokenEndpoint.mockRejectedValue(new Error('OAuth misconfigured'));
+    const { status } = await callPut({ force: 'true' });
+    expect(status).toBe(503);
+    expect(fetchMock).not.toHaveBeenCalled();
     expect(cookieStore.get('jmap_rt')).toBeTruthy();
   });
 
diff --git a/lib/__tests__/offline-shell-route.test.ts b/lib/__tests__/offline-shell-route.test.ts
new file mode 100644
index 000000000..cacd327d7
--- /dev/null
+++ b/lib/__tests__/offline-shell-route.test.ts
@@ -0,0 +1,38 @@
+// @vitest-environment node
+import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from 'node:fs';
+import os from 'node:os';
+import { join } from 'node:path';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+describe('the list of files a start without a network needs', () => {
+  let dir = '';
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    vi.unstubAllEnvs();
+    if (dir) rmSync(dir, { recursive: true, force: true });
+  });
+
+  it('names the store worker with its build id, and the database engine with its .mjs and .wasm', async () => {
+    dir = mkdtempSync(join(os.tmpdir(), 'shell-'));
+    mkdirSync(join(dir, '.next', 'static', 'chunks'), { recursive: true });
+    writeFileSync(join(dir, '.next', 'static', 'chunks', 'app.js'), '');
+    writeFileSync(join(dir, '.next', 'static', 'chunks', 'app.js.map'), '');
+    mkdirSync(join(dir, 'public', 'sqlite3mc', '1.2'), { recursive: true });
+    writeFileSync(join(dir, 'public', 'sqlite3mc', '1.2', 'sqlite3.mjs'), '');
+    writeFileSync(join(dir, 'public', 'sqlite3mc', '1.2', 'sqlite3.wasm'), '');
+    writeFileSync(join(dir, 'public', 'sqlite3mc', '1.2', 'LICENSE'), '');
+    vi.spyOn(process, 'cwd').mockReturnValue(dir);
+    vi.stubEnv('NEXT_PUBLIC_BUILD_ID', 'build a');
+
+    const { GET } = await import('@/app/api/offline/shell/route');
+    const { files, buildId } = await (await GET()).json() as { files: string[]; buildId: string };
+    expect(buildId).toBe('build a');
+    expect(files.sort()).toEqual([
+      '/_next/static/chunks/app.js',
+      '/sqlite3mc/1.2/sqlite3.mjs',
+      '/sqlite3mc/1.2/sqlite3.wasm',
+      '/store-worker.js?v=build%20a',
+    ]);
+  });
+});
diff --git a/lib/__tests__/sw-offline-shell.test.ts b/lib/__tests__/sw-offline-shell.test.ts
index a032751e4..7785e6c28 100644
--- a/lib/__tests__/sw-offline-shell.test.ts
+++ b/lib/__tests__/sw-offline-shell.test.ts
@@ -165,6 +165,31 @@ describe('service worker with offline mode on', () => {
     expect(await worker.request({ url: `${ORIGIN}/mail`, mode: 'navigate' })).toBeNull();
   });
 
+  it('keeps the store\'s worker and database engine, so the store starts offline', async () => {
+    const caches = new FakeCaches();
+    await shellOn(caches, true);
+    let online = true;
+    const fetchMock = vi.fn(async (url: unknown) => {
+      if (!online) throw new TypeError('Failed to fetch');
+      return sameOrigin(`file ${String(url)}`, 'text/javascript');
+    });
+    const worker = loadWorker({ buildId: 'a', caches, clients: [], fetch: fetchMock });
+    await settle();
+    const urls = ['/store-worker.js?v=a', '/sqlite3mc/1.2/sqlite3.mjs', '/sqlite3mc/1.2/sqlite3.wasm'];
+    await worker.dispatch('message', { data: { type: 'offline-shell', on: true, urls, buildId: 'a' } });
+    const shell = await caches.open('bulwark-shell-a');
+    await vi.waitFor(async () => {
+      for (const url of urls) expect(await shell.match(`${ORIGIN}${url}`)).toBeDefined();
+    });
+    online = false;
+    for (const url of urls) {
+      const answer = await worker.request({ url: `${ORIGIN}${url}` });
+      expect(await answer!.text()).toContain(url);
+    }
+    // Only those: another root file still goes to the network.
+    expect(await worker.request({ url: `${ORIGIN}/other.js` })).toBeNull();
+  });
+
   it('keeps a newer tab’s shell in that tab’s build cache, not its own', async () => {
     const caches = new FakeCaches();
     const fetchMock = vi.fn(async () => sameOrigin('x', 'text/javascript'));
diff --git a/lib/jmap/client-interface.ts b/lib/jmap/client-interface.ts
index 9b28a08eb..0c6e9c5fb 100644
--- a/lib/jmap/client-interface.ts
+++ b/lib/jmap/client-interface.ts
@@ -499,8 +499,8 @@ export interface IJMAPClient {
     humanText?: string;
   }): Promise<void>;
 
-  sendRawEmail(blob: Blob, identityId: string, sentMailboxId: string, draftMailboxId?: string, delayedUntil?: string, envelopeRecipients?: string[]): Promise<SendEmailResult>;
-  submitRawEmail(blob: Blob, identityId: string, delayedUntil?: string, envelopeRecipients?: string[]): Promise<SendEmailResult>;
+  sendRawEmail(blob: Blob, identityId: string, sentMailboxId: string, draftMailboxId?: string, delayedUntil?: string, envelopeRecipients?: string[], existingCopyId?: string): Promise<SendEmailResult>;
+  submitRawEmail(blob: Blob, identityId: string, delayedUntil?: string, envelopeRecipients?: string[], existingCopyId?: string): Promise<SendEmailResult>;
   getScheduledEmails(limit?: number, position?: number): Promise<{ emails: ScheduledEmail[]; hasMore: boolean; total: number; totalByAccount?: Record<string, number>; nextPosition: number }>;
   /** Cancels a pending submission, then destroys its record. */
   cancelEmailSubmission(submissionId: string, accountId?: string): Promise<void>;
diff --git a/lib/jmap/client.ts b/lib/jmap/client.ts
index dc9c63c39..914772ce6 100644
--- a/lib/jmap/client.ts
+++ b/lib/jmap/client.ts
@@ -1407,12 +1407,14 @@ function stripMessageIdBrackets(id: string): string {
   return id.trim().replace(/^<+/, '').replace(/>+$/, '').trim();
 }
 
+const GATEWAY_STATUSES = new Set([502, 503, 504]);
+
 // Generate a Message-ID for outgoing mail (bare msg-id, no angle brackets, per
 // RFC 8621 §4.1.2.3). Without one the server synthesizes it from its OS
 // hostname, which leaks internal names (e.g. @ip-10-0-12-97.ec2.internal) into
 // headers — an anti-spam signal and an information disclosure. Use the sender's
 // domain instead, matching what receivers expect a Message-ID to look like.
-function generateMessageId(fromEmail: string): string {
+export function generateMessageId(fromEmail: string): string {
   const at = fromEmail.lastIndexOf('@');
   const domain = at > 0 ? fromEmail.slice(at + 1) : 'localhost';
   // FTM fix (2026-08-22): crypto.randomUUID() only exists in SECURE contexts (https/localhost).
@@ -2219,20 +2221,22 @@ export class JMAPClient implements IJMAPClient {
    * `transfer`: a mail import or export's own request. A 429 throws
    * RateLimitError for the transfer to wait on, without pausing the rest of
    * the client, and a pause the client is in doesn't hold the transfer up.
+   * `networkOnly`: only the server's own word counts. A send or a change the
+   * outbox hands over must never be answered by the device: the device would
+   * queue it again, or answer for the server.
    */
-  private async request(methodCalls: JMAPMethodCall[], using?: string[], opts?: { transfer?: boolean; skipOfflineRecord?: boolean }): Promise<JMAPResponse> {
+  private async request(methodCalls: JMAPMethodCall[], using?: string[], opts?: { transfer?: boolean; skipOfflineRecord?: boolean; networkOnly?: boolean }): Promise<JMAPResponse> {
     if (!this.apiUrl) {
       throw new Error('Not connected. Call connect() first.');
     }
     // Error reports keep the method names of the last calls, nothing else.
     recordJmapCall(methodCalls.map(([name]) => name));
     // Offline mode (#523, lib/offline/): answered from this device when the
-    // browser is offline or the network fails, and every answer from the
-    // server goes to the device's cache. Without offline mode no hooks are
-    // set and this is the plain network request.
+    // browser is offline or the network fails. Without offline mode no hooks
+    // are set and this is the plain network request.
     const offline = getOfflineHooks();
     if (this.offlineOnly || offline?.skipNetwork(this)) {
-      const local = offline ? await offline.answer(this, methodCalls) : null;
+      const local = offline && !opts?.networkOnly ? await offline.answer(this, methodCalls) : null;
       if (local) {
         this.lastAnswerFromDevice = true;
         return local as JMAPResponse;
@@ -2246,7 +2250,7 @@ export class JMAPClient implements IJMAPClient {
     if (standIns.length > 0) {
       const resolved = await offline!.resolveStandIns!(this, standIns);
       if (standIns.some((id) => !resolved[id])) {
-        const local = await offline!.answer(this, methodCalls);
+        const local = opts?.networkOnly ? null : await offline!.answer(this, methodCalls);
         if (local) {
           this.lastAnswerFromDevice = true;
           return local as JMAPResponse;
@@ -2263,8 +2267,8 @@ export class JMAPClient implements IJMAPClient {
     } catch (error) {
       // Only when the server is really gone: a refusal without CORS
       // headers looks the same to the browser and must stay an error.
-      if (offline && isNetworkFailure(error) && await offline.serverGone(this)) {
-        const local = await offline.answer(this, methodCalls);
+      if (offline && isNetworkFailure(error) && await offline.serverGone(this, error)) {
+        const local = opts?.networkOnly ? null : await offline.answer(this, methodCalls);
         if (local) {
           this.lastAnswerFromDevice = true;
           return asAsked(local as JMAPResponse);
@@ -2286,6 +2290,22 @@ export class JMAPClient implements IJMAPClient {
     return this.lastAnswerFromDevice;
   }
 
+  /** A request only the server may answer: for the outbox, which must see outages as outages. */
+  requestNetworkOnly(methodCalls: JMAPMethodCall[], using?: string[]): Promise<JMAPResponse> {
+    return this.request(methodCalls, using, { networkOnly: true, skipOfflineRecord: true });
+  }
+
+  /** The account that holds the submissions of mail in `accountId`. */
+  submissionAccountFor(accountId?: string): string {
+    return this.getSubmissionAccountId(accountId);
+  }
+
+  /** Whether this server reads keyword sort the other way. Null until the client has probed it. */
+  keywordSortInverted(accountId?: string): boolean | null {
+    const polarity = this.keywordSortPolarity.get(accountId ?? this.accountId)?.value;
+    return polarity ? polarity === 'inverted' : null;
+  }
+
   private async networkRequest(methodCalls: JMAPMethodCall[], using?: string[], opts?: { transfer?: boolean }): Promise<JMAPResponse> {
 
     const requestBody = {
@@ -2323,7 +2343,10 @@ export class JMAPClient implements IJMAPClient {
         console.error('Request failed:', response.status, responseText);
         // The status only: the answer may quote what was sent.
         if (!UNREPORTED_STATUSES.has(response.status)) reportJmapFailure({ status: response.status });
-        throw new Error(`Request failed: ${response.status} - ${responseText.substring(0, 200)}`);
+        const failure = new Error(`Request failed: ${response.status} - ${responseText.substring(0, 200)}`);
+        // A proxy in front of a server that's down: to the app, the same as no network.
+        if (GATEWAY_STATUSES.has(response.status)) failure.name = 'GatewayError';
+        throw failure;
       }
 
       let parsed: JMAPResponse;
@@ -3349,16 +3372,6 @@ export class JMAPClient implements IJMAPClient {
     return out;
   }
 
-  /** Changes made offline, sent as they were made: the ids the server refused. */
-  async applyEmailPatches(accountId: string | undefined, update: Record<string, Record<string, unknown>>): Promise<string[]> {
-    const response = await this.request([
-      ["Email/set", { accountId: accountId || this.accountId, update }, "0"],
-    ]);
-    const [name, result] = response.methodResponses?.[0] ?? [];
-    if (name !== "Email/set") throw jmapError(methodErrorMessage(response, 'Failed to update emails'), result);
-    return Object.keys((result?.notUpdated ?? {}) as Record<string, unknown>);
-  }
-
   // The 256000-byte body cap keeps list/thread fetches fast for the common
   // case, but truncation lands mid-tag on large HTML bodies (e.g. a data:image
   // src cut in half), which drops the whole element and can render blank. Only
@@ -5229,8 +5242,10 @@ export class JMAPClient implements IJMAPClient {
     delayedUntil?: string,
     envelopeMailFrom?: string,
     // `draftAccountId`: the account `draftId` lives in when it is not this
-    // one (see createDraft).
-    options?: SubmissionSendOptions & { draftAccountId?: string }
+    // one (see createDraft). `messageId` and `existingCopyId` come from the
+    // offline outbox: a Message-ID fixed when the message was queued, and the
+    // copy already on the server that only needs submitting (lib/store/outbox/dedupe.ts).
+    options?: SubmissionSendOptions & { draftAccountId?: string; messageId?: string; existingCopyId?: string }
   ): Promise<SendEmailResult> {
     const holdForSeconds = delayedUntil ? this.validateDelayedUntil(delayedUntil) : undefined;
     const emailId = `send-${Date.now()}`;
@@ -5338,7 +5353,7 @@ export class JMAPClient implements IJMAPClient {
       cc: cc?.length ? cc.map(parseRecipientString) : undefined,
       bcc: bcc?.length ? bcc.map(parseRecipientString) : undefined,
       subject,
-      messageId: [generateMessageId(senderEmail)],
+      messageId: [options?.messageId ?? generateMessageId(senderEmail)],
       inReplyTo: normalizedInReplyTo?.length ? normalizedInReplyTo : undefined,
       references: normalizedReferences?.length ? normalizedReferences : undefined,
       keywords: { "$seen": true, "$draft": true },
@@ -5433,13 +5448,16 @@ export class JMAPClient implements IJMAPClient {
     // same request meant a failed create/submission - e.g. the outgoing email
     // referencing part blobs of that very draft, which die with it - still
     // deleted the user's only copy of the message.
-    methodCalls.push(["Email/set", {
-      accountId: targetAccountId,
-      create: { [emailId]: emailCreate },
-    }, "0"]);
+    const existingCopyId = options?.existingCopyId;
+    if (!existingCopyId) {
+      methodCalls.push(["Email/set", {
+        accountId: targetAccountId,
+        create: { [emailId]: emailCreate },
+      }, "0"]);
+    }
     methodCalls.push(["EmailSubmission/set", {
       accountId: submissionAccountId,
-      create: buildSubmissionCreate(`#${emailId}`, firstMailFrom),
+      create: buildSubmissionCreate(existingCopyId ?? `#${emailId}`, firstMailFrom),
       ...onSuccess,
     }, "1"]);
     // Which recipients the server took. A refused one is lost without a
@@ -5457,7 +5475,7 @@ export class JMAPClient implements IJMAPClient {
     //   the identity's address - the composer warns about this before sending
     //   (#1009).
     // Stalwart checks the quota first, so both can happen, one after the other.
-    const draftCopyId = response.methodResponses
+    const draftCopyId = existingCopyId ?? response.methodResponses
       ?.find(([name]) => name === 'Email/set')?.[1]?.created?.[emailId]?.id as string | undefined;
     let mailFrom = firstMailFrom;
     let madeRoom = false;
@@ -5480,7 +5498,7 @@ export class JMAPClient implements IJMAPClient {
         accountId: submissionAccountId,
         create: buildSubmissionCreate(draftCopyId, mailFrom),
         ...onSuccess,
-      }, "1"], deliveryStatusCall(submissionAccountId, "1")]);
+      }, "1"], deliveryStatusCall(submissionAccountId, "1")], undefined, { networkOnly: true });
       response = {
         ...retry,
         methodResponses: [
@@ -5495,7 +5513,7 @@ export class JMAPClient implements IJMAPClient {
     const statusReadBack = takeDeliveryStatus(response);
     response = statusReadBack.response;
 
-    let createdEmailId: string | undefined;
+    let createdEmailId: string | undefined = existingCopyId;
     let emailSubmissionId: string | undefined;
     let serverSendAt: string | undefined;
     let filingError: string | undefined;
@@ -6828,17 +6846,18 @@ export class JMAPClient implements IJMAPClient {
     try {
       return await step();
     } catch (error) {
-      if (isNetworkFailure(error) || (error instanceof Error && (error.name === 'RequestTimeoutError' || error.name === 'OfflineUnavailableError'))) {
-        throw new SendNotStartedError(error);
-      }
+      if (isNetworkFailure(error)) throw new SendNotStartedError(error);
       throw error;
     }
   }
 
-  /** The request that sends: only a refusal without touching the network means it didn't start. */
+  /**
+   * The request that sends: only a refusal without touching the network means
+   * it didn't start. The device never answers it: the send may be on its way.
+   */
   private async submissionRequest(methodCalls: JMAPMethodCall[]): Promise<JMAPResponse> {
     try {
-      return await this.request(methodCalls);
+      return await this.request(methodCalls, undefined, { networkOnly: true });
     } catch (error) {
       if (error instanceof Error && error.name === 'OfflineUnavailableError') throw new SendNotStartedError(error);
       throw error;
@@ -11256,6 +11275,7 @@ export class JMAPClient implements IJMAPClient {
     if (eventType === 'state' && dataLines.length > 0) {
       try {
         const change = JSON.parse(dataLines.join('\n')) as StateChange;
+        getOfflineHooks()?.stateChange?.(this, change);
         this.stateChangeCallback?.(change);
       } catch {
         // Malformed SSE data - ignore
@@ -11430,8 +11450,9 @@ export class JMAPClient implements IJMAPClient {
         this.pollingStates[key] = state;
       }
 
-      if (Object.keys(changedByAccount).length > 0 && this.stateChangeCallback) {
-        this.stateChangeCallback({ '@type': 'StateChange', changed: changedByAccount });
+      if (Object.keys(changedByAccount).length > 0) {
+        getOfflineHooks()?.stateChange?.(this, { changed: changedByAccount });
+        this.stateChangeCallback?.({ '@type': 'StateChange', changed: changedByAccount });
       }
     } catch {
       // Silently fail - polling will retry
@@ -11856,11 +11877,13 @@ export class JMAPClient implements IJMAPClient {
     draftMailboxId?: string,
     delayedUntil?: string,
     envelopeRecipients?: string[],
+    /** The offline outbox found this message's copy on the server: submit that one. */
+    existingCopyId?: string,
   ): Promise<SendEmailResult> {
     const holdForSeconds = delayedUntil ? this.validateDelayedUntil(delayedUntil) : undefined;
     // Upload the raw message
     const file = new File([blob], 'message.eml', { type: 'message/rfc822' });
-    const { blobId } = await this.beforeSubmission(() => this.uploadBlob(file));
+    const blobId = existingCopyId ? undefined : (await this.beforeSubmission(() => this.uploadBlob(file))).blobId;
 
     // Import into Drafts first, then move to Sent after submission succeeds.
     // This avoids encrypt-on-append affecting the SMTP send. See #188.
@@ -11873,7 +11896,7 @@ export class JMAPClient implements IJMAPClient {
     const submissionAccountId = this.getSubmissionAccountId();
 
     const { emailId, submissionId: emailSubmissionId, sendAt, rejected } = await this.importAndSubmitRaw(
-      ['Email/import', {
+      existingCopyId ? null : ['Email/import', {
         accountId: this.accountId,
         emails: {
           'raw-import': {
@@ -11883,7 +11906,7 @@ export class JMAPClient implements IJMAPClient {
           },
         },
       }, '0'],
-      'raw-import',
+      existingCopyId ?? 'raw-import',
       submissionAccountId,
       (submitEmailId) => ({
         accountId: submissionAccountId,
@@ -11926,6 +11949,8 @@ export class JMAPClient implements IJMAPClient {
     identityId: string,
     delayedUntil?: string,
     envelopeRecipients?: string[],
+    /** The offline outbox found this message's copy on the server: submit that one. */
+    existingCopyId?: string,
   ): Promise<SendEmailResult> {
     const mailboxes = await this.beforeSubmission(() => this.getMailboxes());
     const draftsMailbox = mailboxes.find(mb => mb.role === 'drafts');
@@ -11936,7 +11961,7 @@ export class JMAPClient implements IJMAPClient {
     const holdForSeconds = delayedUntil ? this.validateDelayedUntil(delayedUntil) : undefined;
     
     const file = new File([blob], 'message.eml', { type: 'message/rfc822' });
-    const { blobId } = await this.beforeSubmission(() => this.uploadBlob(file));
+    const blobId = existingCopyId ? undefined : (await this.beforeSubmission(() => this.uploadBlob(file))).blobId;
 
     const identities = await this.beforeSubmission(() => this.getIdentities());
     const identity = identities.find(item => item.id === identityId);
@@ -11946,7 +11971,7 @@ export class JMAPClient implements IJMAPClient {
     //Temporarily import the raw email into Drafts to satisfy JMAP's requirement that an EmailSubmission references an existing Email.
     // The Email will be destroyed after submission.
     const { submissionId: emailSubmissionId, sendAt, rejected } = await this.importAndSubmitRaw(
-      ['Email/import', {
+      existingCopyId ? null : ['Email/import', {
         accountId: this.accountId,
         emails: {
           'temp-submit': {
@@ -11956,7 +11981,7 @@ export class JMAPClient implements IJMAPClient {
           },
         },
       }, '0'],
-      'temp-submit',
+      existingCopyId ?? 'temp-submit',
       submissionAccountId,
       (submitEmailId) => ({
         accountId: submissionAccountId,
@@ -11993,29 +12018,31 @@ export class JMAPClient implements IJMAPClient {
    * (or in Sent, where it passes for a sent message). So does a submission
    * whose recipients were all refused (#1123): it throws
    * RecipientsRejectedError; the ones refused while others were taken come
-   * back as `rejected`.
+   * back as `rejected`. Without `importCall`, `importCreationId` is the id of a
+   * copy already on the server.
    */
   private async importAndSubmitRaw(
-    importCall: JMAPMethodCall,
+    importCall: JMAPMethodCall | null,
     importCreationId: string,
     submissionAccountId: string,
     submissionSet: (emailId: string) => Record<string, unknown>,
     failureMessage: string,
   ): Promise<{ emailId?: string; submissionId?: string; sendAt?: string; rejected: RejectedRecipient[] }> {
-    const firstSet = submissionSet(`#${importCreationId}`);
+    const firstSet = submissionSet(importCall ? `#${importCreationId}` : importCreationId);
     let response = await this.submissionRequest([
-      importCall,
+      ...(importCall ? [importCall] : []),
       ['EmailSubmission/set', firstSet, '1'],
       deliveryStatusCall(submissionAccountId, 'raw-submit'),
     ]);
-    const importedId = response.methodResponses
-      ?.find(([name]) => name === 'Email/import')?.[1]?.created?.[importCreationId]?.id as string | undefined;
+    const importedId = importCall
+      ? response.methodResponses?.find(([name]) => name === 'Email/import')?.[1]?.created?.[importCreationId]?.id as string | undefined
+      : importCreationId;
     if (importedId && submissionCreateError(response, 'raw-submit')?.type === 'overQuota') {
       await this.makeRoomForSubmission(submissionAccountId);
       const retry = await this.request([
         ['EmailSubmission/set', submissionSet(importedId), '1'],
         deliveryStatusCall(submissionAccountId, 'raw-submit'),
-      ]);
+      ], undefined, { networkOnly: true });
       response = {
         ...retry,
         methodResponses: [
diff --git a/lib/jmap/offline-hooks.ts b/lib/jmap/offline-hooks.ts
index ab746f3bc..fed004080 100644
--- a/lib/jmap/offline-hooks.ts
+++ b/lib/jmap/offline-hooks.ts
@@ -1,7 +1,7 @@
 /**
  * Where the JMAP client hands over to offline mode (#523, lib/offline/).
- * The client knows nothing about the cache: it asks these hooks whether to
- * skip the network, gives them what the server answered, and asks them for
+ * The client knows nothing about the local store: it asks these hooks whether
+ * to skip the network, gives them what the server answered, and asks them for
  * an answer when the network is gone. Nothing is registered while offline
  * mode is off for every account, so the client then behaves as before.
  *
@@ -22,6 +22,8 @@ export interface OfflineClientRef {
   getServerUrl(): string;
   getUsername(): string;
   getAccountId(): string;
+  /** Answers from this device only: a local copy on screen at a start. */
+  isOfflineOnly?(): boolean;
 }
 
 export interface OfflineHooks {
@@ -36,9 +38,11 @@ export interface OfflineHooks {
   /**
    * After a request failed on the network: whether the server can't be
    * reached at all (then the device answers), or it only refused that
-   * request (then it stays an error).
+   * request (then it stays an error). `error` is what the request failed with.
    */
-  serverGone(client: OfflineClientRef): Promise<boolean>;
+  serverGone(client: OfflineClientRef, error?: unknown): Promise<boolean>;
+  /** The server pushed new states, for the local store to catch up. */
+  stateChange?(client: OfflineClientRef, change: { changed?: Record<string, Record<string, string>> }): void;
   /** A blob kept on the device, or null. */
   blob(client: OfflineClientRef, blobId: string, accountId: string): Promise<Blob | null>;
   /** A blob the server sent, for the cache. */
@@ -57,6 +61,8 @@ export interface OfflineHooks {
    * ids as they are.
    */
   resolveStandIns?(client: OfflineClientRef, ids: string[]): Promise<Record<string, string | null>>;
+  /** The user opened this file: the local store keeps recently opened files. */
+  fileOpened?(client: OfflineClientRef, accountId: string, id: string): void;
 }
 
 const KEY = '__bulwarkOfflineHooks';
@@ -71,13 +77,24 @@ export function getOfflineHooks(): OfflineHooks | null {
   return (globalThis as HookGlobal)[KEY] ?? null;
 }
 
-/** The network refused the request (not an HTTP error): offline, DNS, a dropped connection. */
+/**
+ * The server can't be talked to: offline, DNS, a dropped connection, a request
+ * that hung until its deadline, a proxy answering for a server that's down.
+ * Not an answer from the server itself.
+ */
 export function isNetworkFailure(error: unknown): boolean {
   if (!(error instanceof Error)) return false;
-  if (error.name === 'OfflineUnavailableError') return true;
+  if (error.name === 'OfflineUnavailableError' || error.name === 'RequestTimeoutError' || error.name === 'GatewayError') return true;
   return error.name === 'TypeError' && /fetch|network|load failed|internet/i.test(error.message);
 }
 
+/** The connection is fine and a proxy answered: the mail server behind it is what's gone. */
+export function isServerOutage(error: unknown): boolean {
+  if (!(error instanceof Error)) return false;
+  if (error.name === 'GatewayError') return true;
+  return error.name === 'SendNotStartedError' && (error as SendNotStartedError).cause instanceof Error && ((error as SendNotStartedError).cause as Error).name === 'GatewayError';
+}
+
 /** Thrown for a request the device can't answer while the server can't be reached. */
 export class OfflineUnavailableError extends Error {
   constructor(message = 'Not available offline') {
diff --git a/lib/offline/__tests__/cache.test.ts b/lib/offline/__tests__/cache.test.ts
deleted file mode 100644
index 53ffced76..000000000
--- a/lib/offline/__tests__/cache.test.ts
+++ /dev/null
@@ -1,121 +0,0 @@
-import 'fake-indexeddb/auto';
-import { beforeEach, describe, expect, it } from 'vitest';
-import {
-  cacheUsage,
-  emailIndex,
-  emailKey,
-  enforceCap,
-  forgetIndexes,
-  getBlob,
-  getBody,
-  getMisc,
-  patchEmails,
-  putBlob,
-  putEmails,
-  putMisc,
-  wipeAccountCache,
-} from '../cache';
-import { forgetDeviceKey, openJson, sealJson } from '../crypto';
-import { allowOfflineDbCreation, deleteOfflineDb, idbGet, idbGetAll } from '../db';
-
-const day = 24 * 60 * 60 * 1000;
-const email = (id: string, ageDays: number, extra: Record<string, unknown> = {}) => ({
-  id,
-  threadId: `t-${id}`,
-  mailboxIds: { inbox: true },
-  keywords: {},
-  receivedAt: new Date(Date.now() - ageDays * day).toISOString(),
-  subject: `Subject ${id}`,
-  ...extra,
-});
-
-beforeEach(async () => {
-  forgetIndexes();
-  forgetDeviceKey();
-  await deleteOfflineDb();
-  allowOfflineDbCreation();
-});
-
-describe('offline encryption', () => {
-  it('keeps nothing readable and a key that cannot be exported', async () => {
-    const sealed = await sealJson({ subject: 'Quarterly numbers' });
-    expect(new TextDecoder().decode(sealed.data)).not.toContain('Quarterly');
-    expect(await openJson(sealed)).toEqual({ subject: 'Quarterly numbers' });
-    const stored = await idbGet<{ key: CryptoKey }>('keys', 'aes');
-    expect(stored?.key.extractable).toBe(false);
-    await expect(crypto.subtle.exportKey('raw', stored!.key)).rejects.toThrow();
-  });
-
-  it('stores messages encrypted, list part and body apart', async () => {
-    await putEmails('acc', 'j1', [email('m1', 1, { bodyValues: { 1: { value: 'Secret text' } }, textBody: [{ partId: '1' }] })]);
-    const records = await idbGetAll<{ data: ArrayBuffer }>('emails');
-    expect(records).toHaveLength(1);
-    expect(new TextDecoder().decode(records[0].data)).not.toContain('Subject m1');
-    const bodies = await idbGetAll<{ data: ArrayBuffer }>('bodies');
-    expect(new TextDecoder().decode(bodies[0].data)).not.toContain('Secret text');
-
-    forgetIndexes();
-    const index = await emailIndex('acc');
-    const meta = index.get(emailKey('acc', 'j1', 'm1'))!;
-    expect(meta.subject).toBe('Subject m1');
-    expect(meta).not.toHaveProperty('bodyValues');
-    expect((await getBody('acc', 'j1', 'm1'))?.bodyValues).toEqual({ 1: { value: 'Secret text' } });
-  });
-
-  it('merges a later list fetch into the kept message', async () => {
-    await putEmails('acc', 'j1', [email('m1', 1, { bodyValues: { 1: { value: 'x' } } })]);
-    await putEmails('acc', 'j1', [{ id: 'm1', keywords: { $seen: true } }]);
-    const meta = (await emailIndex('acc')).get(emailKey('acc', 'j1', 'm1'))!;
-    expect(meta.keywords).toEqual({ $seen: true });
-    expect(meta.subject).toBe('Subject m1');
-    expect(await getBody('acc', 'j1', 'm1')).not.toBeNull();
-  });
-
-  it('applies keyword and folder patches', async () => {
-    await putEmails('acc', 'j1', [email('m1', 1)]);
-    await patchEmails('acc', 'j1', { m1: { 'keywords/$flagged': true, 'mailboxIds/inbox': null, 'mailboxIds/archive': true } });
-    const meta = (await emailIndex('acc')).get(emailKey('acc', 'j1', 'm1'))!;
-    expect(meta.keywords).toEqual({ $flagged: true });
-    expect(meta.mailboxIds).toEqual({ archive: true });
-  });
-});
-
-describe('the cache cap', () => {
-  it('drops the oldest messages first, with their bodies and attachments', async () => {
-    await putEmails('acc', 'j1', [
-      email('old', 20, { bodyValues: { 1: { value: 'a'.repeat(4000) } } }),
-      email('mid', 10, { bodyValues: { 1: { value: 'b'.repeat(4000) } } }),
-      email('new', 1, { bodyValues: { 1: { value: 'c'.repeat(4000) } } }),
-    ]);
-    await putBlob('acc', 'j1', 'blob-old', new Blob(['x'.repeat(4000)]), Date.now() - 20 * day, emailKey('acc', 'j1', 'old'));
-    const { total } = await cacheUsage();
-    // Room for about two messages.
-    const freed = await enforceCap(total - 6000);
-    expect(freed).toBeGreaterThan(0);
-    const index = await emailIndex('acc');
-    expect(index.has(emailKey('acc', 'j1', 'old'))).toBe(false);
-    expect(index.has(emailKey('acc', 'j1', 'new'))).toBe(true);
-    expect(await getBody('acc', 'j1', 'old')).toBeNull();
-    expect(await getBlob('acc', 'j1', 'blob-old')).toBeNull();
-    expect(await getBody('acc', 'j1', 'new')).not.toBeNull();
-    expect((await cacheUsage()).total).toBeLessThanOrEqual(total - 6000);
-  });
-
-  it('leaves the cache alone under the cap', async () => {
-    await putEmails('acc', 'j1', [email('m1', 1)]);
-    expect(await enforceCap()).toBe(0);
-  });
-});
-
-describe('wiping one account', () => {
-  it('removes that account only', async () => {
-    await putEmails('a', 'j1', [email('m1', 1)]);
-    await putEmails('b', 'j1', [email('m2', 1)]);
-    await putMisc('a', 'session', { apiUrl: 'x' });
-    await wipeAccountCache('a');
-    expect((await emailIndex('a')).size).toBe(0);
-    expect(await getMisc('a', 'session')).toBeNull();
-    forgetIndexes();
-    expect((await emailIndex('b')).size).toBe(1);
-  });
-});
diff --git a/lib/offline/__tests__/client-fallback.test.ts b/lib/offline/__tests__/client-fallback.test.ts
index f7d49e49b..a4aa5ffa5 100644
--- a/lib/offline/__tests__/client-fallback.test.ts
+++ b/lib/offline/__tests__/client-fallback.test.ts
@@ -5,36 +5,44 @@ import { useAuthStore } from '@/stores/auth-store';
 import { useAccountStore } from '@/stores/account-store';
 import { usePolicyStore } from '@/stores/policy-store';
 import { DEFAULT_ORGANISATION_POLICY } from '@/lib/admin/organisation-policy';
+import { setStoreBackend } from '@/lib/store/client/api';
+import { FakeJmapMail } from '@/lib/store/__tests__/helpers/fake-jmap-mail';
+import { InProcessStore } from '@/lib/store/__tests__/helpers/in-process-store';
 import { startOfflineMode, wipeEverything } from '../offline-mode';
-import { forgetIndexes, putEmails, putMisc, getMisc, emailIndex } from '../cache';
-import { forgetDeviceKey } from '../crypto';
-import { allowOfflineDbCreation, deleteOfflineDb } from '../db';
+import { forgetLegacyMove } from '../migrate-legacy';
 import { useOfflineStore, writeEnabled } from '../state';
-import { syncAccount } from '../sync';
 
 const SERVER = 'https://mail.example.org';
 const SESSION = {
   apiUrl: `${SERVER}/jmap/`,
   downloadUrl: `${SERVER}/jmap/download/{accountId}/{blobId}/{name}?accept={type}`,
   uploadUrl: `${SERVER}/jmap/upload/{accountId}/`,
-  accounts: { j1: { name: 'alice', isPersonal: true, accountCapabilities: {} } },
-  primaryAccounts: { 'urn:ietf:params:jmap:mail': 'j1' },
-  capabilities: { 'urn:ietf:params:jmap:core': { maxObjectsInGet: 500 } },
+  accounts: { acc1: { name: 'alice', isPersonal: true, accountCapabilities: { 'urn:ietf:params:jmap:mail': {}, 'urn:ietf:params:jmap:submission': {} } } },
+  primaryAccounts: { 'urn:ietf:params:jmap:mail': 'acc1' },
+  capabilities: { 'urn:ietf:params:jmap:core': { maxObjectsInGet: 500, maxObjectsInSet: 500 }, 'urn:ietf:params:jmap:mail': {} },
   username: 'alice@example.org',
 };
 
 let probeOk = true;
-let apiFails = false;
+let apiFails: 'no' | 'network' | 'gateway' = 'no';
+let server: FakeJmapMail;
+let store: InProcessStore;
 
 beforeEach(async () => {
-  forgetIndexes();
-  forgetDeviceKey();
-  await deleteOfflineDb();
-  allowOfflineDbCreation();
-  localStorage.clear();
   probeOk = true;
-  apiFails = false;
-  useOfflineStore.setState({ downServers: [], browserOffline: false });
+  apiFails = 'no';
+  server = new FakeJmapMail({ mailboxes: [
+    { id: 'inbox', name: 'Inbox', role: 'inbox', totalEmails: 2, unreadEmails: 2 },
+    { id: 'trash', name: 'Trash', role: 'trash', totalEmails: 0, unreadEmails: 0 },
+  ] });
+  server.identities.set('i1', { id: 'i1', email: 'alice@example.org', name: 'Alice' });
+  server.addEmail({ id: 'm1', subject: 'Kept one', threadId: 't1', keywords: {} });
+  server.addEmail({ id: 'm2', subject: 'Kept two', threadId: 't2', keywords: {} });
+  store = new InProcessStore(server, SESSION);
+  setStoreBackend(store);
+  forgetLegacyMove();
+  localStorage.clear();
+  useOfflineStore.setState({ enabled: [], downServers: [], browserOffline: false, outbox: [], pendingChanges: 0, conflicts: [] });
   usePolicyStore.setState({ loaded: true, subject: null, policy: { ...usePolicyStore.getState().policy, organisation: DEFAULT_ORGANISATION_POLICY } });
   useAccountStore.setState({ accounts: [{ id: 'acc', serverUrl: SERVER, username: 'alice@example.org' } as never] });
   vi.stubGlobal('fetch', vi.fn(async (url: string, init?: RequestInit) => {
@@ -43,175 +51,243 @@ beforeEach(async () => {
       return new Response(null, { status: 200 });
     }
     if (String(url).endsWith('/.well-known/jmap')) return new Response(JSON.stringify(SESSION), { status: 200 });
-    if (apiFails) throw new TypeError('Failed to fetch');
-    return new Response(JSON.stringify({ methodResponses: [['Email/get', { accountId: 'j1', list: [], notFound: ['m1'] }, '0']] }), { status: 200 });
+    if (apiFails === 'network') throw new TypeError('Failed to fetch');
+    if (apiFails === 'gateway') return new Response('<html>Bad Gateway</html>', { status: 502 });
+    const body = JSON.parse(String(init?.body)) as { methodCalls: never[] };
+    return new Response(JSON.stringify(await server.request(body.methodCalls)), { status: 200 });
   }));
 });
 
 afterEach(async () => {
   vi.unstubAllGlobals();
   await wipeEverything();
+  setStoreBackend(null);
 });
 
-async function connectedClient(): Promise<JMAPClient> {
+async function ready() {
   const client = new JMAPClient(SERVER, 'alice@example.org', 'pw');
   await client.connect();
   useAuthStore.setState({ client: client as never, activeAccountId: 'acc' });
-  return client;
+  writeEnabled(['acc']);
+  const stop = startOfflineMode();
+  await store.sync('acc');
+  return { client, stop };
+}
+
+async function offline(run: () => Promise<void>): Promise<void> {
+  vi.stubGlobal('navigator', { onLine: false });
+  try {
+    await run();
+  } finally {
+    vi.stubGlobal('navigator', window.navigator);
+  }
 }
 
 describe('falling back to the device', () => {
-  it('answers from the device when the server is gone', async () => {
-    const client = await connectedClient();
-    writeEnabled(['acc']);
-    const stop = startOfflineMode();
-    await putEmails('acc', 'j1', [{ id: 'm1', mailboxIds: { inbox: true }, receivedAt: new Date().toISOString(), subject: 'Kept', bodyValues: { 1: { value: 'x' } } }]);
-    apiFails = true;
+  it('answers from the store when the server is gone', async () => {
+    const { client, stop } = await ready();
+    apiFails = 'network';
     probeOk = false;
     const email = await client.getEmail('m1');
-    expect(email?.subject).toBe('Kept');
+    expect(email?.subject).toBe('Kept one');
     expect(useOfflineStore.getState().downServers).toEqual(['https://mail.example.org']);
     stop();
   });
 
   it('keeps a refused request an error while the server answers', async () => {
-    const client = await connectedClient();
-    writeEnabled(['acc']);
-    const stop = startOfflineMode();
-    await putEmails('acc', 'j1', [{ id: 'm1', mailboxIds: { inbox: true }, receivedAt: new Date().toISOString(), subject: 'Kept', bodyValues: { 1: { value: 'x' } } }]);
-    apiFails = true;
+    const { client, stop } = await ready();
+    apiFails = 'network';
     probeOk = true;
     // getEmail swallows errors into null: the device's copy isn't passed off as the server's answer.
     expect(await client.getEmail('m1')).toBeNull();
     expect(useOfflineStore.getState().downServers).toEqual([]);
     stop();
   });
+
+  it('counts a proxy\'s 5xx as the server being gone, though a probe would pass', async () => {
+    const { client, stop } = await ready();
+    apiFails = 'gateway';
+    probeOk = true;
+    const email = await client.getEmail('m1');
+    expect(email?.subject).toBe('Kept one');
+    expect(useOfflineStore.getState().downServers).toEqual(['https://mail.example.org']);
+    // A later good answer ends it.
+    apiFails = 'no';
+    await client.getEmail('m1');
+    expect(useOfflineStore.getState().downServers).toEqual([]);
+    stop();
+  });
 });
 
-describe('mailbox paging with the device cache', () => {
-  const mailboxes = Array.from({ length: 5 }, (_, i) => ({ id: `box-${i}`, name: `Folder ${i}`, parentId: null }));
-
-  function mailboxServer(failLaterPage = false) {
-    const positions: number[] = [];
-    vi.stubGlobal('fetch', vi.fn(async (url: string, init?: RequestInit) => {
-      if (String(url).endsWith('/.well-known/jmap')) {
-        return new Response(JSON.stringify({
-          ...SESSION,
-          capabilities: { 'urn:ietf:params:jmap:core': { maxObjectsInGet: 2 } },
-        }), { status: 200 });
-      }
-      const { methodCalls } = JSON.parse(String(init?.body));
-      const query = methodCalls.find(([name]: [string]) => name === 'Mailbox/query');
-      const position = query?.[1].position ?? 0;
-      if (query) positions.push(position);
-      const page = mailboxes.slice(position, position + 2);
-      const methodResponses = methodCalls.map(([name, , id]: [string, unknown, string]) => {
-        if (name === 'Identity/get') return [name, { accountId: 'j1', list: [{ id: 'recording-barrier' }] }, id];
-        if (query && failLaterPage && position > 0) return ['error', { type: 'serverFail' }, id];
-        if (name === 'Mailbox/query') return [name, {
-          accountId: 'j1', queryState: 'query-state', position,
-          ids: page.map((box) => box.id), total: mailboxes.length,
-        }, id];
-        return [name, { accountId: 'j1', state: 'mailbox-state', list: page, notFound: [] }, id];
-      });
-      return new Response(JSON.stringify({ methodResponses }), { status: 200 });
-    }));
-    return positions;
-  }
-
-  // Identity recording shares the per-account queue with mailbox recording.
-  // Waiting for this marker also detects erroneous writes queued by failed pages.
-  async function recorded(client: JMAPClient) {
-    await client.getIdentities();
-    await vi.waitFor(async () => {
-      expect(await getMisc('acc', 'identities')).toEqual({ j1: [{ id: 'recording-barrier' }] });
+describe('per-call errors, end to end through the client', () => {
+  it('keeps the results when one call in the request can\'t be answered', async () => {
+    const { client, stop } = await ready();
+    await offline(async () => {
+      // A search with text: Email/query, Email/get, and SearchSnippet/get, which the store refuses.
+      const result = await client.searchEmails('kept');
+      expect(result.emails.map((email) => email.id).sort()).toEqual(['m1', 'm2']);
+      expect(result.emails[0].subject).toBeTruthy();
     });
-  }
+    stop();
+  });
 
-  it('returns a cached list larger than maxObjectsInGet without inventing a collection state', async () => {
-    mailboxServer();
-    const client = await connectedClient();
-    writeEnabled(['acc']);
-    const stop = startOfflineMode();
-    try {
-      await putMisc('acc', 'mailboxes', { j1: mailboxes });
-      vi.stubGlobal('navigator', { onLine: false });
+  it('does a full fetch when /changes is refused: the client reads null', async () => {
+    const { client, stop } = await ready();
+    await offline(async () => {
+      expect(await client.getEmailChanges('s1')).toBeNull();
+      expect(await client.getMailboxChanges('s1')).toBeNull();
+    });
+    stop();
+  });
+
+  it('a draft can\'t be saved yet, and says so the way the composer expects', async () => {
+    const { client, stop } = await ready();
+    await offline(async () => {
+      await expect(client.createDraft(['b@example.org'], 'S', 'x', undefined, undefined, undefined, 'alice@example.org')).rejects.toThrow();
+    });
+    stop();
+  });
+
+  it('queues a delete for good and an emptied folder, and the client sees them done', async () => {
+    const { client, stop } = await ready();
+    await offline(async () => {
+      await client.deleteEmail('m1');
+      expect(await client.getEmail('m1')).toBeNull();
+      await client.moveToTrash('m2', 'trash');
+      expect(await client.emptyMailbox('trash')).toBe(1);
+      const boxes = await client.getMailboxes();
+      expect(boxes.find((box) => box.id === 'inbox')).toMatchObject({ totalEmails: 0, unreadEmails: 0 });
+      expect(boxes.find((box) => box.id === 'trash')).toMatchObject({ totalEmails: 0 });
+    });
+    stop();
+    // Nothing reached the server yet.
+    expect(server.emails.size).toBe(2);
+  });
+
+  it('marks read offline and the change reaches the message and the counts', async () => {
+    const { client, stop } = await ready();
+    await offline(async () => {
+      await client.markAsRead('m1', true);
+      expect((await client.getEmail('m1'))?.keywords).toMatchObject({ $seen: true });
+      const boxes = await client.getMailboxes();
+      expect(boxes.find((box) => box.id === 'inbox')?.unreadEmails).toBe(1);
+    });
+    stop();
+  });
+});
+
+describe('what the store answers and is told', () => {
+  it('answers identities', async () => {
+    const { client, stop } = await ready();
+    await offline(async () => {
+      expect((await client.getIdentities()).map((identity) => identity.id)).toEqual(['i1']);
+    });
+    stop();
+  });
+
+  it('answers the folder list with the server\'s real state', async () => {
+    const { client, stop } = await ready();
+    await offline(async () => {
       const result = await client.getAllMailboxesWithState();
-      expect(result.mailboxes.map((box) => box.id)).toEqual(mailboxes.map((box) => box.id));
-      expect(result.states).toEqual({});
-      // Only session discovery touched the network; both query/get pages are local.
-      expect(fetch).toHaveBeenCalledTimes(1);
-    } finally {
-      stop();
-    }
+      expect(result.mailboxes.map((box) => box.id).sort()).toEqual(['inbox', 'trash']);
+      expect(Object.values(result.states)).toEqual([server.coll.Mailbox.state()]);
+    });
+    stop();
   });
 
-  it('records the complete live multi-page list rather than its final page', async () => {
-    const positions = mailboxServer();
-    const client = await connectedClient();
-    writeEnabled(['acc']);
-    const stop = startOfflineMode();
-    try {
-      const result = await client.getMailboxes();
-      expect(result.map((box) => box.id)).toEqual(mailboxes.map((box) => box.id));
-      expect(positions).toEqual([0, 2, 4]);
-      await recorded(client);
-      expect(await getMisc('acc', 'mailboxes')).toEqual({ j1: mailboxes });
-    } finally {
-      stop();
-    }
+  it('never takes a refusal from the device for the answer to a send', async () => {
+    const { client, stop } = await ready();
+    await client.getMailboxes();
+    await client.getIdentities();
+    const fetchMock = fetch as unknown as ReturnType<typeof vi.fn>;
+    const passThrough = fetchMock.getMockImplementation() as (url: string, init?: RequestInit) => Promise<Response>;
+    fetchMock.mockImplementation(async (url: string, init?: RequestInit) => {
+      if (String(init?.body ?? '').includes('EmailSubmission/set')) {
+        apiFails = 'network';
+        probeOk = false;
+      }
+      return passThrough(url, init);
+    });
+    server.mailboxes.set('drafts', { id: 'drafts', role: 'drafts' });
+    server.mailboxes.set('sent', { id: 'sent', role: 'sent' });
+    const error = await client.sendEmail(['bob@example.org'], 'Hi', 'Body', undefined, undefined, 'i1', 'alice@example.org').catch((e: unknown) => e) as Error;
+    // The connection broke: "may have gone", not a refusal, and not "never started".
+    expect(error).toBeInstanceOf(TypeError);
+    expect(error.message).toBe('Failed to fetch');
+    stop();
   });
 
-  it('retains the previous complete cache when a later live page fails', async () => {
-    const positions = mailboxServer(true);
-    const client = await connectedClient();
-    writeEnabled(['acc']);
-    const stop = startOfflineMode();
-    const previous = [{ id: 'old', name: 'Previously cached', parentId: null }];
-    try {
-      await putMisc('acc', 'mailboxes', { j1: previous });
-      await expect(client.getMailboxes()).rejects.toThrow('Failed to load the complete mailbox list');
-      expect(positions).toEqual([0, 2]);
-      await recorded(client);
-      expect(await getMisc('acc', 'mailboxes')).toEqual({ j1: previous });
-    } finally {
-      stop();
-    }
+  it('never lets the device answer for the server when the outbox asks', async () => {
+    const { client, stop } = await ready();
+    apiFails = 'network';
+    probeOk = false;
+    await expect(client.requestNetworkOnly([['Email/set', { accountId: 'acc1', update: { m1: { 'keywords/$seen': true } } }, '0']])).rejects.toThrow('Failed to fetch');
+    expect(await store.area('acc', 'outbox.read')).toMatchObject({ patches: 0 });
+    stop();
   });
-});
-
-describe('the sync', () => {
-  function fakeClient(opts: { failQuery?: boolean }) {
-    return {
-      getSessionSnapshot: () => SESSION,
-      getAccountId: () => 'j1',
-      getAllMailboxes: vi.fn(async () => { await putMisc('acc', 'mailboxes', { j1: [{ id: 'inbox', role: 'inbox' }] }); return []; }),
-      getMailboxes: vi.fn(async () => []),
-      getIdentities: vi.fn(async () => []),
-      getRecentEmailIds: vi.fn(async (mailboxId: string) => { if (opts.failQuery && mailboxId === 'archive') throw new Error('refused'); return mailboxId === 'inbox' ? ['new'] : []; }),
-      getSomeEmails: vi.fn(async () => []),
-      getFullEmails: vi.fn(async (ids: string[]) => {
-        await putEmails('acc', 'j1', ids.map((id) => ({ id, mailboxIds: { inbox: true }, receivedAt: new Date().toISOString(), bodyValues: {} })));
-        return [];
-      }),
-      fetchBlob: vi.fn(),
-    };
-  }
-  const deps = { stillActive: () => true, recorded: async () => {}, scopeMailboxes: async () => [{ jmap: 'j1', mailboxId: 'inbox', isInbox: true }] };
-
-  it('fetches what is missing and drops what left the Inbox', async () => {
-    await putEmails('acc', 'j1', [{ id: 'gone', mailboxIds: { inbox: true }, receivedAt: new Date().toISOString() }]);
-    const client = fakeClient({});
-    await syncAccount('acc', client as never, deps);
-    expect(client.getFullEmails).toHaveBeenCalledWith(['new'], 'j1');
-    const index = await emailIndex('acc');
-    expect([...index.values()].map((e) => e.id)).toEqual(['new']);
+
+  it('keeps a message opened from outside the window', async () => {
+    server.addEmail({ id: 'old', subject: 'Old', receivedAt: '2019-01-01T00:00:00Z', bodyValues: { 1: { value: 'Old text' } } });
+    const { client, stop } = await ready();
+    store.dbs.get('acc')!.run("DELETE FROM email WHERE id = 'old'");
+    await client.getEmail('old');
+    await vi.waitFor(async () => {
+      const answer = await store.answer('acc', [['Email/get', { ids: ['old'], properties: ['subject', 'bodyValues'], fetchAllBodyValues: true }, '0']]);
+      expect(answer?.methodResponses[0][1].list[0]?.subject).toBe('Old');
+    });
+    stop();
+  });
+
+  it('tells the store what the server pushed', async () => {
+    const { client, stop } = await ready();
+    const note = vi.spyOn(store, 'noteStateChange');
+    const { getOfflineHooks } = await import('@/lib/jmap/offline-hooks');
+    getOfflineHooks()?.stateChange?.(client, { changed: { acc1: { Email: 's99' } } });
+    expect(note).toHaveBeenCalledWith('acc', { acc1: { Email: 's99' } });
+    stop();
+  });
+
+  it('holds a file while offline and hands it back for the message', async () => {
+    const { client, stop } = await ready();
+    await offline(async () => {
+      const held = await client.uploadBlob(new File(['hello'], 'note.txt', { type: 'text/plain' }));
+      expect(held.blobId).toMatch(/^bulwark-local-/);
+      const blob = await client.fetchBlob(held.blobId);
+      expect(await blob.text()).toBe('hello');
+    });
+    stop();
+  });
+
+  it('hands the other areas\u2019 lookups to the store', async () => {
+    const { client, stop } = await ready();
+    const { getOfflineHooks } = await import('@/lib/jmap/offline-hooks');
+    const area = vi.spyOn(store, 'area');
+    const hooks = getOfflineHooks();
+
+    area.mockResolvedValueOnce({ 'bulwark-new-1': 'real-1' });
+    expect(await hooks?.resolveStandIns?.(client, ['bulwark-new-1'])).toEqual({ 'bulwark-new-1': 'real-1' });
+    expect(area).toHaveBeenLastCalledWith('acc', 'calendar.resolveStandIns', { ids: ['bulwark-new-1'] });
+
+    hooks?.fileOpened?.(client, 'acc1', 'node-1');
+    expect(area).toHaveBeenLastCalledWith('acc', 'files.noteOpened', { jmap: 'acc1', id: 'node-1' });
+
+    // Not an attachment of a kept message: maybe a kept file.
+    area.mockResolvedValueOnce(null).mockResolvedValueOnce({ type: 'text/plain', data: new TextEncoder().encode('kept') });
+    const blob = await hooks?.blob(client, 'blob-1', 'acc1');
+    expect(await blob?.text()).toBe('kept');
+    expect(area).toHaveBeenLastCalledWith('acc', 'files.blob', { jmap: 'acc1', blobId: 'blob-1' });
+    area.mockRestore();
+    stop();
   });
 
-  it('keeps everything when a folder couldn\'t be asked', async () => {
-    await putEmails('acc', 'j1', [{ id: 'kept', mailboxIds: { archive: true }, receivedAt: new Date().toISOString() }]);
-    const both = { ...deps, scopeMailboxes: async () => [{ jmap: 'j1', mailboxId: 'inbox', isInbox: true }, { jmap: 'j1', mailboxId: 'archive', isInbox: false }] };
-    await syncAccount('acc', fakeClient({ failQuery: true }) as never, both);
-    expect([...(await emailIndex('acc')).values()].map((e) => e.id).sort()).toEqual(['kept', 'new']);
+  it('answers a search for the merge with the server', async () => {
+    const { client, stop } = await ready();
+    const { getOfflineHooks } = await import('@/lib/jmap/offline-hooks');
+    const answer = await getOfflineHooks()?.searchLocal?.(client, [['Email/query', { filter: { text: 'kept' } }, '0']]);
+    expect(answer?.methodResponses[0][1].ids).toHaveLength(2);
+    useAccountStore.setState({ accounts: [] });
+    useAuthStore.setState({ client: null, activeAccountId: null });
+    expect(await getOfflineHooks()?.searchLocal?.(client, [['Email/query', {}, '0']])).toBeNull();
+    stop();
   });
 });
diff --git a/lib/offline/__tests__/client-send.test.ts b/lib/offline/__tests__/client-send.test.ts
index 05f6e003e..aaed29409 100644
--- a/lib/offline/__tests__/client-send.test.ts
+++ b/lib/offline/__tests__/client-send.test.ts
@@ -34,10 +34,10 @@ beforeEach(() => {
     if (names.includes('EmailSubmission/set')) {
       submissions.push(request);
       if (mode.submissionFails) throw new TypeError('Failed to fetch');
-      const create = request.methodCalls.find(([name]) => name === 'Email/set')?.[1].create as Record<string, unknown>;
-      const key = Object.keys(create)[0];
+      const create = request.methodCalls.find(([name]) => name === 'Email/set')?.[1].create as Record<string, unknown> | undefined;
+      const key = Object.keys(create ?? {})[0];
       return answer({ methodResponses: [
-        ['Email/set', { accountId: 'j1', created: { [key]: { id: 'e1' } } }, '0'],
+        ...(key ? [['Email/set', { accountId: 'j1', created: { [key]: { id: 'e1' } } }, '0']] : []),
         ['EmailSubmission/set', { accountId: 'j1', created: { 1: { id: 'sub1' } } }, '1'],
       ] });
     }
@@ -85,6 +85,27 @@ describe('telling a send that never started from one that may have gone', () =>
     expect(submissions).toHaveLength(1);
   });
 
+  it('sends with a Message-ID fixed by the outbox, and makes one up otherwise', async () => {
+    const c = await client();
+    await c.sendEmail(['bob@example.org'], 'Hi', 'Body', undefined, undefined, 'i1', 'alice@example.org', undefined, 'Alice', undefined, undefined, undefined, undefined, undefined, undefined, { messageId: 'fixed@example.org' });
+    await send(c);
+    const created = (submissions as Array<{ methodCalls: Array<[string, { create?: Record<string, { messageId?: string[] }> }, string]> }>)
+      .map((request) => Object.values(request.methodCalls.find(([name]) => name === 'Email/set')?.[1].create ?? {})[0]?.messageId?.[0]);
+    expect(created[0]).toBe('fixed@example.org');
+    expect(created[1]).toMatch(/@example\.org$/);
+    expect(created[1]).not.toBe('fixed@example.org');
+  });
+
+  it('submits a copy the lookup found, without creating another', async () => {
+    const c = await client();
+    const result = await c.sendEmail(['bob@example.org'], 'Hi', 'Body', undefined, undefined, 'i1', 'alice@example.org', undefined, 'Alice', undefined, undefined, undefined, undefined, undefined, undefined, { existingCopyId: 'copy-1' });
+    expect(result.emailSubmissionId).toBe('sub1');
+    const [request] = submissions as Array<{ methodCalls: Array<[string, Record<string, unknown>, string]> }>;
+    expect(request.methodCalls.map(([name]) => name)).not.toContain('Email/set');
+    const set = request.methodCalls.find(([name]) => name === 'EmailSubmission/set')?.[1] as { create: Record<string, { emailId: string }> };
+    expect(set.create['1'].emailId).toBe('copy-1');
+  });
+
   it('a held send whose hold can’t be read back afterwards still counts as sent', async () => {
     const c = await client();
     mode.readBackFails = true;
diff --git a/lib/offline/__tests__/handoff-wipes.test.ts b/lib/offline/__tests__/handoff-wipes.test.ts
index 84c58ba08..534a060c8 100644
--- a/lib/offline/__tests__/handoff-wipes.test.ts
+++ b/lib/offline/__tests__/handoff-wipes.test.ts
@@ -5,9 +5,8 @@ import { usePolicyStore } from '@/stores/policy-store';
 import { DEFAULT_ORGANISATION_POLICY } from '@/lib/admin/organisation-policy';
 import { handOffFiles, pendingHandoffs } from '@/lib/launch-handoff';
 import { disableOffline, enforcePolicy, wipeEverything } from '../offline-mode';
-import { forgetIndexes } from '../cache';
-import { forgetDeviceKey } from '../crypto';
-import { allowOfflineDbCreation, deleteOfflineDb } from '../db';
+import { setStoreBackend } from '@/lib/store/client/api';
+import { InProcessStore } from '@/lib/store/__tests__/helpers/in-process-store';
 import { useOfflineStore, writeEnabled } from '../state';
 
 // Offline mode's wipes take what was on its way into an account along.
@@ -18,10 +17,7 @@ function waiting() {
 }
 
 beforeEach(async () => {
-  forgetIndexes();
-  forgetDeviceKey();
-  await deleteOfflineDb();
-  allowOfflineDbCreation();
+  setStoreBackend(new InProcessStore());
   localStorage.clear();
   useOfflineStore.setState({ enabled: [], outbox: [], pendingChanges: 0, browserOffline: false, downServers: [], startedOffline: false });
   usePolicyStore.setState({ loaded: true, subject: null, subjectPending: false, policy: { ...usePolicyStore.getState().policy, organisation: DEFAULT_ORGANISATION_POLICY } } as never);
@@ -30,6 +26,7 @@ beforeEach(async () => {
 
 afterEach(async () => {
   await wipeEverything();
+  setStoreBackend(null);
 });
 
 describe('offline wipes and handoffs', () => {
diff --git a/lib/offline/__tests__/migrate-legacy.test.ts b/lib/offline/__tests__/migrate-legacy.test.ts
new file mode 100644
index 000000000..0639de69d
--- /dev/null
+++ b/lib/offline/__tests__/migrate-legacy.test.ts
@@ -0,0 +1,192 @@
+import 'fake-indexeddb/auto';
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { setStoreBackend } from '@/lib/store/client/api';
+import { InProcessStore } from '@/lib/store/__tests__/helpers/in-process-store';
+import { forgetLegacyMove, LEGACY_DB_NAME, moveLegacyOutbox } from '../migrate-legacy';
+import { readQueue } from '../queue';
+import { useOfflineStore } from '../state';
+
+/** The old database, exactly as lib/offline/db.ts laid it out. */
+const STORES = ['keys', 'emails', 'bodies', 'blobs', 'misc', 'ledger', 'queue', 'uploads'];
+
+function openOld(): Promise<IDBDatabase> {
+  return new Promise((resolve, reject) => {
+    const request = indexedDB.open(LEGACY_DB_NAME, 1);
+    request.onupgradeneeded = () => {
+      const db = request.result;
+      for (const name of STORES) {
+        if (name === 'queue') db.createObjectStore(name, { keyPath: 'id', autoIncrement: true }).createIndex('account', 'account');
+        else if (name === 'keys') db.createObjectStore(name, { keyPath: 'id' });
+        else db.createObjectStore(name, { keyPath: 'key' }).createIndex('account', 'account');
+      }
+    };
+    request.onsuccess = () => resolve(request.result);
+    request.onerror = () => reject(request.error);
+  });
+}
+
+function put(db: IDBDatabase, store: string, value: unknown): Promise<void> {
+  return new Promise((resolve, reject) => {
+    const tx = db.transaction(store, 'readwrite');
+    tx.objectStore(store).put(value);
+    tx.oncomplete = () => resolve();
+    tx.onerror = () => reject(tx.error);
+  });
+}
+
+let key: CryptoKey;
+
+async function seal(value: unknown): Promise<{ iv: Uint8Array; data: ArrayBuffer }> {
+  const iv = crypto.getRandomValues(new Uint8Array(12));
+  const bytes = ArrayBuffer.isView(value) ? value as Uint8Array : new TextEncoder().encode(JSON.stringify(value));
+  return { iv, data: await crypto.subtle.encrypt({ name: 'AES-GCM', iv: iv as BufferSource }, key, bytes as BufferSource) };
+}
+
+const RAW = 'Subject: Signed\r\nMessage-ID: <raw-1@example.org>\r\n\r\nbody';
+
+async function seedOld(): Promise<void> {
+  key = await crypto.subtle.generateKey({ name: 'AES-GCM', length: 256 }, false, ['encrypt', 'decrypt']);
+  const db = await openOld();
+  await put(db, 'keys', { id: 'aes', key });
+  await put(db, 'misc', { key: 'acc\u0001misc\u0001session', account: 'acc', ...(await seal({ apiUrl: 'https://old/jmap', accounts: {}, primaryAccounts: {}, capabilities: {}, downloadUrl: '', uploadUrl: '' })) });
+  await put(db, 'queue', { id: 1, account: 'acc', kind: 'patch', createdAt: 1, ...(await seal({ kind: 'patch', jmap: 'acc1', update: { m1: { 'keywords/$seen': true } } })) });
+  await put(db, 'queue', { id: 2, account: 'acc', kind: 'patch', createdAt: 2, ...(await seal({ kind: 'patch', jmap: 'acc1', update: { m1: { 'keywords/$flagged': true } } })) });
+  await put(db, 'queue', {
+    id: 3, account: 'acc', kind: 'send', createdAt: 3, status: 'waiting',
+    ...(await seal({ summary: { subject: 'Waiting', to: ['b@example.org'] }, item: { kind: 'email', args: [['b@example.org'], 'Waiting', 'x', null, null, 'i', 'a@example.org'] }, fingerprint: { labelRequired: false, hasLabel: false, guards: [] } })),
+  });
+  await put(db, 'queue', { id: 4, account: 'acc', kind: 'send', createdAt: 4, status: 'sending', sendingSince: 4, ...(await seal({ summary: { subject: 'On its way', to: [] }, item: { kind: 'email', args: [] } })) });
+  await put(db, 'queue', { id: 5, account: 'acc', kind: 'send', createdAt: 5, status: 'failed', ...(await seal({ summary: { subject: 'Refused', to: [] }, item: { kind: 'email', args: [] }, error: { text: 'No' } })) });
+  await put(db, 'queue', { id: 6, account: 'acc', kind: 'send', createdAt: 6, status: 'waiting', ...(await seal({ summary: { subject: 'Signed', to: [] }, item: { kind: 'raw', blobId: 'bulwark-local-raw', identityId: 'i' } })) });
+  await put(db, 'uploads', { key: 'acc\u0001bulwark-local-raw', account: 'acc', createdAt: 6, meta: await seal({ name: 'message.eml', type: 'message/rfc822' }), ...(await seal(new TextEncoder().encode(RAW))) });
+  // Someone else's, with offline mode off here.
+  await put(db, 'queue', { id: 7, account: 'stranger', kind: 'send', createdAt: 7, status: 'waiting', ...(await seal({ summary: { subject: 'Not moved', to: [] }, item: { kind: 'email', args: [] } })) });
+  db.close();
+}
+
+const oldExists = async () => (await indexedDB.databases()).some((d) => d.name === LEGACY_DB_NAME);
+
+let store: InProcessStore;
+
+beforeEach(async () => {
+  store = new InProcessStore();
+  setStoreBackend(store);
+  forgetLegacyMove();
+  useOfflineStore.setState({ enabled: ['acc'] });
+  await new Promise<void>((resolve) => {
+    const request = indexedDB.deleteDatabase(LEGACY_DB_NAME);
+    request.onsuccess = () => resolve();
+  });
+});
+
+afterEach(() => {
+  setStoreBackend(null);
+});
+
+describe('moving the old outbox into the store', () => {
+  it('gives a sender written "Name <address>" a Message-ID with a clean domain', async () => {
+    await seedOld();
+    const db = await new Promise<IDBDatabase>((resolve) => {
+      const request = indexedDB.open(LEGACY_DB_NAME);
+      request.onsuccess = () => resolve(request.result);
+    });
+    await put(db, 'queue', {
+      id: 20, account: 'acc', kind: 'send', createdAt: 20, status: 'waiting',
+      ...(await seal({ summary: { subject: 'Named', to: [] }, item: { kind: 'email', args: [[], 'Named', 'x', null, null, 'i', 'Alice <a@example.org>'] } })),
+    });
+    db.close();
+    await moveLegacyOutbox();
+    const named = (await readQueue('acc')).outbox.find((entry) => entry.summary.subject === 'Named');
+    expect(named?.messageId).toMatch(/@example\.org$/);
+  });
+
+  it('moves everything that can\'t be fetched again, then deletes the old database', async () => {
+    await seedOld();
+    await moveLegacyOutbox();
+    const { outbox, patches } = await readQueue('acc');
+    expect(outbox.map((entry) => [entry.summary.subject, entry.status])).toEqual([
+      ['Waiting', 'waiting'],
+      ['On its way', 'uncertain'],
+      ['Refused', 'failed'],
+      ['Signed', 'waiting'],
+    ]);
+    expect(outbox[0].createdAt).toBe(3);
+    expect(outbox[0].fingerprint).toEqual({ labelRequired: false, hasLabel: false, guards: [] });
+    expect(outbox[2].error).toEqual({ text: 'No' });
+    // The patches of one message merge.
+    expect(patches).toBe(1);
+    const rows = await store.area<Array<{ patch: unknown }>>('acc', 'outbox.pendingPatches', {});
+    expect(rows[0].patch).toEqual({ 'keywords/$seen': true, 'keywords/$flagged': true });
+    // A waiting message gets a fixed id; one that may have left under another id doesn't pretend.
+    expect(outbox[0].messageId).toMatch(/@example\.org$/);
+    expect(outbox[1].messageId).toBeUndefined();
+    expect(outbox[3].messageId).toBe('raw-1@example.org');
+    const file = await store.area<{ name: string; data: Uint8Array }>('acc', 'outbox.heldFile', { blobId: 'bulwark-local-raw' });
+    expect(file.name).toBe('message.eml');
+    expect(new TextDecoder().decode(file.data)).toBe(RAW);
+    expect(await oldExists()).toBe(false);
+    expect(store.has('stranger')).toBe(false);
+  });
+
+  it('keeps the old database when the store can\'t take it, and moves it next time without doubling', async () => {
+    await seedOld();
+    store.failArea = (name) => name === 'outbox.importLegacy';
+    await moveLegacyOutbox();
+    expect(await oldExists()).toBe(true);
+    expect((await readQueue('acc')).outbox).toEqual([]);
+
+    store.failArea = null;
+    forgetLegacyMove();
+    await moveLegacyOutbox();
+    expect((await readQueue('acc')).outbox).toHaveLength(4);
+    expect(await oldExists()).toBe(false);
+  });
+
+  it('adds nothing when a later account failed and the first runs again', async () => {
+    await seedOld();
+    const db = await openOld();
+    await put(db, 'queue', { id: 8, account: 'second', kind: 'send', createdAt: 8, status: 'waiting', ...(await seal({ summary: { subject: 'Second', to: [] }, item: { kind: 'email', args: [] } })) });
+    db.close();
+    useOfflineStore.setState({ enabled: ['acc', 'second'] });
+    const realArea = store.area.bind(store);
+    let failSecond = true;
+    store.area = (async (account: string, name: string, params?: unknown) => {
+      if (failSecond && account === 'second' && name === 'outbox.importLegacy') throw new Error('full');
+      return realArea(account, name, params);
+    }) as typeof store.area;
+    await moveLegacyOutbox();
+    expect(await oldExists()).toBe(true);
+    expect((await readQueue('acc')).outbox).toHaveLength(4);
+
+    failSecond = false;
+    forgetLegacyMove();
+    await moveLegacyOutbox();
+    expect((await readQueue('acc')).outbox).toHaveLength(4);
+    expect((await readQueue('second')).outbox).toHaveLength(1);
+    expect(await oldExists()).toBe(false);
+  });
+
+  it('hands the kept session to the store, for a first start without a network', async () => {
+    await seedOld();
+    await moveLegacyOutbox();
+    expect(await store.area('acc', 'mail.session')).toMatchObject({ apiUrl: 'https://old/jmap' });
+  });
+
+  it('never creates the old database when it isn\'t there', async () => {
+    await moveLegacyOutbox();
+    expect(await oldExists()).toBe(false);
+    expect(store.has('acc')).toBe(false);
+  });
+
+  it('skips records sealed with a key that\'s gone, and finishes', async () => {
+    await seedOld();
+    const db = await openOld();
+    const other = await crypto.subtle.generateKey({ name: 'AES-GCM', length: 256 }, false, ['encrypt', 'decrypt']);
+    const iv = crypto.getRandomValues(new Uint8Array(12));
+    await put(db, 'queue', { id: 9, account: 'acc', kind: 'send', createdAt: 9, status: 'waiting', iv, data: await crypto.subtle.encrypt({ name: 'AES-GCM', iv: iv as BufferSource }, other, new Uint8Array([1])) });
+    db.close();
+    await moveLegacyOutbox();
+    expect((await readQueue('acc')).outbox).toHaveLength(4);
+    expect(await oldExists()).toBe(false);
+  });
+});
diff --git a/lib/offline/__tests__/outbox.test.ts b/lib/offline/__tests__/outbox.test.ts
index 141217fdb..59fe37929 100644
--- a/lib/offline/__tests__/outbox.test.ts
+++ b/lib/offline/__tests__/outbox.test.ts
@@ -6,25 +6,33 @@ import { useEmailStore } from '@/stores/email-store';
 import { usePolicyStore } from '@/stores/policy-store';
 import { DEFAULT_ORGANISATION_POLICY } from '@/lib/admin/organisation-policy';
 import { passSignOutGates, addSignOutGate, purgeSignedOutData } from '@/lib/sign-out-cleanup';
+import { setStoreBackend } from '@/lib/store/client/api';
+import { FakeJmapMail } from '@/lib/store/__tests__/helpers/fake-jmap-mail';
+import { InProcessStore } from '@/lib/store/__tests__/helpers/in-process-store';
 import { enforcePolicy, startOfflineMode, wipeEverything } from '../offline-mode';
 import { flushQueue } from '../flush';
-import { holdFile, queuePatch, readQueue } from '../queue';
-import { emailIndex, forgetIndexes, putEmails } from '../cache';
-import { forgetDeviceKey } from '../crypto';
-import { allowOfflineDbCreation, deleteOfflineDb } from '../db';
+import { holdFile, readQueue } from '../queue';
+import { forgetLegacyMove } from '../migrate-legacy';
 import { useOfflineStore, writeEnabled, OFFLINE_ACCOUNTS_KEY } from '../state';
 import type { JMAPClient } from '@/lib/jmap/client';
 
+let server: FakeJmapMail;
+let store: InProcessStore;
+
 function fakeClient(overrides: Record<string, unknown> = {}) {
   return {
     getServerUrl: () => 'https://mail.example.org',
     getUsername: () => 'alice@example.org',
-    getAccountId: () => 'j1',
+    getAccountId: () => 'acc1',
     isOfflineOnly: () => false,
-    getSessionSnapshot: () => ({ apiUrl: 'https://mail.example.org/jmap' }),
+    getSessionSnapshot: () => null,
+    getAuthHeader: () => 'Basic x',
+    keywordSortInverted: () => null,
     sendEmail: vi.fn(async () => ({ scheduled: false, emailId: 'sent-1', emailSubmissionId: 'sub-1' })),
     uploadBlob: vi.fn(async (file: File) => ({ blobId: `server-${file.name}`, size: file.size, type: file.type })),
-    applyEmailPatches: vi.fn(async () => []),
+    requestNetworkOnly: vi.fn((calls: never) => server.request(calls)),
+    resolveSendAccountId: vi.fn(async () => 'acc1'),
+    submissionAccountFor: () => 'acc1',
     pruneEmailSubmissions: vi.fn(async () => {}),
     getMailboxes: vi.fn(async () => [{ id: 'sent', role: 'sent' }, { id: 'drafts', role: 'drafts' }]),
     sendRawEmail: vi.fn(async () => ({ scheduled: false })),
@@ -41,20 +49,23 @@ function setOnline(online: boolean) {
 let stop: () => void = () => {};
 
 beforeEach(async () => {
-  forgetIndexes();
-  forgetDeviceKey();
-  await deleteOfflineDb();
-  allowOfflineDbCreation();
+  server = new FakeJmapMail({ mailboxes: [{ id: 'inbox', role: 'inbox' }, { id: 'drafts', role: 'drafts' }, { id: 'sent', role: 'sent' }] });
+  server.addEmail({ id: 'm1', keywords: {}, subject: 'One' });
+  store = new InProcessStore(server);
+  setStoreBackend(store);
+  forgetLegacyMove();
   localStorage.clear();
-  useOfflineStore.setState({ enabled: [], outbox: [], pendingChanges: 0, browserOffline: false, downServers: [], startedOffline: false });
+  useOfflineStore.setState({ enabled: [], outbox: [], pendingChanges: 0, conflicts: [], browserOffline: false, downServers: [], startedOffline: false });
   usePolicyStore.setState({ loaded: true, subject: null, policy: { ...usePolicyStore.getState().policy, organisation: DEFAULT_ORGANISATION_POLICY } });
   useAccountStore.setState({ accounts: [{ id: 'acc', label: 'alice', serverUrl: 'https://mail.example.org', username: 'alice@example.org' } as never] });
 });
 
 afterEach(async () => {
   stop();
+  stop = () => {};
   setOnline(true);
   await wipeEverything();
+  setStoreBackend(null);
 });
 
 const sendArgs = (client: unknown, options: Record<string, unknown>) => useEmailStore.getState().sendEmail(
@@ -62,8 +73,10 @@ const sendArgs = (client: unknown, options: Record<string, unknown>) => useEmail
   'draft-1', 'Alice', '<p>Hi Bob</p>', [{ blobId: 'blob-1', name: 'a.txt', type: 'text/plain', size: 3 }], undefined, undefined, undefined, undefined, options as never,
 );
 
+const patchOffline = (update: Record<string, unknown>) => store.answer('acc', [['Email/set', { update }, '0']]);
+
 describe('the outbox', () => {
-  it('keeps a composer send while offline, with its label, and sends nothing', async () => {
+  it('keeps a composer send while offline, with its label and a fixed Message-ID, and sends nothing', async () => {
     const client = fakeClient();
     useAuthStore.setState({ client: client as never, activeAccountId: 'acc' });
     writeEnabled(['acc']);
@@ -77,11 +90,44 @@ describe('the outbox', () => {
     expect(outbox).toHaveLength(1);
     expect(outbox[0].summary).toEqual({ subject: 'Quarterly numbers', to: ['bob@example.org'] });
     expect(outbox[0].item).toMatchObject({ kind: 'email' });
+    expect(outbox[0].messageId).toMatch(/@example\.org$/);
     const options = (outbox[0].item as { args: unknown[] }).args[15] as Record<string, unknown>;
     expect(options.labelHeaders).toEqual({ 'header:SIO-Label:asRaw': ' marking="CONFIDENTIAL"' });
     expect(options).not.toHaveProperty('outbox');
   });
 
+  it('takes the domain of a Message-ID from a sender written with a name', async () => {
+    const client = fakeClient();
+    useAuthStore.setState({ client: client as never, activeAccountId: 'acc' });
+    writeEnabled(['acc']);
+    stop = startOfflineMode();
+    setOnline(false);
+    await useEmailStore.getState().sendEmail(client as never, ['b@example.org'], 'S', 'x', undefined, undefined, 'i', 'Alice <alice@example.net>', undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, { outbox: true } as never);
+    expect((await readQueue('acc')).outbox[0].messageId).toMatch(/@example\.net$/);
+  });
+
+  it('sends with the Message-ID fixed at queueing, and the same one after a retry', async () => {
+    const client = fakeClient({
+      sendEmail: vi.fn()
+        .mockRejectedValueOnce(Object.assign(new Error('x'), { name: 'SendNotStartedError' }))
+        .mockResolvedValue({ scheduled: false }),
+    });
+    useAuthStore.setState({ client: client as never, activeAccountId: 'acc' });
+    writeEnabled(['acc']);
+    stop = startOfflineMode();
+    setOnline(false);
+    await sendArgs(client, { outbox: true });
+    const fixed = (await readQueue('acc')).outbox[0].messageId;
+    setOnline(true);
+    await flushQueue('acc', client as unknown as JMAPClient, { notify: vi.fn(), allowed: () => true });
+    await flushQueue('acc', client as unknown as JMAPClient, { notify: vi.fn(), allowed: () => true });
+    const calls = (client.sendEmail as ReturnType<typeof vi.fn>).mock.calls as unknown[][];
+    expect(calls).toHaveLength(2);
+    expect((calls[0][15] as { messageId: string }).messageId).toBe(fixed);
+    expect((calls[1][15] as { messageId: string }).messageId).toBe(fixed);
+    expect((await readQueue('acc')).outbox).toEqual([]);
+  });
+
   it('leaves sends from elsewhere (plugin forward, phishing report) to the network', async () => {
     const client = fakeClient({ sendEmail: vi.fn(async () => { throw new TypeError('Failed to fetch'); }) });
     useAuthStore.setState({ client: client as never, activeAccountId: 'acc' });
@@ -105,14 +151,18 @@ describe('the outbox', () => {
   it('sends what waited in order once the server answers: changes first, then mail', async () => {
     const order: string[] = [];
     const client = fakeClient({
-      applyEmailPatches: vi.fn(async () => { order.push('patch'); return []; }),
+      requestNetworkOnly: vi.fn(async (calls: Array<[string]>) => {
+        if (calls[0][0] === 'Email/set') order.push('patch');
+        return server.request(calls as never);
+      }),
       sendEmail: vi.fn(async () => { order.push('send'); return { scheduled: false }; }),
     });
     useAuthStore.setState({ client: client as never, activeAccountId: 'acc' });
     writeEnabled(['acc']);
     stop = startOfflineMode();
+    await store.sync('acc');
     setOnline(false);
-    await queuePatch('acc', 'j1', { m1: { 'keywords/$seen': true } });
+    await patchOffline({ m1: { 'keywords/$seen': true } });
     const held = await holdFile('acc', new File(['hello'], 'note.txt', { type: 'text/plain' }), 'note.txt');
     await useEmailStore.getState().sendEmail(client as never, ['bob@example.org'], 'With file', 'x', undefined, undefined, 'id-1', 'alice@example.org', undefined, 'Alice', undefined,
       [{ blobId: held.blobId, name: 'note.txt', type: 'text/plain', size: 5 }], undefined, undefined, new Date(Date.now() + 5000).toISOString(), undefined, { outbox: true } as never);
@@ -121,7 +171,7 @@ describe('the outbox', () => {
     const notify = vi.fn();
     await flushQueue('acc', client as unknown as JMAPClient, { notify, allowed: () => true });
     expect(order).toEqual(['patch', 'send']);
-    expect(client.applyEmailPatches).toHaveBeenCalledWith('j1', { m1: { 'keywords/$seen': true } });
+    expect(server.emails.get('m1')?.keywords).toEqual({ $seen: true });
     const args = (client.sendEmail as ReturnType<typeof vi.fn>).mock.calls[0] as unknown[];
     expect(args[1]).toBe('With file');
     // The file attached offline was uploaded first; the passed undo hold was dropped.
@@ -130,7 +180,28 @@ describe('the outbox', () => {
     expect(notify).toHaveBeenCalledWith({ kind: 'sent', subject: 'With file' });
     const left = await readQueue('acc');
     expect(left.outbox).toHaveLength(0);
-    expect(left.patches).toHaveLength(0);
+    expect(left.patches).toBe(0);
+  });
+
+  it('a change made after a send goes after it', async () => {
+    const order: string[] = [];
+    const client = fakeClient({
+      requestNetworkOnly: vi.fn(async (calls: Array<[string]>) => {
+        if (calls[0][0] === 'Email/set') order.push('patch');
+        return server.request(calls as never);
+      }),
+      sendEmail: vi.fn(async () => { order.push('send'); return { scheduled: false }; }),
+    });
+    useAuthStore.setState({ client: client as never, activeAccountId: 'acc' });
+    writeEnabled(['acc']);
+    stop = startOfflineMode();
+    await store.sync('acc');
+    setOnline(false);
+    await sendArgs(client, { outbox: true });
+    await patchOffline({ m1: { 'keywords/$answered': true } });
+    setOnline(true);
+    await flushQueue('acc', client as unknown as JMAPClient, { notify: vi.fn(), allowed: () => true });
+    expect(order).toEqual(['send', 'patch']);
   });
 
   it('keeps a send the server refused, marked failed, and one cut off on the way, marked uncertain', async () => {
@@ -146,10 +217,13 @@ describe('the outbox', () => {
     expect(outbox[0].status).toBe('failed');
     expect(outbox[0].error).toEqual({ text: 'Recipient address rejected' });
 
-    const cut = fakeClient({ sendEmail: vi.fn(async () => { throw new TypeError('Failed to fetch'); }) });
-    await wipeEverything();
-    allowOfflineDbCreation();
+    store.stop();
     writeEnabled(['acc']);
+    // The lookup that follows can't reach the server either, so it stays uncertain.
+    const cut = fakeClient({
+      sendEmail: vi.fn(async () => { throw new TypeError('Failed to fetch'); }),
+      requestNetworkOnly: vi.fn(async () => { throw new TypeError('Failed to fetch'); }),
+    });
     useAuthStore.setState({ client: cut as never, activeAccountId: 'acc' });
     setOnline(false);
     await sendArgs(cut, { outbox: true });
@@ -160,13 +234,187 @@ describe('the outbox', () => {
     // Not tried again on its own.
     await flushQueue('acc', cut as unknown as JMAPClient, { notify: vi.fn(), allowed: () => true });
     expect(cut.sendEmail).toHaveBeenCalledTimes(1);
+
+    // With the server still there, nothing else would start the lookup.
+    const entry = (await readQueue('acc')).outbox[0];
+    await store.area('acc', 'outbox.update', { id: entry.id, status: 'waiting' });
+    const retryLater = vi.fn();
+    await flushQueue('acc', cut as unknown as JMAPClient, { notify: vi.fn(), allowed: () => true, retryLater });
+    expect(retryLater).toHaveBeenCalledTimes(1);
   });
 
   it('sends nothing once the organisation forbids offline mode', async () => {
     const client = fakeClient();
-    await queuePatch('acc', 'j1', { m1: { 'keywords/$seen': true } });
+    await store.sync('acc');
+    await patchOffline({ m1: { 'keywords/$seen': true } });
     await flushQueue('acc', client as unknown as JMAPClient, { notify: vi.fn(), allowed: () => false });
-    expect(client.applyEmailPatches).not.toHaveBeenCalled();
+    expect(client.requestNetworkOnly).not.toHaveBeenCalled();
+    expect(server.emails.get('m1')?.keywords).toEqual({});
+  });
+});
+
+describe('a send whose response got lost', () => {
+  async function uncertainSend(client: ReturnType<typeof fakeClient>) {
+    useAuthStore.setState({ client: client as never, activeAccountId: 'acc' });
+    writeEnabled(['acc']);
+    stop = startOfflineMode();
+    setOnline(false);
+    await sendArgs(client, { outbox: true });
+    setOnline(true);
+    const entry = (await readQueue('acc')).outbox[0];
+    await store.area('acc', 'outbox.claim', { id: entry.id });
+    await store.area('acc', 'outbox.update', { id: entry.id, status: 'uncertain' });
+    // The wait before a lookup has passed.
+    store.dbs.get('acc')!.run('UPDATE outbox SET last_attempt_at = ?', [Date.now() - 31_000]);
+    return entry;
+  }
+
+  const flush = (client: ReturnType<typeof fakeClient>, notify = vi.fn()) => flushQueue('acc', client as unknown as JMAPClient, { notify, allowed: () => true });
+
+  const copy = (messageId: string | undefined, over: Record<string, unknown>) => server.addEmail({
+    id: 'copy', messageId: [messageId as string], receivedAt: new Date().toISOString(), ...over,
+  });
+
+  it('never arrived: sends it again, with the same Message-ID', async () => {
+    const client = fakeClient();
+    const entry = await uncertainSend(client);
+    const notify = vi.fn();
+    await flush(client, notify);
+    expect(client.sendEmail).toHaveBeenCalledTimes(1);
+    const args = (client.sendEmail as ReturnType<typeof vi.fn>).mock.calls[0] as unknown[];
+    expect((args[15] as { messageId?: string; existingCopyId?: string })).toMatchObject({ messageId: entry.messageId });
+    expect(args[15]).not.toHaveProperty('existingCopyId');
+    expect(notify).toHaveBeenCalledWith({ kind: 'sent', subject: 'Quarterly numbers' });
+  });
+
+  it('draft arrived, submission didn\'t: submits that copy and uploads nothing again', async () => {
+    const client = fakeClient();
+    const entry = await uncertainSend(client);
+    copy(entry.messageId, { mailboxIds: { drafts: true }, keywords: { $draft: true } });
+    await flush(client);
+    expect(client.sendEmail).toHaveBeenCalledTimes(1);
+    const args = (client.sendEmail as ReturnType<typeof vi.fn>).mock.calls[0] as unknown[];
+    expect(args[15]).toMatchObject({ messageId: entry.messageId, existingCopyId: 'copy' });
+    expect(client.uploadBlob).not.toHaveBeenCalled();
+  });
+
+  it('both arrived: done, nothing sent, and the old draft goes', async () => {
+    const client = fakeClient();
+    const entry = await uncertainSend(client);
+    copy(entry.messageId, { mailboxIds: { sent: true }, keywords: {} });
+    server.addEmail({ id: 'draft-1', mailboxIds: { drafts: true }, keywords: { $draft: true } });
+    const notify = vi.fn();
+    await flush(client, notify);
+    expect(client.sendEmail).not.toHaveBeenCalled();
+    expect((await readQueue('acc')).outbox).toEqual([]);
+    expect(server.emails.has('draft-1')).toBe(false);
+    expect(notify).toHaveBeenCalledWith({ kind: 'sent', subject: 'Quarterly numbers' });
+  });
+
+  it('scheduled: done, the submission stays', async () => {
+    const client = fakeClient();
+    const entry = await uncertainSend(client);
+    copy(entry.messageId, { mailboxIds: { drafts: true }, keywords: { $draft: true } });
+    server.addSubmission('copy', 'pending');
+    await flush(client);
+    expect(client.sendEmail).not.toHaveBeenCalled();
+    expect((await readQueue('acc')).outbox).toEqual([]);
+  });
+
+  it('canceled: done without a "sent" notice, and it doesn\'t go', async () => {
+    const client = fakeClient();
+    const entry = await uncertainSend(client);
+    copy(entry.messageId, { mailboxIds: { drafts: true }, keywords: { $draft: true } });
+    server.addSubmission('copy', 'canceled');
+    const notify = vi.fn();
+    await flush(client, notify);
+    expect(client.sendEmail).not.toHaveBeenCalled();
+    expect((await readQueue('acc')).outbox).toEqual([]);
+    expect(notify).not.toHaveBeenCalledWith(expect.objectContaining({ kind: 'sent' }));
+  });
+
+  it('a lookup that can\'t decide leaves it uncertain for the user, who can still send it', async () => {
+    const client = fakeClient();
+    const entry = await uncertainSend(client);
+    server.failNext.set('Email/query', 'forbidden');
+    await flush(client);
+    expect(client.sendEmail).not.toHaveBeenCalled();
+    expect((await readQueue('acc')).outbox[0].status).toBe('uncertain');
+
+    const { retryOutboxEntry } = await import('../flush');
+    await retryOutboxEntry('acc', entry.id);
+    expect((await readQueue('acc')).outbox[0].status).toBe('waiting');
+    await flush(client);
+    expect(client.sendEmail).toHaveBeenCalledTimes(1);
+  });
+
+  it('a send that fails on the server clears the copy, so a retry starts clean', async () => {
+    const client = fakeClient({ sendEmail: vi.fn(async () => { throw new Error('Refused'); }) });
+    const entry = await uncertainSend(client);
+    copy(entry.messageId, { mailboxIds: { drafts: true }, keywords: { $draft: true } });
+    await flush(client);
+    const [after] = (await readQueue('acc')).outbox;
+    expect(after.status).toBe('failed');
+    expect(after.copyId).toBeUndefined();
+  });
+});
+
+describe('what the other areas queued', () => {
+  const flushWith = async (tally: unknown) => {
+    const { flushAll } = await import('../offline-mode');
+    const client = fakeClient();
+    useAuthStore.setState({ client: client as never, activeAccountId: 'acc' });
+    usePolicyStore.setState({ fetchPolicy: vi.fn(async () => {}), source: 'server' } as never);
+    const realArea = store.area.bind(store);
+    const calls: string[] = [];
+    store.area = (async (account: string, name: string, params?: unknown) => {
+      if (name.endsWith('.flush')) {
+        calls.push(name);
+        return tally;
+      }
+      return realArea(account, name, params);
+    }) as typeof store.area;
+    const { subscribePushStateChanges } = await import('@/lib/push-events');
+    const pushes: unknown[] = [];
+    const unsubscribe = subscribePushStateChanges((change, _client, role) => pushes.push([change.changed, role]));
+    useAccountStore.setState({ accounts: [{ id: 'acc', serverUrl: 'https://mail.example.org', username: 'alice@example.org' } as never] });
+    useAuthStore.setState({ getClientForAccount: () => client } as never);
+    writeEnabled(['acc']);
+    await flushAll();
+    unsubscribe();
+    return { calls, pushes };
+  };
+
+  it('flushes them, also with nothing in the outbox, and has the page read again', async () => {
+    const { calls, pushes } = await flushWith({ sent: 1, conflicts: 0, pending: 0 });
+    expect(calls).toEqual(['calendar.flush', 'contacts.flush']);
+    expect(pushes).toEqual([
+      [{ acc1: { Calendar: 'flushed', CalendarEvent: 'flushed' } }, 'active'],
+      [{ acc1: { AddressBook: 'flushed', ContactCard: 'flushed' } }, 'active'],
+    ]);
+  });
+
+  it('doesn\u2019t have the page read again when nothing went out', async () => {
+    const { pushes } = await flushWith({ sent: 0, conflicts: 0, pending: 0 });
+    expect(pushes).toEqual([]);
+  });
+});
+
+describe('conflicts reach the page', () => {
+  it('lists a refused change and tells the user', async () => {
+    const client = fakeClient();
+    useAuthStore.setState({ client: client as never, activeAccountId: 'acc' });
+    writeEnabled(['acc']);
+    stop = startOfflineMode();
+    await store.sync('acc');
+    await patchOffline({ m1: { 'keywords/$seen': true } });
+    server.refuse.set('m1', { type: 'forbidden' });
+    const notify = vi.fn();
+    await flushQueue('acc', client as unknown as JMAPClient, { notify, allowed: () => true });
+    expect(notify).toHaveBeenCalledWith({ kind: 'conflict', count: 1 });
+    const { conflicts, patches } = await readQueue('acc');
+    expect(patches).toBe(0);
+    expect(conflicts).toEqual([expect.objectContaining({ account: 'acc', recordId: 'm1', summary: expect.objectContaining({ subject: 'One', reason: 'refused' }) })]);
   });
 });
 
@@ -176,39 +424,66 @@ describe('wiping offline data', () => {
     useAuthStore.setState({ client: client as never, activeAccountId: 'acc' });
     writeEnabled(['acc']);
     stop = startOfflineMode();
-    await putEmails('acc', 'j1', [{ id: 'm1', mailboxIds: { inbox: true }, receivedAt: new Date().toISOString() }]);
     usePolicyStore.setState({ policy: { ...usePolicyStore.getState().policy, organisation: { ...DEFAULT_ORGANISATION_POLICY, devices: { ...DEFAULT_ORGANISATION_POLICY.devices, noOffline: true } } } });
     enforcePolicy();
     await vi.waitFor(async () => expect(useOfflineStore.getState().enabled).toEqual([]));
-    // Its only account: the whole database goes.
-    await vi.waitFor(async () => expect((await indexedDB.databases()).map((d) => d.name)).not.toContain('bulwark-offline'));
+    // Its only account: the whole store goes.
+    await vi.waitFor(() => expect(store.stopped).toBeGreaterThan(0));
     expect(localStorage.getItem(OFFLINE_ACCOUNTS_KEY)).toBeNull();
   });
 
-  it('wipes an account that signs out', async () => {
+  it('wipes an account that signs out or is removed on purpose', async () => {
+    useAccountStore.setState({ accounts: [{ id: 'acc' } as never, { id: 'other' } as never] });
     writeEnabled(['acc', 'other']);
     stop = startOfflineMode();
-    await putEmails('acc', 'j1', [{ id: 'm1', mailboxIds: { inbox: true }, receivedAt: new Date().toISOString() }]);
-    await putEmails('other', 'j1', [{ id: 'm2', mailboxIds: { inbox: true }, receivedAt: new Date().toISOString() }]);
-    useAccountStore.setState({ accounts: [{ id: 'other' } as never] });
+    await store.sync('acc');
+    await store.sync('other');
+    useAccountStore.getState().removeAccount('acc');
     await vi.waitFor(() => expect(useOfflineStore.getState().enabled).toEqual(['other']));
-    await vi.waitFor(async () => {
-      forgetIndexes();
-      expect((await emailIndex('acc')).size).toBe(0);
-    });
-    expect((await emailIndex('other')).size).toBe(1);
+    await vi.waitFor(() => expect(store.removed).toEqual(['acc']));
+    expect(store.has('acc')).toBe(false);
+    expect(store.has('other')).toBe(true);
   });
 
-  it('deletes the database and the switch at a full sign-out', async () => {
+  it('keeps the data of an account the app dropped by itself', async () => {
+    useAccountStore.setState({ accounts: [{ id: 'acc' } as never, { id: 'other' } as never] });
+    writeEnabled(['acc', 'other']);
+    stop = startOfflineMode();
+    await store.sync('acc');
+    useAccountStore.getState().removeAccount('acc', 'evicted');
+    await new Promise((r) => setTimeout(r, 20));
+    expect(useAccountStore.getState().accounts.map((a) => a.id)).toEqual(['other']);
+    expect(useOfflineStore.getState().enabled).toEqual(['acc', 'other']);
+    expect(store.removed).toEqual([]);
+  });
+
+  it('deletes the old database, the key database and the switch at a full sign-out', async () => {
     writeEnabled(['acc']);
-    await putEmails('acc', 'j1', [{ id: 'm1', mailboxIds: { inbox: true }, receivedAt: new Date().toISOString() }]);
-    forgetIndexes();
-    purgeSignedOutData();
-    expect(localStorage.getItem(OFFLINE_ACCOUNTS_KEY)).toBeNull();
-    await vi.waitFor(async () => {
-      const dbs = await indexedDB.databases();
-      expect(dbs.map((d) => d.name)).not.toContain('bulwark-offline');
+    await new Promise<void>((resolve) => {
+      const request = indexedDB.open('bulwark-offline');
+      request.onsuccess = () => { request.result.close(); resolve(); };
     });
+    await new Promise<void>((resolve) => {
+      const request = indexedDB.open('bulwark-store');
+      request.onsuccess = () => { request.result.close(); resolve(); };
+    });
+    const removeEntry = vi.fn(async () => {});
+    const getDirectory = vi.fn(async () => ({ removeEntry }));
+    Object.defineProperty(window.navigator, 'storage', { configurable: true, value: { getDirectory } });
+    try {
+      purgeSignedOutData();
+      expect(localStorage.getItem(OFFLINE_ACCOUNTS_KEY)).toBeNull();
+      await vi.waitFor(async () => {
+        const dbs = (await indexedDB.databases()).map((d) => d.name);
+        expect(dbs).not.toContain('bulwark-offline');
+        expect(dbs).not.toContain('bulwark-store');
+      });
+      // With no worker running: straight from the page.
+      await vi.waitFor(() => expect(removeEntry).toHaveBeenCalledWith('.bulwark-store', { recursive: true }));
+      expect(store.stopped).toBeGreaterThan(0);
+    } finally {
+      delete (window.navigator as { storage?: unknown }).storage;
+    }
   });
 });
 
@@ -222,13 +497,14 @@ describe('signing out with unsent mail', () => {
 });
 
 describe('after a sign-out', () => {
-  it('starting offline mode on the sign-in page doesn\'t create the database again', async () => {
-    const stop = startOfflineMode();
+  it('starting offline mode on the sign-in page doesn\'t create the store again', async () => {
+    const stopHere = startOfflineMode();
     await new Promise((r) => setTimeout(r, 50));
     const { refreshQueueState, refreshUsage } = await import('../offline-mode');
     await refreshQueueState();
     await refreshUsage();
-    stop();
-    expect((await indexedDB.databases()).map((d) => d.name)).not.toContain('bulwark-offline');
+    stopHere();
+    expect(store.engines.size).toBe(0);
+    expect((await indexedDB.databases()).map((d) => d.name)).not.toContain('bulwark-store');
   });
 });
diff --git a/lib/offline/__tests__/queue-sync.test.ts b/lib/offline/__tests__/queue-sync.test.ts
index a31f5616e..da3099e06 100644
--- a/lib/offline/__tests__/queue-sync.test.ts
+++ b/lib/offline/__tests__/queue-sync.test.ts
@@ -1,35 +1,53 @@
-import { beforeEach, describe, expect, it, vi } from 'vitest';
-import { queuePatch, queueSend } from '../queue';
+import 'fake-indexeddb/auto';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { setStoreBackend } from '@/lib/store/client/api';
+import { InProcessStore } from '@/lib/store/__tests__/helpers/in-process-store';
+import { getOfflineHooks } from '@/lib/jmap/offline-hooks';
+import { usePolicyStore } from '@/stores/policy-store';
+import { useAccountStore } from '@/stores/account-store';
+import { DEFAULT_ORGANISATION_POLICY } from '@/lib/admin/organisation-policy';
+import { queueSend, readQueue } from '../queue';
+import { registerOfflineHooks } from '../offline-mode';
+import { writeEnabled } from '../state';
 
-// Whatever goes into the queue asks for a Background Sync, once it's stored.
+// Whatever goes into the outbox asks for a Background Sync, once it's stored.
 
-const requestOutboxSync = vi.fn();
-const stored: unknown[] = [];
-vi.mock('@/lib/pwa-notify/outbox-sync', () => ({ requestOutboxSync: () => requestOutboxSync(stored.length) }));
-vi.mock('../db', () => ({
-  idbAdd: vi.fn(async (_store: string, record: unknown) => { stored.push(record); return stored.length; }),
-  idbDeleteAccount: vi.fn(), idbGet: vi.fn(), idbGetAll: vi.fn(), idbGetAllByAccount: vi.fn(), idbUpdate: vi.fn(), idbWrite: vi.fn(),
-}));
-vi.mock('../crypto', () => ({
-  sealJson: vi.fn(async () => ({ iv: 'i', data: 'd' })),
-  openJson: vi.fn(), openBytes: vi.fn(), sealBytes: vi.fn(),
-}));
+const seen = vi.hoisted(() => ({ calls: 0, onCall: (() => {}) as () => void }));
+vi.mock('@/lib/pwa-notify/outbox-sync', () => ({ requestOutboxSync: () => { seen.calls += 1; seen.onCall(); } }));
+
+let store: InProcessStore;
 
 beforeEach(() => {
-  stored.length = 0;
-  requestOutboxSync.mockClear();
+  store = new InProcessStore();
+  setStoreBackend(store);
+  seen.calls = 0;
+  seen.onCall = () => {};
+  usePolicyStore.setState({ loaded: true, subject: null, policy: { ...usePolicyStore.getState().policy, organisation: DEFAULT_ORGANISATION_POLICY } });
+  useAccountStore.setState({ accounts: [{ id: 'acc', serverUrl: 'https://mail.example.org', username: 'alice@example.org' } as never] });
 });
 
-describe('the offline queue', () => {
-  it('asks for a sync after storing a change', async () => {
-    await queuePatch('acc', 'jmap', {} as never);
-    expect(requestOutboxSync).toHaveBeenCalledTimes(1);
-    expect(requestOutboxSync).toHaveBeenCalledWith(1);
-  });
+afterEach(() => {
+  setStoreBackend(null);
+  writeEnabled([]);
+});
 
+describe('the outbox', () => {
   it('asks for a sync after storing a message, and still returns its id', async () => {
-    const id = await queueSend('acc', {} as never, {} as never);
+    let storedWhenAsked = -1;
+    seen.onCall = () => { void readQueue('acc').then(({ outbox }) => { storedWhenAsked = outbox.length; }); };
+    const id = await queueSend('acc', { subject: 'S', to: [] }, { kind: 'email', args: [] });
     expect(id).toBe(1);
-    expect(requestOutboxSync).toHaveBeenCalledWith(1);
+    expect(seen.calls).toBe(1);
+    await vi.waitFor(() => expect(storedWhenAsked).toBe(1));
+  });
+
+  it('asks for a sync after keeping a change the client made, not after a read', async () => {
+    writeEnabled(['acc']);
+    registerOfflineHooks();
+    const client = { getServerUrl: () => 'https://mail.example.org', getUsername: () => 'alice@example.org', getAccountId: () => 'acc1' };
+    await getOfflineHooks()?.answer(client, [['Email/set', { update: { m: { 'keywords/$seen': true } } }, '0']]);
+    expect(seen.calls).toBe(1);
+    await getOfflineHooks()?.answer(client, [['Email/get', { ids: [] }, '0']]);
+    expect(seen.calls).toBe(1);
   });
 });
diff --git a/lib/offline/__tests__/responder.test.ts b/lib/offline/__tests__/responder.test.ts
deleted file mode 100644
index b8617fdd1..000000000
--- a/lib/offline/__tests__/responder.test.ts
+++ /dev/null
@@ -1,122 +0,0 @@
-import 'fake-indexeddb/auto';
-import { beforeEach, describe, expect, it, vi } from 'vitest';
-import { answerOffline, type ResponderContext } from '../responder';
-import { emailIndex, emailKey, forgetIndexes, putEmails, putMisc } from '../cache';
-import { forgetDeviceKey } from '../crypto';
-import { allowOfflineDbCreation, deleteOfflineDb } from '../db';
-
-const day = 24 * 60 * 60 * 1000;
-const at = (ageDays: number) => new Date(Date.now() - ageDays * day).toISOString();
-
-let queued: Array<{ jmap: string; update: Record<string, Record<string, unknown>> }>;
-let refused: string[];
-const ctx: ResponderContext = {
-  account: 'acc',
-  defaultJmap: 'j1',
-  queuePatch: async (jmap, update) => { queued.push({ jmap, update }); },
-  onRefused: (what) => { refused.push(what); },
-};
-
-beforeEach(async () => {
-  forgetIndexes();
-  forgetDeviceKey();
-  await deleteOfflineDb();
-  allowOfflineDbCreation();
-  queued = [];
-  refused = [];
-  await putEmails('acc', 'j1', [
-    { id: 'a', threadId: 't1', mailboxIds: { inbox: true }, keywords: {}, receivedAt: at(3), subject: 'Older', bodyValues: { 1: { value: 'Body A' } }, textBody: [{ partId: '1' }] },
-    { id: 'b', threadId: 't1', mailboxIds: { inbox: true }, keywords: { $flagged: true }, receivedAt: at(1), subject: 'Newer' },
-    { id: 'c', threadId: 't2', mailboxIds: { archive: true }, keywords: {}, receivedAt: at(2), subject: 'Archived' },
-  ]);
-  await putMisc('acc', 'mailboxes', { j1: [
-    { id: 'inbox', name: 'Inbox', role: 'inbox', totalEmails: 2, unreadEmails: 1 },
-    { id: 'archive', name: 'Archive', role: 'archive', totalEmails: 1, unreadEmails: 1 },
-  ] });
-});
-
-describe('answering a folder list offline', () => {
-  it('answers the list request the client makes, back-references included', async () => {
-    const response = await answerOffline(ctx, [
-      ['Email/query', { accountId: 'j1', filter: { inMailbox: 'inbox' }, sort: [{ property: 'receivedAt', isAscending: false }], limit: 50, position: 0, calculateTotal: true }, '0'],
-      ['Email/get', { accountId: 'j1', '#ids': { resultOf: '0', name: 'Email/query', path: '/ids' }, properties: ['id', 'threadId', 'subject', 'keywords'] }, '1'],
-      ['Thread/get', { accountId: 'j1', '#ids': { resultOf: '1', name: 'Email/get', path: '/list/*/threadId' } }, '2'],
-    ]);
-    expect(response).not.toBeNull();
-    const [query, get, thread] = response!.methodResponses;
-    expect(query[1].ids).toEqual(['b', 'a']);
-    expect(query[1].total).toBe(2);
-    expect(get[1].list).toEqual([
-      { id: 'b', threadId: 't1', subject: 'Newer', keywords: { $flagged: true } },
-      { id: 'a', threadId: 't1', subject: 'Older', keywords: {} },
-    ]);
-    expect(thread[1].list).toEqual([{ id: 't1', emailIds: ['a', 'b'] }]);
-  });
-
-  it('pins flagged mail first when the list sorts that way', async () => {
-    const response = await answerOffline(ctx, [
-      ['Email/query', { filter: { inMailbox: 'inbox' }, sort: [{ property: 'receivedAt', isAscending: true }] }, '0'],
-    ]);
-    expect(response!.methodResponses[0][1].ids).toEqual(['a', 'b']);
-    const pinned = await answerOffline(ctx, [
-      ['Email/query', { filter: { inMailbox: 'inbox' }, sort: [{ property: 'hasKeyword', keyword: '$flagged', isAscending: false }, { property: 'receivedAt', isAscending: true }] }, '0'],
-    ]);
-    expect(pinned!.methodResponses[0][1].ids).toEqual(['b', 'a']);
-  });
-
-  it('opens a kept message with its body and refuses one without', async () => {
-    const full = { properties: ['id', 'subject', 'bodyValues', 'textBody'], fetchTextBodyValues: true };
-    const response = await answerOffline(ctx, [['Email/get', { ids: ['a', 'b'], ...full }, '0']]);
-    const result = response!.methodResponses[0][1];
-    expect(result.list).toEqual([{ id: 'a', subject: 'Older', bodyValues: { 1: { value: 'Body A' } }, textBody: [{ partId: '1' }] }]);
-    expect(result.notFound).toEqual(['b']);
-  });
-
-  it('answers the folder list', async () => {
-    const response = await answerOffline(ctx, [['Mailbox/get', { accountId: 'j1' }, '0']]);
-    expect(response!.methodResponses[0][1].list.map((m: { id: string }) => m.id)).toEqual(['inbox', 'archive']);
-  });
-
-  it('leaves search to the server', async () => {
-    expect(await answerOffline(ctx, [['Email/query', { filter: { text: 'invoice' } }, '0']])).toBeNull();
-    expect(await answerOffline(ctx, [['SearchSnippet/get', {}, '0']])).toBeNull();
-  });
-});
-
-describe('changes made offline', () => {
-  it('queues read, flag and move, and shows them at once', async () => {
-    const response = await answerOffline(ctx, [
-      ['Email/set', { accountId: 'j1', update: { a: { 'keywords/$seen': true, 'keywords/$flagged': true }, c: { 'mailboxIds/archive': null, 'mailboxIds/inbox': true } } }, '0'],
-    ]);
-    expect(response!.methodResponses[0][1].updated).toEqual({ a: null, c: null });
-    expect(queued).toEqual([{ jmap: 'j1', update: { a: { 'keywords/$seen': true, 'keywords/$flagged': true }, c: { 'mailboxIds/archive': null, 'mailboxIds/inbox': true } } }]);
-    const index = await emailIndex('acc');
-    expect(index.get(emailKey('acc', 'j1', 'a'))?.keywords).toEqual({ $seen: true, $flagged: true });
-    const inbox = await answerOffline(ctx, [['Email/query', { filter: { inMailbox: 'inbox' } }, '0']]);
-    expect(inbox!.methodResponses[0][1].ids).toEqual(['b', 'c', 'a']);
-  });
-
-  it('keeps the folder counts in step', async () => {
-    await answerOffline(ctx, [['Email/set', { update: { a: { 'keywords/$seen': true }, c: { 'mailboxIds/archive': null, 'mailboxIds/inbox': true } } }, '0']]);
-    const boxes = (await answerOffline(ctx, [['Mailbox/get', {}, '0']]))!.methodResponses[0][1].list;
-    expect(boxes.find((b: { id: string }) => b.id === 'inbox')).toMatchObject({ totalEmails: 3, unreadEmails: 1 });
-    expect(boxes.find((b: { id: string }) => b.id === 'archive')).toMatchObject({ totalEmails: 0, unreadEmails: 0 });
-  });
-
-  it('refuses deleting for good and emptying a folder', async () => {
-    expect(await answerOffline(ctx, [['Email/set', { destroy: ['a'] }, '0']])).toBeNull();
-    expect(await answerOffline(ctx, [['Email/set', { update: { a: { mailboxIds: {} } } }, '0']])).toBeNull();
-    expect(await answerOffline(ctx, [['Email/set', { update: { c: { 'mailboxIds/archive': null } } }, '0']])).toBeNull();
-    expect(refused).toEqual(['destroy', 'destroy', 'destroy']);
-    expect(queued).toEqual([]);
-    expect((await emailIndex('acc')).size).toBe(3);
-  });
-
-  it('refuses other changes and new messages without queueing', async () => {
-    const onRefused = vi.fn();
-    expect(await answerOffline({ ...ctx, onRefused }, [['Email/set', { update: { a: { subject: 'x' } } }, '0']])).toBeNull();
-    expect(await answerOffline({ ...ctx, onRefused }, [['Email/set', { create: { d: { subject: 'draft' } } }, '0']])).toBeNull();
-    expect(onRefused).toHaveBeenCalledTimes(1);
-    expect(queued).toEqual([]);
-  });
-});
diff --git a/lib/offline/__tests__/review-fixes.test.ts b/lib/offline/__tests__/review-fixes.test.ts
index db4e4e7ab..a5bbc6a0d 100644
--- a/lib/offline/__tests__/review-fixes.test.ts
+++ b/lib/offline/__tests__/review-fixes.test.ts
@@ -9,31 +9,35 @@ import { runBeforeSignOut } from '@/lib/sign-out-cleanup';
 import { setSendGuardSource } from '@/lib/plugin-send-guards';
 import { clearAllHooks, emailHooks } from '@/lib/plugin-hooks';
 import { beginComposeTakeover, completesComposeTakeover, endComposeTakeover, resetComposeTakeovers } from '@/lib/outgoing/compose-takeover';
+import { setStoreBackend } from '@/lib/store/client/api';
+import { InProcessStore } from '@/lib/store/__tests__/helpers/in-process-store';
+import { FakeJmapMail } from '@/lib/store/__tests__/helpers/fake-jmap-mail';
+import { JMAP_ACCOUNT } from '@/lib/store/__tests__/helpers/fake-jmap';
 import type { JMAPClient } from '@/lib/jmap/client';
 import type { InstalledPlugin } from '@/lib/plugin-types';
 import {
   confirmLoss,
   enforcePolicy,
-  inScope,
   offlineSessionFor,
+  offlineSupported,
   pluginsNotRunning,
-  recordAnswer,
-  scopeOf,
+  refreshQueueState,
+  setOfflineNotifier,
   startOfflineMode,
   stricterNow,
+  unsentCount,
   wipeEverything,
 } from '../offline-mode';
-import { flushQueue, settleStaleSends, SENDING_STALE_MS } from '../flush';
-import { claimForSending, holdFile, queueSend, readQueue } from '../queue';
-import { emailIndex, emailKey, forgetIndexes, getBlob, messageOfBlob, putBlob, putEmails, putMisc, removeEmails } from '../cache';
-import { forgetDeviceKey } from '../crypto';
-import { allowOfflineDbCreation, deleteOfflineDb, idbGetAll, openOfflineDb } from '../db';
+import { flushQueue, forgetOrphanCheck, LOOKUP_WAIT_MS, ORPHAN_FILE_AGE_MS, settleStaleSends, SENDING_STALE_MS } from '../flush';
+import { installMayPass } from '@/lib/store/adapters/wasm';
+import { isServerOutage, SendNotStartedError } from '@/lib/jmap/offline-hooks';
+import { claimForSending, holdFile, LOCAL_BLOB_PREFIX, queueSend, readQueue, updateOutboxEntry } from '../queue';
+import { forgetLegacyMove, strandedLegacyMessages } from '../migrate-legacy';
 import { consumeLost } from '../lost';
+import { getOutboxHooks } from '../outbox-hooks';
 import { shellFiles } from '../shell';
-import { isOfflineNow, OFFLINE_ACCOUNTS_KEY, setServerDown, useOfflineStore, writeEnabled } from '../state';
-
-const day = 24 * 60 * 60 * 1000;
-const recent = () => new Date(Date.now() - day).toISOString();
+import { DEFAULT_SCOPE } from '@/lib/store/area';
+import { isOfflineNow, OFFLINE_ACCOUNTS_KEY, OFFLINE_EVICTED_KEY, OFFLINE_SCOPE_KEY, offlineScopeFor, setServerDown, useOfflineStore, writeEnabled } from '../state';
 
 function fakeClient(server = 'https://mail.example.org', overrides: Record<string, unknown> = {}) {
   return {
@@ -42,9 +46,10 @@ function fakeClient(server = 'https://mail.example.org', overrides: Record<strin
     getAccountId: () => 'j1',
     isOfflineOnly: () => false,
     getSessionSnapshot: () => ({ apiUrl: `${server}/jmap` }),
+    getAuthHeader: () => 'Basic x',
+    keywordSortInverted: () => null,
     sendEmail: vi.fn(async () => ({ scheduled: false, emailId: 'sent-1', emailSubmissionId: 'sub-1' })),
     uploadBlob: vi.fn(async (file: File) => ({ blobId: `server-${file.name}`, size: file.size, type: file.type })),
-    applyEmailPatches: vi.fn(async () => []),
     pruneEmailSubmissions: vi.fn(async () => {}),
     ...overrides,
   };
@@ -59,16 +64,17 @@ function setOnline(online: boolean) {
 }
 
 let stop: () => void = () => {};
+const useRealClient = useAuthStore.getState().getClientForAccount;
+let store: InProcessStore;
 
 beforeEach(async () => {
-  forgetIndexes();
-  forgetDeviceKey();
-  await deleteOfflineDb();
-  allowOfflineDbCreation();
+  store = new InProcessStore();
+  setStoreBackend(store);
+  forgetLegacyMove();
   localStorage.clear();
   sessionStorage.clear();
   setOnline(true);
-  useOfflineStore.setState({ enabled: [], outbox: [], pendingChanges: 0, browserOffline: false, downServers: [], startedOffline: false });
+  useOfflineStore.setState({ enabled: [], outbox: [], pendingChanges: 0, conflicts: [], browserOffline: false, downServers: [], startedOffline: false });
   setPolicyOrg({});
   useAccountStore.setState({ accounts: [{ id: 'acc', label: 'alice', serverUrl: 'https://mail.example.org', username: 'alice@example.org' } as never] });
   useAuthStore.setState({ isAuthenticated: true, activeAccountId: 'acc', client: null });
@@ -82,19 +88,20 @@ afterEach(async () => {
   setOnline(true);
   setSendGuardSource(null);
   await wipeEverything();
+  setStoreBackend(null);
 });
 
 describe('1: two tabs never send the same message', () => {
   it('only one claim wins', async () => {
     const id = await queueSend('acc', { subject: 'S', to: [] }, { kind: 'email', args: [] });
-    const results = await Promise.all([claimForSending(id), claimForSending(id)]);
+    const results = await Promise.all([claimForSending('acc', id), claimForSending('acc', id)]);
     expect(results.filter(Boolean)).toHaveLength(1);
     expect((await readQueue('acc')).outbox[0].status).toBe('sending');
   });
 
   it('a message another tab took isn’t sent here', async () => {
     const id = await queueSend('acc', { subject: 'S', to: [] }, { kind: 'email', args: [['b@example.org'], 'S', 'x'] });
-    await claimForSending(id);
+    await claimForSending('acc', id);
     const client = fakeClient();
     await flushQueue('acc', client as unknown as JMAPClient, { notify: vi.fn(), allowed: () => true });
     expect(client.sendEmail).not.toHaveBeenCalled();
@@ -112,7 +119,7 @@ describe('1: two tabs never send the same message', () => {
   });
 });
 
-describe('2: a send that may have reached the server is never queued or sent again', () => {
+describe('2: a send that may have reached the server is never queued or sent again blindly', () => {
   it('puts a send back to waiting only when it never started', async () => {
     const notStarted = Object.assign(new Error('x'), { name: 'SendNotStartedError' });
     const client = fakeClient(undefined, { sendEmail: vi.fn(async () => { throw notStarted; }) });
@@ -158,7 +165,7 @@ describe('3: every sign-out the user didn’t agree to names the lost messages',
     setOfflineNotifier((n) => notices.push(n));
     stop = startOfflineMode();
     await queueSend('acc', { subject: 'Lost one', to: [] }, { kind: 'email', args: [] });
-    useAccountStore.setState({ accounts: [{ id: 'other' } as never] });
+    useAccountStore.getState().removeAccount('acc');
     await vi.waitFor(() => expect(notices).toContainEqual({ kind: 'lost', subjects: ['Lost one'] }));
     setOfflineNotifier(() => {});
   });
@@ -186,16 +193,17 @@ describe('4: no queueing while a plugin isn’t running', () => {
 });
 
 describe('5: another tab switching it off sticks', () => {
-  it('follows the switch from another tab and doesn’t create the database again', async () => {
+  it('follows the switch from another tab and doesn’t open the store for it again', async () => {
     writeEnabled(['acc']);
     stop = startOfflineMode();
-    await putEmails('acc', 'j1', [{ id: 'm1', mailboxIds: { inbox: true }, receivedAt: recent() }]);
-    // The other tab: switched off, database deleted.
-    await deleteOfflineDb();
+    await vi.waitFor(() => expect(store.has('acc')).toBe(true));
+    await new Promise((r) => setTimeout(r, 10));
+    store.stop();
     window.dispatchEvent(new StorageEvent('storage', { key: OFFLINE_ACCOUNTS_KEY, newValue: null }));
     expect(useOfflineStore.getState().enabled).toEqual([]);
-    await expect(openOfflineDb()).rejects.toMatchObject({ name: 'OfflineDbMissingError' });
-    expect((await indexedDB.databases()).map((d) => d.name)).not.toContain('bulwark-offline');
+    await new Promise((r) => setTimeout(r, 20));
+    expect(store.has('acc')).toBe(false);
+    expect((await indexedDB.databases()).map((d) => d.name)).not.toContain('bulwark-store');
   });
 });
 
@@ -216,7 +224,7 @@ describe('6: queued mail and a stricter policy', () => {
 describe('7: a send of a closed tab isn’t stuck', () => {
   it('becomes uncertain after a minute', async () => {
     const id = await queueSend('acc', { subject: 'S', to: [] }, { kind: 'email', args: [] });
-    await claimForSending(id);
+    await claimForSending('acc', id);
     await settleStaleSends('acc');
     expect((await readQueue('acc')).outbox[0].status).toBe('sending');
     await settleStaleSends('acc', Date.now() + SENDING_STALE_MS + 1000);
@@ -225,21 +233,31 @@ describe('7: a send of a closed tab isn’t stuck', () => {
 });
 
 describe('8: only parts of kept messages are kept, and go with them', () => {
-  it('knows which message a blob belongs to and deletes it with the message', async () => {
-    await putEmails('acc', 'j1', [{ id: 'm1', mailboxIds: { inbox: true }, receivedAt: recent(), bodyValues: {}, attachments: [{ blobId: 'b1', name: 'a.pdf' }] }]);
-    expect(await messageOfBlob('acc', 'j1', 'b1')).toMatchObject({ key: emailKey('acc', 'j1', 'm1') });
-    expect(await messageOfBlob('acc', 'j1', 'export-of-a-whole-message')).toBeNull();
-    await putBlob('acc', 'j1', 'b1', new Blob(['x']), Date.now(), emailKey('acc', 'j1', 'm1'));
-    await removeEmails('acc', [emailKey('acc', 'j1', 'm1')]);
-    expect(await getBlob('acc', 'j1', 'b1')).toBeNull();
+  it('files a blob under its message and deletes it with the message', async () => {
+    const server = new FakeJmapMail();
+    server.addEmail({ id: 'm1', attachments: [{ blobId: 'b1', name: 'a.pdf', size: 99_999_999 }] });
+    store = new InProcessStore(server);
+    setStoreBackend(store);
+    await store.sync('acc');
+    expect(await store.area('acc', 'mail.recordBlob', { jmap: JMAP_ACCOUNT, blobId: 'export-of-a-whole-message', type: null, data: new Uint8Array([1]) })).toBe(false);
+    expect(await store.area('acc', 'mail.recordBlob', { jmap: JMAP_ACCOUNT, blobId: 'b1', type: null, data: new Uint8Array([1]) })).toBe(true);
+    server.destroyEmail('m1');
+    await store.sync('acc');
+    expect(await store.area('acc', 'mail.getBlob', { jmap: JMAP_ACCOUNT, blobId: 'b1' })).toBeNull();
   });
 });
 
 describe('9: folders that went away', () => {
-  it('drops opened folders the folder list no longer has', async () => {
-    await putMisc('acc', 'mailboxes', { j1: [{ id: 'inbox', role: 'inbox' }, { id: 'kept' }] });
-    await putMisc('acc', 'opened', { j1: ['kept', 'deleted'] });
-    expect((await scopeOf('acc')).opened).toEqual({ j1: ['kept'] });
+  it('drops a folder the server no longer has', async () => {
+    const server = new FakeJmapMail({ mailboxes: [{ id: 'inbox', role: 'inbox' }, { id: 'kept' }, { id: 'deleted' }] });
+    store = new InProcessStore(server);
+    setStoreBackend(store);
+    await store.sync('acc');
+    server.mailboxes.delete('deleted');
+    server.coll.Mailbox.push('destroyed', 'deleted');
+    await store.sync('acc');
+    const answer = await store.answer('acc', [['Mailbox/get', {}, '0']]);
+    expect(answer?.methodResponses[0][1].list.map((box: { id: string }) => box.id).sort()).toEqual(['inbox', 'kept']);
   });
 });
 
@@ -259,7 +277,6 @@ describe('10: no decision on an account whose groups aren’t known yet', () =>
 describe('11: starting from the device', () => {
   it('uses the policy kept from the last fetch, never the defaults', async () => {
     writeEnabled(['acc']);
-    await putMisc('acc', 'session', { apiUrl: 'x' });
     localStorage.setItem('bulwark-policy-last', JSON.stringify({ ...usePolicyStore.getState().policy, organisation: { ...DEFAULT_ORGANISATION_POLICY, devices: { ...DEFAULT_ORGANISATION_POLICY.devices, noOffline: true } } }));
     usePolicyStore.setState({ loaded: false, fetching: false, source: 'none' });
     vi.stubGlobal('fetch', vi.fn(async () => { throw new TypeError('Failed to fetch'); }));
@@ -270,6 +287,390 @@ describe('11: starting from the device', () => {
       vi.unstubAllGlobals();
     }
   });
+
+  it('hands out the session kept with the account', async () => {
+    writeEnabled(['acc']);
+    expect(await offlineSessionFor('acc')).toMatchObject({ primaryAccounts: { 'urn:ietf:params:jmap:mail': JMAP_ACCOUNT } });
+  });
+
+  it('gives up on a policy fetch that never answers', async () => {
+    writeEnabled(['acc']);
+    usePolicyStore.setState({ loaded: false, fetching: false, source: 'none' });
+    vi.useFakeTimers();
+    vi.stubGlobal('fetch', vi.fn(() => new Promise(() => {})));
+    try {
+      const session = offlineSessionFor('acc');
+      await vi.advanceTimersByTimeAsync(10_000);
+      expect(await session).toBeNull();
+    } finally {
+      vi.unstubAllGlobals();
+      vi.useRealTimers();
+    }
+  });
+
+  it('doesn\'t wait for the old database to finish moving', async () => {
+    writeEnabled(['acc']);
+    forgetLegacyMove();
+    const legacy = indexedDB.open;
+    vi.spyOn(indexedDB, 'open').mockImplementation(((name: string, version?: number) => {
+      // A database that never opens.
+      if (name === 'bulwark-offline') return { result: null } as never;
+      return legacy.call(indexedDB, name, version);
+    }) as never);
+    vi.useFakeTimers();
+    try {
+      const session = offlineSessionFor('acc');
+      await vi.advanceTimersByTimeAsync(10_000);
+      expect(await session).toMatchObject({ primaryAccounts: { 'urn:ietf:params:jmap:mail': JMAP_ACCOUNT } });
+    } finally {
+      vi.useRealTimers();
+      vi.restoreAllMocks();
+    }
+  });
+
+  it('doesn\'t offer a quick start before the store has its folders', async () => {
+    store = new InProcessStore(new FakeJmapMail());
+    setStoreBackend(store);
+    writeEnabled(['acc']);
+    expect(await offlineSessionFor('acc', { withFolders: true })).toBeNull();
+    await store.sync('acc');
+    expect(await offlineSessionFor('acc', { withFolders: true })).toMatchObject({ primaryAccounts: { 'urn:ietf:params:jmap:mail': JMAP_ACCOUNT } });
+  });
+});
+
+describe('what a sign-out would delete', () => {
+  beforeEach(() => writeEnabled(['acc', 'other']));
+
+  const addCalendarEdit = async (account: string) => {
+    await store.ensureOpen(account);
+    store.dbs.get(account)!.run("INSERT INTO calendar_pending (jmap, record_id, kind, patch, queued_at) VALUES ('j1', 'ev', 'update', '{}', 1)");
+  };
+
+  it('counts the queue itself, not what the screen last saw', async () => {
+    await queueSend('acc', { subject: 'A', to: [] }, { kind: 'email', args: [] });
+    await queueSend('other', { subject: 'B', to: [] }, { kind: 'email', args: [] });
+    expect(useOfflineStore.getState().outbox).toEqual([]);
+    expect(await unsentCount('acc')).toEqual({ messages: 1, changes: 0 });
+    expect(await unsentCount('all')).toEqual({ messages: 2, changes: 0 });
+  });
+
+  it('counts changes and calendar edits, for the account asked about', async () => {
+    await addCalendarEdit('acc');
+    await store.area('acc', 'outbox.queueSend', { summary: { subject: 'A', to: [] }, item: { kind: 'email', args: [] } });
+    expect(await unsentCount('other')).toEqual({ messages: 0, changes: 0 });
+    expect(await unsentCount('acc')).toEqual({ messages: 1, changes: 1 });
+  });
+
+  it('counts an area that isn\'t here as nothing', async () => {
+    store.failArea = (name) => name === 'contacts.pending';
+    await addCalendarEdit('acc');
+    expect((await unsentCount('acc')).changes).toBe(1);
+  });
+
+  it('answers with the last known count when the store hangs', async () => {
+    useOfflineStore.setState({ outbox: [{ id: 1, account: 'acc', createdAt: 1, subject: 'A', to: [], status: 'waiting' }] as never, pendingChanges: 2 });
+    const hung: Array<(error: Error) => void> = [];
+    vi.spyOn(store, 'area').mockImplementation(() => new Promise((_resolve, reject) => { hung.push(reject); }));
+    expect(await unsentCount('acc', 10)).toEqual({ messages: 1, changes: 2 });
+    for (const reject of hung) reject(new Error('Gone'));
+  });
+
+  it('doesn\'t count another signed-out account\'s waiting mail', async () => {
+    await queueSend('other', { subject: 'B', to: [] }, { kind: 'email', args: [] });
+    localStorage.setItem(OFFLINE_EVICTED_KEY, JSON.stringify({ other: Date.now() }));
+    expect(await unsentCount('all')).toEqual({ messages: 0, changes: 0 });
+  });
+});
+
+describe('a store that won\'t open', () => {
+  beforeEach(() => writeEnabled(['acc', 'other']));
+
+  it('holds up no other account, and keeps what it last showed', async () => {
+    await queueSend('acc', { subject: 'A', to: [] }, { kind: 'email', args: [] });
+    await queueSend('other', { subject: 'B', to: [] }, { kind: 'email', args: [] });
+    await refreshQueueState();
+    const area = store.area.bind(store);
+    vi.spyOn(store, 'area').mockImplementation(((account: string, name: string, params: unknown) => (account === 'other' ? Promise.reject(new Error('The local store could not start')) : area(account, name, params))) as never);
+    const notify = vi.fn();
+    setOfflineNotifier(notify);
+    await refreshQueueState();
+    expect(useOfflineStore.getState().outbox.map((row) => row.subject).sort()).toEqual(['A', 'B']);
+    expect(notify).toHaveBeenCalledWith({ kind: 'store-unavailable' });
+    // Not again right away.
+    notify.mockClear();
+    await refreshQueueState();
+    expect(notify).not.toHaveBeenCalled();
+  });
+
+  it('doesn\'t call an unreadable queue empty', async () => {
+    await queueSend('acc', { subject: 'A', to: [] }, { kind: 'email', args: [] });
+    await refreshQueueState();
+    vi.spyOn(store, 'area').mockRejectedValue(new Error('The local store could not start'));
+    await refreshQueueState();
+    expect(useOfflineStore.getState().outbox.map((row) => row.subject)).toEqual(['A']);
+    await expect(readQueue()).rejects.toThrow('could not start');
+  });
+});
+
+describe('a send the server couldn\'t take right now', () => {
+  const statusAfter = async (error: Error) => {
+    writeEnabled(['acc']);
+    await queueSend('acc', { subject: 'Hello', to: [] }, { kind: 'email', args: [] });
+    const notify = vi.fn();
+    const retryLater = vi.fn();
+    const sendEmail = vi.fn(async () => { throw error; });
+    await flushQueue('acc', fakeClient('https://mail.example.org', { sendEmail }) as unknown as JMAPClient, { notify, allowed: () => true, retryLater });
+    const row = (await readQueue('acc')).outbox[0];
+    return { row, notify, retryLater };
+  };
+
+  it.each([
+    ['a rate limit', Object.assign(new Error('Rate limited by server'), { name: 'RateLimitError' })],
+    ['a login that needs renewing', new Error('Request failed: 401 - ')],
+    ['a store that went away', Object.assign(new Error('gone'), { name: 'StoreOwnerGoneError' })],
+    ['a full disk', Object.assign(new Error('full'), { name: 'QuotaExceededError' })],
+  ])('goes back to waiting, on a timer, after %s', async (_name, error) => {
+    const { row, notify, retryLater } = await statusAfter(error);
+    expect(row.status).toBe('waiting');
+    expect(retryLater).toHaveBeenCalled();
+    expect(notify).not.toHaveBeenCalled();
+  });
+
+  it.each(['Request failed: 500 - oops', 'Request failed: 501 - nope'])('is looked up after %s, which may have got through', async (message) => {
+    const { row, notify, retryLater } = await statusAfter(new Error(message));
+    expect(row.status).toBe('uncertain');
+    expect(retryLater).toHaveBeenCalled();
+    expect(notify).not.toHaveBeenCalled();
+  });
+
+  it('fails, for the user to see, on a refusal', async () => {
+    const { row, notify } = await statusAfter(new Error('Request failed: 400 - {"type":"urn:ietf:params:jmap:error:notRequest"}'));
+    expect(row.status).toBe('failed');
+    expect(notify).toHaveBeenCalledWith(expect.objectContaining({ kind: 'send-failed' }));
+  });
+
+  it('keeps the copy on the server through a wait', async () => {
+    writeEnabled(['acc']);
+    const id = await queueSend('acc', { subject: 'Hello', to: [] }, { kind: 'email', args: [] });
+    const [entry] = (await readQueue('acc')).outbox;
+    await updateOutboxEntry(entry, { status: 'waiting', copyId: 'copy-1' });
+    const sendEmail = vi.fn(async () => { throw new Error('Request failed: 429 - '); });
+    await flushQueue('acc', fakeClient('https://mail.example.org', { sendEmail }) as unknown as JMAPClient, { notify: vi.fn(), allowed: () => true });
+    const row = (await readQueue('acc')).outbox.find((candidate) => candidate.id === id);
+    expect(row).toMatchObject({ status: 'waiting', copyId: 'copy-1' });
+  });
+
+  it('doesn\'t hand an online send a stand-in for a file the upload held again', async () => {
+    writeEnabled(['acc']);
+    stop = startOfflineMode();
+    const { blobId } = await holdFile('acc', new File(['x'], 'x.txt', { type: 'text/plain' }), 'x.txt');
+    const client = fakeClient('https://mail.example.org', { uploadBlob: vi.fn(async () => ({ blobId: `${LOCAL_BLOB_PREFIX}stand-in`, size: 1, type: 'text/plain' })) });
+    useAuthStore.setState({ client: client as never, activeAccountId: 'acc', getClientForAccount: () => client } as never);
+    try {
+      await expect(getOutboxHooks()!.resolveHeldAttachments(client as never, [{ blobId }])).rejects.toMatchObject({ name: 'SendNotStartedError' });
+    } finally {
+      useAuthStore.setState({ getClientForAccount: useRealClient, client: null });
+    }
+  });
+
+  it('doesn\'t send a stand-in for a file the upload held again', async () => {
+    writeEnabled(['acc']);
+    const { blobId } = await holdFile('acc', new File(['x'], 'x.txt', { type: 'text/plain' }), 'x.txt');
+    await queueSend('acc', { subject: 'Hello', to: [] }, { kind: 'email', args: [undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, [{ blobId, name: 'x.txt', type: 'text/plain', size: 1 }]] });
+    const sendEmail = vi.fn(async () => ({ scheduled: false, emailId: 'e', emailSubmissionId: 's' }));
+    const uploadBlob = vi.fn(async () => ({ blobId: `${LOCAL_BLOB_PREFIX}stand-in`, size: 1, type: 'text/plain' }));
+    await flushQueue('acc', fakeClient('https://mail.example.org', { sendEmail, uploadBlob }) as unknown as JMAPClient, { notify: vi.fn(), allowed: () => true });
+    expect(sendEmail).not.toHaveBeenCalled();
+    expect((await readQueue('acc')).outbox[0].status).toBe('waiting');
+  });
+});
+
+describe('waiting mail after a normal start', () => {
+  const realFetchPolicy = usePolicyStore.getState().fetchPolicy;
+
+  beforeEach(() => {
+    vi.useFakeTimers();
+    // rawPolicy: what the policy is worked out from again when the subject changes.
+    usePolicyStore.setState({ fetchPolicy: vi.fn(async () => {}), source: 'server', rawPolicy: usePolicyStore.getState().policy } as never);
+    useOfflineStore.setState({ downServers: [] });
+    writeEnabled(['acc']);
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+    usePolicyStore.setState({ fetchPolicy: realFetchPolicy });
+    useOfflineStore.setState({ downServers: [] });
+  });
+
+  it('goes when the client becomes real after the flush at the start', async () => {
+    await queueSend('acc', { subject: 'Hello', to: [] }, { kind: 'email', args: [] });
+    stop = startOfflineMode();
+    // The flush at the start finds no client yet.
+    await vi.advanceTimersByTimeAsync(5_000);
+    const client = fakeClient();
+    useAuthStore.setState({ getClientForAccount: () => client, client: client as never } as never);
+    try {
+      await vi.advanceTimersByTimeAsync(1_500);
+      expect(client.sendEmail).toHaveBeenCalledTimes(1);
+    } finally {
+      useAuthStore.setState({ getClientForAccount: useRealClient, client: null });
+    }
+  });
+
+  it('comes back to a send a closed tab left behind', async () => {
+    const id = await queueSend('acc', { subject: 'Hello', to: [] }, { kind: 'email', args: [] });
+    await claimForSending('acc', id);
+    stop = startOfflineMode();
+    await vi.advanceTimersByTimeAsync(5_000);
+    expect((await readQueue('acc')).outbox[0].status).toBe('sending');
+    await vi.advanceTimersByTimeAsync(SENDING_STALE_MS);
+    expect((await readQueue('acc')).outbox[0].status).toBe('uncertain');
+  });
+
+  it('asks a server that was down, on an interval, and flushes when it answers', async () => {
+    const fetcher = vi.fn(async (_url: string) => new Response(null, { status: 200 }));
+    vi.stubGlobal('fetch', fetcher);
+    try {
+      stop = startOfflineMode();
+      await vi.advanceTimersByTimeAsync(5_000);
+      setServerDown('https://mail.example.org', true);
+      await vi.advanceTimersByTimeAsync(30_000);
+      expect(fetcher.mock.calls.map(([url]) => String(url))).toContain('https://mail.example.org/.well-known/jmap');
+      expect(isOfflineNow('https://mail.example.org')).toBe(false);
+    } finally {
+      vi.unstubAllGlobals();
+    }
+  });
+});
+
+describe('old files', () => {
+  it('go after a flush, once a day, not a file that\'s still recent', async () => {
+    forgetOrphanCheck();
+    writeEnabled(['acc']);
+    const { blobId } = await holdFile('acc', new File(['x'], 'x.txt', { type: 'text/plain' }), 'x.txt');
+    const client = fakeClient() as unknown as JMAPClient;
+    const flush = () => flushQueue('acc', client, { notify: vi.fn(), allowed: () => true });
+    await flush();
+    expect(await store.area('acc', 'outbox.heldFile', { blobId })).not.toBeNull();
+
+    const area = vi.spyOn(store, 'area');
+    await flush();
+    expect(area.mock.calls.some(([, name]) => name === 'outbox.dropOrphans')).toBe(false);
+
+    const later = Date.now() + ORPHAN_FILE_AGE_MS + 1000;
+    const clock = vi.spyOn(Date, 'now').mockReturnValue(later);
+    try {
+      await flush();
+      expect(area.mock.calls.some(([, name]) => name === 'outbox.dropOrphans')).toBe(true);
+      expect(await store.area('acc', 'outbox.heldFile', { blobId })).toBeNull();
+    } finally {
+      clock.mockRestore();
+      area.mockRestore();
+    }
+  });
+});
+
+describe('a browser that can\'t run the store', () => {
+  it('says so when the old database holds unsent mail', async () => {
+    await new Promise<void>((resolve) => {
+      const request = indexedDB.open('bulwark-offline', 1);
+      request.onupgradeneeded = () => { request.result.createObjectStore('queue', { keyPath: 'id' }); };
+      request.onsuccess = () => {
+        const put = request.result.transaction('queue', 'readwrite').objectStore('queue');
+        put.put({ id: 1, kind: 'patch' });
+        put.put({ id: 2, kind: 'send' });
+        put.transaction.oncomplete = () => { request.result.close(); resolve(); };
+      };
+    });
+    expect(await strandedLegacyMessages()).toBe(1);
+    store.isSupported = false;
+    const notify = vi.fn();
+    setOfflineNotifier(notify);
+    stop = startOfflineMode();
+    await vi.waitFor(() => expect(notify).toHaveBeenCalledWith({ kind: 'legacy-stranded' }));
+    store.isSupported = true;
+    await new Promise<void>((resolve) => {
+      const remove = indexedDB.deleteDatabase('bulwark-offline');
+      remove.onsuccess = () => resolve();
+    });
+    expect(await strandedLegacyMessages()).toBe(0);
+  });
+
+  it('turns the switch off in a window that refuses the private file system, and wipes nothing', async () => {
+    writeEnabled(['acc']);
+    Object.defineProperty(window.navigator, 'storage', { configurable: true, value: { getDirectory: async () => { throw new DOMException('The operation is insecure.', 'SecurityError'); } } });
+    try {
+      stop = startOfflineMode();
+      await vi.waitFor(() => expect(useOfflineStore.getState().storageBlocked).toBe(true));
+      expect(offlineSupported()).toBe(false);
+      enforcePolicy();
+      await new Promise((resolve) => setTimeout(resolve, 20));
+      expect(useOfflineStore.getState().enabled).toEqual(['acc']);
+    } finally {
+      delete (window.navigator as { storage?: unknown }).storage;
+      useOfflineStore.setState({ storageBlocked: false });
+    }
+  });
+
+  it('doesn\'t retry the install where the browser refuses it', () => {
+    expect(installMayPass(new DOMException('The operation is insecure.', 'SecurityError'))).toBe(false);
+    expect(installMayPass(new DOMException('Handle is busy', 'NoModificationAllowedError'))).toBe(true);
+  });
+});
+
+describe('the wording of an outage', () => {
+  it('tells a proxy with no server behind it from a missing connection', () => {
+    const gateway = Object.assign(new Error('Request failed: 502'), { name: 'GatewayError' });
+    expect(isServerOutage(gateway)).toBe(true);
+    expect(isServerOutage(new SendNotStartedError(gateway))).toBe(true);
+    expect(isServerOutage(new SendNotStartedError(new TypeError('Failed to fetch')))).toBe(false);
+    expect(isServerOutage(new TypeError('Failed to fetch'))).toBe(false);
+  });
+});
+
+describe('looking up a send that may have gone', () => {
+  it('waits until about 30 seconds after the last try', async () => {
+    writeEnabled(['acc']);
+    const id = await queueSend('acc', { subject: 'Hello', to: [] }, { kind: 'email', args: [] }, undefined, 'fixed@example.org');
+    await claimForSending('acc', id);
+    await updateOutboxEntry({ account: 'acc', id }, { status: 'uncertain' });
+    const requestNetworkOnly = vi.fn(async () => { throw new TypeError('Failed to fetch'); });
+    const client = fakeClient('https://mail.example.org', { requestNetworkOnly, resolveSendAccountId: async () => 'j1', submissionAccountFor: () => 'j1' }) as unknown as JMAPClient;
+    const retryLater = vi.fn();
+    await flushQueue('acc', client, { notify: vi.fn(), allowed: () => true, retryLater });
+    expect(requestNetworkOnly).not.toHaveBeenCalled();
+    expect(retryLater).toHaveBeenCalled();
+    const later = Date.now() + LOOKUP_WAIT_MS + 1000;
+    const clock = vi.spyOn(Date, 'now').mockReturnValue(later);
+    try {
+      await flushQueue('acc', client, { notify: vi.fn(), allowed: () => true, retryLater });
+      expect(requestNetworkOnly).toHaveBeenCalled();
+    } finally {
+      clock.mockRestore();
+    }
+  });
+});
+
+describe('what the store is told to keep', () => {
+  it('follows what the account chose, on top of the defaults', () => {
+    expect(offlineScopeFor('acc')).toEqual(DEFAULT_SCOPE);
+    localStorage.setItem(OFFLINE_SCOPE_KEY, JSON.stringify({ acc: { attachments: false, days: 7 } }));
+    expect(offlineScopeFor('acc')).toEqual({ ...DEFAULT_SCOPE, attachments: false, days: 7 });
+    expect(offlineScopeFor('other')).toEqual(DEFAULT_SCOPE);
+  });
+});
+
+describe('a send on the local copy', () => {
+  it('queues, before the swap too, while the probes say the server is up', () => {
+    writeEnabled(['acc']);
+    stop = startOfflineMode();
+    useAuthStore.setState({ client: fakeClient('https://mail.example.org', { isOfflineOnly: () => true }) as never });
+    const client = useAuthStore.getState().client as never;
+    expect(isOfflineNow('https://mail.example.org')).toBe(false);
+    expect(getOutboxHooks()?.shouldQueue(client)).toBe(true);
+    useAuthStore.setState({ client: fakeClient() as never });
+    expect(getOutboxHooks()?.shouldQueue(useAuthStore.getState().client as never)).toBe(false);
+  });
 });
 
 describe('12: one server down doesn’t hold another’s mail', () => {
@@ -281,10 +682,13 @@ describe('12: one server down doesn’t hold another’s mail', () => {
 });
 
 describe('13: file names stay sealed', () => {
-  it('keeps no name or type of a held file readable', async () => {
-    await holdFile('acc', new File(['x'], 'merger-plan.pdf', { type: 'application/pdf' }), 'merger-plan.pdf');
-    const records = await idbGetAll<Record<string, unknown>>('uploads');
-    expect(JSON.stringify(records.map((r) => ({ ...r, data: undefined, iv: undefined, meta: undefined })))).not.toMatch(/merger|pdf/);
+  it('keeps the name and type of a held file only in the encrypted store', async () => {
+    const held = await holdFile('acc', new File(['x'], 'merger-plan.pdf', { type: 'application/pdf' }), 'merger-plan.pdf');
+    expect(held.blobId).not.toMatch(/merger|pdf/);
+    const db = store.dbs.get('acc')!;
+    expect(db.get<{ name: string }>('SELECT name FROM upload')?.name).toBe('merger-plan.pdf');
+    const everythingElse = JSON.stringify({ local: { ...localStorage }, session: { ...sessionStorage }, dbs: await indexedDB.databases() });
+    expect(everythingElse).not.toMatch(/merger/);
   });
 });
 
@@ -318,25 +722,3 @@ describe('15: only the plugin running the composer’s send counts', () => {
     expect(completesComposeTakeover('smime', 'i1')).toBe(false);
   });
 });
-
-describe('recording: what the cache takes', () => {
-  it('keeps recent mail of the Inbox and opened folders, refreshes kept messages, skips the rest', async () => {
-    const scope = { inbox: { j1: 'inbox' }, opened: { j1: ['projects'] } };
-    expect(inScope(scope, 'j1', { id: 'a', mailboxIds: { inbox: true }, receivedAt: recent() })).toBe(true);
-    expect(inScope(scope, 'j1', { id: 'b', mailboxIds: { projects: true }, receivedAt: recent() })).toBe(true);
-    expect(inScope(scope, 'j1', { id: 'c', mailboxIds: { archive: true }, receivedAt: recent() })).toBe(false);
-    expect(inScope(scope, 'j1', { id: 'd', mailboxIds: { inbox: true }, receivedAt: new Date(Date.now() - 40 * day).toISOString() })).toBe(false);
-
-    await putMisc('acc', 'mailboxes', { j1: [{ id: 'inbox', role: 'inbox', name: 'Inbox' }] });
-    await recordAnswer('acc', 'j1', [['Email/get', { ids: ['a', 'c'] }, '0'], ['Mailbox/get', { properties: ['id', 'role'] }, '1']], {
-      methodResponses: [
-        ['Email/get', { accountId: 'j1', list: [{ id: 'a', mailboxIds: { inbox: true }, receivedAt: recent() }, { id: 'c', mailboxIds: { archive: true }, receivedAt: recent() }] }, '0'],
-        ['Mailbox/get', { accountId: 'j1', list: [{ id: 'inbox', role: 'inbox' }] }, '1'],
-      ],
-    });
-    const index = await emailIndex('acc');
-    expect([...index.values()].map((e) => e.id)).toEqual(['a']);
-    // A partial folder list (id and role only) doesn't replace the full one.
-    expect((await scopeOf('acc')).inbox).toEqual({ j1: 'inbox' });
-  });
-});
diff --git a/lib/offline/cache.ts b/lib/offline/cache.ts
deleted file mode 100644
index 0411a5bde..000000000
--- a/lib/offline/cache.ts
+++ /dev/null
@@ -1,310 +0,0 @@
-/**
- * The mail kept on this device for offline mode (#523), per Bulwark account
- * (`account`, the local account id) and JMAP account (`jmap`).
- *
- * Messages are kept in two parts: what the list shows (emails) and the text
- * and structure of the message (bodies), so a folder list never decrypts
- * the bodies. Attachments and inline images are blobs. Every value is
- * encrypted (crypto.ts); only the ledger (size, date) and the keys (ids) are
- * not.
- *
- * The cache holds at most CACHE_CAP_BYTES on the device, across accounts;
- * the oldest messages go first, with their bodies and attachments. The
- * outbox (queue.ts) doesn't count and never goes.
- */
-
-import { idbDeleteAccount, idbGet, idbGetAll, idbGetAllByAccount, idbWrite, type StoreName } from './db';
-import { openBytes, openJson, sealBytes, sealJson, type Sealed } from './crypto';
-
-/** Most bytes the cache keeps on the device (messages, bodies, attachments). */
-export const CACHE_CAP_BYTES = 250 * 1024 * 1024;
-/** How far back the Inbox (and the folders the user opened) are kept. */
-export const CACHE_DAYS = 30;
-export const CACHE_WINDOW_MS = CACHE_DAYS * 24 * 60 * 60 * 1000;
-
-/** Where the metadata keeps the blob ids of a message's parts (never handed out). */
-export const BLOBS = '_bulwarkBlobs';
-
-/** The parts of a message that only the reader needs. */
-const BODY_KEYS = ['bodyValues', 'textBody', 'htmlBody', 'bodyStructure', 'headers', 'attachments'] as const;
-
-export type CachedEmail = Record<string, unknown> & {
-  id: string;
-  threadId?: string;
-  mailboxIds?: Record<string, boolean>;
-  keywords?: Record<string, boolean>;
-  receivedAt?: string;
-};
-
-interface SealedRecord extends Sealed {
-  key: string;
-  account: string;
-}
-
-interface LedgerEntry {
-  key: string;
-  account: string;
-  store: StoreName;
-  ref: string;
-  /** The message's date (ms), for oldest-first eviction. */
-  at: number;
-  bytes: number;
-  /** The message a body or blob belongs to. */
-  emailKey?: string;
-}
-
-const join = (...parts: string[]) => parts.join('\u0001');
-export const emailKey = (account: string, jmap: string, id: string) => join(account, jmap, id);
-const blobKey = (account: string, jmap: string, blobId: string) => join(account, jmap, 'blob', blobId);
-const miscKey = (account: string, name: string) => join(account, 'misc', name);
-const ledgerKey = (store: StoreName, key: string) => `${store}:${key}`;
-
-const dateOf = (email: { receivedAt?: unknown }) => {
-  const at = typeof email.receivedAt === 'string' ? Date.parse(email.receivedAt) : NaN;
-  return Number.isFinite(at) ? at : 0;
-};
-
-const byteSize = (sealed: Sealed) => sealed.data.byteLength + 64;
-
-// Decrypted message metadata per account, loaded on first use.
-const indexes = new Map<string, Promise<Map<string, CachedEmail>>>();
-
-/** The decrypted metadata of every cached message of an account, by emailKey. */
-export function emailIndex(account: string): Promise<Map<string, CachedEmail>> {
-  let index = indexes.get(account);
-  if (!index) {
-    index = (async () => {
-      const map = new Map<string, CachedEmail>();
-      const records = await idbGetAllByAccount<SealedRecord>('emails', account);
-      for (const record of records) {
-        try {
-          map.set(record.key, await openJson<CachedEmail>(record));
-        } catch {
-          // Sealed with a key that is gone: dropped at the next write.
-        }
-      }
-      return map;
-    })();
-    index.catch(() => indexes.delete(account));
-    indexes.set(account, index);
-  }
-  return index;
-}
-
-/** Forget what is held in memory (after a wipe). */
-export function forgetIndexes(account?: string): void {
-  if (account) indexes.delete(account);
-  else indexes.clear();
-}
-
-function splitBody(email: CachedEmail): { meta: CachedEmail; body: Record<string, unknown> | null } {
-  const meta: CachedEmail = { ...email };
-  let body: Record<string, unknown> | null = null;
-  for (const key of BODY_KEYS) {
-    if (key in meta) {
-      body ??= {};
-      body[key] = meta[key];
-      delete meta[key];
-    }
-  }
-  // Only a fetch with the text counts as the message's body.
-  return { meta, body: body && 'bodyValues' in body ? body : null };
-}
-
-/** Keep messages (as the server sent them, any properties) and their bodies when they came with one. */
-export async function putEmails(account: string, jmap: string, emails: CachedEmail[]): Promise<void> {
-  if (emails.length === 0) return;
-  const index = await emailIndex(account);
-  const ops: Array<{ store: StoreName; put?: unknown; del?: IDBValidKey }> = [];
-  for (const email of emails) {
-    if (!email || typeof email.id !== 'string') continue;
-    const key = emailKey(account, jmap, email.id);
-    const { meta, body } = splitBody(email);
-    const merged = { ...(index.get(key) ?? {}), ...meta } as CachedEmail;
-    // The attachments and inline images of the message: only these blobs are kept (blobsOf).
-    if (body && Array.isArray(body.attachments)) {
-      merged[BLOBS] = (body.attachments as Array<{ blobId?: unknown }>).map((a) => a.blobId).filter((id): id is string => typeof id === 'string');
-    }
-    index.set(key, merged);
-    const at = dateOf(merged);
-    const sealed = await sealJson(merged);
-    ops.push({ store: 'emails', put: { key, account, ...sealed } });
-    ops.push({ store: 'ledger', put: { key: ledgerKey('emails', key), account, store: 'emails', ref: key, at, bytes: byteSize(sealed), emailKey: key } satisfies LedgerEntry });
-    if (body) {
-      const sealedBody = await sealJson(body);
-      ops.push({ store: 'bodies', put: { key, account, ...sealedBody } });
-      ops.push({ store: 'ledger', put: { key: ledgerKey('bodies', key), account, store: 'bodies', ref: key, at, bytes: byteSize(sealedBody), emailKey: key } satisfies LedgerEntry });
-    }
-  }
-  await idbWrite(ops);
-}
-
-/** Apply a change made to messages (keywords, folders), here or on the server. */
-export async function patchEmails(account: string, jmap: string, patches: Record<string, Record<string, unknown>>): Promise<void> {
-  const index = await emailIndex(account);
-  const changed: CachedEmail[] = [];
-  for (const [id, patch] of Object.entries(patches)) {
-    const current = index.get(emailKey(account, jmap, id));
-    if (!current) continue;
-    changed.push(applyPatch(current, patch));
-  }
-  if (changed.length) await putEmails(account, jmap, changed);
-}
-
-/** A JMAP PatchObject (RFC 8620 §5.3) applied to a message, for the properties offline mode changes. */
-export function applyPatch(email: CachedEmail, patch: Record<string, unknown>): CachedEmail {
-  const next: CachedEmail = { ...email, keywords: { ...(email.keywords ?? {}) }, mailboxIds: { ...(email.mailboxIds ?? {}) } };
-  for (const [path, value] of Object.entries(patch)) {
-    const [prop, ...rest] = path.split('/');
-    if (rest.length === 0) {
-      (next as Record<string, unknown>)[prop] = value;
-      continue;
-    }
-    if (prop !== 'keywords' && prop !== 'mailboxIds') continue;
-    const name = rest.join('/').replace(/~1/g, '/').replace(/~0/g, '~');
-    const map = next[prop] as Record<string, boolean>;
-    if (value === null || value === false) delete map[name];
-    else map[name] = true;
-  }
-  return next;
-}
-
-export async function removeEmails(account: string, keys: string[]): Promise<void> {
-  if (keys.length === 0) return;
-  const index = await emailIndex(account);
-  const ops: Array<{ store: StoreName; del: IDBValidKey }> = [];
-  const gone = new Set(keys);
-  for (const key of keys) {
-    index.delete(key);
-    ops.push({ store: 'emails', del: key }, { store: 'bodies', del: key });
-    ops.push({ store: 'ledger', del: ledgerKey('emails', key) }, { store: 'ledger', del: ledgerKey('bodies', key) });
-  }
-  // Their attachments go with them.
-  for (const entry of await idbGetAllByAccount<LedgerEntry>('ledger', account)) {
-    if (entry.store === 'blobs' && entry.emailKey && gone.has(entry.emailKey)) {
-      ops.push({ store: 'blobs', del: entry.ref }, { store: 'ledger', del: entry.key });
-    }
-  }
-  await idbWrite(ops);
-}
-
-/** The kept message a blob (attachment, inline image) belongs to, with its date. */
-export async function messageOfBlob(account: string, jmap: string, blobId: string): Promise<{ key: string; at: number } | null> {
-  const index = await emailIndex(account);
-  const prefix = `${account}\u0001${jmap}\u0001`;
-  for (const [key, email] of index) {
-    if (!key.startsWith(prefix)) continue;
-    const blobs = email[BLOBS];
-    if (Array.isArray(blobs) && blobs.includes(blobId)) return { key, at: dateOf(email) };
-  }
-  return null;
-}
-
-/** A message's body parts, or null when only its list entry is kept. */
-export async function getBody(account: string, jmap: string, id: string): Promise<Record<string, unknown> | null> {
-  const record = await idbGet<SealedRecord>('bodies', emailKey(account, jmap, id));
-  if (!record) return null;
-  try {
-    return await openJson<Record<string, unknown>>(record);
-  } catch {
-    return null;
-  }
-}
-
-export async function hasBody(account: string, jmap: string, id: string): Promise<boolean> {
-  return (await idbGet<SealedRecord>('bodies', emailKey(account, jmap, id))) !== undefined;
-}
-
-export async function putBlob(account: string, jmap: string, blobId: string, blob: Blob, at: number, ofEmail?: string): Promise<void> {
-  const key = blobKey(account, jmap, blobId);
-  const sealed = await sealBytes(await blob.arrayBuffer());
-  // The media type too says something about the message: sealed as well.
-  const meta = await sealJson({ type: blob.type });
-  await idbWrite([
-    { store: 'blobs', put: { key, account, meta, ...sealed } },
-    { store: 'ledger', put: { key: ledgerKey('blobs', key), account, store: 'blobs', ref: key, at, bytes: byteSize(sealed), emailKey: ofEmail } satisfies LedgerEntry },
-  ]);
-}
-
-export async function getBlob(account: string, jmap: string, blobId: string): Promise<Blob | null> {
-  const record = await idbGet<SealedRecord & { meta?: Sealed }>('blobs', blobKey(account, jmap, blobId));
-  if (!record) return null;
-  try {
-    const meta = record.meta ? await openJson<{ type?: string }>(record.meta) : {};
-    return new Blob([await openBytes(record)], { type: meta.type || 'application/octet-stream' });
-  } catch {
-    return null;
-  }
-}
-
-export async function hasBlob(account: string, jmap: string, blobId: string): Promise<boolean> {
-  return (await idbGet<SealedRecord>('blobs', blobKey(account, jmap, blobId))) !== undefined;
-}
-
-/** Small named values of an account (session, folders, identities, opened folders). */
-export async function putMisc(account: string, name: string, value: unknown): Promise<void> {
-  const key = miscKey(account, name);
-  await idbWrite([{ store: 'misc', put: { key, account, ...(await sealJson(value)) } }]);
-}
-
-export async function getMisc<T>(account: string, name: string): Promise<T | null> {
-  const record = await idbGet<SealedRecord>('misc', miscKey(account, name));
-  if (!record) return null;
-  try {
-    return await openJson<T>(record);
-  } catch {
-    return null;
-  }
-}
-
-/** Bytes the cache uses on this device, and per account. */
-export async function cacheUsage(): Promise<{ total: number; byAccount: Record<string, number> }> {
-  const entries = await idbGetAll<LedgerEntry>('ledger');
-  const byAccount: Record<string, number> = {};
-  let total = 0;
-  for (const entry of entries) {
-    total += entry.bytes;
-    byAccount[entry.account] = (byAccount[entry.account] ?? 0) + entry.bytes;
-  }
-  return { total, byAccount };
-}
-
-/**
- * Keeps the cache under `cap`: the oldest messages go first, each with its
- * body and attachments. Returns the bytes freed.
- */
-export async function enforceCap(cap: number = CACHE_CAP_BYTES): Promise<number> {
-  const entries = await idbGetAll<LedgerEntry>('ledger');
-  let total = entries.reduce((sum, entry) => sum + entry.bytes, 0);
-  if (total <= cap) return 0;
-  // Group by message: a message and everything that belongs to it go together.
-  const groups = new Map<string, { at: number; bytes: number; account: string; entries: LedgerEntry[] }>();
-  for (const entry of entries) {
-    const id = entry.emailKey ?? entry.key;
-    const group = groups.get(id) ?? { at: entry.at, bytes: 0, account: entry.account, entries: [] };
-    group.at = Math.max(group.at, entry.at);
-    group.bytes += entry.bytes;
-    group.entries.push(entry);
-    groups.set(id, group);
-  }
-  const oldestFirst = [...groups.values()].sort((a, b) => a.at - b.at);
-  let freed = 0;
-  const ops: Array<{ store: StoreName; del: IDBValidKey }> = [];
-  for (const group of oldestFirst) {
-    if (total <= cap) break;
-    for (const entry of group.entries) {
-      ops.push({ store: entry.store, del: entry.ref }, { store: 'ledger', del: entry.key });
-      if (entry.store === 'emails') (await indexes.get(entry.account))?.delete(entry.ref);
-    }
-    total -= group.bytes;
-    freed += group.bytes;
-  }
-  await idbWrite(ops);
-  return freed;
-}
-
-/** Everything cached for one account (not its outbox). */
-export async function wipeAccountCache(account: string): Promise<void> {
-  forgetIndexes(account);
-  await idbDeleteAccount(account, ['emails', 'bodies', 'blobs', 'misc', 'ledger']);
-}
diff --git a/lib/offline/credentials-rejected.ts b/lib/offline/credentials-rejected.ts
new file mode 100644
index 000000000..a42282998
--- /dev/null
+++ b/lib/offline/credentials-rejected.ts
@@ -0,0 +1,26 @@
+/**
+ * The server really refused this login (`invalid_grant`), which the auth store
+ * follows with a sign-out that wipes the account's local data. An outage or any
+ * other refusal doesn't come here, and keeps the data. HOOK: lib/store/wipe
+ * registers here for what else a permanent rejection should do. Free of the
+ * stores, so the auth store can call it.
+ */
+
+type Listener = (accountId: string) => void;
+
+const listeners = new Set<Listener>();
+
+export function onCredentialsRejected(listener: Listener): () => void {
+  listeners.add(listener);
+  return () => listeners.delete(listener);
+}
+
+export function noteCredentialsRejected(accountId: string): void {
+  for (const listener of [...listeners]) {
+    try {
+      listener(accountId);
+    } catch {
+      // A sign-out must go on whatever a listener does.
+    }
+  }
+}
diff --git a/lib/offline/crypto.ts b/lib/offline/crypto.ts
deleted file mode 100644
index 13b53b01c..000000000
--- a/lib/offline/crypto.ts
+++ /dev/null
@@ -1,59 +0,0 @@
-/**
- * Encryption at rest for offline mode (#523): AES-GCM with a 256-bit key
- * the browser generates as non-extractable and keeps in the offline
- * database. Script on this origin can't read the key's bytes, only use it.
- *
- * What it protects against: someone who copies the browser profile's files
- * (a backup, a stolen disk image) without being able to run this site in
- * that profile. What it doesn't: someone using the unlocked browser profile,
- * or a script running on this origin, can decrypt everything. The docs say
- * so and recommend disk encryption.
- */
-
-import { idbGet, idbWrite } from './db';
-
-export interface Sealed {
-  iv: Uint8Array;
-  data: ArrayBuffer;
-}
-
-let keyPromise: Promise<CryptoKey> | null = null;
-
-async function loadOrCreateKey(): Promise<CryptoKey> {
-  const stored = await idbGet<{ id: string; key: CryptoKey }>('keys', 'aes');
-  if (stored?.key) return stored.key;
-  const key = await crypto.subtle.generateKey({ name: 'AES-GCM', length: 256 }, false, ['encrypt', 'decrypt']);
-  await idbWrite([{ store: 'keys', put: { id: 'aes', key } }]);
-  return key;
-}
-
-function deviceKey(): Promise<CryptoKey> {
-  if (!keyPromise) {
-    keyPromise = loadOrCreateKey();
-    keyPromise.catch(() => { keyPromise = null; });
-  }
-  return keyPromise;
-}
-
-/** Forget the key in memory (the database with it was deleted). */
-export function forgetDeviceKey(): void {
-  keyPromise = null;
-}
-
-export async function sealBytes(bytes: ArrayBuffer | Uint8Array): Promise<Sealed> {
-  const iv = crypto.getRandomValues(new Uint8Array(12));
-  const data = await crypto.subtle.encrypt({ name: 'AES-GCM', iv }, await deviceKey(), bytes as BufferSource);
-  return { iv, data };
-}
-
-export async function openBytes(sealed: Sealed): Promise<ArrayBuffer> {
-  return crypto.subtle.decrypt({ name: 'AES-GCM', iv: sealed.iv as BufferSource }, await deviceKey(), sealed.data);
-}
-
-export async function sealJson(value: unknown): Promise<Sealed> {
-  return sealBytes(new TextEncoder().encode(JSON.stringify(value)));
-}
-
-export async function openJson<T>(sealed: Sealed): Promise<T> {
-  return JSON.parse(new TextDecoder().decode(await openBytes(sealed))) as T;
-}
diff --git a/lib/offline/db.ts b/lib/offline/db.ts
deleted file mode 100644
index 066910a49..000000000
--- a/lib/offline/db.ts
+++ /dev/null
@@ -1,219 +0,0 @@
-/**
- * The IndexedDB database of offline mode (#523): one per browser profile,
- * deleted as a whole at a full sign-out (lib/sign-out-cleanup.ts) and when
- * the last account switches offline mode off.
- *
- * Stores (every value but the key and the ledger is encrypted, see crypto.ts):
- * - keys: the AES-GCM key, non-extractable.
- * - emails: message metadata (what the list shows), per account and JMAP account.
- * - bodies: the text of a message (bodyValues and the parts that say how to show it).
- * - blobs: attachments and inline images.
- * - misc: the session, folders, identities, the folders the user opened.
- * - ledger: size and date of each cached record, unencrypted, so the cache
- *   can be kept under its cap without decrypting everything.
- * - queue: changes and messages waiting for the network (never evicted).
- * - uploads: files attached while offline, until their message is sent.
- */
-
-export const OFFLINE_DB_NAME = 'bulwark-offline';
-const VERSION = 1;
-
-export const STORES = ['keys', 'emails', 'bodies', 'blobs', 'misc', 'ledger', 'queue', 'uploads'] as const;
-export type StoreName = (typeof STORES)[number];
-
-let dbPromise: Promise<IDBDatabase> | null = null;
-/**
- * Only switching offline mode on may create the database. Everything else
- * opens it only when it exists: another tab may have deleted it (offline
- * mode switched off, a sign-out), and opening it would create it anew.
- */
-let mayCreate = false;
-
-export function allowOfflineDbCreation(): void {
-  mayCreate = true;
-}
-
-async function offlineDbExists(): Promise<boolean> {
-  try {
-    if (typeof indexedDB.databases !== 'function') return true;
-    return (await indexedDB.databases()).some((d) => d.name === OFFLINE_DB_NAME);
-  } catch {
-    return true;
-  }
-}
-
-/** Thrown when the database was deleted (or never made) and may not be created here. */
-export class OfflineDbMissingError extends Error {
-  constructor() {
-    super('The offline database is not set up');
-    this.name = 'OfflineDbMissingError';
-  }
-}
-
-export function hasIndexedDb(): boolean {
-  try {
-    return typeof indexedDB !== 'undefined' && indexedDB !== null;
-  } catch {
-    return false;
-  }
-}
-
-export function openOfflineDb(): Promise<IDBDatabase> {
-  if (dbPromise) return dbPromise;
-  const opening = (async () => {
-    if (!mayCreate && !(await offlineDbExists())) throw new OfflineDbMissingError();
-    return openNow();
-  })();
-  dbPromise = opening;
-  opening.catch(() => {
-    if (dbPromise === opening) dbPromise = null;
-  });
-  return opening;
-}
-
-function openNow(): Promise<IDBDatabase> {
-  return new Promise<IDBDatabase>((resolve, reject) => {
-    const request = indexedDB.open(OFFLINE_DB_NAME, VERSION);
-    request.onupgradeneeded = () => {
-      const db = request.result;
-      for (const name of STORES) {
-        if (db.objectStoreNames.contains(name)) continue;
-        if (name === 'queue') {
-          db.createObjectStore(name, { keyPath: 'id', autoIncrement: true }).createIndex('account', 'account');
-        } else if (name === 'keys') {
-          db.createObjectStore(name, { keyPath: 'id' });
-        } else {
-          db.createObjectStore(name, { keyPath: 'key' }).createIndex('account', 'account');
-        }
-      }
-    };
-    request.onsuccess = () => {
-      const db = request.result;
-      // A sign-out in this or another tab deletes the database: let it.
-      db.onversionchange = () => {
-        db.close();
-        dbPromise = null;
-        mayCreate = false;
-      };
-      db.onclose = () => {
-        dbPromise = null;
-      };
-      resolve(db);
-    };
-    request.onerror = () => reject(request.error);
-    request.onblocked = () => reject(new Error('offline database blocked'));
-  });
-}
-
-function done(tx: IDBTransaction): Promise<void> {
-  return new Promise((resolve, reject) => {
-    tx.oncomplete = () => resolve();
-    tx.onerror = () => reject(tx.error);
-    tx.onabort = () => reject(tx.error ?? new Error('transaction aborted'));
-  });
-}
-
-function result<T>(request: IDBRequest<T>): Promise<T> {
-  return new Promise((resolve, reject) => {
-    request.onsuccess = () => resolve(request.result);
-    request.onerror = () => reject(request.error);
-  });
-}
-
-export async function idbGet<T>(store: StoreName, key: IDBValidKey): Promise<T | undefined> {
-  const db = await openOfflineDb();
-  return result(db.transaction(store, 'readonly').objectStore(store).get(key)) as Promise<T | undefined>;
-}
-
-export async function idbGetAllByAccount<T>(store: StoreName, account: string): Promise<T[]> {
-  const db = await openOfflineDb();
-  return result(db.transaction(store, 'readonly').objectStore(store).index('account').getAll(account)) as Promise<T[]>;
-}
-
-export async function idbGetAll<T>(store: StoreName): Promise<T[]> {
-  const db = await openOfflineDb();
-  return result(db.transaction(store, 'readonly').objectStore(store).getAll()) as Promise<T[]>;
-}
-
-/** Writes and deletes in several stores at once. */
-export async function idbWrite(ops: Array<{ store: StoreName; put?: unknown; del?: IDBValidKey }>): Promise<void> {
-  if (ops.length === 0) return;
-  const db = await openOfflineDb();
-  const names = [...new Set(ops.map((op) => op.store))];
-  const tx = db.transaction(names, 'readwrite');
-  for (const op of ops) {
-    const store = tx.objectStore(op.store);
-    if (op.put !== undefined) store.put(op.put);
-    else if (op.del !== undefined) store.delete(op.del);
-  }
-  await done(tx);
-}
-
-/**
- * Reads a record and writes what `change` makes of it in one transaction;
- * `change` returns undefined to leave it. True when it wrote.
- */
-export async function idbUpdate<T>(store: StoreName, key: IDBValidKey, change: (value: T | undefined) => T | undefined): Promise<boolean> {
-  const db = await openOfflineDb();
-  const tx = db.transaction(store, 'readwrite');
-  const objects = tx.objectStore(store);
-  let wrote = false;
-  const read = objects.get(key);
-  read.onsuccess = () => {
-    const next = change(read.result as T | undefined);
-    if (next !== undefined) {
-      objects.put(next);
-      wrote = true;
-    }
-  };
-  await done(tx);
-  return wrote;
-}
-
-export async function idbAdd(store: StoreName, value: unknown): Promise<IDBValidKey> {
-  const db = await openOfflineDb();
-  const tx = db.transaction(store, 'readwrite');
-  const key = result(tx.objectStore(store).add(value));
-  await done(tx);
-  return key;
-}
-
-/** Deletes every record of one account in the given stores. */
-export async function idbDeleteAccount(account: string, stores: readonly StoreName[]): Promise<void> {
-  const db = await openOfflineDb();
-  const tx = db.transaction([...stores], 'readwrite');
-  for (const name of stores) {
-    const index = tx.objectStore(name).index('account');
-    const request = index.openKeyCursor(IDBKeyRange.only(account));
-    request.onsuccess = () => {
-      const cursor = request.result;
-      if (!cursor) return;
-      tx.objectStore(name).delete(cursor.primaryKey);
-      cursor.continue();
-    };
-  }
-  await done(tx);
-}
-
-/** Deletes the whole database (sign-out, offline mode off everywhere). */
-export async function deleteOfflineDb(): Promise<void> {
-  if (!hasIndexedDb()) return;
-  mayCreate = false;
-  const open = dbPromise;
-  dbPromise = null;
-  try {
-    (await open)?.close();
-  } catch {
-    /* it never opened */
-  }
-  await new Promise<void>((resolve) => {
-    try {
-      const request = indexedDB.deleteDatabase(OFFLINE_DB_NAME);
-      request.onsuccess = () => resolve();
-      request.onerror = () => resolve();
-      request.onblocked = () => resolve();
-    } catch {
-      resolve();
-    }
-  });
-}
diff --git a/lib/offline/flush.ts b/lib/offline/flush.ts
index 347c0998d..3aa05b411 100644
--- a/lib/offline/flush.ts
+++ b/lib/offline/flush.ts
@@ -1,22 +1,25 @@
 /**
  * Sends what waited on this device (#523), once the server answers again:
- * first the changes (read, flagged, tags, moves) in the order they were
- * made, then the outbox, oldest first.
+ * changes (read, flagged, tags, moves, deletes) and messages, in the order
+ * they were made.
  *
  * - One tab at a time per account (Web Locks), and each message is taken
- *   for sending in one database transaction (claimForSending), so two tabs
- *   never send it twice.
- * - Changes and messages go in the order they were made.
- * - A change the server refuses (the message is gone, moved elsewhere) is
- *   dropped: the server's state wins.
+ *   for sending in one transaction (claimForSending), so two tabs never send
+ *   it twice.
+ * - A change the server refuses, or that meets a record changed since, goes
+ *   to the user as a conflict (lib/store/outbox/flush-patches.ts).
  * - A message is sent as it was finished at Send (queue.ts); files attached
  *   offline are uploaded first. A hold for undo-send that has passed is
  *   dropped, so the message goes at once.
- * - Only a failure before the submission request (SendNotStartedError, a
- *   file upload on a dead network) puts a message back to waiting. A send
- *   whose connection broke after that is marked uncertain and never sent
- *   again by itself: it may have gone out. A refusal by the server is marked
- *   failed, with the reason.
+ * - A failure before the submission request (SendNotStartedError, a file
+ *   upload on a dead network), a rate limit, a login that needs renewing and
+ *   trouble with this device's store put a message back to waiting. A send whose
+ *   connection broke, or that got a 5xx, is marked uncertain. A refusal by the
+ *   server is marked failed, with the reason.
+ * - An uncertain message is looked up when the server is back, by the
+ *   Message-ID fixed when it was queued (lib/store/outbox/dedupe.ts): it's
+ *   done, its copy gets submitted, or it goes again. Only when the lookup
+ *   can't tell does it stay uncertain, for the user to decide.
  * - A message taken for sending by a tab that was closed on the way is
  *   uncertain after a minute.
  * - A message finished under rules the organisation has since made stricter
@@ -26,17 +29,22 @@
 import type { JMAPClient } from '@/lib/jmap/client';
 import { isNetworkFailure } from '@/lib/jmap/offline-hooks';
 import type { SendEmailResult } from '@/lib/jmap/types';
+import { getStore } from '@/lib/store/client/api';
+import { isStorageFailure } from '@/lib/store/storage';
+import type { MethodCall } from '@/lib/store/engine/transport';
+import { decideRetry, type LookupIo, type RetryDecision } from '@/lib/store/outbox/dedupe';
+import { flushPatches, type PatchIo, type PatchOutcome, type PendingPatch } from '@/lib/store/outbox/flush-patches';
 import {
   claimForSending,
   heldFile,
   isLocalBlobId,
   readQueue,
   removeOutboxEntry,
-  removeQueued,
   updateOutboxEntry,
   type OutboxEntry,
   type OutboxError,
 } from './queue';
+import { visibleAccounts } from './state';
 import type { OfflineNotice } from './offline-mode';
 
 export interface FlushDeps {
@@ -46,8 +54,13 @@ export interface FlushDeps {
   stricterNow?: (entry: OutboxEntry) => boolean;
   /** A held send went out (an undo window still open). */
   onScheduled?: (entry: OutboxEntry, result: SendEmailResult) => void;
+  /** A send's connection broke though the server may be fine: look it up again soon. */
+  retryLater?: () => void;
 }
 
+/** A message that just went may not show in a lookup yet, which would send it twice. */
+export const LOOKUP_WAIT_MS = 30_000;
+
 /** A send is taken for at most this long before a closed tab's send counts as uncertain. */
 export const SENDING_STALE_MS = 60_000;
 
@@ -64,6 +77,23 @@ class OutboxPrepError extends Error {
   }
 }
 
+/**
+ * Not the server's word about this message: it's rate limiting, the login needs
+ * renewing, or this device's store is in the way. The next try goes as usual.
+ */
+function waitsForNextTry(error: unknown): boolean {
+  if (!(error instanceof Error)) return false;
+  if (error.name === 'RateLimitError' || error.name === 'StoreOwnerGoneError' || error.name === 'StoreKeyError') return true;
+  if (isStorageFailure(error)) return true;
+  return /^Request failed: (401|408|429)\b/.test(error.message);
+}
+
+/** A server error can come after the message went through: looked up before it goes again. */
+function mayHaveArrived(error: unknown): boolean {
+  if (isNetworkFailure(error)) return true;
+  return error instanceof Error && (error.name === 'SendUnconfirmedError' || /^Request failed: 5\d\d\b/.test(error.message));
+}
+
 function notStartedError(message: string): Error {
   return Object.assign(new Error(message), { name: 'SendNotStartedError' });
 }
@@ -81,12 +111,16 @@ function notStarted(error: unknown): boolean {
 async function uploadHeld(account: string, client: JMAPClient, blobId: string): Promise<string> {
   const file = await heldFile(account, blobId);
   if (!file) throw new OutboxPrepError('file_missing');
+  let uploaded: string;
   try {
-    return (await client.uploadBlob(file)).blobId;
+    uploaded = (await client.uploadBlob(file)).blobId;
   } catch (error) {
     if (isNetworkFailure(error)) throw notStartedError('upload failed');
     throw error;
   }
+  // The server went away just now, and offline mode held the file again.
+  if (isLocalBlobId(uploaded)) throw notStartedError('upload held');
+  return uploaded;
 }
 
 async function sendEntry(account: string, client: JMAPClient, entry: OutboxEntry): Promise<SendEmailResult> {
@@ -95,7 +129,7 @@ async function sendEntry(account: string, client: JMAPClient, entry: OutboxEntry
     const file = await heldFile(account, item.blobId);
     if (!file) throw new OutboxPrepError('file_missing');
     const delayed = item.delayedUntil && Date.parse(item.delayedUntil) - Date.now() > MIN_HOLD_MS ? item.delayedUntil : undefined;
-    if (item.submitOnly) return client.submitRawEmail(file, item.identityId, delayed, item.envelopeRecipients);
+    if (item.submitOnly) return client.submitRawEmail(file, item.identityId, delayed, item.envelopeRecipients, entry.copyId);
     let mailboxes;
     try {
       mailboxes = await client.getMailboxes();
@@ -106,11 +140,12 @@ async function sendEntry(account: string, client: JMAPClient, entry: OutboxEntry
     const sent = mailboxes.find((m) => m.role === 'sent');
     if (!sent) throw new OutboxPrepError('no_sent_mailbox');
     const drafts = mailboxes.find((m) => m.role === 'drafts');
-    return client.sendRawEmail(file, item.identityId, sent.id, drafts?.id, delayed, item.envelopeRecipients);
+    return client.sendRawEmail(file, item.identityId, sent.id, drafts?.id, delayed, item.envelopeRecipients, entry.copyId);
   }
   const args = [...item.args];
   const attachments = args[10];
-  if (Array.isArray(attachments)) {
+  // A copy on the server has its files already.
+  if (Array.isArray(attachments) && !entry.copyId) {
     const resolved = [];
     for (const attachment of attachments as Array<{ blobId: string }>) {
       resolved.push(isLocalBlobId(attachment.blobId) ? { ...attachment, blobId: await uploadHeld(account, client, attachment.blobId) } : attachment);
@@ -119,6 +154,13 @@ async function sendEntry(account: string, client: JMAPClient, entry: OutboxEntry
   }
   const delayedUntil = args[13] as string | undefined;
   if (delayedUntil && Date.parse(delayedUntil) - Date.now() <= MIN_HOLD_MS) args[13] = undefined;
+  if (entry.messageId || entry.copyId) {
+    args[15] = {
+      ...((args[15] as Record<string, unknown> | undefined) ?? {}),
+      ...(entry.messageId ? { messageId: entry.messageId } : {}),
+      ...(entry.copyId ? { existingCopyId: entry.copyId } : {}),
+    };
+  }
   const send = client.sendEmail.bind(client) as (...a: unknown[]) => Promise<SendEmailResult>;
   return send(...args);
 }
@@ -134,14 +176,106 @@ export async function flushQueue(account: string, client: JMAPClient, deps: Flus
   await run();
 }
 
+/** A file attached offline to something that was then discarded goes after this long. */
+export const ORPHAN_FILE_AGE_MS = 7 * 24 * 60 * 60 * 1000;
+const ORPHAN_CHECK_MS = 24 * 60 * 60 * 1000;
+const orphansCheckedAt = new Map<string, number>();
+
+async function dropOrphanFiles(account: string): Promise<void> {
+  const now = Date.now();
+  if (now - (orphansCheckedAt.get(account) ?? 0) < ORPHAN_CHECK_MS) return;
+  orphansCheckedAt.set(account, now);
+  await getStore().area(account, 'outbox.dropOrphans', { olderThan: now - ORPHAN_FILE_AGE_MS }).catch(() => {});
+}
+
+/** Tests only. */
+export function forgetOrphanCheck(): void {
+  orphansCheckedAt.clear();
+}
+
 /** Marks sends of closed tabs uncertain (they may have gone out). */
 export async function settleStaleSends(account?: string, now = Date.now()): Promise<void> {
+  const accounts = account ? [account] : visibleAccounts();
+  // One account's store in trouble doesn't hold up another's.
+  await Promise.allSettled(accounts.map((id) => getStore().area(id, 'outbox.settleStale', { before: now - SENDING_STALE_MS })));
+}
+
+/** The changes queued before `upToSeq` (all, with null). False when the run stopped on an outage. */
+async function sendPatches(account: string, client: JMAPClient, deps: FlushDeps, upToSeq: number | null): Promise<boolean> {
+  const pending = await getStore().area<PendingPatch[]>(account, 'outbox.pendingPatches', { upToSeq });
+  if (pending.length === 0) return true;
+  const io: PatchIo = {
+    request: (calls: MethodCall[], using: string[]) => client.requestNetworkOnly(calls, using),
+  };
+  return flushPatches(io, pending, async (outcomes: PatchOutcome[]) => {
+    const conflicts = await getStore().area<number>(account, 'outbox.patchResults', { outcomes });
+    if (conflicts > 0) deps.notify({ kind: 'conflict', count: conflicts });
+  });
+}
+
+async function lookUp(client: JMAPClient, entry: OutboxEntry): Promise<RetryDecision> {
+  const io: LookupIo = { request: (calls, using) => client.requestNetworkOnly(calls, using) };
+  const fromEmail = entry.item.kind === 'email' ? entry.item.args[6] as string | undefined : undefined;
+  const jmap = await client.resolveSendAccountId(fromEmail);
+  const options = entry.item.kind === 'email' ? entry.item.args[15] as { noSentCopy?: boolean } | undefined : undefined;
+  return decideRetry(io, {
+    jmap,
+    submissionJmap: client.submissionAccountFor(jmap),
+    messageId: entry.messageId,
+    attemptAt: entry.firstAttemptAt ?? entry.createdAt,
+    now: Date.now(),
+    copyKept: entry.item.kind === 'raw' ? !entry.item.submitOnly : !options?.noSentCopy,
+  });
+}
+
+/** The draft the send was meant to replace: the lost response left it behind. Best effort. */
+async function dropOldDraft(client: JMAPClient, entry: OutboxEntry): Promise<void> {
+  if (entry.item.kind !== 'email' || typeof entry.item.args[7] !== 'string') return;
+  const options = entry.item.args[15] as { draftAccountId?: string } | undefined;
+  try {
+    await client.requestNetworkOnly([['Email/set', { accountId: options?.draftAccountId || client.getAccountId(), destroy: [entry.item.args[7]] }, '0']]);
+  } catch {
+    // An orphan in Drafts, nothing worse.
+  }
+}
+
+/** Uncertain messages, looked up now that the server answers. False when the run stopped on an outage. */
+async function settleUncertain(account: string, client: JMAPClient, deps: FlushDeps): Promise<boolean> {
   const { outbox } = await readQueue(account);
   for (const entry of outbox) {
-    if (entry.status === 'sending' && (entry.sendingSince ?? 0) < now - SENDING_STALE_MS) {
-      await updateOutboxEntry(entry, { status: 'uncertain' });
+    if (entry.status !== 'uncertain') continue;
+    if (stillOffline() || !deps.allowed()) return false;
+    if (entry.lastAttemptAt && Date.now() - entry.lastAttemptAt < LOOKUP_WAIT_MS) {
+      deps.retryLater?.();
+      continue;
+    }
+    let decision: RetryDecision;
+    try {
+      decision = await lookUp(client, entry);
+    } catch (error) {
+      // The lookup failed: it stays uncertain, for this time.
+      if (isNetworkFailure(error)) return false;
+      continue;
+    }
+    switch (decision.action) {
+      case 'done':
+        await removeOutboxEntry(entry);
+        await dropOldDraft(client, entry);
+        void client.pruneEmailSubmissions();
+        // A canceled one wasn't sent: someone decided that, and it's in Drafts.
+        if (decision.why !== 'canceled') deps.notify({ kind: 'sent', subject: entry.summary.subject });
+        break;
+      case 'submit':
+        await updateOutboxEntry(entry, { status: 'waiting', copyId: decision.emailId });
+        break;
+      case 'send':
+        await updateOutboxEntry(entry, { status: 'waiting', copyId: null });
+        break;
+      case 'undecided':
+        break;
     }
   }
+  return true;
 }
 
 async function flushLocked(account: string, client: JMAPClient, deps: FlushDeps): Promise<void> {
@@ -149,36 +283,21 @@ async function flushLocked(account: string, client: JMAPClient, deps: FlushDeps)
   flushing.add(account);
   try {
     await settleStaleSends(account);
-    const { patches, outbox } = await readQueue(account);
+    if (!(await settleUncertain(account, client, deps))) return;
     // In the order they were made: a reply's $answered, queued after the
     // reply, goes after it.
-    const items = [
-      ...patches.map((patch) => ({ id: patch.id, patch })),
-      ...outbox.map((entry) => ({ id: entry.id, entry })),
-    ].sort((x, y) => x.id - y.id);
-
-    for (const item of items) {
-      if ('patch' in item && item.patch) {
-        if (stillOffline()) return;
-        try {
-          await client.applyEmailPatches(item.patch.item.jmap, item.patch.item.update);
-        } catch (error) {
-          // Still no server: try again later. Anything else: the server's state wins.
-          if (isNetworkFailure(error)) return;
-        }
-        await removeQueued([item.patch.id]);
-        continue;
-      }
-      const entry = (item as { entry: OutboxEntry }).entry;
+    const { outbox } = await readQueue(account);
+    for (const entry of outbox) {
       if (entry.status !== 'waiting') continue;
       if (stillOffline() || !deps.allowed()) return;
+      if (!(await sendPatches(account, client, deps, entry.seq))) return;
       if (deps.stricterNow?.(entry)) {
         await updateOutboxEntry(entry, { status: 'held' });
         deps.notify({ kind: 'held', subject: entry.summary.subject });
         continue;
       }
       // Another tab took it, or it was deleted meanwhile.
-      if (!(await claimForSending(entry.id))) continue;
+      if (!(await claimForSending(account, entry.id))) continue;
       let result: SendEmailResult;
       try {
         result = await sendEntry(account, client, entry);
@@ -190,17 +309,24 @@ async function flushLocked(account: string, client: JMAPClient, deps: FlushDeps)
         }
         if (error instanceof Error && error.name === 'OutboxPrepError') {
           const code = (error as OutboxPrepError).code;
-          await updateOutboxEntry(entry, { status: 'failed', error: { code } });
+          await updateOutboxEntry(entry, { status: 'failed', error: { code }, copyId: null });
           deps.notify({ kind: 'send-failed', subject: entry.summary.subject, error: { code } });
           continue;
         }
-        if (isNetworkFailure(error) || (error instanceof Error && (error.name === 'RequestTimeoutError' || error.name === 'SendUnconfirmedError'))) {
-          // It may have reached the server: never sent again by itself.
+        if (waitsForNextTry(error)) {
+          // Nothing the user can do about it, and the copy on the server stays useful.
+          await updateOutboxEntry(entry, { status: 'waiting' });
+          deps.retryLater?.();
+          return;
+        }
+        if (mayHaveArrived(error)) {
           await updateOutboxEntry(entry, { status: 'uncertain' });
+          deps.retryLater?.();
           return;
         }
         const text = error instanceof Error ? error.message : String(error);
-        await updateOutboxEntry(entry, { status: 'failed', error: { text } });
+        // The client took back the copy of a refused send.
+        await updateOutboxEntry(entry, { status: 'failed', error: { text }, copyId: null });
         deps.notify({ kind: 'send-failed', subject: entry.summary.subject, error: { text } });
         continue;
       }
@@ -209,21 +335,22 @@ async function flushLocked(account: string, client: JMAPClient, deps: FlushDeps)
       if (result.scheduled) deps.onScheduled?.(entry, result);
       deps.notify({ kind: 'sent', subject: entry.summary.subject });
     }
+    if (stillOffline() || !deps.allowed()) return;
+    await sendPatches(account, client, deps, null);
+    await dropOrphanFiles(account);
   } finally {
     flushing.delete(account);
   }
 }
 
 /** "Send again" for a failed or uncertain message (a held one waits for its rules). */
-export async function retryOutboxEntry(id: number): Promise<void> {
-  const { outbox } = await readQueue();
+export async function retryOutboxEntry(account: string, id: number): Promise<void> {
+  const { outbox } = await readQueue(account);
   const entry = outbox.find((e) => e.id === id);
   if (entry && (entry.status === 'failed' || entry.status === 'uncertain')) await updateOutboxEntry(entry, { status: 'waiting' });
 }
 
 /** "Delete" in the outbox. */
-export async function deleteOutboxEntry(id: number): Promise<void> {
-  const { outbox } = await readQueue();
-  const entry = outbox.find((e) => e.id === id);
-  if (entry) await removeOutboxEntry(entry);
+export async function deleteOutboxEntry(account: string, id: number): Promise<void> {
+  await removeOutboxEntry({ account, id });
 }
diff --git a/lib/offline/migrate-legacy.ts b/lib/offline/migrate-legacy.ts
new file mode 100644
index 000000000..12877bc98
--- /dev/null
+++ b/lib/offline/migrate-legacy.ts
@@ -0,0 +1,211 @@
+/**
+ * One time, on the first start after the update: what can't be fetched again
+ * moves from the old IndexedDB `bulwark-offline` into the local store. That's
+ * the outbox, the changes that wait, the files they hold and the session kept
+ * for a start without the server. The mail itself syncs again.
+ *
+ * The old database holds its own key, so it goes only after the store has
+ * committed every account. A move that fails leaves it in place and the next
+ * start tries again; the store takes each account's part only once.
+ */
+
+import { generateMessageId } from '@/lib/jmap/client';
+import { getStore } from '@/lib/store/client/api';
+import type { StoreSession } from '@/lib/store/engine/transport';
+import type { LegacyImport } from '@/lib/store/outbox/calls';
+import type { OutboxError, OutboxStatus, OutboxSummary, PolicyFingerprint, SendItem } from '@/lib/store/outbox/items';
+import { useOfflineStore } from './state';
+
+export const LEGACY_DB_NAME = 'bulwark-offline';
+
+interface Sealed {
+  iv: Uint8Array;
+  data: ArrayBuffer;
+}
+
+interface QueueRecord extends Sealed {
+  id: number;
+  account: string;
+  kind: 'patch' | 'send';
+  createdAt: number;
+  status?: string;
+}
+
+interface UploadRecord extends Sealed {
+  key: string;
+  account: string;
+  meta: Sealed;
+}
+
+interface SendPayload {
+  summary: OutboxSummary;
+  item: SendItem;
+  fingerprint?: PolicyFingerprint;
+  error?: OutboxError;
+}
+
+function result<T>(request: IDBRequest<T>): Promise<T> {
+  return new Promise((resolve, reject) => {
+    request.onsuccess = () => resolve(request.result);
+    request.onerror = () => reject(request.error);
+  });
+}
+
+/** Opens the old database only if it exists: opening it must never create it. */
+function openLegacy(): Promise<IDBDatabase | null> {
+  return new Promise((resolve, reject) => {
+    const request = indexedDB.open(LEGACY_DB_NAME);
+    let creating = false;
+    request.onupgradeneeded = () => {
+      creating = true;
+      request.transaction?.abort();
+    };
+    request.onsuccess = () => resolve(request.result);
+    request.onerror = () => {
+      if (creating) resolve(null);
+      else reject(request.error);
+    };
+    request.onblocked = () => resolve(null);
+  });
+}
+
+function deleteLegacy(): Promise<void> {
+  return new Promise((resolve) => {
+    const request = indexedDB.deleteDatabase(LEGACY_DB_NAME);
+    request.onsuccess = () => resolve();
+    request.onerror = () => resolve();
+    // An old tab still has it open: it goes when that tab does.
+    request.onblocked = () => resolve();
+  });
+}
+
+function storeNamesHold(db: IDBDatabase, ...names: string[]): boolean {
+  return names.every((name) => db.objectStoreNames.contains(name));
+}
+
+async function open(key: CryptoKey, sealed: Sealed): Promise<ArrayBuffer> {
+  return crypto.subtle.decrypt({ name: 'AES-GCM', iv: sealed.iv as BufferSource }, key, sealed.data);
+}
+
+async function openJson<T>(key: CryptoKey, sealed: Sealed): Promise<T> {
+  return JSON.parse(new TextDecoder().decode(await open(key, sealed))) as T;
+}
+
+/** The Message-ID of a finished raw message, from its head. */
+function rawMessageId(bytes: Uint8Array): string | undefined {
+  const head = new TextDecoder().decode(bytes.subarray(0, 64 * 1024));
+  const end = head.search(/\r?\n\r?\n/);
+  const block = (end >= 0 ? head.slice(0, end) : head).replace(/\r?\n[ \t]+/g, ' ');
+  return block.match(/^message-id:\s*<([^>\s]+)>/im)?.[1];
+}
+
+interface AccountPart extends LegacyImport {
+  session: StoreSession | null;
+}
+
+async function readAccount(db: IDBDatabase, key: CryptoKey | null, account: string): Promise<AccountPart> {
+  const part: AccountPart = { entries: [], patches: [], files: [], session: null };
+  if (!key) return part;
+  const stores = db.transaction(['queue', 'uploads', 'misc'], 'readonly');
+  const [queue, uploads, session] = await Promise.all([
+    result(stores.objectStore('queue').index('account').getAll(account)) as Promise<QueueRecord[]>,
+    result(stores.objectStore('uploads').index('account').getAll(account)) as Promise<UploadRecord[]>,
+    result(stores.objectStore('misc').get(`${account}\u0001misc\u0001session`)) as Promise<Sealed | undefined>,
+  ]);
+  if (session) part.session = await openJson<StoreSession>(key, session).catch(() => null);
+
+  const rawIds = new Map<string, string | undefined>();
+  for (const record of uploads) {
+    // Sealed with a key that is gone, as the old code skipped it.
+    try {
+      const meta = await openJson<{ name?: string; type?: string }>(key, record.meta);
+      const data = new Uint8Array(await open(key, record));
+      const blobId = record.key.split('\u0001')[1];
+      part.files.push({ blobId, name: meta.name || 'attachment', type: meta.type || 'application/octet-stream', data });
+      rawIds.set(blobId, rawMessageId(data));
+    } catch {
+      continue;
+    }
+  }
+
+  // In the order they were made.
+  for (const record of [...queue].sort((a, b) => a.id - b.id)) {
+    try {
+      if (record.kind === 'patch') {
+        const item = await openJson<{ jmap: string; update: Record<string, Record<string, unknown>> }>(key, record);
+        part.patches.push({ jmap: item.jmap, update: item.update });
+        continue;
+      }
+      const payload = await openJson<SendPayload>(key, record);
+      // Sent by a tab that's gone: it may have left, so it's looked up or asked about.
+      const status = (record.status === 'sending' ? 'uncertain' : record.status ?? 'waiting') as OutboxStatus;
+      const item = payload.item;
+      let messageId: string | undefined;
+      if (item.kind === 'raw') messageId = rawIds.get(item.blobId);
+      // Not sent yet: it can still get a fixed id. One that left under the old
+      // code had another id, which nothing here knows.
+      // Only its domain is used, and the sender may be written "Name <address>".
+      else if (status === 'waiting' && typeof item.args[6] === 'string') messageId = generateMessageId(item.args[6].replace(/>.*$/, ''));
+      part.entries.push({
+        summary: payload.summary,
+        item,
+        fingerprint: payload.fingerprint,
+        error: payload.error,
+        status,
+        createdAt: record.createdAt,
+        messageId,
+      });
+    } catch {
+      continue;
+    }
+  }
+  return part;
+}
+
+let moving: Promise<void> | null = null;
+
+async function moveNow(): Promise<void> {
+  if (typeof indexedDB === 'undefined') return;
+  const db = await openLegacy();
+  if (!db) return;
+  try {
+    if (!storeNamesHold(db, 'keys', 'queue', 'uploads', 'misc')) return;
+    const keyRecord = await result(db.transaction('keys', 'readonly').objectStore('keys').get('aes')) as { key: CryptoKey } | undefined;
+    const key = keyRecord?.key ?? null;
+    for (const account of useOfflineStore.getState().enabled) {
+      const part = await readAccount(db, key, account);
+      const { session, ...content } = part;
+      if (session) await getStore().ensureOpen(account, session);
+      if (content.entries.length + content.patches.length + content.files.length === 0) continue;
+      await getStore().area(account, 'outbox.importLegacy', content);
+    }
+  } finally {
+    db.close();
+  }
+  await deleteLegacy();
+}
+
+/** Runs the move once per page. A failure is kept for nobody to see: the old database stays and the next start tries again. */
+export function moveLegacyOutbox(): Promise<void> {
+  moving ??= moveNow().catch(() => {});
+  return moving;
+}
+
+/** Messages an earlier version left in its database. For a browser the store can't run in, which can't move them. */
+export async function strandedLegacyMessages(): Promise<number> {
+  if (typeof indexedDB === 'undefined') return 0;
+  const db = await openLegacy().catch(() => null);
+  if (!db) return 0;
+  try {
+    if (!storeNamesHold(db, 'queue')) return 0;
+    const records = await result(db.transaction('queue', 'readonly').objectStore('queue').getAll()) as Array<{ kind?: string }>;
+    return records.filter((record) => record.kind !== 'patch').length;
+  } finally {
+    db.close();
+  }
+}
+
+/** Tests only: forget that this page already ran it. */
+export function forgetLegacyMove(): void {
+  moving = null;
+}
diff --git a/lib/offline/offline-mode.ts b/lib/offline/offline-mode.ts
index 356bf131c..836e1286b 100644
--- a/lib/offline/offline-mode.ts
+++ b/lib/offline/offline-mode.ts
@@ -4,19 +4,22 @@
  * - Opt-in per account and per browser (state.ts), off by default, hidden
  *   and wiped when the organisation forbids it (policy.json
  *   `organisation.devices.noOffline`, per account) and in Lite.
- * - While on, the JMAP client hands every answer of the mail server to the
- *   cache (cache.ts) and asks this device when the network is gone
- *   (responder.ts); a background sync keeps the last 30 days of the Inbox
- *   and of the folders the user opened, with bodies and attachments, under
- *   a cap (sync.ts).
- * - Changes and sends made offline wait in the queue (queue.ts) and go out
- *   in order once the server answers again and the organisation's policy
- *   was fetched afresh (flush.ts).
- * - Everything is wiped at a full sign-out and the automatic sign-outs
- *   (lib/sign-out-cleanup.ts deletes the database), for one account when it
- *   signs out or switches offline mode off, and when the organisation
- *   forbids it (checked on every policy fetch). Unsent messages a sign-out
- *   deletes without the user's word are named (lost.ts).
+ * - While on, the local store (lib/store, a database in a worker) keeps the
+ *   account's mail in sync by itself, and the JMAP client asks it when the
+ *   network is gone. This file is the orchestration around it: who may use
+ *   it, when it syncs and flushes, the wipes.
+ * - Changes and sends made offline wait in the store's outbox and go out in
+ *   order once the server answers again and the organisation's policy was
+ *   fetched afresh (flush.ts).
+ * - Everything is wiped at a full sign-out, at the session limits and when the
+ *   server really refuses the login (`invalid_grant`), by
+ *   lib/sign-out-cleanup.ts; for one account when it signs out, is removed or
+ *   switches offline mode off, and when the organisation forbids it (checked on
+ *   every policy fetch). An account the app drops by itself because it couldn't
+ *   confirm the login (an outage, an unknown refusal, a session cookie that ran
+ *   out) keeps its data for 30 days or the next sign-in, hidden from everyone
+ *   else. Unsent messages a sign-out deletes without the user's word are named
+ *   (lost.ts).
  */
 
 import { IS_LITE } from '@/lib/lite';
@@ -25,52 +28,36 @@ import { devicesForAccount } from '@/lib/device-policy';
 import { accountSubjectPending, useAccountSubjects } from '@/lib/org/account-subjects';
 import { labelsPolicyFor } from '@/lib/outgoing/classification';
 import { getSendGuardSource, guardState, guardsSending } from '@/lib/plugin-send-guards';
-import { useAccountStore } from '@/stores/account-store';
+import { emitPushStateChange } from '@/lib/push-events';
+import { requestOutboxSync } from '@/lib/pwa-notify/outbox-sync';
+import { STORAGE_ERROR_AREA } from '@/lib/store/area';
+import { configureStore, getStore, type StorePageHooks } from '@/lib/store/client/api';
+import { purgeStoreFiles } from '@/lib/store/client/purge';
+import type { StoreSession } from '@/lib/store/engine/transport';
+import { onAccountRemoved, useAccountStore } from '@/stores/account-store';
 import { useAuthStore } from '@/stores/auth-store';
 import { useEmailStore } from '@/stores/email-store';
 import { usePolicyStore, whenPolicySettled } from '@/stores/policy-store';
 import { onBeforeSignOut, onFullSignOut } from '@/lib/sign-out-cleanup';
-import { setOfflineHooks, type OfflineClientRef, type OfflineHooks, type OfflineMethodCall, type OfflineResponse } from '@/lib/jmap/offline-hooks';
+import { generateMessageId } from '@/lib/jmap/client';
+import { SendNotStartedError, setOfflineHooks, type OfflineClientRef, type OfflineHooks, type OfflineMethodCall, type OfflineResponse } from '@/lib/jmap/offline-hooks';
 import type { SendEmailResult } from '@/lib/jmap/types';
 import { setOutboxHooks, type OutboxHooks } from './outbox-hooks';
-import { answerOffline } from './responder';
-import {
-  CACHE_WINDOW_MS,
-  cacheUsage,
-  emailIndex,
-  enforceCap,
-  forgetIndexes,
-  getBlob,
-  getMisc,
-  messageOfBlob,
-  patchEmails,
-  putBlob,
-  putEmails,
-  putMisc,
-  removeEmails,
-  wipeAccountCache,
-  emailKey,
-  type CachedEmail,
-} from './cache';
-import { allowOfflineDbCreation, deleteOfflineDb, hasIndexedDb } from './db';
-import { forgetDeviceKey } from './crypto';
 import {
   heldFile,
   holdFile,
   isLocalBlobId,
-  queuePatch,
   queueSend,
   readQueue,
-  wipeAccountQueue,
   type OutboxEntry,
   type OutboxError,
   type OutboxSummary,
   type PolicyFingerprint,
 } from './queue';
 import { clearHandoffs } from '@/lib/launch-handoff';
-import { isOfflineNow, OFFLINE_ACCOUNTS_KEY, readEnabledFrom, serverKey, setServerDown, useOfflineStore, writeEnabled, type OutboxRow } from './state';
-import { flushQueue, settleStaleSends } from './flush';
-import { syncAccount } from './sync';
+import { clearEvicted, EVICTED_KEEP_MS, forgetMailSnapshot, isEvicted, offlineScopeFor, isOfflineNow, OFFLINE_ACCOUNTS_KEY, readEnabledFrom, readEvicted, visibleAccounts, serverKey, setServerDown, useOfflineStore, writeEnabled, type OutboxRow } from './state';
+import { flushQueue, LOOKUP_WAIT_MS, SENDING_STALE_MS, settleStaleSends } from './flush';
+import { LEGACY_DB_NAME, moveLegacyOutbox, strandedLegacyMessages } from './migrate-legacy';
 import { deleteShellCaches, tellServiceWorker } from './shell';
 import { rememberLost } from './lost';
 
@@ -80,6 +67,11 @@ export type OfflineNotice =
   | { kind: 'send-failed'; subject: string; error: OutboxError }
   | { kind: 'held'; subject: string }
   | { kind: 'lost'; subjects: string[] }
+  | { kind: 'conflict'; count: number }
+  | { kind: 'storage-failed' }
+  | { kind: 'store-unavailable' }
+  | { kind: 'store-reset' }
+  | { kind: 'legacy-stranded' }
   | { kind: 'refused-delete' }
   | { kind: 'refused-other' }
   | { kind: 'forbidden' }
@@ -98,11 +90,20 @@ export function offlineNotify(notice: OfflineNotice): void {
 
 // ---- Who may use it ----
 
-/** Offline mode is possible here at all: not in Lite, with IndexedDB and WebCrypto. */
+function hasIndexedDb(): boolean {
+  try {
+    return typeof indexedDB !== 'undefined' && indexedDB !== null;
+  } catch {
+    return false;
+  }
+}
+
+/** Offline mode is possible here at all: not in Lite, with what the store needs. */
 export function offlineSupported(): boolean {
   if (IS_LITE || !hasIndexedDb()) return false;
+  if (useOfflineStore.getState().storageBlocked) return false;
   try {
-    return typeof crypto !== 'undefined' && !!crypto.subtle;
+    return typeof crypto !== 'undefined' && !!crypto.subtle && getStore().supported();
   } catch {
     return false;
   }
@@ -139,179 +140,88 @@ function onlineClientFor(account: string) {
   return client;
 }
 
-function serverOf(account: string): string | undefined {
-  return useAccountStore.getState().accounts.find((a) => a.id === account)?.serverUrl;
+// ---- The store's way to this tab ----
+
+/** A full disk stays full: once in a while is enough to say so. */
+const STORAGE_NOTICE_MS = 30 * 60_000;
+let lastStorageNotice = 0;
+let lastUnavailableNotice = 0;
+
+/** The store won't open: what waits in it is out of reach, and the user should know why. */
+function noteStoreUnavailable(): void {
+  if (useOfflineStore.getState().enabled.length === 0) return;
+  const now = Date.now();
+  if (now - lastUnavailableNotice < STORAGE_NOTICE_MS) return;
+  lastUnavailableNotice = now;
+  notify({ kind: 'store-unavailable' });
 }
 
-// ---- What the server sends, into the cache ----
-
-export interface Scope {
-  inbox: Record<string, string>;
-  opened: Record<string, string[]>;
-}
-
-const MAX_OPENED_FOLDERS = 10;
-
-/** The Inbox and the opened folders that still exist, per JMAP account. */
-export async function scopeOf(account: string): Promise<Scope> {
-  const mailboxes = (await getMisc<Record<string, Array<{ id: string; role?: string | null }>>>(account, 'mailboxes')) ?? {};
-  const inbox: Record<string, string> = {};
-  for (const [jmap, list] of Object.entries(mailboxes)) {
-    const box = list.find((m) => m.role === 'inbox');
-    if (box) inbox[jmap] = box.id;
-  }
-  const stored = (await getMisc<Record<string, string[]>>(account, 'opened')) ?? {};
-  // A folder deleted or moved away is no longer opened.
-  const opened: Record<string, string[]> = {};
-  let pruned = false;
-  for (const [jmap, ids] of Object.entries(stored)) {
-    const list = mailboxes[jmap];
-    const kept = list ? ids.filter((id) => list.some((m) => m.id === id)) : ids;
-    if (kept.length !== ids.length) pruned = true;
-    opened[jmap] = kept;
-  }
-  if (pruned) await putMisc(account, 'opened', opened);
-  return { inbox, opened };
-}
-
-export async function scopeMailboxes(account: string): Promise<Array<{ jmap: string; mailboxId: string; isInbox: boolean }>> {
-  const scope = await scopeOf(account);
-  const out: Array<{ jmap: string; mailboxId: string; isInbox: boolean }> = [];
-  for (const [jmap, id] of Object.entries(scope.inbox)) out.push({ jmap, mailboxId: id, isInbox: true });
-  for (const [jmap, ids] of Object.entries(scope.opened)) {
-    for (const id of ids) if (scope.inbox[jmap] !== id) out.push({ jmap, mailboxId: id, isInbox: false });
-  }
-  return out;
-}
-
-function keptFolders(scope: Scope): Record<string, string[]> {
-  const out: Record<string, string[]> = {};
-  for (const [jmap, id] of Object.entries(scope.inbox)) out[jmap] = [id];
-  for (const [jmap, ids] of Object.entries(scope.opened)) out[jmap] = [...(out[jmap] ?? []), ...ids];
-  return out;
-}
-
-/** A message the cache keeps: received in the last 30 days, in the Inbox or an opened folder. */
-export function inScope(scope: Scope, jmap: string, email: CachedEmail, now = Date.now()): boolean {
-  const at = Date.parse(String(email.receivedAt ?? ''));
-  if (Number.isFinite(at) && at < now - CACHE_WINDOW_MS) return false;
-  const boxes = Object.keys(email.mailboxIds ?? {});
-  const wanted = new Set([...(scope.opened[jmap] ?? []), ...(scope.inbox[jmap] ? [scope.inbox[jmap]] : [])]);
-  return boxes.some((id) => wanted.has(id));
-}
-
-/** The folder a list query opened, if it is one. */
-function openedFolder(args: Record<string, unknown>): string | null {
-  if (typeof args.limit !== 'number') return null;
-  const filter = args.filter as Record<string, unknown> | undefined;
-  if (!filter) return null;
-  if (typeof filter.inMailbox === 'string' && Object.keys(filter).every((k) => k === 'inMailbox' || k === 'hasKeyword')) return filter.inMailbox;
-  if (filter.operator === 'AND' && Array.isArray(filter.conditions)) {
-    for (const c of filter.conditions as Array<Record<string, unknown>>) if (typeof c.inMailbox === 'string' && Object.keys(c).length === 1) return c.inMailbox;
-  }
-  return null;
-}
-
-async function noteOpenedFolder(account: string, jmap: string, mailboxId: string): Promise<void> {
-  const opened = (await getMisc<Record<string, string[]>>(account, 'opened')) ?? {};
-  const list = opened[jmap] ?? [];
-  if (list[0] === mailboxId) return;
-  opened[jmap] = [mailboxId, ...list.filter((id) => id !== mailboxId)].slice(0, MAX_OPENED_FOLDERS);
-  await putMisc(account, 'opened', opened);
-  scheduleSync(account, 5_000);
-}
-
-async function putList(account: string, name: 'mailboxes' | 'identities', jmap: string, list: unknown[]): Promise<void> {
-  const all = (await getMisc<Record<string, unknown[]>>(account, name)) ?? {};
-  all[jmap] = list;
-  await putMisc(account, name, all);
-}
-
-/** The methods whose answers the cache takes. */
-const RECORDED = new Set(['Mailbox/get', 'Identity/get', 'Email/get', 'Email/query', 'Email/set']);
-
-/** What the server answered, into the cache. */
-export async function recordAnswer(account: string, defaultJmap: string, calls: OfflineMethodCall[], response: OfflineResponse): Promise<void> {
-  const scope = await scopeOf(account);
-  for (const [name, result, callId] of response.methodResponses) {
-    if (!result || typeof result !== 'object') continue;
-    const call = calls.find(([n, , id]) => id === callId && n === name);
-    const args = call?.[1] ?? {};
-    const jmap = (result.accountId as string) || (args.accountId as string) || defaultJmap;
-    const properties = args.properties as string[] | undefined;
-    switch (name) {
-      case 'Mailbox/get':
-        if (!args.ids && (!properties || properties.includes('name')) && Array.isArray(result.list)) {
-          await putList(account, 'mailboxes', jmap, result.list);
-        }
-        break;
-      case 'Identity/get':
-        if (!args.ids && Array.isArray(result.list)) await putList(account, 'identities', jmap, result.list);
-        break;
-      case 'Email/get': {
-        const list = (Array.isArray(result.list) ? result.list : []) as CachedEmail[];
-        // Fresh state for every message already kept; new ones only within the scope.
-        const index = await emailIndex(account);
-        const keep = list.filter((email) => index.has(emailKey(account, jmap, email.id)) || inScope(scope, jmap, email));
-        await putEmails(account, jmap, keep);
-        if (keep.length) scheduleCapCheck();
-        break;
-      }
-      case 'Email/query': {
-        const folder = openedFolder(args);
-        if (folder) await noteOpenedFolder(account, jmap, folder);
-        break;
-      }
-      case 'Email/set': {
-        const update = (args.update ?? {}) as Record<string, Record<string, unknown>>;
-        const updated = Object.keys((result.updated ?? {}) as object);
-        if (updated.length) await patchEmails(account, jmap, Object.fromEntries(updated.filter((id) => update[id]).map((id) => [id, update[id]])));
-        const destroyed = (Array.isArray(result.destroyed) ? result.destroyed : []) as string[];
-        if (destroyed.length) await removeEmails(account, destroyed.map((id) => emailKey(account, jmap, id)));
-        break;
-      }
-      default:
-        break;
+const storeHooks: StorePageHooks = {
+  inputs(account) {
+    const client = onlineClientFor(account);
+    return {
+      session: (client?.getSessionSnapshot() as StoreSession | undefined) ?? null,
+      auth: client?.getAuthHeader() ?? null,
+      invertedKeywordSort: client?.keywordSortInverted() ?? null,
+      scope: offlineScopeFor(account),
+    };
+  },
+  async refreshAuth(account) {
+    const client = onlineClientFor(account);
+    if (!client) return null;
+    // Through the client: a 401 there runs its token renewal or re-auth.
+    await client.requestNetworkOnly([['Core/echo', {}, '0']]);
+    return client.getAuthHeader();
+  },
+  onStoreLost(account) {
+    // Whoever is here wasn't signed in to a dropped account: nothing to tell them.
+    if (isEvicted(account)) return;
+    useOfflineStore.setState((s) => ({ storeLost: [...new Set([...s.storeLost, account])] }));
+    notify({ kind: 'store-reset' });
+  },
+  onEvent(event) {
+    if (event.type === 'synced') {
+      useOfflineStore.setState((s) => ({ lastSyncedAt: { ...s.lastSyncedAt, [event.account]: event.at } }));
+      forgetMailSnapshot(event.account);
+      void refreshUsage();
     }
-  }
+    if (event.type === 'error' && event.area === STORAGE_ERROR_AREA) {
+      const now = Date.now();
+      if (now - lastStorageNotice < STORAGE_NOTICE_MS) return;
+      lastStorageNotice = now;
+      notify({ kind: 'storage-failed' });
+    }
+  },
+};
+
+// ---- What the client asks and tells ----
+
+/** Parts cut short for a list view aren't what the user opened. */
+function hasWholeText(email: { bodyValues?: Record<string, { isTruncated?: boolean }> }): boolean {
+  const values = Object.values(email.bodyValues ?? {});
+  return values.length > 0 && !values.some((value) => value?.isTruncated);
 }
 
-// One write after the other per account, so a list and its refresh land in order.
-const recording = new Map<string, Promise<void>>();
-
-function enqueueRecord(account: string, task: () => Promise<void>): void {
-  const previous = recording.get(account) ?? Promise.resolve();
-  const next = previous.then(task).catch(() => {});
-  recording.set(account, next);
-}
-
-let capTimer: ReturnType<typeof setTimeout> | null = null;
-
-/** The cap holds between syncs too: checked shortly after writes. */
-function scheduleCapCheck(delayMs = 5_000): void {
-  if (capTimer) return;
-  capTimer = setTimeout(() => {
-    capTimer = null;
-    if (useOfflineStore.getState().enabled.length === 0) return;
-    void enforceCap().then(() => refreshUsage()).catch(() => {});
-  }, delayMs);
-}
-
-/** Mutating calls the device can't take: a send, an import, calendar and contact changes. */
+/** Mutating calls the device can't take: an import, calendar and contact changes. */
 const NEEDS_SERVER = /^(EmailSubmission|Email\/import|CalendarEvent\/set|ContactCard\/set|AddressBook\/set|Calendar\/set|Mailbox\/set|FileNode\/set|SieveScript\/set|VacationResponse\/set|Identity\/set)/;
 let lastRefusalNotice = 0;
 
-function noticeRefused(methodCalls: OfflineMethodCall[]): void {
-  if (!methodCalls.some(([name]) => NEEDS_SERVER.test(name))) return;
+function noticeRefused(answered: OfflineResponse | null, methodCalls: OfflineMethodCall[]): void {
+  const refusedCall = methodCalls.some(([name, , id]) => NEEDS_SERVER.test(name)
+    && (!answered || answered.methodResponses.some(([responseName, , responseId]) => responseId === id && responseName === 'error')));
+  const refusedChange = answered?.methodResponses.some(([name, result]) => name === 'Email/set' && result?.notUpdated) ?? false;
+  if (!refusedCall && !refusedChange) return;
   const now = Date.now();
   if (now - lastRefusalNotice < 5_000) return;
   lastRefusalNotice = now;
-  notify({ kind: 'refused-other' });
+  const emptied = answered?.methodResponses.some(([name, result]) => name === 'Email/set'
+    && Object.values((result?.notUpdated ?? {}) as Record<string, { type?: string }>).some((error) => error.type === 'invalidProperties'));
+  notify({ kind: emptied ? 'refused-delete' : 'refused-other' });
 }
 
-// ---- Hooks for the JMAP client ----
-
 const probes = new Map<string, Promise<boolean>>();
+/** A black-holed connection never answers the probe either. */
+const PROBE_TIMEOUT_MS = 5_000;
 
 /**
  * Whether a mail server is gone. Browsers report a refusal without CORS
@@ -326,7 +236,7 @@ export function probeServer(serverUrl: string): Promise<boolean> {
   if (running) return running;
   const probe = (async () => {
     try {
-      await fetch(`${desktopJmapBase(serverUrl.replace(/\/+$/, ''))}/.well-known/jmap`, { mode: 'no-cors', cache: 'no-store', credentials: 'omit' });
+      await fetch(`${desktopJmapBase(serverUrl.replace(/\/+$/, ''))}/.well-known/jmap`, { mode: 'no-cors', cache: 'no-store', credentials: 'omit', signal: AbortSignal.timeout(PROBE_TIMEOUT_MS) });
       if (setServerDown(serverUrl, false)) scheduleFlushAll(500);
       return false;
     } catch {
@@ -346,32 +256,53 @@ const hooks: OfflineHooks = {
   async answer(client, methodCalls) {
     const account = accountForClient(client);
     if (!offlineActive(account) || !account) return null;
-    const scope = await scopeOf(account).catch(() => null);
-    const answered = await answerOffline({
-      account,
-      defaultJmap: client.getAccountId(),
-      keptFolders: scope ? keptFolders(scope) : undefined,
-      queuePatch: async (jmap, update) => {
-        await queuePatch(account, jmap, update);
-        void refreshQueueState();
-      },
-      onRefused: (what) => notify({ kind: what === 'destroy' ? 'refused-delete' : 'refused-other' }),
-    }, methodCalls);
-    if (!answered) noticeRefused(methodCalls);
+    let answered: OfflineResponse | null = null;
+    try {
+      answered = await getStore().answer(account, methodCalls);
+    } catch {
+      // The store couldn't start or lost its owner: as if nothing were kept.
+    }
+    noticeRefused(answered, methodCalls);
+    if (methodCalls.some(([name]) => name === 'Email/set') && answered) {
+      requestOutboxSync();
+      void refreshQueueState();
+    }
     return answered;
   },
-  record(client, methodCalls, response) {
+  async resolveStandIns(client, ids) {
+    const account = accountForClient(client);
+    if (!offlineActive(account) || !account) return {};
+    return getStore().area<Record<string, string | null>>(account, 'calendar.resolveStandIns', { ids }).catch(() => ({}));
+  },
+  fileOpened(client, accountId, id) {
     const account = accountForClient(client);
     if (!offlineActive(account) || !account) return;
-    // Only the answers the cache takes; copied now, because callers change
-    // the answer's objects after this returns.
-    const wanted = response.methodResponses.filter(([name]) => RECORDED.has(name));
-    if (wanted.length === 0) return;
-    const ids = new Set(wanted.map(([, , id]) => id));
-    const copy = JSON.parse(JSON.stringify({ methodResponses: wanted })) as OfflineResponse;
-    const calls = JSON.parse(JSON.stringify(methodCalls.filter(([, , id]) => ids.has(id)))) as OfflineMethodCall[];
-    const jmap = client.getAccountId();
-    enqueueRecord(account, () => recordAnswer(account, jmap, calls, copy));
+    void getStore().area(account, 'files.noteOpened', { jmap: accountId, id }).catch(() => {});
+  },
+  async searchLocal(client, methodCalls) {
+    const account = accountForClient(client);
+    if (!offlineActive(account) || !account) return null;
+    try {
+      return await getStore().answer(account, methodCalls);
+    } catch {
+      return null;
+    }
+  },
+  record(client, methodCalls, response) {
+    // The store syncs by itself. What it may not have is a message the user
+    // opened from outside the chosen window, so only those come through here.
+    const account = accountForClient(client);
+    if (!offlineActive(account) || !account) return;
+    for (const [name, result, callId] of response.methodResponses) {
+      if (name !== 'Email/get' || !Array.isArray(result?.list)) continue;
+      const opened = (result.list as Array<{ bodyValues?: Record<string, { isTruncated?: boolean }> }>).filter(hasWholeText);
+      if (opened.length === 0) continue;
+      const args = methodCalls.find(([n, , id]) => id === callId && n === name)?.[1];
+      const jmap = (result.accountId as string) || (args?.accountId as string) || client.getAccountId();
+      // Copied now: callers change the answer's objects after this returns.
+      const emails = JSON.parse(JSON.stringify(opened)) as unknown[];
+      void getStore().area(account, 'mail.recordOpened', { jmap, emails }).catch(() => {});
+    }
   },
   noteNetwork(client, reachable) {
     if (reachable) {
@@ -380,36 +311,48 @@ const hooks: OfflineHooks = {
       void probeServer(client.getServerUrl());
     }
   },
-  async serverGone(client) {
+  async serverGone(client, error) {
     if (!offlineActive(accountForClient(client))) return false;
     if (typeof navigator !== 'undefined' && navigator.onLine === false) return true;
+    // The proxy answered, so a probe would pass; the server behind it is what's gone.
+    if (error instanceof Error && error.name === 'GatewayError') {
+      setServerDown(client.getServerUrl(), true);
+      return true;
+    }
     return probeServer(client.getServerUrl());
   },
+  stateChange(client, change) {
+    const account = accountForClient(client);
+    if (!offlineActive(account) || !account || !change.changed) return;
+    void getStore().noteStateChange(account, change.changed).catch(() => {});
+  },
   async blob(client, blobId, jmap) {
     const account = accountForClient(client);
     if (!account || !offlineActive(account)) return null;
     if (isLocalBlobId(blobId)) return heldFile(account, blobId);
-    return getBlob(account, jmap, blobId);
+    // An attachment, or a file from the Files area.
+    const kept = await getStore().area<KeptBlob | null>(account, 'mail.getBlob', { jmap, blobId }).catch(() => null)
+      ?? await getStore().area<KeptBlob | null>(account, 'files.blob', { jmap, blobId }).catch(() => null);
+    return kept ? new Blob([kept.data as BlobPart], { type: kept.type || 'application/octet-stream' }) : null;
   },
   recordBlob(client, blobId, jmap, blob) {
     const account = accountForClient(client);
     if (!account || !offlineActive(account) || blob.size > MAX_RECORDED_BLOB_BYTES) return;
-    // Only a part of a kept message (an attachment, an inline image), filed
-    // with it: never a whole message an export reads, never a stray file.
-    enqueueRecord(account, async () => {
-      const owner = await messageOfBlob(account, jmap, blobId);
-      if (!owner) return;
-      await putBlob(account, jmap, blobId, blob, owner.at, owner.key);
-      scheduleCapCheck();
-    });
+    // Filed under its kept message by the store: never a whole message an
+    // export reads, never a stray file.
+    void blob.arrayBuffer()
+      .then((buffer) => getStore().area(account, 'mail.recordBlob', { jmap, blobId, type: blob.type || null, data: new Uint8Array(buffer) }))
+      .catch(() => {});
   },
-  async holdUpload(client, file) {
+  async holdUpload(client, file, accountId) {
     const account = accountForClient(client);
     if (!account || !offlineActive(account)) return null;
-    return holdFile(account, file, file.name);
+    return holdFile(account, file, file.name, accountId);
   },
 };
 
+interface KeptBlob { type: string | null; data: Uint8Array }
+
 /** Attachments and images opened while online are kept up to this size. */
 const MAX_RECORDED_BLOB_BYTES = 5 * 1024 * 1024;
 
@@ -472,6 +415,8 @@ const outbox: OutboxHooks = {
   shouldQueue(client) {
     const account = accountForClient(client);
     if (!account || !offlineActive(account)) return false;
+    // A local copy has no way to the server, whatever the probes last said.
+    if (client.isOfflineOnly?.()) return true;
     return isOfflineNow(client.getServerUrl()) || (typeof navigator !== 'undefined' && navigator.onLine === false);
   },
   async queueEmail(client, args) {
@@ -483,7 +428,11 @@ const outbox: OutboxHooks = {
     const stored = [...args.slice(0, 15), options];
     const summary = summaryOf(stored);
     const labelled = !!options.labelHeaders && Object.keys(options.labelHeaders as object).length > 0;
-    const id = await queueSend(account, summary, { kind: 'email', args: stored }, policyFingerprint(account, labelled));
+    // Fixed now and kept across retries: how a lost response is told from a send that never arrived.
+    // Only its domain is used, and the sender may be written "Name <address>".
+    const sender = ((args[6] as string | undefined) || client.getUsername()).replace(/>.*$/, '');
+    const messageId = generateMessageId(sender);
+    const id = await queueSend(account, summary, { kind: 'email', args: stored }, policyFingerprint(account, labelled), messageId);
     await refreshQueueState();
     notify({ kind: 'queued', subject: summary.subject });
     return queuedResult(id);
@@ -493,8 +442,8 @@ const outbox: OutboxHooks = {
     if (!account) throw new Error('No account for this send');
     if (pluginsNotRunning()) throw new OfflinePluginsDownError();
     const held = await holdFile(account, raw, 'message.eml');
-    const { summary, labelled } = await rawSummary(raw);
-    const id = await queueSend(account, summary, { kind: 'raw', blobId: held.blobId, ...options }, policyFingerprint(account, labelled));
+    const { summary, labelled, messageId } = await rawSummary(raw);
+    const id = await queueSend(account, summary, { kind: 'raw', blobId: held.blobId, ...options }, policyFingerprint(account, labelled), messageId);
     await refreshQueueState();
     notify({ kind: 'queued', subject: summary.subject });
     return queuedResult(id);
@@ -510,20 +459,26 @@ const outbox: OutboxHooks = {
       const file = await heldFile(account, attachment.blobId);
       if (!file) throw Object.assign(new Error('A file attached offline is no longer on this device'), { name: 'OfflineFileMissingError' });
       const { blobId } = await real.uploadBlob(file);
+      // The server went away just now, and offline mode held the file again.
+      if (isLocalBlobId(blobId)) throw new SendNotStartedError();
       out.push({ ...attachment, blobId });
     }
     return out;
   },
 };
 
-/** Subject, recipients and label of a raw message, for the outbox list. */
-async function rawSummary(raw: Blob): Promise<{ summary: OutboxSummary; labelled: boolean }> {
+/** Subject, recipients, label and Message-ID of a raw message, for the outbox. */
+async function rawSummary(raw: Blob): Promise<{ summary: OutboxSummary; labelled: boolean; messageId?: string }> {
   const head = await raw.slice(0, 64 * 1024).text();
   const end = head.search(/\r?\n\r?\n/);
   const block = (end >= 0 ? head.slice(0, end) : head).replace(/\r?\n[ \t]+/g, ' ');
   const header = (name: string) => block.split(/\r?\n/).find((line) => line.toLowerCase().startsWith(`${name}:`))?.slice(name.length + 1).trim() ?? '';
   const to = ['to', 'cc'].flatMap((name) => header(name).split(',')).map((s) => s.trim()).filter(Boolean);
-  return { summary: { subject: decodeMimeWords(header('subject')), to }, labelled: header('sio-label') !== '' };
+  return {
+    summary: { subject: decodeMimeWords(header('subject')), to },
+    labelled: header('sio-label') !== '',
+    messageId: header('message-id').match(/<([^>\s]+)>/)?.[1],
+  };
 }
 
 function decodeMimeWords(value: string): string {
@@ -543,15 +498,16 @@ function decodeMimeWords(value: string): string {
 export async function refreshQueueState(): Promise<void> {
   if (!offlineSupported()) return;
   // Nothing is kept for an account that hasn't it on; and opening the
-  // database would create it (on the sign-in page, after a sign-out).
-  if (useOfflineStore.getState().enabled.length === 0) {
-    useOfflineStore.setState({ outbox: [], pendingChanges: 0 });
+  // store would create it (on the sign-in page, after a sign-out).
+  if (visibleAccounts().length === 0) {
+    useOfflineStore.setState({ outbox: [], pendingChanges: 0, conflicts: [] });
     return;
   }
   try {
-    // Sends of a tab closed on the way: uncertain, so they can be retried or deleted.
+    // Sends of a tab closed on the way: uncertain, so they can be looked up.
     await settleStaleSends();
-    const { patches, outbox: entries } = await readQueue();
+    const { failed, patches, outbox: entries, conflicts } = await readQueue();
+    if (failed.length > 0) noteStoreUnavailable();
     const rows: OutboxRow[] = entries.map((entry) => ({
       id: entry.id,
       account: entry.account,
@@ -561,16 +517,21 @@ export async function refreshQueueState(): Promise<void> {
       status: entry.status,
       error: entry.error,
     }));
-    useOfflineStore.setState({ outbox: rows, pendingChanges: patches.length });
+    // What an account's store can't tell right now is still there.
+    const unread = useOfflineStore.getState().outbox.filter((row) => failed.includes(row.account));
+    useOfflineStore.setState({ outbox: [...unread, ...rows], pendingChanges: patches, conflicts });
+    if (rows.some((row) => row.status === 'sending')) checkStaleSendsLater();
   } catch {
-    // The database is being deleted.
+    // The store is being deleted, or can't start.
+    noteStoreUnavailable();
   }
 }
 
 export async function refreshUsage(): Promise<void> {
-  if (!offlineSupported() || useOfflineStore.getState().enabled.length === 0) return;
+  if (!offlineSupported() || visibleAccounts().length === 0) return;
   try {
-    useOfflineStore.setState({ usageBytes: (await cacheUsage()).total });
+    const usage = await Promise.all(visibleAccounts().map((account) => getStore().area<{ bytes: number }>(account, 'mail.usage')));
+    useOfflineStore.setState({ usageBytes: usage.reduce((sum, { bytes }) => sum + bytes, 0) });
   } catch {
     /* deleted meanwhile */
   }
@@ -599,12 +560,9 @@ export async function runSync(account: string): Promise<void> {
   syncsRunning.add(account);
   useOfflineStore.setState((s) => ({ syncing: [...new Set([...s.syncing, account])] }));
   try {
-    await syncAccount(account, client, {
-      stillActive: () => offlineActive(account),
-      recorded: async () => { await recording.get(account); },
-      scopeMailboxes,
-    });
-    useOfflineStore.setState((s) => ({ lastSyncedAt: { ...s.lastSyncedAt, [account]: Date.now() } }));
+    await getStore().ensureOpen(account);
+    getStore().refresh(account);
+    await getStore().sync(account);
   } catch {
     // Tried again at the next change or in 15 minutes.
   } finally {
@@ -626,6 +584,8 @@ export function scheduleFlushAll(delayMs = 1_000): void {
 
 /** How long after a failed policy fetch the outbox asks again. */
 const POLICY_RETRY_MS = 60_000;
+/** A lost response with the server still there: nothing else would start the lookup. */
+const LOOKUP_AGAIN_MS = LOOKUP_WAIT_MS + 1_000;
 
 /** A send held by the server for undo, from the outbox: the undo toast as after any send. */
 function offerUndo(entry: OutboxEntry, result: SendEmailResult): void {
@@ -644,13 +604,37 @@ function offerUndo(entry: OutboxEntry, result: SendEmailResult): void {
   });
 }
 
+/**
+ * What the other areas queued. The page may hold stand-in ids for what just
+ * went out, so it reads again, the way a push makes it. Only the types go by
+ * that way: the "state" isn't one, and nothing stores it.
+ */
+const AREA_FLUSHES = [
+  { call: 'calendar.flush', types: ['Calendar', 'CalendarEvent'] },
+  { call: 'contacts.flush', types: ['AddressBook', 'ContactCard'] },
+];
+
+async function flushAreas(account: string, client: NonNullable<ReturnType<typeof onlineClientFor>>): Promise<void> {
+  for (const { call, types } of AREA_FLUSHES) {
+    // Contacts may not be there in this build: nothing to flush then.
+    const tally = await getStore().area<{ sent?: number; conflicts?: number | unknown[] } | null>(account, call).catch(() => null);
+    if (!tally) continue;
+    const conflicts = Array.isArray(tally.conflicts) ? tally.conflicts.length : tally.conflicts ?? 0;
+    if (!tally.sent && !conflicts) continue;
+    const role = (useAuthStore.getState().client as unknown) === client ? 'active' : 'background';
+    const changed = { [client.getAccountId()]: Object.fromEntries(types.map((type) => [type, 'flushed'])) };
+    emitPushStateChange({ '@type': 'StateChange', changed } as never, client, role);
+  }
+}
+
 export async function flushAll(): Promise<void> {
   if (useOfflineStore.getState().startedOffline) {
     void leaveOfflineStart();
     return;
   }
-  const { outbox: rows, pendingChanges } = useOfflineStore.getState();
-  if (rows.length === 0 && pendingChanges === 0) return;
+  // Calendar and contact edits wait in their own areas, so what waits isn't known here.
+  const { outbox: rows, enabled } = useOfflineStore.getState();
+  if (rows.length === 0 && enabled.length === 0) return;
   // The organisation's current word before anything goes: a label now
   // required, a send check now required or offline mode now forbidden must
   // stop what waited under the old rules.
@@ -660,8 +644,7 @@ export async function flushAll(): Promise<void> {
     return;
   }
   enforcePolicy();
-  const accounts = new Set(rows.map((r) => r.account));
-  if (pendingChanges > 0) for (const id of useOfflineStore.getState().enabled) accounts.add(id);
+  const accounts = new Set([...rows.map((r) => r.account), ...useOfflineStore.getState().enabled]);
   for (const account of accounts) {
     const client = onlineClientFor(account);
     if (!client || !offlineActive(account)) continue;
@@ -670,7 +653,9 @@ export async function flushAll(): Promise<void> {
       allowed: () => offlineAllowed(account),
       stricterNow,
       onScheduled: offerUndo,
-    });
+      retryLater: () => scheduleFlushAll(LOOKUP_AGAIN_MS),
+    }).catch(() => {});
+    await flushAreas(account, client);
   }
   await refreshQueueState();
   for (const account of useOfflineStore.getState().enabled) scheduleSync(account, 3_000);
@@ -680,7 +665,6 @@ export async function flushAll(): Promise<void> {
 
 export async function enableOffline(account: string): Promise<void> {
   if (!offlineAllowed(account)) return;
-  allowOfflineDbCreation();
   const enabled = useOfflineStore.getState().enabled;
   if (!enabled.includes(account)) writeEnabled([...enabled, account]);
   // Ask the browser not to clear it when space runs low (it may say no).
@@ -689,8 +673,7 @@ export async function enableOffline(account: string): Promise<void> {
   } catch {
     /* no Storage API */
   }
-  const client = onlineClientFor(account);
-  if (client) await putMisc(account, 'session', client.getSessionSnapshot());
+  await getStore().ensureOpen(account).catch(() => {});
   await tellServiceWorker(true);
   scheduleSync(account, 0);
 }
@@ -717,16 +700,40 @@ export function confirmLoss(scope: string): void {
 
 async function unsentSubjects(scope: string): Promise<string[]> {
   let rows = useOfflineStore.getState().outbox;
+  // Reading an account's store would create it if it never had one.
+  if (scope !== 'all' && !useOfflineStore.getState().enabled.includes(scope)) return rows.filter((row) => row.account === scope).map((row) => row.subject);
   try {
     rows = (await readQueue(scope === 'all' ? undefined : scope)).outbox.map((entry) => ({
       id: entry.id, account: entry.account, createdAt: entry.createdAt, subject: entry.summary.subject, to: entry.summary.to, status: entry.status,
     }));
   } catch {
-    // No database: what the store last saw.
+    // No store: what the state last saw.
   }
   return rows.filter((row) => scope === 'all' || row.account === scope).map((row) => row.subject);
 }
 
+/** How long a sign-out waits for the store's word on what would be lost. */
+const UNSENT_READ_MS = 2_000;
+
+/** What a sign-out of `scope` would delete: messages, and edits the server hasn't got. */
+export async function unsentCount(scope: string, waitMs = UNSENT_READ_MS): Promise<{ messages: number; changes: number }> {
+  const shown = useOfflineStore.getState();
+  const known = { messages: shown.outbox.filter((row) => scope === 'all' || row.account === scope).length, changes: shown.pendingChanges };
+  const accounts = (scope === 'all' ? visibleAccounts() : [scope]).filter((account) => shown.enabled.includes(account));
+  if (accounts.length === 0) return known;
+  const pendingIn = (account: string, area: string) => getStore().area<number>(account, `${area}.pending`).catch(() => 0);
+  const read = (async () => {
+    const { failed, outbox, patches } = await readQueue(scope === 'all' ? undefined : scope);
+    const edits = await Promise.all(accounts.flatMap((account) => [pendingIn(account, 'calendar'), pendingIn(account, 'contacts')]));
+    return {
+      // An account that can't answer counts with what it last said.
+      messages: outbox.length + shown.outbox.filter((row) => failed.includes(row.account)).length,
+      changes: patches + edits.reduce((sum, count) => sum + count, 0),
+    };
+  })().catch(() => known);
+  return Promise.race([read, new Promise<typeof known>((resolve) => setTimeout(() => resolve(known), waitMs))]);
+}
+
 /** Names the unsent messages a wipe of `scope` deletes, unless the user agreed. */
 async function nameLost(scope: string, stillSignedIn: boolean): Promise<void> {
   if (named.has(scope) || named.has('all')) return;
@@ -748,25 +755,26 @@ export async function wipeAccount(account: string): Promise<void> {
   const timer = syncTimers.get(account);
   if (timer) clearTimeout(timer);
   syncTimers.delete(account);
-  await recording.get(account)?.catch(() => {});
+  // Waited for a sign-in that never came: whoever is here now mustn't read its subjects.
+  if (isEvicted(account)) named.add(account);
   if (useOfflineStore.getState().enabled.includes(account) || useOfflineStore.getState().outbox.some((row) => row.account === account)) {
     await nameLost(account, useAuthStore.getState().isAuthenticated);
   }
   named.delete(account);
+  clearEvicted(account);
   if (useOfflineStore.getState().enabled.includes(account)) {
     writeEnabled(useOfflineStore.getState().enabled.filter((id) => id !== account));
   }
-  // Nobody keeps mail here any more: the whole database goes (and isn't
-  // opened again, which would create it anew).
+  // Nobody keeps mail here any more: everything goes (and isn't opened
+  // again, which would create it anew).
   if (useOfflineStore.getState().enabled.length === 0) {
     await wipeEverything();
     return;
   }
   try {
-    await wipeAccountCache(account);
-    await wipeAccountQueue(account);
+    await getStore().remove(account);
   } catch {
-    // No database: nothing to remove.
+    // No store: nothing to remove. The key is gone in any case.
   }
   await refreshQueueState();
   await refreshUsage();
@@ -777,19 +785,25 @@ export async function wipeEverything(): Promise<void> {
   for (const timer of syncTimers.values()) clearTimeout(timer);
   syncTimers.clear();
   writeEnabled([]);
-  forgetIndexes();
-  forgetDeviceKey();
-  await deleteOfflineDb();
+  getStore().stop();
+  await purgeStoreFiles();
+  try {
+    indexedDB.deleteDatabase(LEGACY_DB_NAME);
+  } catch {
+    /* no IndexedDB */
+  }
   await tellServiceWorker(false);
   await deleteShellCaches();
   clearHandoffs();
   confirmed.clear();
   named.clear();
-  useOfflineStore.setState({ outbox: [], pendingChanges: 0, usageBytes: 0, syncing: [], lastSyncedAt: {} });
+  useOfflineStore.setState({ outbox: [], pendingChanges: 0, conflicts: [], usageBytes: 0, syncing: [], lastSyncedAt: {} });
 }
 
 /** Whether the policy of an account is known well enough to decide on it. */
 function policyDecided(account: string): boolean {
+  // Dropped, with no groups to wait for: what applies to everyone reaches it.
+  if (isEvicted(account)) return true;
   const auth = useAuthStore.getState();
   if (account === auth.activeAccountId || !auth.activeAccountId) return !usePolicyStore.getState().subjectPending;
   // Another signed-in account: its groups have to be known first (a group
@@ -804,10 +818,14 @@ export function enforcePolicy(): void {
   if (!loaded) return;
   for (const account of useOfflineStore.getState().enabled) {
     if (!policyDecided(account)) continue;
-    if (!offlineAllowed(account)) {
+    // What the organisation says, not whether this window can open the store:
+    // a blocked store says nothing against the data in it.
+    if (devicesForAccount(account).noOffline) {
+      // Whoever is here now wasn't signed in to a dropped account.
+      const someoneElses = isEvicted(account);
       clearHandoffs();
       void wipeAccount(account);
-      notify({ kind: 'forbidden' });
+      if (!someoneElses) notify({ kind: 'forbidden' });
     }
   }
 }
@@ -852,18 +870,35 @@ async function leaveOfflineStart(): Promise<void> {
 let started = false;
 const cleanups: Array<() => void> = [];
 
-/** Runs offline mode in this tab. Safe to call more than once. */
-export function startOfflineMode(): () => void {
-  if (started || !offlineSupported()) return () => {};
-  started = true;
+/**
+ * The JMAP client's hooks. Separate from startOfflineMode because the auth
+ * store needs them before it restores accounts: a start from the local copy
+ * asks the store long before the host component mounts.
+ */
+export function registerOfflineHooks(): void {
+  if (!offlineSupported()) return;
+  configureStore(storeHooks);
   setOfflineHooks(hooks);
   setOutboxHooks(outbox);
+  void moveLegacyOutbox();
+}
+
+/** Runs offline mode in this tab. Safe to call more than once. */
+export function startOfflineMode(): () => void {
+  if (!started && !offlineSupported()) void noteStrandedMail();
+  if (started || !offlineSupported()) return () => {};
+  started = true;
+  registerOfflineHooks();
 
   const onOnline = () => {
     useOfflineStore.setState({ browserOffline: false });
+    void getStore().setOnline(true).catch(() => {});
     scheduleFlushAll(500);
   };
-  const onOffline = () => useOfflineStore.setState({ browserOffline: true });
+  const onOffline = () => {
+    useOfflineStore.setState({ browserOffline: true });
+    void getStore().setOnline(false).catch(() => {});
+  };
   window.addEventListener('online', onOnline);
   window.addEventListener('offline', onOffline);
   cleanups.push(() => {
@@ -871,8 +906,17 @@ export function startOfflineMode(): () => void {
     window.removeEventListener('offline', onOffline);
   });
 
+  // Back in front: catch up now rather than at the next interval.
+  const onVisible = () => {
+    if (document.visibilityState !== 'visible') return;
+    for (const account of useOfflineStore.getState().enabled) scheduleSync(account, 0);
+  };
+  document.addEventListener('visibilitychange', onVisible);
+  cleanups.push(() => document.removeEventListener('visibilitychange', onVisible));
+
   // Another tab switched it off for an account (or everyone signed out
-  // there): stop here too, and don't write anything for that account.
+  // there): stop here too, and don't write anything for that account. One
+  // switched on there has to be opened here if this tab owns the store.
   const onStorage = (event: StorageEvent) => {
     if (event.key !== OFFLINE_ACCOUNTS_KEY && event.key !== null) return;
     const next = readEnabledFrom(event.key === null ? null : event.newValue);
@@ -882,13 +926,9 @@ export function startOfflineMode(): () => void {
       const timer = syncTimers.get(id);
       if (timer) clearTimeout(timer);
       syncTimers.delete(id);
-      forgetIndexes(id);
-    }
-    if (next.length === 0) {
-      forgetIndexes();
-      forgetDeviceKey();
     }
     useOfflineStore.setState({ enabled: next });
+    for (const id of next) if (!before.includes(id)) void getStore().ensureOpen(id).catch(() => {});
     void refreshQueueState();
   };
   window.addEventListener('storage', onStorage);
@@ -902,22 +942,32 @@ export function startOfflineMode(): () => void {
   cleanups.push(useAccountSubjects.subscribe(() => enforcePolicy()));
   enforcePolicy();
 
-  // An account that signs out (or is removed) takes its offline data with it.
-  let known = new Set(useAccountStore.getState().accounts.map((a) => a.id));
-  cleanups.push(useAccountStore.subscribe((state) => {
-    const now = new Set(state.accounts.map((a) => a.id));
-    for (const id of known) if (!now.has(id)) void wipeAccount(id);
-    known = now;
+  // An account signed out or removed takes its data with it. One the app
+  // dropped by itself doesn't: its session ran out, or the server can't
+  // confirm it right now, and that says nothing against the mail on this device.
+  cleanups.push(onAccountRemoved((id, reason) => {
+    if (reason === 'explicit') void wipeAccount(id);
   }));
+  void sweepAccountsGone();
+  void checkStorageAccess();
 
   // Session, then a sync, for every account signed in with offline mode on.
+  // A client that just became real is what the waiting mail was waiting for:
+  // the flush at the start may have run before it was connected.
+  const flushedFor = new WeakSet<object>();
   const syncSignedIn = () => {
+    let connected = false;
     for (const account of useOfflineStore.getState().enabled) {
       const client = onlineClientFor(account);
       if (!client || !offlineActive(account)) continue;
-      void putMisc(account, 'session', client.getSessionSnapshot()).catch(() => {});
+      void getStore().ensureOpen(account).then(() => getStore().refresh(account)).catch(() => {});
       scheduleSync(account, 3_000);
+      if (!flushedFor.has(client)) {
+        flushedFor.add(client);
+        if (!isOfflineNow(client.getServerUrl())) connected = true;
+      }
     }
+    if (connected) scheduleFlushAll(1_000);
   };
   cleanups.push(useAuthStore.subscribe((state, prev) => {
     if (state.client !== prev.client || state.connectedAccountsRevision !== prev.connectedAccountsRevision) syncSignedIn();
@@ -927,15 +977,22 @@ export function startOfflineMode(): () => void {
   const interval = setInterval(() => {
     for (const account of useOfflineStore.getState().enabled) scheduleSync(account, 0);
   }, SYNC_INTERVAL_MS);
-  const reconnect = setInterval(() => { void leaveOfflineStart(); }, RECONNECT_MS);
+  const reconnect = setInterval(() => {
+    void leaveOfflineStart();
+    // Nothing else tells a server that was down is back: a client that thinks
+    // it's down has no reason to ask it. A passing probe starts the flush.
+    for (const server of useOfflineStore.getState().downServers) void probeServer(server);
+  }, RECONNECT_MS);
   cleanups.push(() => {
     clearInterval(interval);
     clearInterval(reconnect);
+    if (staleCheck) clearTimeout(staleCheck);
+    staleCheck = null;
   });
 
   if (useOfflineStore.getState().enabled.length > 0) void tellServiceWorker(true);
   void (async () => {
-    if (useOfflineStore.getState().enabled.length > 0) await settleStaleSends().catch(() => {});
+    await moveLegacyOutbox();
     await refreshQueueState();
     if (!isOfflineNow()) scheduleFlushAll(2_000);
   })();
@@ -945,28 +1002,75 @@ export function startOfflineMode(): () => void {
     for (const cleanup of cleanups.splice(0)) cleanup();
     setOfflineHooks(null);
     setOutboxHooks(null);
+    configureStore(null);
     started = false;
   };
 }
 
-/** How often the cache catches up while the tab is open. */
+/**
+ * Data no signed-in account vouches for. A dropped account's waits 30 days. One
+ * that left the registry on purpose before this ran (a login without "remember
+ * me" ends at a reload, before the host mounts) goes now, naming lost mail.
+ */
+async function sweepAccountsGone(now = Date.now()): Promise<void> {
+  const evicted = readEvicted();
+  const accounts = useAccountStore.getState().accounts;
+  for (const account of useOfflineStore.getState().enabled) {
+    const at = evicted[account];
+    const gone = at !== undefined ? now - at > EVICTED_KEEP_MS : !accounts.some((entry) => entry.id === account);
+    if (gone) await wipeAccount(account).catch(() => {});
+  }
+}
+
+let staleCheck: ReturnType<typeof setTimeout> | null = null;
+
+/** A send taken by a tab that closed on the way: nothing else comes back to it. */
+function checkStaleSendsLater(): void {
+  if (staleCheck) return;
+  staleCheck = setTimeout(() => {
+    staleCheck = null;
+    void refreshQueueState().then(() => scheduleFlushAll(0));
+  }, SENDING_STALE_MS + 1_000);
+}
+
+/** Firefox's private windows refuse this at once, where the worker would try for half a minute. */
+async function checkStorageAccess(): Promise<void> {
+  try {
+    await navigator.storage.getDirectory();
+  } catch (error) {
+    if ((error as Error)?.name === 'SecurityError') useOfflineStore.setState({ storageBlocked: true });
+  }
+}
+
+let strandedNoted = false;
+
+/** An earlier version's unsent mail, in a browser that can't run what would move it. */
+async function noteStrandedMail(): Promise<void> {
+  if (strandedNoted || IS_LITE || !hasIndexedDb()) return;
+  if ((await strandedLegacyMessages().catch(() => 0)) === 0) return;
+  strandedNoted = true;
+  notify({ kind: 'legacy-stranded' });
+}
+
+/** How often the store catches up while the tab is open, on top of pushes. */
 export const SYNC_INTERVAL_MS = 15 * 60 * 1000;
 
-// A full sign-out deletes the database (lib/sign-out-cleanup.ts); forget
-// what is held in memory as well.
-onFullSignOut(() => {
+// A full sign-out deletes the store (lib/sign-out-cleanup.ts); forget what
+// is held in memory as well.
+onFullSignOut(({ keepLocalStore }) => {
   for (const timer of syncTimers.values()) clearTimeout(timer);
   syncTimers.clear();
-  forgetIndexes();
-  forgetDeviceKey();
+  if (!keepLocalStore) getStore().stop();
   confirmed.clear();
   named.clear();
-  useOfflineStore.setState({ enabled: [], outbox: [], pendingChanges: 0, usageBytes: 0, syncing: [], lastSyncedAt: {}, startedOffline: false });
+  useOfflineStore.setState((s) => ({ enabled: keepLocalStore ? s.enabled : [], outbox: [], pendingChanges: 0, conflicts: [], usageBytes: 0, syncing: [], lastSyncedAt: {}, startedOffline: false }));
 });
 
 // Every sign-out the user didn't agree to lose mail at (the session limits,
 // a refused token renewal, a removed account) names the unsent messages.
-onBeforeSignOut(async (accountId) => {
+onBeforeSignOut(async (accountId, { keepLocalStore }) => {
+  // Nothing is lost: it waits for the next sign-in.
+  if (keepLocalStore) return;
   const stillSignedIn = accountId !== 'all' && useAccountStore.getState().accounts.some((a) => a.id !== accountId);
   await nameLost(accountId, stillSignedIn);
 });
@@ -977,16 +1081,35 @@ export async function serverUnreachable(serverUrl: string): Promise<boolean> {
   return probeServer(serverUrl);
 }
 
-/** The session kept for an account, for starting without the server. */
-export async function offlineSessionFor(account: string): Promise<unknown | null> {
+/** How long a start waits for the store before it signs in the usual way. */
+const SESSION_READ_TIMEOUT_MS = 5_000;
+
+/** The session kept for an account, for starting from the local copy. */
+/** A start doesn't hang on a black-holed fetch or a stuck database. */
+const BOOT_WAIT_MS = 3_000;
+
+function withinBootWait(work: Promise<unknown>): Promise<unknown> {
+  return Promise.race([work.catch(() => {}), new Promise((resolve) => setTimeout(resolve, BOOT_WAIT_MS))]);
+}
+
+export async function offlineSessionFor(account: string, options: { withFolders?: boolean } = {}): Promise<unknown | null> {
   // The organisation's last word: the policy kept from the last fetch (the
   // fetch itself fails without a network), never the defaults.
   const policy = usePolicyStore.getState();
-  if (!policy.loaded && !policy.fetching) await policy.fetchPolicy();
-  else await whenPolicySettled(3000);
-  if (!offlineActive(account)) return null;
+  await withinBootWait(!policy.loaded && !policy.fetching ? policy.fetchPolicy() : whenPolicySettled(BOOT_WAIT_MS));
+  // Still nothing to go on: the usual start, which has its own errors.
+  if (!usePolicyStore.getState().loaded || !offlineActive(account)) return null;
+  registerOfflineHooks();
   try {
-    return await getMisc<unknown>(account, 'session');
+    // What's in the old database goes on moving behind the start.
+    await withinBootWait(moveLegacyOutbox());
+    return await Promise.race([
+      (async () => {
+        if (options.withFolders && !(await getStore().area<boolean>(account, 'mail.hasFolders'))) return null;
+        return getStore().area<unknown>(account, 'mail.session');
+      })(),
+      new Promise<null>((resolve) => setTimeout(() => resolve(null), SESSION_READ_TIMEOUT_MS)),
+    ]);
   } catch {
     return null;
   }
diff --git a/lib/offline/queue.ts b/lib/offline/queue.ts
index 4da2d5bf0..b9e0232be 100644
--- a/lib/offline/queue.ts
+++ b/lib/offline/queue.ts
@@ -1,254 +1,96 @@
 /**
- * What waits on this device for the network (#523): changes made offline
- * (read, flagged, tags, moves) and the outbox. Both are kept encrypted in
- * the offline database and sent in the order they were made.
- *
- * An outbox entry is a finished message: everything a send does up to the
- * transport ran when the user clicked Send (the organisation's checks,
- * the classification label, signatures and disclaimers, plugin send checks,
- * S/MIME or PGP with the user present). What is kept is the arguments of the
- * final send, with the files that couldn't be uploaded yet, or the finished
- * raw message of a plugin's send. Sending it later can't skip any of that.
- *
- * The state of an outbox entry (waiting, sending, ...) is kept unencrypted
- * next to it, so that taking an entry for sending is one database
- * transaction: two tabs can't both take it (claimForSending).
+ * What waits on this device for the network (#523): the page's view of the
+ * outbox in the local store (lib/store/outbox). Changes made offline wait there
+ * merged per record; messages wait as finished sends. Everything is kept
+ * encrypted in the store, and taking an entry for sending is one SQLite
+ * transaction, so two tabs can't both take it (claimForSending).
  */
 
-import { idbAdd, idbDeleteAccount, idbGet, idbGetAll, idbGetAllByAccount, idbUpdate, idbWrite } from './db';
-import { openBytes, openJson, sealBytes, sealJson, type Sealed } from './crypto';
-import { generateUUID } from '@/lib/utils';
 import { requestOutboxSync } from '@/lib/pwa-notify/outbox-sync';
+import { getStore } from '@/lib/store/client/api';
+import type { ConflictSummary, OutboxError, OutboxStatus, OutboxSummary, PolicyFingerprint, SendItem, StoredConflict, StoredOutboxEntry } from '@/lib/store/outbox/items';
+import { visibleAccounts } from './state';
 
-export interface PatchItem {
-  kind: 'patch';
-  jmap: string;
-  update: Record<string, Record<string, unknown>>;
+export { LOCAL_BLOB_PREFIX, heldBlobIds, isLocalBlobId } from '@/lib/store/outbox/items';
+export type { EmailSendItem, OutboxError, OutboxStatus, OutboxSummary, PolicyFingerprint, RawSendItem, SendItem } from '@/lib/store/outbox/items';
+
+export interface OutboxEntry extends StoredOutboxEntry {
+  account: string;
 }
 
-/** The arguments of useEmailStore.sendEmail after the client (positional, as the client takes them). */
-export interface EmailSendItem {
-  kind: 'email';
-  args: unknown[];
-}
-
-export interface RawSendItem {
-  kind: 'raw';
-  /** The finished message, kept as an upload until it is sent. */
-  blobId: string;
-  identityId: string;
-  delayedUntil?: string;
-  envelopeRecipients?: string[];
-  /** submitRaw: no copy in Sent. */
-  submitOnly?: boolean;
-}
-
-export type SendItem = EmailSendItem | RawSendItem;
-
-export interface OutboxSummary {
-  subject: string;
-  to: string[];
-}
-
-/**
- * - waiting: goes out by itself when the server answers;
- * - sending: on its way (a tab took it);
- * - failed: the server refused it; the error says why;
- * - uncertain: the connection broke after it may have reached the server;
- *   never sent again by itself;
- * - held: the organisation's rules got stricter while it waited.
- */
-export type OutboxStatus = 'waiting' | 'sending' | 'failed' | 'uncertain' | 'held';
-
-/** Why an entry failed: one of ours (a code the UI translates) or the server's own words. */
-export interface OutboxError {
-  code?: 'file_missing' | 'no_sent_mailbox' | 'no_drafts_mailbox';
-  text?: string;
-}
-
-/** What the organisation required when the message was finished (see offline-mode.ts policyFingerprint). */
-export interface PolicyFingerprint {
-  labelRequired: boolean;
-  hasLabel: boolean;
-  guards: string[];
-}
-
-export interface OutboxEntry {
+export interface ConflictEntry {
   id: number;
   account: string;
+  recordId: string;
   createdAt: number;
-  summary: OutboxSummary;
-  status: OutboxStatus;
-  /** When a tab took it for sending (ms). */
-  sendingSince?: number;
-  error?: OutboxError;
-  item: SendItem;
-  fingerprint?: PolicyFingerprint;
+  summary: ConflictSummary;
 }
 
-interface QueueRecord extends Sealed {
-  id?: number;
-  account: string;
-  kind: 'patch' | 'send';
-  createdAt: number;
-  status?: OutboxStatus;
-  sendingSince?: number;
-}
-
-interface SendPayload {
-  summary: OutboxSummary;
-  error?: OutboxError;
-  item: SendItem;
-  fingerprint?: PolicyFingerprint;
-}
-
-export async function queuePatch(account: string, jmap: string, update: PatchItem['update']): Promise<void> {
-  const item: PatchItem = { kind: 'patch', jmap, update };
-  await idbAdd('queue', { account, kind: 'patch', createdAt: Date.now(), ...(await sealJson(item)) } satisfies QueueRecord);
-  requestOutboxSync();
-}
-
-export async function queueSend(account: string, summary: OutboxSummary, item: SendItem, fingerprint?: PolicyFingerprint): Promise<number> {
-  const payload: SendPayload = { summary, item, fingerprint };
-  const id = Number(await idbAdd('queue', { account, kind: 'send', createdAt: Date.now(), status: 'waiting', ...(await sealJson(payload)) } satisfies QueueRecord));
+export async function queueSend(account: string, summary: OutboxSummary, item: SendItem, fingerprint?: PolicyFingerprint, messageId?: string): Promise<number> {
+  const id = await getStore().area<number>(account, 'outbox.queueSend', { summary, item, fingerprint, messageId });
   requestOutboxSync();
   return id;
 }
 
-export interface QueuedPatch { id: number; account: string; item: PatchItem }
-
-/** Everything waiting for one account (or all), oldest first. */
-export async function readQueue(account?: string): Promise<{ patches: QueuedPatch[]; outbox: OutboxEntry[] }> {
-  const records = account ? await idbGetAllByAccount<QueueRecord>('queue', account) : await idbGetAll<QueueRecord>('queue');
-  records.sort((a, b) => (a.id ?? 0) - (b.id ?? 0));
-  const patches: QueuedPatch[] = [];
-  const outbox: OutboxEntry[] = [];
-  for (const record of records) {
-    try {
-      if (record.kind === 'patch') {
-        patches.push({ id: record.id!, account: record.account, item: await openJson<PatchItem>(record) });
-      } else {
-        const payload = await openJson<SendPayload>(record);
-        outbox.push({
-          id: record.id!,
-          account: record.account,
-          createdAt: record.createdAt,
-          status: record.status ?? 'waiting',
-          sendingSince: record.sendingSince,
-          ...payload,
-        });
-      }
-    } catch {
-      // Sealed with a key that is gone; removed with the account.
-    }
-  }
-  return { patches, outbox };
+interface StoredQueue {
+  patches: number;
+  entries: StoredOutboxEntry[];
+  conflicts: StoredConflict[];
 }
 
-/**
- * Takes a waiting entry for sending, in one transaction: false when it
- * isn't waiting any more (another tab took it, the user deleted it).
- */
-export async function claimForSending(id: number): Promise<boolean> {
-  return idbUpdate<QueueRecord>('queue', id, (record) => {
-    if (!record || record.kind !== 'send' || (record.status ?? 'waiting') !== 'waiting') return undefined;
-    return { ...record, status: 'sending', sendingSince: Date.now() };
-  });
-}
-
-/** Sets an entry's state; with an error or a new after-send list, its payload too. */
-export async function updateOutboxEntry(
-  entry: OutboxEntry,
-  patch: { status: OutboxStatus; error?: OutboxError },
-): Promise<void> {
-  const payload: SendPayload = {
-    summary: entry.summary,
-    item: entry.item,
-    fingerprint: entry.fingerprint,
-    error: patch.error,
+/** Everything waiting for one account (or every account with it on), oldest first. */
+export async function readQueue(account?: string): Promise<{ failed: string[]; patches: number; outbox: OutboxEntry[]; conflicts: ConflictEntry[] }> {
+  const accounts = account ? [account] : visibleAccounts();
+  const settled = await Promise.allSettled(accounts.map(async (id) => ({ id, queue: await getStore().area<StoredQueue>(id, 'outbox.read') })));
+  const read = settled.flatMap((result) => (result.status === 'fulfilled' ? [result.value] : []));
+  const failed = accounts.filter((_, index) => settled[index].status === 'rejected');
+  // Nothing could be read: that isn't an empty queue.
+  if (read.length === 0 && failed.length > 0) throw (settled[0] as PromiseRejectedResult).reason;
+  return {
+    failed,
+    patches: read.reduce((sum, { queue }) => sum + queue.patches, 0),
+    outbox: read.flatMap(({ id, queue }) => queue.entries.map((entry) => ({ ...entry, account: id }))),
+    conflicts: read.flatMap(({ id, queue }) => queue.conflicts.map((conflict) => ({
+      id: conflict.id,
+      account: id,
+      recordId: conflict.recordId,
+      createdAt: conflict.createdAt,
+      summary: conflict.summary,
+    }))),
   };
-  const sealed = await sealJson(payload);
-  await idbUpdate<QueueRecord>('queue', entry.id, (record) => {
-    // Deleted meanwhile: stays deleted.
-    if (!record) return undefined;
-    return { ...record, status: patch.status, sendingSince: patch.status === 'sending' ? Date.now() : undefined, ...sealed };
-  });
 }
 
-export async function removeQueued(ids: number[]): Promise<void> {
-  await idbWrite(ids.map((id) => ({ store: 'queue' as const, del: id })));
+/** Takes a waiting entry for sending: false when it isn't waiting any more (another tab took it, the user deleted it). */
+export function claimForSending(account: string, id: number): Promise<boolean> {
+  return getStore().area<boolean>(account, 'outbox.claim', { id });
+}
+
+export function updateOutboxEntry(
+  entry: Pick<OutboxEntry, 'account' | 'id'>,
+  patch: { status: OutboxStatus; error?: OutboxError; copyId?: string | null },
+): Promise<void> {
+  return getStore().area(entry.account, 'outbox.update', { id: entry.id, ...patch });
 }
 
 /** Removes an outbox entry and the files it held. */
-export async function removeOutboxEntry(entry: OutboxEntry): Promise<void> {
-  const blobIds = heldBlobIds(entry.item);
-  await idbWrite([
-    { store: 'queue', del: entry.id },
-    ...blobIds.map((blobId) => ({ store: 'uploads' as const, del: uploadKey(entry.account, blobId) })),
-  ]);
+export function removeOutboxEntry(entry: Pick<OutboxEntry, 'account' | 'id'>): Promise<void> {
+  return getStore().area(entry.account, 'outbox.remove', { id: entry.id });
+}
+
+export function dismissConflict(account: string, id: number): Promise<void> {
+  return getStore().area(account, 'outbox.dismissConflict', { id });
 }
 
 // ---- Files attached while offline ----
 
-/** Stand-in blob ids of files kept on this device start with this. */
-export const LOCAL_BLOB_PREFIX = 'bulwark-local-';
-
-const uploadKey = (account: string, blobId: string) => `${account}\u0001${blobId}`;
-
-export function isLocalBlobId(blobId: unknown): blobId is string {
-  return typeof blobId === 'string' && blobId.startsWith(LOCAL_BLOB_PREFIX);
-}
-
-interface UploadRecord extends Sealed {
-  key: string;
-  account: string;
-  createdAt: number;
-  /** The file's name and type, sealed: names say a lot about a message. */
-  meta: Sealed;
-}
-
 /** Keeps a file under a stand-in blob id until its message is sent. */
-export async function holdFile(account: string, file: Blob, name: string): Promise<{ blobId: string; size: number; type: string }> {
-  const blobId = `${LOCAL_BLOB_PREFIX}${generateUUID()}`;
-  const sealed = await sealBytes(await file.arrayBuffer());
-  const meta = await sealJson({ name, type: file.type });
-  await idbWrite([{ store: 'uploads', put: { key: uploadKey(account, blobId), account, createdAt: Date.now(), meta, ...sealed } satisfies UploadRecord }]);
-  return { blobId, size: file.size, type: file.type || 'application/octet-stream' };
+export async function holdFile(account: string, file: Blob, name: string, jmap?: string): Promise<{ blobId: string; size: number; type: string }> {
+  const data = new Uint8Array(await file.arrayBuffer());
+  return getStore().area(account, 'outbox.holdFile', { jmap, name, type: file.type, data });
 }
 
 export async function heldFile(account: string, blobId: string): Promise<File | null> {
-  const record = await idbGet<UploadRecord>('uploads', uploadKey(account, blobId));
-  if (!record) return null;
-  try {
-    const meta = await openJson<{ name?: string; type?: string }>(record.meta);
-    return new File([await openBytes(record)], meta.name || 'attachment', { type: meta.type || 'application/octet-stream' });
-  } catch {
-    return null;
-  }
-}
-
-/** The stand-in blob ids an outbox entry needs uploaded first. */
-export function heldBlobIds(item: SendItem): string[] {
-  if (item.kind === 'raw') return isLocalBlobId(item.blobId) ? [item.blobId] : [];
-  const attachments = item.args[10];
-  if (!Array.isArray(attachments)) return [];
-  return attachments.map((a) => (a as { blobId?: unknown }).blobId).filter(isLocalBlobId);
-}
-
-/** Files held for no outbox entry (attached offline to a message that was then discarded). */
-export async function dropOrphanFiles(account: string, olderThanMs = 24 * 60 * 60 * 1000): Promise<void> {
-  const { outbox } = await readQueue(account);
-  const needed = new Set(outbox.flatMap((entry) => heldBlobIds(entry.item)));
-  const held = await idbGetAllByAccount<{ key: string; createdAt?: number }>('uploads', account);
-  const cutoff = Date.now() - olderThanMs;
-  const stale = held.filter((record) => {
-    const blobId = record.key.split('\u0001')[1];
-    return !needed.has(blobId) && (record.createdAt ?? 0) < cutoff;
-  });
-  await idbWrite(stale.map((record) => ({ store: 'uploads' as const, del: record.key })));
-}
-
-/** The queue and held files of one account. */
-export async function wipeAccountQueue(account: string): Promise<void> {
-  await idbDeleteAccount(account, ['queue', 'uploads']);
+  const held = await getStore().area<{ name: string; type: string; data: Uint8Array } | null>(account, 'outbox.heldFile', { blobId });
+  if (!held) return null;
+  return new File([held.data as BlobPart], held.name, { type: held.type });
 }
diff --git a/lib/offline/responder.ts b/lib/offline/responder.ts
deleted file mode 100644
index 9495ee9a2..000000000
--- a/lib/offline/responder.ts
+++ /dev/null
@@ -1,394 +0,0 @@
-/**
- * Answers JMAP requests from the mail kept on this device while the server
- * can't be reached (#523), so the app works as usual: the folder list, the
- * message list of a cached folder, opening a cached message, threads.
- *
- * Changes are queued (queue.ts) and applied to the cache at once: keywords
- * (read, flagged, any tag) and folders (move, delete to Trash). Deleting for
- * good, emptying a folder and everything else that would change the server
- * is refused, as are calls the cache can't answer (search, changes since a
- * state): the whole request then fails as it would without offline mode.
- *
- * Answers carry no collection state strings: a made-up one would end up in an
- * Email/changes once the server is back, which refuses it.
- */
-
-import { BLOBS, emailIndex, getBody, getMisc, patchEmails, putMisc, type CachedEmail } from './cache';
-import type { OfflineMethodCall, OfflineResponse } from '@/lib/jmap/offline-hooks';
-
-export type MethodResult = Record<string, unknown>;
-
-export interface ResponderContext {
-  account: string;
-  /** The client's own JMAP account (calls without accountId use it). */
-  defaultJmap: string;
-  /** Queue changes to messages; resolves once they are kept. */
-  queuePatch: (jmap: string, update: Record<string, Record<string, unknown>>) => Promise<void>;
-  /** A change offline mode refuses (delete for good); the caller tells the user. */
-  onRefused: (what: 'destroy' | 'other') => void;
-  /**
-   * The folders whose mail is kept here, per JMAP account. A list of any
-   * other folder isn't answered (it would look empty while its count says
-   * otherwise). Without it, every folder is answered.
-   */
-  keptFolders?: Record<string, readonly string[]>;
-}
-
-/** The folders a filter lists, as far as it names them. */
-function filterFolders(filter: Filter | undefined | null, out: string[] = []): string[] {
-  if (!filter) return out;
-  if (typeof filter.inMailbox === 'string') out.push(filter.inMailbox);
-  if (Array.isArray(filter.conditions)) for (const c of filter.conditions as Filter[]) filterFolders(c, out);
-  return out;
-}
-
-class Unanswerable extends Error {}
-
-/** RFC 8620 §3.7 result references, with the `*` array step. */
-function resolvePointer(value: unknown, path: string): unknown {
-  const steps = path.split('/').slice(1).map((s) => s.replace(/~1/g, '/').replace(/~0/g, '~'));
-  const walk = (node: unknown, i: number): unknown => {
-    if (i === steps.length) return node;
-    const step = steps[i];
-    if (step === '*') {
-      if (!Array.isArray(node)) throw new Unanswerable();
-      return node.flatMap((item) => {
-        const out = walk(item, i + 1);
-        return Array.isArray(out) ? out : [out];
-      });
-    }
-    if (node === null || typeof node !== 'object') throw new Unanswerable();
-    return walk((node as Record<string, unknown>)[step], i + 1);
-  };
-  return walk(value, 0);
-}
-
-function resolveArgs(args: Record<string, unknown>, done: Array<[string, MethodResult, string]>): Record<string, unknown> {
-  const out: Record<string, unknown> = {};
-  for (const [key, value] of Object.entries(args)) {
-    if (!key.startsWith('#')) {
-      out[key] = value;
-      continue;
-    }
-    const ref = value as { resultOf?: string; name?: string; path?: string };
-    const source = done.find(([name, , id]) => id === ref.resultOf && name === ref.name);
-    if (!source || typeof ref.path !== 'string') throw new Unanswerable();
-    out[key.slice(1)] = resolvePointer(source[1], ref.path);
-  }
-  return out;
-}
-
-// ---- Email/query filters and sort ----
-
-type Filter = Record<string, unknown>;
-
-function matches(email: CachedEmail, filter: Filter | undefined | null): boolean {
-  if (!filter || Object.keys(filter).length === 0) return true;
-  if (typeof filter.operator === 'string') {
-    const conditions = Array.isArray(filter.conditions) ? (filter.conditions as Filter[]) : [];
-    if (filter.operator === 'AND') return conditions.every((c) => matches(email, c));
-    if (filter.operator === 'OR') return conditions.some((c) => matches(email, c));
-    if (filter.operator === 'NOT') return !conditions.some((c) => matches(email, c));
-    throw new Unanswerable();
-  }
-  for (const [key, value] of Object.entries(filter)) {
-    switch (key) {
-      case 'inMailbox':
-        if (!email.mailboxIds?.[value as string]) return false;
-        break;
-      case 'inMailboxOtherThan':
-        if (!Object.keys(email.mailboxIds ?? {}).some((id) => !(value as string[]).includes(id))) return false;
-        break;
-      case 'hasKeyword':
-        if (!email.keywords?.[value as string]) return false;
-        break;
-      case 'notKeyword':
-        if (email.keywords?.[value as string]) return false;
-        break;
-      case 'after':
-        if (Date.parse(String(email.receivedAt)) < Date.parse(String(value))) return false;
-        break;
-      case 'before':
-        if (Date.parse(String(email.receivedAt)) >= Date.parse(String(value))) return false;
-        break;
-      case 'hasAttachment':
-        if (Boolean(email.hasAttachment) !== Boolean(value)) return false;
-        break;
-      default:
-        // Text search and the rest need the server.
-        throw new Unanswerable();
-    }
-  }
-  return true;
-}
-
-interface Comparator { property?: string; isAscending?: boolean; keyword?: string }
-
-function firstAddress(value: unknown): string {
-  const first = Array.isArray(value) ? (value[0] as { name?: string; email?: string } | undefined) : undefined;
-  return (first?.name || first?.email || '').toLowerCase();
-}
-
-function compareBy(sort: Comparator[]): (a: CachedEmail, b: CachedEmail) => number {
-  const levels = sort.length > 0 ? sort : [{ property: 'receivedAt', isAscending: false }];
-  return (a, b) => {
-    for (const level of levels) {
-      let diff = 0;
-      switch (level.property) {
-        case 'receivedAt':
-        case 'sentAt':
-          diff = (Date.parse(String(a[level.property] ?? a.receivedAt)) || 0) - (Date.parse(String(b[level.property] ?? b.receivedAt)) || 0);
-          break;
-        case 'size':
-          diff = Number(a.size ?? 0) - Number(b.size ?? 0);
-          break;
-        case 'subject':
-          diff = String(a.subject ?? '').localeCompare(String(b.subject ?? ''));
-          break;
-        case 'from':
-          diff = firstAddress(a.from).localeCompare(firstAddress(b.from));
-          break;
-        case 'to':
-          diff = firstAddress(a.to).localeCompare(firstAddress(b.to));
-          break;
-        case 'hasKeyword':
-          diff = Number(Boolean(a.keywords?.[level.keyword ?? ''])) - Number(Boolean(b.keywords?.[level.keyword ?? '']));
-          break;
-        default:
-          diff = 0;
-      }
-      if (diff !== 0) return level.isAscending === false ? -diff : diff;
-    }
-    return 0;
-  };
-}
-
-async function emailsOf(ctx: ResponderContext, jmap: string): Promise<CachedEmail[]> {
-  const index = await emailIndex(ctx.account);
-  const prefix = `${ctx.account}\u0001${jmap}\u0001`;
-  const out: CachedEmail[] = [];
-  for (const [key, email] of index) if (key.startsWith(prefix)) out.push(email);
-  return out;
-}
-
-async function emailQuery(ctx: ResponderContext, args: Record<string, unknown>): Promise<MethodResult> {
-  const jmap = (args.accountId as string) || ctx.defaultJmap;
-  if (args.anchor !== undefined) throw new Unanswerable();
-  if (ctx.keptFolders) {
-    const kept = ctx.keptFolders[jmap] ?? [];
-    if (filterFolders(args.filter as Filter).some((id) => !kept.includes(id))) throw new Unanswerable();
-  }
-  let list = (await emailsOf(ctx, jmap)).filter((email) => matches(email, args.filter as Filter));
-  list.sort(compareBy((args.sort as Comparator[]) ?? []));
-  if (args.collapseThreads) {
-    const seen = new Set<string>();
-    list = list.filter((email) => {
-      const thread = email.threadId ?? email.id;
-      if (seen.has(thread)) return false;
-      seen.add(thread);
-      return true;
-    });
-  }
-  const position = Math.max(0, Number(args.position ?? 0));
-  const limit = typeof args.limit === 'number' ? args.limit : list.length;
-  return {
-    accountId: jmap,
-    canCalculateChanges: false,
-    position,
-    ids: list.slice(position, position + limit).map((email) => email.id),
-    total: list.length,
-  };
-}
-
-function pick(email: Record<string, unknown>, properties: unknown): Record<string, unknown> {
-  if (!Array.isArray(properties)) {
-    const all = { ...email };
-    delete all[BLOBS];
-    return all;
-  }
-  const out: Record<string, unknown> = { id: email.id };
-  for (const prop of properties as string[]) if (prop in email) out[prop] = email[prop];
-  return out;
-}
-
-const NEEDS_BODY = new Set(['bodyValues', 'textBody', 'htmlBody', 'bodyStructure', 'headers', 'attachments']);
-
-async function emailGet(ctx: ResponderContext, args: Record<string, unknown>): Promise<MethodResult> {
-  const jmap = (args.accountId as string) || ctx.defaultJmap;
-  const index = await emailIndex(ctx.account);
-  const ids = Array.isArray(args.ids) ? (args.ids as string[]) : null;
-  if (!ids) throw new Unanswerable();
-  const properties = args.properties as string[] | undefined;
-  const wantsBody = args.fetchTextBodyValues || args.fetchHTMLBodyValues || args.fetchAllBodyValues
-    || !properties || properties.some((p) => NEEDS_BODY.has(p));
-  const list: Record<string, unknown>[] = [];
-  const notFound: string[] = [];
-  for (const id of ids) {
-    const meta = index.get(`${ctx.account}\u0001${jmap}\u0001${id}`);
-    if (!meta) { notFound.push(id); continue; }
-    if (!wantsBody) { list.push(pick(meta, properties)); continue; }
-    const body = await getBody(ctx.account, jmap, id);
-    // Asked for the text and it isn't here: as if the message weren't
-    // there, rather than an empty message.
-    if (!body && (args.fetchTextBodyValues || args.fetchHTMLBodyValues || args.fetchAllBodyValues || properties?.includes('bodyValues'))) {
-      notFound.push(id);
-      continue;
-    }
-    list.push(pick({ ...(body ?? {}), ...meta }, properties));
-  }
-  return { accountId: jmap, list, notFound };
-}
-
-async function threadGet(ctx: ResponderContext, args: Record<string, unknown>): Promise<MethodResult> {
-  const jmap = (args.accountId as string) || ctx.defaultJmap;
-  const ids = Array.isArray(args.ids) ? (args.ids as string[]) : [];
-  const emails = await emailsOf(ctx, jmap);
-  const list = [...new Set(ids)].map((id) => ({
-    id,
-    emailIds: emails
-      .filter((email) => email.threadId === id)
-      .sort((a, b) => (Date.parse(String(a.receivedAt)) || 0) - (Date.parse(String(b.receivedAt)) || 0))
-      .map((email) => email.id),
-  }));
-  return { accountId: jmap, list: list.filter((t) => t.emailIds.length > 0), notFound: list.filter((t) => t.emailIds.length === 0).map((t) => t.id) };
-}
-
-async function listGet(ctx: ResponderContext, args: Record<string, unknown>, name: 'mailboxes' | 'identities'): Promise<MethodResult> {
-  const jmap = (args.accountId as string) || ctx.defaultJmap;
-  const all = await getMisc<Record<string, Record<string, unknown>[]>>(ctx.account, name);
-  const list = all?.[jmap];
-  if (!list) throw new Unanswerable();
-  const ids = Array.isArray(args.ids) ? new Set(args.ids as string[]) : null;
-  const chosen = ids ? list.filter((item) => ids.has(item.id as string)) : list;
-  return {
-    accountId: jmap,
-    list: chosen.map((item) => pick(item, args.properties)),
-    notFound: ids ? [...ids].filter((id) => !list.some((item) => item.id === id)) : [],
-  };
-}
-
-/** Unfiltered mailbox pages used to load a complete folder list offline. */
-async function mailboxQuery(ctx: ResponderContext, args: Record<string, unknown>): Promise<MethodResult> {
-  if (args.filter || args.sort || args.anchor || args.sortAsTree) throw new Unanswerable();
-  const { list } = await listGet(ctx, { accountId: args.accountId }, 'mailboxes');
-  const mailboxes = list as Record<string, unknown>[];
-  const position = typeof args.position === 'number' ? args.position : 0;
-  const limit = typeof args.limit === 'number' ? args.limit : mailboxes.length;
-  return {
-    accountId: (args.accountId as string) || ctx.defaultJmap,
-    // A query token only, never a Mailbox collection state for /changes.
-    queryState: JSON.stringify(mailboxes),
-    position,
-    ids: mailboxes.slice(position, position + limit).map((mailbox) => mailbox.id),
-    ...(args.calculateTotal ? { total: mailboxes.length } : {}),
-  };
-}
-
-/** Whether a PatchObject only changes what offline mode may queue. */
-function queueablePatch(patch: Record<string, unknown>): boolean {
-  return Object.keys(patch).length > 0 && Object.keys(patch).every((path) =>
-    path === 'keywords' || path === 'mailboxIds' || path.startsWith('keywords/') || path.startsWith('mailboxIds/'));
-}
-
-async function emailSet(ctx: ResponderContext, args: Record<string, unknown>): Promise<MethodResult> {
-  const jmap = (args.accountId as string) || ctx.defaultJmap;
-  // A new message (a draft saved while offline) needs the server; the
-  // composer says the draft wasn't saved, so no notice here.
-  if (args.create && Object.keys(args.create as object).length > 0) throw new Unanswerable();
-  if (Array.isArray(args.destroy) && args.destroy.length > 0) { ctx.onRefused('destroy'); throw new Unanswerable(); }
-  const update = (args.update ?? {}) as Record<string, Record<string, unknown>>;
-  if (!Object.values(update).every(queueablePatch)) { ctx.onRefused('other'); throw new Unanswerable(); }
-  // A message moved out of every folder would be gone: that is a delete.
-  const index = await emailIndex(ctx.account);
-  for (const [id, patch] of Object.entries(update)) {
-    if ('mailboxIds' in patch && Object.keys((patch.mailboxIds as object) ?? {}).length === 0) { ctx.onRefused('destroy'); throw new Unanswerable(); }
-    const current = index.get(`${ctx.account}\u0001${jmap}\u0001${id}`);
-    if (current && Object.keys(patch).some((p) => p.startsWith('mailboxIds/'))) {
-      const after = new Set(Object.keys(current.mailboxIds ?? {}));
-      for (const [path, value] of Object.entries(patch)) {
-        if (!path.startsWith('mailboxIds/')) continue;
-        const box = path.slice('mailboxIds/'.length);
-        if (value) after.add(box); else after.delete(box);
-      }
-      if (after.size === 0) { ctx.onRefused('destroy'); throw new Unanswerable(); }
-    }
-  }
-  await ctx.queuePatch(jmap, update);
-  const before = new Map(Object.keys(update).map((id) => [id, index.get(`${ctx.account}\u0001${jmap}\u0001${id}`)]));
-  await patchEmails(ctx.account, jmap, update);
-  await adjustFolderCounts(ctx, jmap, before, index);
-  return {
-    accountId: jmap,
-    updated: Object.fromEntries(Object.keys(update).map((id) => [id, null])),
-  };
-}
-
-/** The folder counts kept with the folder list follow a change made offline (read state, moves). */
-async function adjustFolderCounts(
-  ctx: ResponderContext,
-  jmap: string,
-  before: Map<string, CachedEmail | undefined>,
-  index: Map<string, CachedEmail>,
-): Promise<void> {
-  const delta = new Map<string, { total: number; unread: number }>();
-  const bump = (box: string, total: number, unread: number) => {
-    const d = delta.get(box) ?? { total: 0, unread: 0 };
-    d.total += total;
-    d.unread += unread;
-    delta.set(box, d);
-  };
-  for (const [id, old] of before) {
-    const now = index.get(`${ctx.account}\u0001${jmap}\u0001${id}`);
-    if (!old || !now) continue;
-    const wasUnread = !old.keywords?.$seen ? 1 : 0;
-    const isUnread = !now.keywords?.$seen ? 1 : 0;
-    const oldBoxes = new Set(Object.keys(old.mailboxIds ?? {}));
-    const newBoxes = new Set(Object.keys(now.mailboxIds ?? {}));
-    for (const box of oldBoxes) if (!newBoxes.has(box)) bump(box, -1, -wasUnread);
-    for (const box of newBoxes) {
-      if (!oldBoxes.has(box)) bump(box, 1, isUnread);
-      else if (wasUnread !== isUnread) bump(box, 0, isUnread - wasUnread);
-    }
-  }
-  if (delta.size === 0) return;
-  const all = await getMisc<Record<string, Array<Record<string, unknown>>>>(ctx.account, 'mailboxes');
-  const list = all?.[jmap];
-  if (!all || !list) return;
-  all[jmap] = list.map((box) => {
-    const d = delta.get(box.id as string);
-    if (!d) return box;
-    const count = (key: string, by: number) => (typeof box[key] === 'number' ? Math.max(0, (box[key] as number) + by) : box[key]);
-    // Messages only: how the conversations change can't be told from here.
-    return { ...box, totalEmails: count('totalEmails', d.total), unreadEmails: count('unreadEmails', d.unread) };
-  });
-  await putMisc(ctx.account, 'mailboxes', all);
-}
-
-/**
- * The answer to a whole request from this device, or null when any call in
- * it needs the server.
- */
-export async function answerOffline(ctx: ResponderContext, methodCalls: OfflineMethodCall[]): Promise<OfflineResponse | null> {
-  const done: Array<[string, MethodResult, string]> = [];
-  try {
-    for (const [name, rawArgs, callId] of methodCalls) {
-      const args = resolveArgs(rawArgs, done);
-      let result: MethodResult;
-      switch (name) {
-        case 'Email/query': result = await emailQuery(ctx, args); break;
-        case 'Email/get': result = await emailGet(ctx, args); break;
-        case 'Thread/get': result = await threadGet(ctx, args); break;
-        case 'Mailbox/query': result = await mailboxQuery(ctx, args); break;
-        case 'Mailbox/get': result = await listGet(ctx, args, 'mailboxes'); break;
-        case 'Identity/get': result = await listGet(ctx, args, 'identities'); break;
-        case 'Email/set': result = await emailSet(ctx, args); break;
-        default: throw new Unanswerable();
-      }
-      done.push([name, result, callId]);
-    }
-  } catch (error) {
-    if (error instanceof Unanswerable) return null;
-    throw error;
-  }
-  return { methodResponses: done };
-}
diff --git a/lib/offline/state.ts b/lib/offline/state.ts
index 14f64d32d..cfff48f59 100644
--- a/lib/offline/state.ts
+++ b/lib/offline/state.ts
@@ -1,13 +1,14 @@
 /**
  * What offline mode (#523) shows: which accounts keep mail on this device,
  * whether the browser is offline, what waits in the outbox, how much the
- * cache uses. The switch itself ("Keep mail on this device") is per account
+ * local store uses. The switch itself ("Keep mail on this device") is per account
  * and per browser, in localStorage, never synced: it is off until the user
  * turns it on here.
  */
 
 import { create } from 'zustand';
-import type { OutboxEntry, OutboxError } from './queue';
+import { DEFAULT_SCOPE, type StoreScope } from '@/lib/store/area';
+import type { ConflictEntry, OutboxEntry, OutboxError } from './queue';
 
 /** localStorage: the local account ids that keep mail on this device. */
 export const OFFLINE_ACCOUNTS_KEY = 'bulwark-offline-accounts';
@@ -31,8 +32,17 @@ interface OfflineState {
   downServers: string[];
   /** The app started without the server, from the mail on this device. */
   startedOffline: boolean;
+  /** The browser won't hand out the private file system here: a private window, say. */
+  storageBlocked: boolean;
+  /**
+   * Accounts whose store came back empty since this page loaded: the browser
+   * cleared their key or file. Whatever warns about eviction can go by this.
+   */
+  storeLost: string[];
   outbox: OutboxRow[];
   pendingChanges: number;
+  /** Changes the server refused, or that met a message changed on another device. */
+  conflicts: ConflictEntry[];
   usageBytes: number;
   /** Accounts whose mail is being brought onto the device right now. */
   syncing: string[];
@@ -54,8 +64,11 @@ export const useOfflineStore = create<OfflineState>()(() => ({
   browserOffline: typeof navigator !== 'undefined' && navigator.onLine === false,
   downServers: [],
   startedOffline: false,
+  storeLost: [],
+  storageBlocked: false,
   outbox: [],
   pendingChanges: 0,
+  conflicts: [],
   usageBytes: 0,
   syncing: [],
   lastSyncedAt: {},
@@ -71,6 +84,78 @@ export function writeEnabled(enabled: string[]): void {
   }
 }
 
+/** localStorage: what each account chose to keep offline, on top of the defaults. */
+export const OFFLINE_SCOPE_KEY = 'bulwark-offline-scope';
+
+export function offlineScopeFor(account: string): StoreScope {
+  try {
+    const chosen = (JSON.parse(localStorage.getItem(OFFLINE_SCOPE_KEY) ?? '{}') as Record<string, Partial<StoreScope>>)[account];
+    return { ...DEFAULT_SCOPE, ...chosen };
+  } catch {
+    return DEFAULT_SCOPE;
+  }
+}
+
+/** localStorage: accounts the app dropped by itself, and when. Their data waits for a new sign-in. */
+export const OFFLINE_EVICTED_KEY = 'bulwark-offline-evicted';
+/** How long that data waits. */
+export const EVICTED_KEEP_MS = 30 * 24 * 60 * 60 * 1000;
+
+export function readEvicted(): Record<string, number> {
+  try {
+    const parsed = JSON.parse(localStorage.getItem(OFFLINE_EVICTED_KEY) ?? '{}') as unknown;
+    return parsed && typeof parsed === 'object' ? parsed as Record<string, number> : {};
+  } catch {
+    return {};
+  }
+}
+
+function writeEvicted(evicted: Record<string, number>): void {
+  try {
+    if (Object.keys(evicted).length > 0) localStorage.setItem(OFFLINE_EVICTED_KEY, JSON.stringify(evicted));
+    else localStorage.removeItem(OFFLINE_EVICTED_KEY);
+  } catch {
+    /* storage unavailable */
+  }
+}
+
+/** Only an account that keeps mail here has anything to wait for. */
+export function markEvicted(account: string, now = Date.now()): void {
+  if (useOfflineStore.getState().enabled.includes(account)) writeEvicted({ ...readEvicted(), [account]: now });
+}
+
+export function clearEvicted(account: string): void {
+  const evicted = readEvicted();
+  if (!(account in evicted)) return;
+  delete evicted[account];
+  writeEvicted(evicted);
+}
+
+export function isEvicted(account: string): boolean {
+  return account in readEvicted();
+}
+
+/** The accounts whose data may show here: not those waiting for a sign-in, which may be someone else's. */
+export function visibleAccounts(): string[] {
+  const evicted = readEvicted();
+  return useOfflineStore.getState().enabled.filter((account) => !(account in evicted));
+}
+
+/**
+ * Drops the plain-text list kept in localStorage for a quick start (email-store)
+ * once the store can do that job. Until an account's first sync finishes it's
+ * what stays on screen, so turning the store on alone doesn't remove it.
+ */
+export function forgetMailSnapshot(account: string): void {
+  try {
+    const raw = localStorage.getItem('email-snapshot');
+    if (raw && (JSON.parse(raw) as { account?: unknown } | null)?.account !== account) return;
+    localStorage.removeItem('email-snapshot');
+  } catch {
+    localStorage.removeItem('email-snapshot');
+  }
+}
+
 export function serverKey(url: string): string {
   return url.replace(/\/+$/, '').toLowerCase();
 }
diff --git a/lib/offline/sync.ts b/lib/offline/sync.ts
deleted file mode 100644
index c998aef45..000000000
--- a/lib/offline/sync.ts
+++ /dev/null
@@ -1,137 +0,0 @@
-/**
- * Brings an account's recent mail onto the device (#523): the last 30 days
- * of the Inbox and of the folders the user opened (at most INBOX_LIMIT and
- * FOLDER_LIMIT messages), with bodies, and the attachments and inline
- * images of those messages up to ATTACHMENT_MAX_BYTES each. Messages that
- * left that window or the folders are removed; then the cache is brought
- * under its cap, oldest first.
- *
- * Everything goes through the JMAP client, whose answers the cache records
- * (offline-mode.ts), so the sync only asks.
- */
-
-import type { JMAPClient } from '@/lib/jmap/client';
-import { CACHE_WINDOW_MS, emailIndex, emailKey, enforceCap, getBody, hasBlob, hasBody, putBlob, putMisc, removeEmails, type CachedEmail } from './cache';
-
-export const INBOX_LIMIT = 500;
-export const FOLDER_LIMIT = 200;
-export const ATTACHMENT_MAX_BYTES = 5 * 1024 * 1024;
-/** Attachment bytes one sync run fetches at most. */
-const ATTACHMENT_BUDGET_BYTES = 100 * 1024 * 1024;
-
-interface SyncDeps {
-  stillActive: () => boolean;
-  /** Resolves once the cache has written every answer the client recorded so far. */
-  recorded: () => Promise<void>;
-  scopeMailboxes: (account: string) => Promise<Array<{ jmap: string; mailboxId: string; isInbox: boolean }>>;
-}
-
-interface AttachmentPart {
-  blobId?: string;
-  name?: string | null;
-  type?: string;
-  size?: number;
-}
-
-/** Once more after a second: Stalwart refuses requests beyond its limit of parallel ones. */
-async function twice<T>(run: () => Promise<T>): Promise<T> {
-  try {
-    return await run();
-  } catch {
-    await new Promise((r) => setTimeout(r, 1000));
-    return run();
-  }
-}
-
-export async function syncAccount(account: string, client: JMAPClient, deps: SyncDeps): Promise<void> {
-  await putMisc(account, 'session', client.getSessionSnapshot());
-  // Folders and identities are recorded from these answers.
-  await twice(() => client.getAllMailboxes()).catch(() => client.getMailboxes());
-  await twice(() => client.getIdentities()).catch(() => []);
-  // The folder list says which folder is the Inbox.
-  await deps.recorded();
-  if (!deps.stillActive()) return;
-
-  const since = new Date(Date.now() - CACHE_WINDOW_MS).toISOString();
-  const wanted = new Map<string, Set<string>>();
-  const scopes = await deps.scopeMailboxes(account);
-  // Per folder: which ones were asked, and which couldn't be.
-  const scopeFolders = new Map<string, Set<string>>();
-  const failedFolders = new Map<string, Set<string>>();
-  const add = (map: Map<string, Set<string>>, jmap: string, id: string) => {
-    const set = map.get(jmap) ?? new Set<string>();
-    set.add(id);
-    map.set(jmap, set);
-  };
-  for (const { jmap, mailboxId, isInbox } of scopes) {
-    add(scopeFolders, jmap, mailboxId);
-    let ids: string[];
-    try {
-      ids = await twice(() => client.getRecentEmailIds(mailboxId, jmap, since, isInbox ? INBOX_LIMIT : FOLDER_LIMIT));
-    } catch {
-      add(failedFolders, jmap, mailboxId);
-      continue;
-    }
-    const set = wanted.get(jmap) ?? new Set<string>();
-    ids.forEach((id) => set.add(id));
-    wanted.set(jmap, set);
-  }
-  if (!deps.stillActive()) return;
-
-  for (const [jmap, idSet] of wanted) {
-    const ids = [...idSet];
-    // Fresh keywords and folders for all of them (cheap: list properties).
-    if (ids.length) await twice(() => client.getSomeEmails(ids, jmap === client.getAccountId() ? undefined : jmap)).catch(() => []);
-    // Bodies for the ones that don't have one yet, a batch at a time.
-    const missing: string[] = [];
-    for (const id of ids) if (!(await hasBody(account, jmap, id))) missing.push(id);
-    for (let i = 0; i < missing.length; i += 20) {
-      // Fetched again at the next sync.
-      await twice(() => client.getFullEmails(missing.slice(i, i + 20), jmap)).catch(() => {});
-      if (!deps.stillActive()) return;
-    }
-  }
-  await deps.recorded();
-
-  // What left the window or the folders goes; a folder that couldn't be
-  // asked keeps what it had, the others are brought up to date.
-  const index = await emailIndex(account);
-  const stale: string[] = [];
-  if (scopes.length > 0) {
-    for (const [key, email] of index) {
-      const jmap = key.split('\u0001')[1];
-      if (wanted.get(jmap)?.has(email.id)) continue;
-      const folders = Object.keys(email.mailboxIds ?? {}).filter((id) => scopeFolders.get(jmap)?.has(id));
-      if (folders.some((id) => failedFolders.get(jmap)?.has(id))) continue;
-      stale.push(key);
-    }
-  }
-  await removeEmails(account, stale);
-
-  // Attachments and inline images, newest messages first, within the budget.
-  let budget = ATTACHMENT_BUDGET_BYTES;
-  const newestFirst = [...index.entries()].sort(([, a], [, b]) => (Date.parse(String(b.receivedAt)) || 0) - (Date.parse(String(a.receivedAt)) || 0));
-  for (const [key, email] of newestFirst) {
-    if (budget <= 0 || !deps.stillActive()) break;
-    const jmap = key.split('\u0001')[1];
-    for (const part of await attachmentsOf(account, email, jmap)) {
-      if (!part.blobId || !part.size || part.size > ATTACHMENT_MAX_BYTES || part.size > budget) continue;
-      if (await hasBlob(account, jmap, part.blobId)) continue;
-      try {
-        const blob = await client.fetchBlob(part.blobId, part.name ?? undefined, part.type, jmap);
-        await putBlob(account, jmap, part.blobId, blob, Date.parse(String(email.receivedAt)) || Date.now(), emailKey(account, jmap, email.id));
-        budget -= blob.size;
-      } catch {
-        // Fetched again at the next sync.
-      }
-    }
-  }
-
-  await enforceCap();
-}
-
-async function attachmentsOf(account: string, email: CachedEmail, jmap: string): Promise<AttachmentPart[]> {
-  const body = await getBody(account, jmap, email.id);
-  const parts = body?.attachments;
-  return Array.isArray(parts) ? (parts as AttachmentPart[]) : [];
-}
diff --git a/lib/sign-out-cleanup.ts b/lib/sign-out-cleanup.ts
index af06ead2b..531c99f7f 100644
--- a/lib/sign-out-cleanup.ts
+++ b/lib/sign-out-cleanup.ts
@@ -2,6 +2,7 @@ import { fileStorage } from '@/lib/plugin-storage';
 import { clearHandoffs } from '@/lib/launch-handoff';
 import { clearAllCheckpoints } from '@/lib/mail-import/checkpoints';
 import { sweepPrivateExports } from '@/lib/mail-export/sinks';
+import { purgeStoreFiles } from '@/lib/store/client/purge';
 
 /**
  * What a full sign-out removes from this browser beyond the stores that
@@ -35,26 +36,40 @@ const SIGNED_OUT_STORAGE_KEYS = [
   // Offline mode's "Keep mail on this device" (lib/offline/state.ts): the
   // next person signing in here starts with it off.
   'bulwark-offline-accounts',
+  // Which accounts' data waits for a new sign-in, and until when.
+  'bulwark-offline-evicted',
+  'bulwark-store-opened',
 ];
 
+const LOCAL_STORE_KEYS = new Set(['bulwark-offline-accounts', 'bulwark-offline-evicted', 'bulwark-store-opened']);
+
 const SIGNED_OUT_SIGNAL = 'bulwark:signed-out';
 export { SIGNED_OUT_SIGNAL as SIGNED_OUT_KEY };
 
 // Stores the auth store can't import (they import it) clear themselves here.
-const signedOutCleanups = new Set<() => void>();
+const signedOutCleanups = new Set<(options: SignOutCleanupOptions) => void>();
+
+export interface SignOutCleanupOptions {
+  /**
+   * Keep the local store and its keys. For a sign-out the app decided on
+   * because it couldn't confirm the login (an outage, an unknown refusal), or
+   * when an account that was dropped that way still has data here.
+   */
+  keepLocalStore?: boolean;
+}
 
 /** Run `cleanup` when everyone signs out in this tab. */
-export function onFullSignOut(cleanup: () => void): void {
+export function onFullSignOut(cleanup: (options: SignOutCleanupOptions) => void): void {
   signedOutCleanups.add(cleanup);
 }
 
 // Work that has to reach the server before an account signs out (changes
 // still queued for it). The auth store waits for it within its sign-out
 // budget, next to the plugins' onBeforeLogout.
-const beforeSignOutTasks = new Set<(accountId: string) => Promise<void>>();
+const beforeSignOutTasks = new Set<(accountId: string, options: SignOutCleanupOptions) => Promise<void>>();
 
 /** Run `task` before an account signs out; `accountId` is 'all' when every account does. */
-export function onBeforeSignOut(task: (accountId: string) => Promise<void>): () => void {
+export function onBeforeSignOut(task: (accountId: string, options: SignOutCleanupOptions) => Promise<void>): () => void {
   beforeSignOutTasks.add(task);
   return () => beforeSignOutTasks.delete(task);
 }
@@ -81,14 +96,15 @@ export async function passSignOutGates(accountId: string): Promise<boolean> {
   return true;
 }
 
-export async function runBeforeSignOut(accountId: string): Promise<void> {
-  await Promise.all([...beforeSignOutTasks].map((task) => task(accountId).catch(() => {})));
+export async function runBeforeSignOut(accountId: string, options: SignOutCleanupOptions = {}): Promise<void> {
+  await Promise.all([...beforeSignOutTasks].map((task) => task(accountId, options).catch(() => {})));
 }
 
 /** Remove the accounts' leftovers from browser storage. */
-export function purgeSignedOutData(): void {
+export function purgeSignedOutData(options: SignOutCleanupOptions = {}): void {
   if (typeof window === 'undefined') return;
   for (const key of SIGNED_OUT_STORAGE_KEYS) {
+    if (options.keepLocalStore && LOCAL_STORE_KEYS.has(key)) continue;
     try {
       window.localStorage.removeItem(key);
     } catch {
@@ -108,19 +124,23 @@ export function purgeSignedOutData(): void {
   void clearAllCheckpoints().catch(() => {});
   // Mail exports written to the browser's private files and not deleted yet.
   void sweepPrivateExports({ force: true }).catch(() => {});
-  // Offline mode (#523): the mail kept on this device, the outbox, the key
-  // they were encrypted with, and the app shell the service worker kept.
-  try {
-    window.indexedDB?.deleteDatabase('bulwark-offline');
-  } catch {
-    /* storage unavailable */
+  // Offline mode (#523): the local store with the mail and the outbox, the keys
+  // it was encrypted with, and the app shell the service worker kept. Also the
+  // database of older versions, in case it wasn't moved yet.
+  if (!options.keepLocalStore) {
+    void purgeStoreFiles();
+    try {
+      window.indexedDB?.deleteDatabase('bulwark-offline');
+    } catch {
+      /* storage unavailable */
+    }
+    forgetOfflineShell();
   }
-  forgetOfflineShell();
   // Files and links on their way into a draft or an import.
   clearHandoffs();
   for (const cleanup of signedOutCleanups) {
     try {
-      cleanup();
+      cleanup(options);
     } catch {
       /* one store failing must not keep the others' data */
     }
diff --git a/lib/store/__tests__/helpers/fake-jmap-mail.ts b/lib/store/__tests__/helpers/fake-jmap-mail.ts
new file mode 100644
index 000000000..b09683999
--- /dev/null
+++ b/lib/store/__tests__/helpers/fake-jmap-mail.ts
@@ -0,0 +1,170 @@
+/**
+ * FakeJmap with what the mail answers and the outbox talk to: identities,
+ * quotas, Email/set and submissions. Follows what was measured on Stalwart
+ * (stalwart-changes-prf.md section 1): `header` and `text` filters find no
+ * Message-ID, a second create or submission of the same message is accepted,
+ * a canceled submission still shows in EmailSubmission/query.
+ */
+
+import { FakeJmap, type FakeEmail } from './fake-jmap';
+
+export interface FakeSubmission {
+  id: string;
+  emailId: string;
+  identityId?: string;
+  undoStatus: 'pending' | 'final' | 'canceled';
+}
+
+type Filter = Record<string, unknown>;
+
+export class FakeJmapMail extends FakeJmap {
+  readonly identities = new Map<string, Record<string, unknown> & { id: string }>();
+  readonly quotas: Array<Record<string, unknown> & { id: string }> = [];
+  readonly submissions = new Map<string, FakeSubmission>();
+  /** Email/set update or destroy of these ids is refused with this error. */
+  readonly refuse = new Map<string, { type: string; description?: string }>();
+  /** A method answered with a per-call error once. */
+  readonly failNext = new Map<string, string>();
+  identityState = 0;
+  nextSubmission = 1;
+
+  private matches(email: FakeEmail, filter: Filter | undefined): boolean {
+    if (!filter) return true;
+    if (filter.operator === 'AND') return (filter.conditions as Filter[]).every((c) => this.matches(email, c));
+    if (filter.operator === 'OR') return (filter.conditions as Filter[]).some((c) => this.matches(email, c));
+    if (filter.operator === 'NOT') return !(filter.conditions as Filter[]).some((c) => this.matches(email, c));
+    for (const [key, value] of Object.entries(filter)) {
+      switch (key) {
+        case 'inMailbox':
+          if (!(email.mailboxIds as Record<string, boolean>)[value as string]) return false;
+          break;
+        case 'after':
+          if (Date.parse(String(email.receivedAt)) < Date.parse(String(value))) return false;
+          break;
+        // The filters that find nothing on Stalwart for a Message-ID.
+        case 'header':
+        case 'text':
+          return false;
+        default:
+          throw new Error(`FakeJmapMail: filter ${key} isn't modelled`);
+      }
+    }
+    return true;
+  }
+
+  private applyPatch(email: FakeEmail, patch: Record<string, unknown>): void {
+    const keywords = { ...(email.keywords as Record<string, boolean>) };
+    const boxes = { ...(email.mailboxIds as Record<string, boolean>) };
+    let wholeKeywords = keywords;
+    let wholeBoxes = boxes;
+    for (const [path, value] of Object.entries(patch)) {
+      if (path === 'keywords') wholeKeywords = { ...(value as Record<string, boolean>) };
+      else if (path === 'mailboxIds') wholeBoxes = { ...(value as Record<string, boolean>) };
+      else if (path.startsWith('keywords/')) {
+        const name = path.slice('keywords/'.length).replace(/~1/g, '/').replace(/~0/g, '~');
+        if (value) wholeKeywords[name] = true;
+        else delete wholeKeywords[name];
+      } else if (path.startsWith('mailboxIds/')) {
+        const name = path.slice('mailboxIds/'.length);
+        if (value) wholeBoxes[name] = true;
+        else delete wholeBoxes[name];
+      }
+    }
+    this.updateEmail(email.id, { keywords: wholeKeywords, mailboxIds: wholeBoxes });
+  }
+
+  protected override handle(name: string, args: Record<string, unknown>): Record<string, unknown> {
+    const failure = this.failNext.get(name);
+    if (failure) {
+      this.failNext.delete(name);
+      throw Object.assign(new Error(failure), { jmapError: failure });
+    }
+    switch (name) {
+      case 'Identity/get': {
+        const ids = args.ids as string[] | null;
+        const all = [...this.identities.values()];
+        return { accountId: args.accountId, state: `s${this.identityState}`, list: ids ? all.filter((i) => ids.includes(i.id)) : all, notFound: [] };
+      }
+      case 'Identity/changes':
+        return {
+          accountId: args.accountId,
+          oldState: args.sinceState,
+          newState: `s${this.identityState}`,
+          hasMoreChanges: false,
+          created: args.sinceState === `s${this.identityState}` ? [] : [...this.identities.keys()],
+          updated: [],
+          destroyed: [],
+        };
+      case 'Quota/get':
+        return { accountId: args.accountId, list: this.quotas, notFound: [] };
+      case 'Email/query': {
+        const matched = [...this.emails.values()]
+          .filter((email) => this.matches(email, args.filter as Filter | undefined))
+          .sort((a, b) => Date.parse(String(b.receivedAt)) - Date.parse(String(a.receivedAt)));
+        return {
+          accountId: args.accountId,
+          queryState: this.coll.Email.state(),
+          canCalculateChanges: true,
+          ...this.pageOf(matched.map((email) => email.id), args),
+          ...(args.calculateTotal ? { total: matched.length } : {}),
+        };
+      }
+      case 'Email/set': {
+        const out: Record<string, unknown> = { accountId: args.accountId };
+        if (args.update) {
+          const updated: Record<string, null> = {};
+          const notUpdated: Record<string, unknown> = {};
+          for (const [id, patch] of Object.entries(args.update as Record<string, Record<string, unknown>>)) {
+            const email = this.emails.get(id);
+            if (this.refuse.has(id)) notUpdated[id] = this.refuse.get(id);
+            else if (!email) notUpdated[id] = { type: 'notFound' };
+            else {
+              this.applyPatch(email, patch);
+              updated[id] = null;
+            }
+          }
+          out.updated = updated;
+          if (Object.keys(notUpdated).length > 0) out.notUpdated = notUpdated;
+        }
+        if (args.destroy) {
+          const destroyed: string[] = [];
+          const notDestroyed: Record<string, unknown> = {};
+          for (const id of args.destroy as string[]) {
+            if (this.refuse.has(id)) notDestroyed[id] = this.refuse.get(id);
+            else if (!this.emails.has(id)) notDestroyed[id] = { type: 'notFound' };
+            else {
+              this.destroyEmail(id);
+              destroyed.push(id);
+            }
+          }
+          out.destroyed = destroyed;
+          if (Object.keys(notDestroyed).length > 0) out.notDestroyed = notDestroyed;
+        }
+        return out;
+      }
+      case 'EmailSubmission/query': {
+        const emailIds = ((args.filter as Filter | undefined)?.emailIds ?? []) as string[];
+        const ids = [...this.submissions.values()].filter((s) => emailIds.includes(s.emailId)).map((s) => s.id);
+        return { accountId: args.accountId, queryState: 'q', canCalculateChanges: false, position: 0, ids };
+      }
+      case 'EmailSubmission/get': {
+        const ids = (args.ids ?? []) as string[];
+        return {
+          accountId: args.accountId,
+          state: 'q',
+          list: ids.flatMap((id) => (this.submissions.has(id) ? [this.submissions.get(id)] : [])),
+          notFound: ids.filter((id) => !this.submissions.has(id)),
+        };
+      }
+      default:
+        return super.handle(name, args);
+    }
+  }
+
+  /** A submission record, as if a send got that far. */
+  addSubmission(emailId: string, undoStatus: FakeSubmission['undoStatus'] = 'pending'): FakeSubmission {
+    const submission: FakeSubmission = { id: `sub${this.nextSubmission++}`, emailId, undoStatus };
+    this.submissions.set(submission.id, submission);
+    return submission;
+  }
+}
diff --git a/lib/store/__tests__/helpers/fake-jmap.ts b/lib/store/__tests__/helpers/fake-jmap.ts
index bac572400..b218138f8 100644
--- a/lib/store/__tests__/helpers/fake-jmap.ts
+++ b/lib/store/__tests__/helpers/fake-jmap.ts
@@ -82,6 +82,8 @@ export class FakeJmap implements JmapTransport {
   offline = false;
   /** Fails the next N requests as busy. */
   busyNext = 0;
+  /** Ids Email/query leaves out while Email/get still has them: a pass that missed a message. */
+  readonly hiddenFromQuery = new Set<string>();
   /** Called before each request; can change data while a sync is running. */
   beforeRequest: ((n: number) => void) | null = null;
   nextId = 1;
@@ -160,6 +162,18 @@ export class FakeJmap implements JmapTransport {
     this.coll[type].truncatedBelow = this.coll[type].log.length;
   }
 
+  /** The ids of a query's page, by position or by anchor, as Stalwart answers. */
+  protected pageOf(ids: string[], args: Record<string, unknown>): { position: number; ids: string[] } {
+    const limit = Math.min(Number(args.limit ?? 5000) || 5000, 5000);
+    let position = Number(args.position ?? 0);
+    if (args.anchor !== undefined) {
+      const at = ids.indexOf(String(args.anchor));
+      if (at < 0) throw Object.assign(new Error('anchor gone'), { jmapError: 'anchorNotFound' });
+      position = Math.max(0, at + Number(args.anchorOffset ?? 0));
+    }
+    return { position, ids: ids.slice(position, position + limit) };
+  }
+
   private queryIds(args: Record<string, unknown>): string[] {
     const filter = args.filter as { after?: string; inMailbox?: string } | undefined;
     let list = [...this.emails.values()];
@@ -169,7 +183,7 @@ export class FakeJmap implements JmapTransport {
     return list.map((e) => e.id);
   }
 
-  private handle(name: string, args: Record<string, unknown>): Record<string, unknown> {
+  protected handle(name: string, args: Record<string, unknown>): Record<string, unknown> {
     switch (name) {
       case 'Mailbox/get': {
         const ids = args.ids as string[] | null;
@@ -178,15 +192,12 @@ export class FakeJmap implements JmapTransport {
         return { accountId: args.accountId, state: this.coll.Mailbox.state(), list, notFound: [] };
       }
       case 'Email/query': {
-        const ids = this.queryIds(args);
-        const position = Number(args.position ?? 0);
-        const limit = Number(args.limit ?? 5000) || 5000;
+        const ids = this.queryIds(args).filter((id) => !this.hiddenFromQuery.has(id));
         return {
           accountId: args.accountId,
           queryState: this.coll.Email.state(),
           canCalculateChanges: true,
-          position,
-          ids: ids.slice(position, position + Math.min(limit, 5000)),
+          ...this.pageOf(ids, args),
           ...(args.calculateTotal ? { total: ids.length } : {}),
         };
       }
diff --git a/lib/store/__tests__/helpers/in-process-store.ts b/lib/store/__tests__/helpers/in-process-store.ts
new file mode 100644
index 000000000..81699f3a3
--- /dev/null
+++ b/lib/store/__tests__/helpers/in-process-store.ts
@@ -0,0 +1,104 @@
+/**
+ * The local store for tests of lib/offline: the real engine on node:sqlite in
+ * the same process, behind the seam the page uses. Fetches nothing unless a
+ * test hands it a transport.
+ */
+
+import { DEFAULT_SCOPE } from '../../area';
+import { STORE_AREAS } from '../../areas';
+import type { StoreBackend } from '../../client/api';
+import { AccountEngine } from '../../engine/account-engine';
+import type { JmapTransport, MethodCall, StoreSession } from '../../engine/transport';
+import type { StorageAdapter } from '../../storage';
+import { FAKE_SESSION } from './fake-jmap';
+import { openMemoryStore } from './node-adapter';
+
+const NO_SERVER: JmapTransport = {
+  request: async () => { throw new Error('This test has no server for the store'); },
+  download: async () => new Uint8Array(),
+  upload: async () => ({ blobId: 'x', type: '', size: 0 }),
+};
+
+export class InProcessStore implements StoreBackend {
+  readonly engines = new Map<string, AccountEngine>();
+  readonly dbs = new Map<string, StorageAdapter>();
+  /** What a test wants a failing store to do. */
+  failArea: ((name: string) => boolean) | null = null;
+  removed: string[] = [];
+  stopped = 0;
+  isSupported = true;
+
+  constructor(private readonly transport: JmapTransport = NO_SERVER, private readonly session: StoreSession = FAKE_SESSION) {}
+
+  supported(): boolean {
+    return this.isSupported;
+  }
+
+  engine(account: string, session?: StoreSession | null): AccountEngine {
+    let engine = this.engines.get(account);
+    if (!engine) {
+      const db = openMemoryStore();
+      this.dbs.set(account, db);
+      engine = new AccountEngine({
+        account,
+        db,
+        session: session ?? this.session,
+        transport: this.transport,
+        areas: STORE_AREAS,
+        scope: { ...DEFAULT_SCOPE, days: null },
+        sleep: async () => {},
+      });
+      this.engines.set(account, engine);
+    }
+    return engine;
+  }
+
+  has(account: string): boolean {
+    return this.engines.has(account);
+  }
+
+  async ensureOpen(account: string, session?: StoreSession | null): Promise<void> {
+    this.engine(account, session);
+  }
+
+  refresh(): void {}
+
+  async answer(account: string, calls: MethodCall[]) {
+    const answer = await this.engine(account).answer(calls);
+    // Across the worker boundary answers are copies.
+    return answer ? structuredClone(answer) : null;
+  }
+
+  async area<T = unknown>(account: string, name: string, params?: unknown): Promise<T> {
+    if (this.failArea?.(name)) throw new Error(`${name} failed`);
+    const result = await this.engine(account).areaCall(name, structuredClone(params));
+    return (result === undefined ? undefined : structuredClone(result)) as T;
+  }
+
+  async sync(account: string): Promise<void> {
+    await this.engine(account).requestSync();
+  }
+
+  async noteStateChange(account: string, changed: Record<string, Record<string, string>>): Promise<void> {
+    this.engine(account).noteStateChange(changed);
+  }
+
+  async setOnline(online: boolean): Promise<void> {
+    for (const engine of this.engines.values()) engine.setOnline(online);
+  }
+
+  async remove(account: string): Promise<void> {
+    this.removed.push(account);
+    await this.engines.get(account)?.close();
+    this.dbs.get(account)?.close();
+    this.engines.delete(account);
+    this.dbs.delete(account);
+  }
+
+  stop(): void {
+    this.stopped += 1;
+    for (const engine of this.engines.values()) void engine.close();
+    this.engines.clear();
+    this.dbs.clear();
+  }
+}
diff --git a/lib/store/__tests__/helpers/node-adapter.ts b/lib/store/__tests__/helpers/node-adapter.ts
index 421324cfa..7c662687e 100644
--- a/lib/store/__tests__/helpers/node-adapter.ts
+++ b/lib/store/__tests__/helpers/node-adapter.ts
@@ -1,14 +1,17 @@
 /** The storage adapter for tests: real SQLite with FTS5 through node:sqlite. */
 
-import { DatabaseSync, type SQLInputValue } from 'node:sqlite';
+import type { DatabaseSync, SQLInputValue } from 'node:sqlite';
 import { runTransaction, type SqlRow, type SqlValue, type StorageAdapter } from '../../storage';
 
+// Not an import: Vite refuses node:sqlite in the jsdom tests of lib/offline.
+const sqlite = process.getBuiltinModule('node:sqlite');
+
 export function openMemoryStore(): StorageAdapter {
-  return adapterFor(new DatabaseSync(':memory:'));
+  return adapterFor(new sqlite.DatabaseSync(':memory:'));
 }
 
 export function openFileStore(file: string): StorageAdapter {
-  return adapterFor(new DatabaseSync(file));
+  return adapterFor(new sqlite.DatabaseSync(file));
 }
 
 function adapterFor(db: DatabaseSync): StorageAdapter {
diff --git a/lib/store/__tests__/mail-answers.test.ts b/lib/store/__tests__/mail-answers.test.ts
new file mode 100644
index 000000000..980b6ea12
--- /dev/null
+++ b/lib/store/__tests__/mail-answers.test.ts
@@ -0,0 +1,571 @@
+// @vitest-environment node
+import { describe, expect, it } from 'vitest';
+import { DEFAULT_SCOPE } from '../area';
+import { AccountEngine } from '../engine/account-engine';
+import { TransportError, type MethodCall, type StoreSession } from '../engine/transport';
+import { mailArea } from '../mail';
+import { headerValue, parseHeaderProperty } from '../mail/headers';
+import { FAKE_SESSION, JMAP_ACCOUNT } from './helpers/fake-jmap';
+import { FakeJmapMail } from './helpers/fake-jmap-mail';
+import { openMemoryStore } from './helpers/node-adapter';
+
+const EVERYTHING = { ...DEFAULT_SCOPE, days: null };
+
+const FULL_SESSION: StoreSession = {
+  ...FAKE_SESSION,
+  accounts: {
+    [JMAP_ACCOUNT]: {
+      name: 'a@example.org',
+      isPersonal: true,
+      accountCapabilities: {
+        'urn:ietf:params:jmap:mail': {},
+        'urn:ietf:params:jmap:submission': {},
+        'urn:ietf:params:jmap:quota': {},
+      },
+    },
+  },
+};
+
+function engineFor(server: FakeJmapMail, scope = EVERYTHING, session = FULL_SESSION) {
+  const db = openMemoryStore();
+  const engine = new AccountEngine({
+    account: 'a@fake.test',
+    db,
+    session,
+    transport: server,
+    areas: [mailArea],
+    scope,
+    now: () => Date.UTC(2026, 10, 3),
+    sleep: async () => {},
+  });
+  return { engine, db };
+}
+
+async function one(engine: AccountEngine, call: MethodCall) {
+  const response = await engine.answer([call]);
+  return response?.methodResponses[0];
+}
+
+const HEADERS = [
+  { name: 'List-Id', value: ' Old list <old.example.org>' },
+  { name: 'List-Id', value: ' =?UTF-8?B?VGVzdA==?= list\r\n <list.example.org>' },
+  { name: 'From', value: ' "Doe, Jane" <jane@example.org>, Bob <bob@example.org>' },
+  { name: 'To', value: ' Team: a@example.org, b@example.org;, c@example.org' },
+  { name: 'Message-ID', value: ' <abc@example.org>' },
+  { name: 'Date', value: ' Tue, 03 Nov 2026 10:00:00 +0100' },
+  { name: 'List-Unsubscribe', value: ' <https://example.org/u>, <mailto:u@example.org>' },
+];
+
+describe('Email/get property forms', () => {
+  async function seeded() {
+    const server = new FakeJmapMail();
+    server.addEmail({ id: 'm', headers: HEADERS, cc: [{ name: 'Carol', email: 'carol@example.org' }] });
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    return engine;
+  }
+
+  it('answers every header form from the raw headers', async () => {
+    const engine = await seeded();
+    const [, result] = (await one(engine, ['Email/get', {
+      ids: ['m'],
+      properties: [
+        'header:List-Id',
+        'header:List-Id:asText',
+        'header:list-id:asText:all',
+        'header:List-Id:all',
+        'header:From:asAddresses',
+        'header:To:asGroupedAddresses',
+        'header:Message-ID:asMessageIds',
+        'header:Date:asDate',
+        'header:List-Unsubscribe:asURLs',
+        'header:Nope:asText',
+        'header:Nope:all',
+      ],
+    }, 'g']))!;
+    const got = result.list[0];
+    expect(got['header:List-Id']).toBe(' =?UTF-8?B?VGVzdA==?= list\r\n <list.example.org>');
+    expect(got['header:List-Id:asText']).toBe('Test list <list.example.org>');
+    expect(got['header:list-id:asText:all']).toEqual(['Old list <old.example.org>', 'Test list <list.example.org>']);
+    expect(got['header:List-Id:all']).toHaveLength(2);
+    expect(got['header:From:asAddresses']).toEqual([{ name: 'Doe, Jane', email: 'jane@example.org' }, { name: 'Bob', email: 'bob@example.org' }]);
+    expect(got['header:To:asGroupedAddresses']).toEqual([
+      { name: 'Team', addresses: [{ name: null, email: 'a@example.org' }, { name: null, email: 'b@example.org' }] },
+      { name: null, addresses: [{ name: null, email: 'c@example.org' }] },
+    ]);
+    expect(got['header:Message-ID:asMessageIds']).toEqual(['abc@example.org']);
+    expect(got['header:Date:asDate']).toBe('2026-11-03T09:00:00.000Z');
+    expect(got['header:List-Unsubscribe:asURLs']).toEqual(['https://example.org/u', 'mailto:u@example.org']);
+    expect(got['header:Nope:asText']).toBeNull();
+    expect(got['header:Nope:all']).toEqual([]);
+  });
+
+  it('prefers a form the list already stored, and has no header values for a message without a body', async () => {
+    const server = new FakeJmapMail();
+    server.addEmail({ id: 'm', headers: HEADERS, 'header:Authentication-Results:all': ['dkim=pass'] });
+    const { engine, db } = engineFor(server);
+    await engine.requestSync();
+    db.run('DELETE FROM email_body');
+    const [, result] = (await one(engine, ['Email/get', {
+      ids: ['m'],
+      properties: ['id', 'header:Authentication-Results:all', 'header:List-Id:asText'],
+    }, 'g']))!;
+    expect(result.list).toEqual([{ id: 'm', 'header:Authentication-Results:all': ['dkim=pass'] }]);
+  });
+
+  it('cuts body parts to bodyProperties, in the structure too', async () => {
+    const server = new FakeJmapMail();
+    server.addEmail({
+      id: 'm',
+      attachments: [{ partId: '2', blobId: 'b', name: 'a.pdf', type: 'application/pdf', size: 3, language: ['de'] }],
+      bodyStructure: { type: 'multipart/mixed', subParts: [{ partId: '1', type: 'text/plain', language: ['de'] }] },
+    });
+    const { engine } = engineFor(server, { ...EVERYTHING, attachments: false });
+    await engine.requestSync();
+    const [, result] = (await one(engine, ['Email/get', {
+      ids: ['m'],
+      properties: ['attachments', 'bodyStructure', 'textBody'],
+      bodyProperties: ['partId', 'blobId', 'size', 'name', 'type'],
+    }, 'g']))!;
+    expect(result.list[0].attachments).toEqual([{ partId: '2', blobId: 'b', name: 'a.pdf', type: 'application/pdf', size: 3 }]);
+    expect(result.list[0].bodyStructure).toEqual({ type: 'multipart/mixed', subParts: [{ partId: '1', type: 'text/plain' }] });
+  });
+
+  it('gives the whole text with no truncation mark, whatever maxBodyValueBytes says', async () => {
+    const long = 'x'.repeat(5000);
+    const server = new FakeJmapMail();
+    server.addEmail({ id: 'm', bodyValues: { 1: { value: long, isTruncated: false, isEncodingProblem: false } } });
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    const [, result] = (await one(engine, ['Email/get', { ids: ['m'], properties: ['bodyValues'], fetchAllBodyValues: true, maxBodyValueBytes: 100 }, 'g']))!;
+    expect(result.list[0].bodyValues['1'].value).toBe(long);
+    expect(result.list[0].bodyValues['1'].isTruncated).toBe(false);
+  });
+
+  it('returns only the body values asked for', async () => {
+    const server = new FakeJmapMail();
+    server.addEmail({
+      id: 'm',
+      textBody: [{ partId: 't', type: 'text/plain' }],
+      htmlBody: [{ partId: 'h', type: 'text/html' }],
+      bodyValues: { t: { value: 'text' }, h: { value: '<p>html</p>' } },
+    });
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    const values = async (flags: Record<string, unknown>) => (await one(engine, ['Email/get', { ids: ['m'], properties: ['bodyValues'], ...flags }, 'g']))![1].list[0].bodyValues;
+    expect(Object.keys(await values({ fetchTextBodyValues: true }))).toEqual(['t']);
+    expect(Object.keys(await values({ fetchHTMLBodyValues: true }))).toEqual(['h']);
+    expect(Object.keys(await values({ fetchAllBodyValues: true })).sort()).toEqual(['h', 't']);
+    expect(await values({})).toEqual({});
+  });
+
+  it('keeps refusing ids: null, because the server gives only the first 500 there', async () => {
+    const engine = await seeded();
+    const response = await engine.answer([['Email/get', { ids: null }, 'g'], ['Core/echo', {}, 'e']]);
+    expect(response?.methodResponses[0]).toEqual(['error', expect.objectContaining({ type: 'requestTooLarge' }), 'g']);
+  });
+});
+
+describe('header property parsing', () => {
+  it('leaves out what is not a header form', () => {
+    expect(parseHeaderProperty('subject')).toBeNull();
+    expect(parseHeaderProperty('header:')).toBeNull();
+    expect(parseHeaderProperty('header:X:asWhat')).toBeNull();
+    expect(parseHeaderProperty('header:X-Label:asText')).toEqual({ name: 'X-Label', form: 'asText', all: false });
+    expect(headerValue({ name: 'x', form: 'asRaw', all: false }, [{ name: 'X', value: ' 1' }, { name: 'x', value: ' 2' }])).toBe(' 2');
+  });
+});
+
+describe('Email/query filters and sorts', () => {
+  async function seeded() {
+    const server = new FakeJmapMail({
+      mailboxes: [
+        { id: 'inbox', name: 'Inbox', role: 'inbox' },
+        { id: 'trash', name: 'Trash', role: 'trash' },
+        { id: 'work', name: 'Work' },
+      ],
+    });
+    server.addEmail({
+      id: 'a', subject: 'Rechnung', from: [{ name: 'Anna', email: 'anna@example.org' }], to: [{ email: 'x@example.org' }],
+      cc: [{ name: 'Carol', email: 'carol@example.org' }], keywords: { $seen: true, '$label:work': true }, size: 500,
+      receivedAt: '2026-10-01T00:00:00Z', hasAttachment: true, headers: [{ name: 'X-Tag', value: ' blue' }], bcc: [{ email: 'hidden@example.org' }],
+    });
+    server.addEmail({
+      id: 'b', subject: 'Hello', from: [{ name: 'Bert', email: 'bert@example.org' }], to: [{ email: 'y@example.org' }],
+      keywords: { $flagged: true }, size: 100, receivedAt: '2026-10-02T00:00:00Z', mailboxIds: { inbox: true, work: true },
+    });
+    server.addEmail({
+      id: 'c', subject: 'Trash mail', from: [{ name: 'Cora', email: 'cora@example.org' }], to: [{ email: 'y@example.org' }],
+      keywords: {}, size: 2000, receivedAt: '2026-10-03T00:00:00Z', mailboxIds: { trash: true },
+    });
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    return engine;
+  }
+
+  const ids = async (engine: AccountEngine, args: Record<string, unknown>) => (await one(engine, ['Email/query', args, 'q']))![1].ids;
+
+  it('answers every shape the UI sends', async () => {
+    const engine = await seeded();
+    const newest = [{ property: 'receivedAt', isAscending: false }];
+    const cases: Array<[Record<string, unknown>, string[]]> = [
+      [{ inMailbox: 'inbox' }, ['b', 'a']],
+      [{ hasKeyword: '$seen' }, ['a']],
+      [{ notKeyword: '$seen' }, ['c', 'b']],
+      [{ operator: 'AND', conditions: [{ inMailbox: 'inbox' }, { notKeyword: '$seen' }] }, ['b']],
+      [{ operator: 'NOT', conditions: [{ hasKeyword: '$label:work' }] }, ['c', 'b']],
+      [{ operator: 'OR', conditions: [{ inMailbox: 'trash' }, { inMailbox: 'work' }] }, ['c', 'b']],
+      [{ inMailboxOtherThan: ['trash'] }, ['b', 'a']],
+      [{ text: 'rechnung' }, ['a']],
+      [{ subject: 'hello' }, ['b']],
+      [{ from: 'anna' }, ['a']],
+      [{ to: 'y@example.org' }, ['c', 'b']],
+      [{ cc: 'carol' }, ['a']],
+      [{ bcc: 'hidden' }, ['a']],
+      [{ header: ['X-Tag'] }, ['a']],
+      [{ header: ['X-Tag', 'blue'] }, ['a']],
+      [{ header: ['X-Tag', 'red'] }, []],
+      [{ hasAttachment: true }, ['a']],
+      [{ after: '2026-10-02T00:00:00Z' }, ['c', 'b']],
+      [{ before: '2026-10-02T00:00:00Z' }, ['a']],
+      [{ minSize: 500 }, ['c', 'a']],
+      [{ maxSize: 500 }, ['b']],
+      [{ operator: 'AND', conditions: [{ inMailbox: 'inbox' }, { operator: 'OR', conditions: [{ to: 'x@example.org' }, { cc: 'nobody' }] }] }, ['a']],
+    ];
+    for (const [filter, want] of cases) expect([filter, await ids(engine, { filter, sort: newest })]).toEqual([filter, want]);
+    expect(await ids(engine, { sort: newest })).toEqual(['c', 'b', 'a']);
+  });
+
+  it('sorts by every level the list offers', async () => {
+    const engine = await seeded();
+    const sorted = (sort: unknown[]) => ids(engine, { sort });
+    expect(await sorted([{ property: 'size', isAscending: true }])).toEqual(['b', 'a', 'c']);
+    expect(await sorted([{ property: 'subject', isAscending: true }])).toEqual(['b', 'a', 'c']);
+    expect(await sorted([{ property: 'from', isAscending: false }])).toEqual(['c', 'b', 'a']);
+    expect(await sorted([{ property: 'sentAt', isAscending: true }])).toHaveLength(3);
+    expect(await sorted([{ property: 'hasKeyword', keyword: '$flagged', isAscending: false }, { property: 'receivedAt', isAscending: false }])).toEqual(['b', 'c', 'a']);
+  });
+
+  it('gives a per-call error for a filter it can\'t answer, and no made-up state', async () => {
+    const engine = await seeded();
+    const response = await engine.answer([['Email/query', { filter: { allInThreadHaveKeyword: '$seen' } }, 'q'], ['Core/echo', {}, 'e']]);
+    expect(response?.methodResponses[0][0]).toBe('error');
+    expect(response?.methodResponses[0][1].type).toBe('unsupportedFilter');
+    expect(await engine.answer([['Email/query', { filter: { allInThreadHaveKeyword: '$seen' } }, 'q']])).toBeNull();
+  });
+
+  it('says total only when asked, and pages by position', async () => {
+    const engine = await seeded();
+    const [, plain] = (await one(engine, ['Email/query', {}, 'q']))!;
+    expect(plain).not.toHaveProperty('total');
+    const [, page] = (await one(engine, ['Email/query', { position: 1, limit: 1, calculateTotal: true, sort: [{ property: 'receivedAt', isAscending: false }] }, 'q']))!;
+    expect(page).toMatchObject({ ids: ['b'], total: 3, position: 1 });
+  });
+});
+
+describe('a store without its mail yet', () => {
+  it('says so rather than answering an empty list, until the first sync has finished', async () => {
+    const server = new FakeJmapMail();
+    server.addEmail({ id: 'one' });
+    const { engine } = engineFor(server);
+    const inbox = Object.keys((server.emails.get('one')!.mailboxIds) as Record<string, boolean>)[0];
+    const query = () => one(engine, ['Email/query', { filter: { inMailbox: inbox } }, 'q']);
+    // No answer: the client reports it can't tell, and the list on screen stays.
+    expect(await query()).toBeUndefined();
+    await engine.requestSync();
+    expect((await query())![1].ids).toEqual(['one']);
+    // After a finished sync, an empty folder really is empty.
+    server.destroyEmail('one');
+    await engine.requestSync();
+    expect((await query())![1].ids).toEqual([]);
+  });
+
+  it('tells a start whether there are folders to show', async () => {
+    const server = new FakeJmapMail();
+    const { engine } = engineFor(server);
+    expect(await engine.areaCall('mail.hasFolders', {})).toBe(false);
+    await engine.requestSync();
+    expect(await engine.areaCall('mail.hasFolders', {})).toBe(true);
+  });
+});
+
+describe('keyword case, as measured on both Stalwart versions', () => {
+  it('keeps two keywords differing only in case, and sync doesn\'t stop on them', async () => {
+    const server = new FakeJmapMail();
+    server.addEmail({ id: 'both', keywords: { Tag: true, tag: true, $seen: true } });
+    server.addEmail({ id: 'upper', keywords: { Tag: true, $SEEN: true, $seen: true } });
+    server.addEmail({ id: 'none', keywords: {} });
+    const { engine, db } = engineFor(server);
+    await engine.requestSync();
+    expect(db.get<{ n: number }>('SELECT COUNT(*) AS n FROM email')?.n).toBe(3);
+    const has = async (keyword: string) => (await one(engine, ['Email/query', { filter: { hasKeyword: keyword }, sort: [{ property: 'receivedAt', isAscending: false }] }, 'q']))![1].ids;
+    expect(await has('Tag')).toEqual(['upper', 'both']);
+    expect(await has('tag')).toEqual(['both']);
+    expect(await has('TAG')).toEqual([]);
+    expect(await has('$SEEN')).toEqual(['upper', 'both']);
+    const [, counts] = (await one(engine, ['Keyword/get', { ids: ['Tag', 'tag', '$SEEN'] }, 'k']))!;
+    expect(counts.list).toEqual([{ id: 'Tag', total: 2, unread: 0 }, { id: 'tag', total: 1, unread: 0 }, { id: '$SEEN', total: 2, unread: 0 }]);
+  });
+});
+
+describe('the rest of the mail methods', () => {
+  it('answers Core/echo with what it was given', async () => {
+    const { engine } = engineFor(new FakeJmapMail());
+    expect(await one(engine, ['Core/echo', { ping: 'pong' }, 'e'])).toEqual(['Core/echo', { ping: 'pong' }, 'e']);
+  });
+
+  it('answers /changes with an error, so the client does a full fetch', async () => {
+    const server = new FakeJmapMail();
+    server.addEmail();
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    const response = await engine.answer([
+      ['Email/changes', { sinceState: 's1' }, 'e'],
+      ['Mailbox/changes', { sinceState: 's1' }, 'm'],
+      ['Core/echo', {}, 'x'],
+    ]);
+    expect(response?.methodResponses[0]).toEqual(['error', expect.objectContaining({ type: 'cannotCalculateChanges' }), 'e']);
+    expect(response?.methodResponses[1]).toEqual(['error', expect.objectContaining({ type: 'cannotCalculateChanges' }), 'm']);
+  });
+
+  it('answers a search with its snippets in one request', async () => {
+    const server = new FakeJmapMail();
+    server.addEmail({ subject: 'Findme' });
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    const response = await engine.answer([
+      ['Email/query', { filter: { text: 'findme' } }, '0'],
+      ['SearchSnippet/get', { filter: { text: 'findme' }, '#emailIds': { resultOf: '0', name: 'Email/query', path: '/ids' } }, 'snippets'],
+    ]);
+    expect(response?.methodResponses[0][1].ids).toHaveLength(1);
+    expect(response?.methodResponses[1][0]).toBe('SearchSnippet/get');
+  });
+
+  it('counts keywords for Keyword/get', async () => {
+    const server = new FakeJmapMail();
+    server.addEmail({ keywords: { '$label:a': true, $seen: true } });
+    server.addEmail({ keywords: { '$label:a': true } });
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    const [, wanted] = (await one(engine, ['Keyword/get', { ids: ['$label:a', '$label:none'] }, 'k']))!;
+    expect(wanted.list).toEqual([{ id: '$label:a', total: 2, unread: 1 }, { id: '$label:none', total: 0, unread: 0 }]);
+    const [, all] = (await one(engine, ['Keyword/get', {}, 'k']))!;
+    expect(all.totalEmails).toBe(2);
+    expect(all.list.map((k: { id: string }) => k.id).sort()).toEqual(['$label:a', '$seen']);
+  });
+
+  it('keeps identities through a sync and answers them, with the real state', async () => {
+    const server = new FakeJmapMail();
+    server.identities.set('i1', { id: 'i1', email: 'a@example.org', name: 'A' });
+    const { engine } = engineFor(server);
+    expect((await one(engine, ['Identity/get', {}, 'i']))).toBeUndefined();
+    await engine.requestSync();
+    const [, result] = (await one(engine, ['Identity/get', {}, 'i']))!;
+    expect(result.list).toEqual([{ id: 'i1', email: 'a@example.org', name: 'A' }]);
+    expect(result.state).toBe('s0');
+
+    server.identities.set('i2', { id: 'i2', email: 'b@example.org', name: 'B' });
+    server.identityState = 1;
+    await engine.requestSync();
+    expect((await one(engine, ['Identity/get', { ids: ['i2'] }, 'i']))![1].list).toEqual([{ id: 'i2', email: 'b@example.org', name: 'B' }]);
+  });
+
+  it('keeps the last quota', async () => {
+    const server = new FakeJmapMail();
+    server.quotas.push({ id: 'q', used: 10, hardLimit: 100 });
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    server.offline = true;
+    expect((await one(engine, ['Quota/get', {}, 'q']))![1].list).toEqual([{ id: 'q', used: 10, hardLimit: 100 }]);
+  });
+
+  it('keeps going when one account has no submission capability', async () => {
+    const server = new FakeJmapMail();
+    server.addEmail();
+    const { engine, db } = engineFor(server, EVERYTHING, FAKE_SESSION);
+    await engine.requestSync();
+    expect(db.get('SELECT 1 AS x FROM email')).toBeTruthy();
+    expect(server.calls.some(([name]) => name === 'Identity/get')).toBe(false);
+  });
+
+  it('removes a folder deleted on the server, and answers what is left', async () => {
+    const server = new FakeJmapMail({ mailboxes: [{ id: 'inbox', name: 'Inbox', role: 'inbox' }, { id: 'old', name: 'Old' }] });
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    server.mailboxes.delete('old');
+    server.coll.Mailbox.push('destroyed', 'old');
+    await engine.requestSync();
+    const [, result] = (await one(engine, ['Mailbox/get', {}, 'm']))!;
+    expect(result.list.map((box: { id: string }) => box.id)).toEqual(['inbox']);
+    const [, queried] = (await one(engine, ['Mailbox/query', { filter: { role: 'inbox' } }, 'q']))!;
+    expect(queried).toMatchObject({ ids: ['inbox'], queryState: server.coll.Mailbox.state() });
+  });
+});
+
+describe('attachments', () => {
+  class Files extends FakeJmapMail {
+    downloads: string[] = [];
+    missing = new Set<string>();
+    override async download(_jmap?: string, blobId?: string): Promise<Uint8Array> {
+      this.downloads.push(String(blobId));
+      if (this.offline) throw new TransportError('network', 'Failed to fetch');
+      if (this.missing.has(String(blobId))) throw new TransportError('http', 'Gone', 404);
+      return new Uint8Array([1, 2, 3]);
+    }
+  }
+
+  const withFile = (server: Files, id: string, blobId: string, size = 3) => server.addEmail({
+    id,
+    attachments: [{ partId: '2', blobId, name: `${blobId}.pdf`, type: 'application/pdf', size }],
+  });
+
+  it('keeps the files of kept messages within the chosen size, and deletes them with the message', async () => {
+    const server = new Files();
+    withFile(server, 'small', 'b-small');
+    withFile(server, 'big', 'b-big', 10_000);
+    const { engine, db } = engineFor(server, { ...EVERYTHING, maxAttachmentBytes: 1000 });
+    await engine.requestSync();
+    expect(server.downloads).toEqual(['b-small']);
+    const stored = await engine.areaCall('mail.getBlob', { jmap: JMAP_ACCOUNT, blobId: 'b-small' }) as { type: string; data: Uint8Array };
+    expect(stored.type).toBe('application/pdf');
+    expect([...stored.data]).toEqual([1, 2, 3]);
+
+    server.destroyEmail('small');
+    await engine.requestSync();
+    expect(await engine.areaCall('mail.getBlob', { jmap: JMAP_ACCOUNT, blobId: 'b-small' })).toBeNull();
+    expect(db.get('SELECT 1 AS x FROM email_part WHERE blob_id = ?', ['b-small'])).toBeUndefined();
+  });
+
+  it('keeps a shared file until the last message using it goes', async () => {
+    const server = new Files();
+    withFile(server, 'one', 'b-same');
+    withFile(server, 'two', 'b-same');
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    server.destroyEmail('one');
+    await engine.requestSync();
+    expect(await engine.areaCall('mail.getBlob', { jmap: JMAP_ACCOUNT, blobId: 'b-same' })).not.toBeNull();
+    server.destroyEmail('two');
+    await engine.requestSync();
+    expect(await engine.areaCall('mail.getBlob', { jmap: JMAP_ACCOUNT, blobId: 'b-same' })).toBeNull();
+  });
+
+  it('keeps none when the user chose so, stops at the total, and doesn\'t ask again for a file the server refused', async () => {
+    const off = new Files();
+    withFile(off, 'm', 'b-1');
+    await engineFor(off, { ...EVERYTHING, attachments: false }).engine.requestSync();
+    expect(off.downloads).toEqual([]);
+
+    const capped = new Files();
+    withFile(capped, 'old', 'b-old', 3);
+    withFile(capped, 'new', 'b-new', 3);
+    await engineFor(capped, { ...EVERYTHING, maxTotalBytes: 4 }).engine.requestSync();
+    expect(capped.downloads).toEqual(['b-new']);
+
+    const refused = new Files();
+    refused.missing.add('b-gone');
+    withFile(refused, 'm', 'b-gone');
+    const { engine } = engineFor(refused);
+    await engine.requestSync();
+    await engine.requestSync();
+    expect(refused.downloads).toEqual(['b-gone']);
+  });
+
+  it.each([500, 503, 429, 401])('tries a file again after a %i, which says nothing about the file', async (status) => {
+    class Failing extends Files {
+      fails = true;
+      override async download(jmap?: string, blobId?: string): Promise<Uint8Array> {
+        if (this.fails) throw new TransportError('http', 'Nope', status);
+        return super.download(jmap, blobId);
+      }
+    }
+    const server = new Failing();
+    server.addEmail({ id: 'm', attachments: [{ blobId: 'b', size: 10, type: 'image/png' }] });
+    const { engine, db } = engineFor(server);
+    await engine.requestSync();
+    expect(db.get<{ refused: number }>('SELECT refused FROM email_part')?.refused).toBe(0);
+    server.fails = false;
+    server.addEmail({ id: 'n' });
+    await engine.requestSync();
+    expect(await engine.areaCall('mail.getBlob', { jmap: JMAP_ACCOUNT, blobId: 'b' })).not.toBeNull();
+  });
+
+  it.each([403, 404, 410])('gives up on a file after a %i', async (status) => {
+    class Refusing extends Files {
+      override async download(): Promise<Uint8Array> {
+        throw new TransportError('http', 'Nope', status);
+      }
+    }
+    const server = new Refusing();
+    server.addEmail({ id: 'm', attachments: [{ blobId: 'b', size: 10, type: 'image/png' }] });
+    const { engine, db } = engineFor(server);
+    await engine.requestSync();
+    expect(db.get<{ refused: number }>('SELECT refused FROM email_part')?.refused).toBe(1);
+  });
+
+  it('files a blob the user opened only as far as the chosen scope allows', async () => {
+    const server = new Files();
+    server.addEmail({ id: 'm', attachments: [{ blobId: 'b-kept', size: 10, type: 'image/png' }] });
+    const data = new Uint8Array(10);
+    const record = { jmap: JMAP_ACCOUNT, blobId: 'b-kept', type: 'image/png', data };
+
+    const none = engineFor(server, { ...EVERYTHING, attachments: false });
+    await none.engine.requestSync();
+    expect(await none.engine.areaCall('mail.recordBlob', record)).toBe(false);
+    expect(await none.engine.areaCall('mail.getBlob', { jmap: JMAP_ACCOUNT, blobId: 'b-kept' })).toBeNull();
+
+    const small = engineFor(server, { ...EVERYTHING, attachments: true, maxAttachmentBytes: 9 });
+    await small.engine.requestSync();
+    expect(await small.engine.areaCall('mail.recordBlob', record)).toBe(false);
+
+    const fits = engineFor(server, { ...EVERYTHING, attachments: true, maxAttachmentBytes: 10 });
+    await fits.engine.requestSync();
+    expect(await fits.engine.areaCall('mail.recordBlob', record)).toBe(true);
+  });
+
+  it('files a blob the user opened only under a kept message: never a stray file', async () => {
+    const server = new Files();
+    server.addEmail({ id: 'm', attachments: [{ blobId: 'b-kept', size: 99_999_999, type: 'image/png' }] });
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    expect(await engine.areaCall('mail.recordBlob', { jmap: JMAP_ACCOUNT, blobId: 'export-of-a-message', type: null, data: new Uint8Array([1]) })).toBe(false);
+    expect(await engine.areaCall('mail.getBlob', { jmap: JMAP_ACCOUNT, blobId: 'export-of-a-message' })).toBeNull();
+    expect(await engine.areaCall('mail.recordBlob', { jmap: JMAP_ACCOUNT, blobId: 'b-kept', type: 'image/png', data: new Uint8Array([7]) })).toBe(true);
+    expect(await engine.areaCall('mail.getBlob', { jmap: JMAP_ACCOUNT, blobId: 'b-kept' })).toMatchObject({ type: 'image/png' });
+  });
+});
+
+describe('what the user opened online', () => {
+  it('keeps a message from outside the window with its text, and leaves kept ones alone', async () => {
+    const server = new FakeJmapMail();
+    server.addEmail({ id: 'kept', subject: 'Kept' });
+    const { engine } = engineFor(server);
+    await engine.requestSync();
+    const opened = {
+      id: 'old', threadId: 'told', mailboxIds: { inbox: true }, keywords: {}, receivedAt: '2019-01-01T00:00:00Z', subject: 'Old',
+      textBody: [{ partId: '1', type: 'text/plain' }], htmlBody: [], attachments: [], bodyValues: { 1: { value: 'Old text' } }, headers: [{ name: 'X', value: ' y' }],
+    };
+    await engine.areaCall('mail.recordOpened', {
+      jmap: JMAP_ACCOUNT,
+      emails: [
+        opened,
+        { id: 'kept', subject: 'Changed?', bodyValues: { 1: { value: 'other' } }, mailboxIds: {}, receivedAt: '2019-01-01T00:00:00Z' },
+        { id: 'cut', mailboxIds: { inbox: true }, receivedAt: '2019-01-01T00:00:00Z', bodyValues: { 1: { value: 'par', isTruncated: true } } },
+        { id: 'nobody', mailboxIds: { inbox: true }, receivedAt: '2019-01-01T00:00:00Z' },
+      ],
+    });
+    const [, result] = (await one(engine, ['Email/get', { ids: ['old', 'kept', 'cut', 'nobody'], properties: ['subject', 'bodyValues', 'header:X:asText'], fetchAllBodyValues: true }, 'g']))!;
+    expect(result.notFound).toEqual(['cut', 'nobody']);
+    expect(result.list[0]).toMatchObject({ id: 'old', subject: 'Old', 'header:X:asText': 'y' });
+    expect(result.list[0].bodyValues['1'].value).toBe('Old text');
+    expect(result.list[1].subject).toBe('Kept');
+  });
+});
+
+describe('usage and session', () => {
+  it('reports the bytes of the file and the kept session', async () => {
+    const { engine } = engineFor(new FakeJmapMail());
+    expect((await engine.areaCall('mail.usage', {}) as { bytes: number }).bytes).toBeGreaterThan(0);
+    expect(await engine.areaCall('mail.session', {})).toEqual(FULL_SESSION);
+  });
+});
diff --git a/lib/store/__tests__/mail-speed.test.ts b/lib/store/__tests__/mail-speed.test.ts
new file mode 100644
index 000000000..3e9212e9a
--- /dev/null
+++ b/lib/store/__tests__/mail-speed.test.ts
@@ -0,0 +1,276 @@
+// @vitest-environment node
+import { beforeEach, describe, expect, it } from 'vitest';
+import { DEFAULT_SCOPE, STORAGE_ERROR_AREA, type StoreEvent } from '../area';
+import { AccountEngine } from '../engine/account-engine';
+import { TransportError } from '../engine/transport';
+import { mailArea } from '../mail';
+import { outboxArea } from '../outbox';
+import { isStorageFailure, type SqlValue, type StorageAdapter } from '../storage';
+import { FAKE_SESSION } from './helpers/fake-jmap';
+import { FakeJmapMail } from './helpers/fake-jmap-mail';
+import { openMemoryStore } from './helpers/node-adapter';
+
+/** Records the SQL of a query, so its plan can be read. */
+function spying(db: StorageAdapter) {
+  const seen: Array<{ sql: string; params: readonly SqlValue[] }> = [];
+  const spied: StorageAdapter = {
+    exec: (sql) => db.exec(sql),
+    run: (sql, params) => db.run(sql, params),
+    all: <T extends object>(sql: string, params?: readonly SqlValue[]) => {
+      seen.push({ sql, params: params ?? [] });
+      return db.all<T>(sql, params);
+    },
+    get: <T extends object>(sql: string, params?: readonly SqlValue[]) => {
+      seen.push({ sql, params: params ?? [] });
+      return db.get<T>(sql, params);
+    },
+    transaction: (fn) => db.transaction(fn),
+    close: () => db.close(),
+  };
+  return { spied, seen };
+}
+
+function setup(emails: Array<{ id: string; keywords?: Record<string, boolean>; mailboxIds?: Record<string, boolean> }>) {
+  const server = new FakeJmapMail({ mailboxes: [{ id: 'inbox', role: 'inbox' }, { id: 'other' }] });
+  emails.forEach((email, i) => server.addEmail({
+    keywords: {},
+    mailboxIds: { inbox: true },
+    receivedAt: new Date(Date.UTC(2026, 9, 1) + i * 60_000).toISOString(),
+    ...email,
+  }));
+  const raw = openMemoryStore();
+  const { spied, seen } = spying(raw);
+  const engine = new AccountEngine({
+    account: 'a', db: spied, session: FAKE_SESSION, transport: server, areas: [mailArea, outboxArea],
+    scope: { ...DEFAULT_SCOPE, days: null, attachments: false }, sleep: async () => {},
+  });
+  return { server, raw, seen, engine };
+}
+
+const NEWEST = { property: 'receivedAt', isAscending: false };
+const PINNED = { property: 'hasKeyword', keyword: '$pinned', isAscending: false };
+const UNREAD_FIRST = { property: 'hasKeyword', keyword: '$seen', isAscending: true };
+const IN_INBOX = { inMailbox: 'inbox' };
+
+async function ids(engine: AccountEngine, args: Record<string, unknown>): Promise<string[]> {
+  const answer = await engine.answer([['Email/query', args, 'q']]);
+  return answer?.methodResponses[0][1].ids;
+}
+
+async function plans(t: ReturnType<typeof setup>, args: Record<string, unknown>) {
+  t.seen.length = 0;
+  await t.engine.answer([['Email/query', args, 'q']]);
+  const reads = t.seen.filter(({ sql }) => /^SELECT (e\.id|COUNT)/.test(sql) && !sql.includes('sync_state'));
+  return reads.map(({ sql, params }) => ({
+    sql,
+    plan: t.raw.all<{ detail: string }>(`EXPLAIN QUERY PLAN ${sql}`, params).map((row) => row.detail).join('; '),
+  }));
+}
+
+describe('pinned and unread first', () => {
+  const MAIL: Array<{ id: string; keywords?: Record<string, boolean>; mailboxIds?: Record<string, boolean> }> = [
+    { id: 'old-read', keywords: { $seen: true } },
+    { id: 'old-unread' },
+    { id: 'pin-read', keywords: { $seen: true, $pinned: true } },
+    { id: 'mid-read', keywords: { $seen: true } },
+    { id: 'pin-unread', keywords: { $pinned: true } },
+    { id: 'new-unread' },
+    { id: 'new-read', keywords: { $seen: true } },
+    { id: 'elsewhere', keywords: { $pinned: true }, mailboxIds: { other: true } },
+  ];
+
+  let t: ReturnType<typeof setup>;
+
+  beforeEach(async () => {
+    t = setup(MAIL);
+    await t.engine.requestSync();
+  });
+
+  it('comes out the same as sorting the whole folder would', async () => {
+    expect(await ids(t.engine, { filter: IN_INBOX, sort: [PINNED, NEWEST] }))
+      .toEqual(['pin-unread', 'pin-read', 'new-read', 'new-unread', 'mid-read', 'old-unread', 'old-read']);
+    expect(await ids(t.engine, { filter: IN_INBOX, sort: [UNREAD_FIRST, NEWEST] }))
+      .toEqual(['new-unread', 'pin-unread', 'old-unread', 'new-read', 'mid-read', 'pin-read', 'old-read']);
+    expect(await ids(t.engine, { filter: IN_INBOX, sort: [PINNED, UNREAD_FIRST, NEWEST] }))
+      .toEqual(['pin-unread', 'pin-read', 'new-unread', 'old-unread', 'new-read', 'mid-read', 'old-read']);
+    // No date level at all: the same.
+    expect(await ids(t.engine, { filter: IN_INBOX, sort: [PINNED] }))
+      .toEqual(['pin-unread', 'pin-read', 'new-read', 'new-unread', 'mid-read', 'old-unread', 'old-read']);
+  });
+
+  it('pages across the groups', async () => {
+    const whole = await ids(t.engine, { filter: IN_INBOX, sort: [PINNED, NEWEST] });
+    for (let position = 0; position < whole.length + 2; position += 1) {
+      for (const limit of [1, 2, 3, 50]) {
+        expect(await ids(t.engine, { filter: IN_INBOX, sort: [PINNED, NEWEST], position, limit })).toEqual(whole.slice(position, position + limit));
+      }
+    }
+  });
+
+  it('keeps conditions, across the whole account too', async () => {
+    expect(await ids(t.engine, { filter: { operator: 'AND', conditions: [IN_INBOX, { notKeyword: '$seen' }] }, sort: [PINNED, NEWEST] }))
+      .toEqual(['pin-unread', 'new-unread', 'old-unread']);
+    expect(await ids(t.engine, { sort: [PINNED, NEWEST], limit: 2 })).toEqual(['elsewhere', 'pin-unread']);
+    expect(await ids(t.engine, { filter: { text: 'nothing-matches-this' }, sort: [PINNED, NEWEST] })).toEqual([]);
+  });
+
+  it('reads the comparator the way the client sends it for a server that flips it', async () => {
+    t.engine.setInvertedKeywordSort(true);
+    expect((await ids(t.engine, { filter: IN_INBOX, sort: [{ ...PINNED, isAscending: true }, NEWEST], limit: 2 }))).toEqual(['pin-unread', 'pin-read']);
+    expect((await ids(t.engine, { filter: IN_INBOX, sort: [{ ...PINNED, isAscending: false }, NEWEST], limit: 1 }))).toEqual(['new-read']);
+  });
+
+  it('answers the client\'s polarity probe the way a server would', async () => {
+    const asc = await ids(t.engine, { sort: [{ property: 'hasKeyword', keyword: '$seen', isAscending: true }, NEWEST], limit: 1 });
+    const desc = await ids(t.engine, { sort: [{ property: 'hasKeyword', keyword: '$seen', isAscending: false }, NEWEST], limit: 1 });
+    expect(asc).toEqual(['elsewhere']);
+    expect(desc).toEqual(['new-read']);
+  });
+
+  it('never sorts the folder', async () => {
+    for (const sort of [[PINNED, NEWEST], [UNREAD_FIRST, NEWEST], [PINNED, UNREAD_FIRST, NEWEST]]) {
+      const reads = await plans(t, { filter: IN_INBOX, sort, limit: 5 });
+      expect(reads.length).toBeGreaterThan(0);
+      for (const { plan, sql } of reads) {
+        // A rare keyword's own rows may be sorted. The folder's never are.
+        if (sql.includes('email_keyword r')) expect(plan).toContain('email_keyword_lookup');
+        else expect(plan).not.toContain('TEMP B-TREE');
+      }
+    }
+  });
+
+  it('reads a rare keyword off its index first, and the rest off the folder\'s', async () => {
+    const reads = await plans(t, { filter: IN_INBOX, sort: [PINNED, NEWEST], limit: 3 });
+    const pages = reads.filter(({ sql }) => sql.startsWith('SELECT e.id'));
+    expect(pages[0].plan).toContain('email_keyword_lookup');
+    expect(pages[1].plan).toContain('email_mailbox_list');
+    expect(pages[1].plan).not.toContain('TEMP B-TREE');
+  });
+
+  it('counts what it skips without reading a message', async () => {
+    const reads = await plans(t, { filter: IN_INBOX, sort: [PINNED, NEWEST], position: 3, limit: 1 });
+    const counts = reads.filter(({ sql }) => sql.startsWith('SELECT COUNT'));
+    expect(counts.length).toBeGreaterThan(0);
+    for (const { plan } of counts) expect(plan).not.toMatch(/\bSCAN e\b|SEARCH e\b/);
+  });
+
+  it('leaves other orders to a full sort, and they still work', async () => {
+    expect(await ids(t.engine, { filter: IN_INBOX, sort: [PINNED, { property: 'size', isAscending: true }, NEWEST], limit: 2 })).toHaveLength(2);
+    expect(await ids(t.engine, { filter: IN_INBOX, sort: [NEWEST], collapseThreads: true, limit: 2 })).toHaveLength(2);
+  });
+});
+
+describe('calculateTotal', () => {
+  it('counts folder conditions off the index and the keyword rows, reading no message', async () => {
+    const t = setup([{ id: 'a' }, { id: 'b', keywords: { $seen: true } }]);
+    await t.engine.requestSync();
+    t.seen.length = 0;
+    const answer = await t.engine.answer([['Email/query', {
+      filter: { operator: 'AND', conditions: [IN_INBOX, { notKeyword: '$seen' }, { after: '2020-01-01T00:00:00Z' }] },
+      sort: [NEWEST],
+      limit: 1,
+      calculateTotal: true,
+    }, 'q']]);
+    expect(answer?.methodResponses[0][1].total).toBe(1);
+    const count = t.seen.find(({ sql }) => sql.startsWith('SELECT COUNT'))!;
+    const plan = t.raw.all<{ detail: string }>(`EXPLAIN QUERY PLAN ${count.sql}`, count.params).map((row) => row.detail).join('; ');
+    expect(plan).toContain('email_mailbox_list');
+    expect(plan).not.toMatch(/\bSCAN e\b|SEARCH e\b/);
+  });
+
+  it('still reads the message for a condition only it can answer', async () => {
+    const t = setup([{ id: 'a', size: 5 } as never, { id: 'b', size: 500 } as never]);
+    await t.engine.requestSync();
+    const answer = await t.engine.answer([['Email/query', { filter: { operator: 'AND', conditions: [IN_INBOX, { minSize: 100 }] }, calculateTotal: true }, 'q']]);
+    expect(answer?.methodResponses[0][1].total).toBe(1);
+  });
+});
+
+describe('a failed write', () => {
+  function failing(now: { at: number }) {
+    const server = new FakeJmapMail();
+    for (let i = 0; i < 400; i += 1) server.addEmail({ bodyValues: { 1: { value: 'x'.repeat(2000) } } });
+    const db = openMemoryStore();
+    const events: StoreEvent[] = [];
+    const engine = new AccountEngine({
+      account: 'a', db, session: FAKE_SESSION, transport: server, areas: [mailArea, outboxArea],
+      scope: { ...DEFAULT_SCOPE, days: null, attachments: false }, sleep: async () => {},
+      emit: (event) => events.push(event), now: () => now.at,
+    });
+    // A real full disk, as SQLite reports it.
+    const pages = Number(db.get<{ page_count: number }>('PRAGMA page_count')?.page_count);
+    db.exec(`PRAGMA max_page_count = ${pages + 40}`);
+    return { server, db, events, engine };
+  }
+
+  const storageErrors = (events: StoreEvent[]) => events.filter((event) => event.type === 'error' && event.area === STORAGE_ERROR_AREA);
+
+  it('tells the page, says no "synced", and doesn\'t try again on every push', async () => {
+    const now = { at: 1_000_000 };
+    const t = failing(now);
+    await t.engine.requestSync();
+    expect(storageErrors(t.events)).toHaveLength(1);
+    expect(t.events.some((event) => event.type === 'synced')).toBe(false);
+
+    const requests = t.server.requests;
+    t.engine.noteStateChange({ acc1: { Email: 'whatever' } });
+    await t.engine.requestSync();
+    await t.engine.requestSync();
+    expect(t.server.requests).toBe(requests);
+    expect(storageErrors(t.events)).toHaveLength(1);
+  });
+
+  it('tries again after a while, longer each time, and carries on once there\'s room', async () => {
+    const now = { at: 1_000_000 };
+    const t = failing(now);
+    await t.engine.requestSync();
+
+    now.at += 61_000;
+    await t.engine.requestSync();
+    expect(storageErrors(t.events)).toHaveLength(2);
+
+    // Now it waits two minutes.
+    now.at += 61_000;
+    const requests = t.server.requests;
+    await t.engine.requestSync();
+    expect(t.server.requests).toBe(requests);
+
+    now.at += 61_000;
+    t.db.exec('PRAGMA max_page_count = 1000000');
+    await t.engine.requestSync();
+    expect(t.events.some((event) => event.type === 'synced')).toBe(true);
+    expect(t.db.get<{ n: number }>('SELECT COUNT(*) AS n FROM email')?.n).toBe(400);
+  });
+
+  it('lets the user make room by keeping less, without waiting', async () => {
+    const now = { at: 1_000_000 };
+    const t = failing(now);
+    await t.engine.requestSync();
+    const requests = t.server.requests;
+    t.engine.setScope({ ...DEFAULT_SCOPE, days: 1 });
+    await t.engine.requestSync();
+    expect(t.server.requests).toBeGreaterThan(requests);
+  });
+
+  it('reports a change that couldn\'t be kept, and fails it rather than pretending', async () => {
+    const now = { at: 1_000_000 };
+    const t = failing(now);
+    t.db.exec('PRAGMA max_page_count = 1000000');
+    await t.engine.requestSync();
+    const pages = Number(t.db.get<{ page_count: number }>('PRAGMA page_count')?.page_count);
+    t.db.exec(`PRAGMA max_page_count = ${pages}`);
+    const big = 'x'.repeat(5_000_000);
+    await expect(t.engine.areaCall('outbox.queueSend', { summary: { subject: big, to: [] }, item: { kind: 'email', args: [] } })).rejects.toThrow(/full/);
+    expect(storageErrors(t.events)).toHaveLength(1);
+    t.db.exec('PRAGMA max_page_count = 1000000');
+    expect((await t.engine.areaCall('outbox.read', {}) as { entries: unknown[] }).entries).toEqual([]);
+  });
+
+  it('knows these errors from others', () => {
+    expect(isStorageFailure(new Error('database or disk is full'))).toBe(true);
+    expect(isStorageFailure(new Error('SQLITE_FULL: sqlite3 result code 13'))).toBe(true);
+    expect(isStorageFailure(Object.assign(new Error('x'), { name: 'QuotaExceededError' }))).toBe(true);
+    expect(isStorageFailure(new Error('no such table: x'))).toBe(false);
+    expect(isStorageFailure(new TransportError('network', 'Failed to fetch'))).toBe(false);
+  });
+});
diff --git a/lib/store/__tests__/mail-sync.test.ts b/lib/store/__tests__/mail-sync.test.ts
index a5ddae149..13d438c6c 100644
--- a/lib/store/__tests__/mail-sync.test.ts
+++ b/lib/store/__tests__/mail-sync.test.ts
@@ -130,11 +130,116 @@ describe('persisted state', () => {
       await engineFor(server, second).requestSync();
       expect(count(second, 'email')).toBe(4500);
       const firstQuery = callsNamed(server, 'Email/query')[0];
-      expect(firstQuery[1].position).toBe(listed);
+      expect(firstQuery[1]).toMatchObject({ anchorOffset: 1 });
+      expect(second.get<{ id: string }>('SELECT id FROM email WHERE id = ?', [firstQuery[1].anchor as string])).toBeTruthy();
+      expect(firstQuery[1]).not.toHaveProperty('position');
       second.close();
     } finally {
       rmSync(dir, { recursive: true, force: true });
     }
+  }, 30_000);
+});
+
+describe('a full pass while the server changes', () => {
+  // Newest first, four pages of 500 to a request: the second request starts at 2000.
+  function bigServer() {
+    const server = new FakeJmap();
+    for (let i = 0; i < 2600; i += 1) server.addEmail({ id: `m${i}` });
+    return server;
+  }
+
+  it('misses no message when something before its place is deleted, which would shift positions', async () => {
+    const server = bigServer();
+    const db = openMemoryStore();
+    let deleted = false;
+    server.beforeRequest = () => {
+      // Once the first request of the list has been answered: the newest
+      // message, long passed by the pass.
+      if (!deleted && callsNamed(server, 'Email/query').length >= 4) {
+        deleted = true;
+        server.destroyEmail('m2599');
+      }
+    };
+    await engineFor(server, db).requestSync();
+    expect(deleted).toBe(true);
+    expect(count(db, 'email')).toBe(2599);
+    for (let i = 0; i < 2599; i += 1) expect(db.get('SELECT 1 AS x FROM email WHERE id = ?', [`m${i}`])).toBeTruthy();
+  });
+
+  it('goes back to positions, with an overlap, when the anchor itself is deleted', async () => {
+    const server = bigServer();
+    const db = openMemoryStore();
+    let deleted = false;
+    server.beforeRequest = () => {
+      if (deleted || server.calls.filter(([n]) => n === 'Email/query').length < 4) return;
+      deleted = true;
+      // The last id of the first request, and one before it.
+      const newestFirst = [...server.emails.keys()].reverse();
+      server.destroyEmail(newestFirst[1999]);
+      server.destroyEmail(newestFirst[0]);
+    };
+    await engineFor(server, db).requestSync();
+    expect(deleted).toBe(true);
+    expect(count(db, 'email')).toBe(2598);
+    expect(callsNamed(server, 'Email/query').some(([, args]) => args.anchor === undefined && Number(args.position) > 0)).toBe(true);
+    expect(server.emails.size).toBe(2598);
+    for (const id of server.emails.keys()) expect(db.get('SELECT 1 AS x FROM email WHERE id = ?', [id])).toBeTruthy();
+  });
+
+  it('keeps what a pass missed but the server still has, and drops only what is gone or out of the window', async () => {
+    const server = new FakeJmap();
+    server.addEmail({ id: 'stays', subject: 'Before', receivedAt: '2026-11-01T00:00:00Z' });
+    server.addEmail({ id: 'gone', receivedAt: '2026-11-01T00:00:01Z' });
+    server.addEmail({ id: 'old', receivedAt: '2026-10-01T00:00:00Z' });
+    const db = openMemoryStore();
+    const engine = new AccountEngine({
+      account: 'a@fake.test', db, session: FAKE_SESSION, transport: server, areas: [mailArea],
+      scope: { ...DEFAULT_SCOPE, days: null }, now: () => Date.UTC(2026, 10, 3), sleep: async () => {},
+    });
+    await engine.requestSync();
+    expect(count(db, 'email')).toBe(3);
+
+    // A start over, in a narrower window, where paging misses `stays`.
+    engine.setScope({ ...DEFAULT_SCOPE, days: 10 });
+    server.hiddenFromQuery.add('stays');
+    server.updateEmail('stays', { subject: 'After' });
+    server.destroyEmail('gone');
+    server.truncateLog('Email');
+    server.calls.length = 0;
+    await engine.requestSync();
+    expect(db.all('SELECT id FROM email').map((row) => row.id)).toEqual(['stays']);
+    expect(JSON.parse(String(db.get<{ json: string }>('SELECT json FROM email WHERE id = ?', ['stays'])?.json)).subject).toBe('After');
+    // Its text wasn't thrown away either.
+    expect(count(db, 'email_body')).toBe(1);
+    expect(callsNamed(server, 'Email/get').some(([, args]) => (args.ids as string[] | undefined)?.includes('gone'))).toBe(true);
+  });
+
+  it('picks the check up again after a stop, and asks 500 at a time', async () => {
+    const server = new FakeJmap();
+    for (let i = 0; i < 700; i += 1) server.addEmail({ id: `m${i}` });
+    const db = openMemoryStore();
+    const engine = engineFor(server, db);
+    await engine.requestSync();
+    for (let i = 0; i < 700; i += 1) server.hiddenFromQuery.add(`m${i}`);
+    server.truncateLog('Email');
+    server.calls.length = 0;
+    let gets = 0;
+    server.beforeRequest = () => {
+      if (callsNamed(server, 'Email/get').filter(([, args]) => Array.isArray(args.ids) && (args.ids as string[]).length > 0).length > gets) gets += 1;
+      if (gets === 1) server.offline = true;
+    };
+    await engine.requestSync();
+    expect(count(db, 'email')).toBe(700);
+    server.offline = false;
+    server.beforeRequest = null;
+    await engine.requestSync();
+    expect(count(db, 'email')).toBe(700);
+    const sizes = callsNamed(server, 'Email/get').map(([, args]) => (args.ids as string[] | undefined)?.length ?? 0);
+    expect(Math.max(...sizes)).toBeLessThanOrEqual(500);
+    // The pass finished: back to /changes.
+    server.calls.length = 0;
+    await engine.requestSync();
+    expect(callsNamed(server, 'Email/query')).toHaveLength(0);
   });
 });
 
@@ -338,7 +443,7 @@ describe('query plans', () => {
       },
     };
     const answer = await answerRequest(
-      { account: 'a', db: spied as typeof db, session: FAKE_SESSION, scope: EVERYTHING, now: Date.now, emit: () => {}, defaultJmap: JMAP_ACCOUNT, invertedKeywordSort: false },
+      { account: 'a', db: spied as typeof db, session: FAKE_SESSION, scope: EVERYTHING, now: Date.now, emit: () => {}, overlay: (_jmap, _type, records) => records, defaultJmap: JMAP_ACCOUNT, invertedKeywordSort: false },
       buildMethodTable([mailArea]),
       [['Email/query', { filter: INBOX, sort: [{ property: 'receivedAt', isAscending: false }], limit: 5 }, 'q']],
     );
diff --git a/lib/store/__tests__/outbox.test.ts b/lib/store/__tests__/outbox.test.ts
new file mode 100644
index 000000000..d820ab2d5
--- /dev/null
+++ b/lib/store/__tests__/outbox.test.ts
@@ -0,0 +1,665 @@
+// @vitest-environment node
+import { beforeEach, describe, expect, it } from 'vitest';
+import { DEFAULT_SCOPE } from '../area';
+import { AccountEngine } from '../engine/account-engine';
+import { TransportError, type MethodCall } from '../engine/transport';
+import { mailArea } from '../mail';
+import { outboxArea } from '../outbox';
+import { CLOCK_SKEW_MARGIN_MS, decideRetry, LOOKUP_TRUSTED_MS, type LookupArgs } from '../outbox/dedupe';
+import { addHeldFileSource } from '../outbox/calls';
+import { flushPatches, type PatchOutcome, type PendingPatch } from '../outbox/flush-patches';
+import type { StoredConflict, StoredOutboxEntry } from '../outbox/items';
+import { mergePatches, patchConflicts } from '../outbox/patches';
+import { FAKE_SESSION, JMAP_ACCOUNT, type FakeEmail } from './helpers/fake-jmap';
+import { FakeJmapMail } from './helpers/fake-jmap-mail';
+import { openMemoryStore } from './helpers/node-adapter';
+
+const NOW = Date.UTC(2026, 10, 3);
+const BOXES = [
+  { id: 'inbox', name: 'Inbox', role: 'inbox', totalEmails: 2, unreadEmails: 1 },
+  { id: 'trash', name: 'Trash', role: 'trash', totalEmails: 1, unreadEmails: 0 },
+  { id: 'drafts', name: 'Drafts', role: 'drafts', totalEmails: 0, unreadEmails: 0 },
+  { id: 'sent', name: 'Sent', role: 'sent', totalEmails: 0, unreadEmails: 0 },
+];
+
+function setup() {
+  const server = new FakeJmapMail({ mailboxes: BOXES.map((box) => ({ ...box })) });
+  server.addEmail({ id: 'a', threadId: 't1', subject: 'Aye', keywords: {}, mailboxIds: { inbox: true } });
+  server.addEmail({ id: 'b', threadId: 't1', subject: 'Bee', keywords: { $seen: true }, mailboxIds: { inbox: true } });
+  server.addEmail({ id: 'c', threadId: 't2', subject: 'Sea', keywords: { $seen: true }, mailboxIds: { trash: true } });
+  const db = openMemoryStore();
+  const engine = new AccountEngine({
+    account: 'a@fake.test',
+    db,
+    session: FAKE_SESSION,
+    transport: server,
+    areas: [mailArea, outboxArea],
+    scope: { ...DEFAULT_SCOPE, days: null },
+    now: () => clock,
+    sleep: async () => {},
+  });
+  return { server, db, engine };
+}
+
+let t: ReturnType<typeof setup>;
+
+beforeEach(async () => {
+  clock = NOW;
+  t = setup();
+  await t.engine.requestSync();
+});
+
+const set = (args: Record<string, unknown>) => t.engine.answer([['Email/set', args, 's']]);
+const update = (patches: Record<string, Record<string, unknown>>) => set({ update: patches });
+const pending = () => t.engine.areaCall('outbox.pendingPatches', {}) as Promise<PendingPatch[]>;
+const read = () => t.engine.areaCall('outbox.read', {}) as Promise<{ patches: number; entries: StoredOutboxEntry[]; conflicts: StoredConflict[] }>;
+
+async function local(id: string) {
+  const answer = await t.engine.answer([['Email/get', { ids: [id], properties: ['keywords', 'mailboxIds', 'subject'] }, 'g']]);
+  return answer?.methodResponses[0][1].list[0];
+}
+
+let clock = NOW;
+
+async function boxes() {
+  const answer = await t.engine.answer([['Mailbox/get', {}, 'm']]);
+  return Object.fromEntries((answer?.methodResponses[0][1].list as Array<{ id: string; totalEmails: number; unreadEmails: number }>).map((box) => [box.id, [box.totalEmails, box.unreadEmails]]));
+}
+
+const io = (server: FakeJmapMail = t.server) => ({
+  request: (calls: MethodCall[]) => server.request(calls),
+});
+
+async function flush(ioOverride = io()) {
+  const outcomes: PatchOutcome[] = [];
+  const finished = await flushPatches(ioOverride, await pending(), async (batch) => {
+    outcomes.push(...batch);
+    await t.engine.areaCall('outbox.patchResults', { outcomes: batch });
+  });
+  return { outcomes, finished };
+}
+
+describe('merging patches per record', () => {
+  it('keeps one row per record, with later paths on top of earlier ones', async () => {
+    await update({ a: { 'keywords/$seen': true } });
+    await update({ a: { 'keywords/$flagged': true } });
+    await update({ a: { 'keywords/$seen': null } });
+    const rows = await pending();
+    expect(rows).toHaveLength(1);
+    expect(rows[0].patch).toEqual({ 'keywords/$seen': null, 'keywords/$flagged': true });
+    expect((await local('a')).keywords).toEqual({ $flagged: true });
+  });
+
+  it('lets a whole map replace earlier paths into it, and takes later paths into the map', () => {
+    expect(mergePatches({ 'keywords/$seen': true, 'mailboxIds/x': true }, { keywords: { $flagged: true } }))
+      .toEqual({ keywords: { $flagged: true }, 'mailboxIds/x': true });
+    expect(mergePatches({ keywords: { $flagged: true } }, { 'keywords/$seen': true }))
+      .toEqual({ keywords: { $flagged: true, $seen: true } });
+    expect(mergePatches({ keywords: { $flagged: true } }, { 'keywords/$flagged': null })).toEqual({ keywords: {} });
+    expect(mergePatches({ mailboxIds: { a: true } }, { mailboxIds: { b: true } })).toEqual({ mailboxIds: { b: true } });
+  });
+
+  it('reads escaped keyword names', () => {
+    expect(mergePatches({ keywords: {} }, { 'keywords/a~1b': true })).toEqual({ keywords: { 'a/b': true } });
+  });
+
+  it('queues a change to a message it doesn\'t keep, and answers it as done', async () => {
+    const answer = await update({ unknown: { 'keywords/$seen': true } });
+    expect(answer?.methodResponses[0][1].updated).toEqual({ unknown: null });
+    expect((await pending()).map((row) => [row.recordId, row.base])).toEqual([['unknown', null]]);
+  });
+
+  it('refuses per record what can\'t wait: other properties, a new folder, no folder at all', async () => {
+    const answer = await update({
+      a: { subject: 'x' },
+      b: { 'mailboxIds/#new': true },
+      c: { mailboxIds: {} },
+    });
+    const result = answer?.methodResponses[0][1];
+    expect(Object.keys(result.notUpdated).sort()).toEqual(['a', 'b', 'c']);
+    expect(result.notUpdated.a.type).toBe('forbidden');
+    expect(result.notUpdated.c.type).toBe('invalidProperties');
+    expect(await pending()).toEqual([]);
+    const emptied = await update({ c: { 'mailboxIds/trash': null } });
+    expect(emptied?.methodResponses[0][1].notUpdated.c.type).toBe('invalidProperties');
+    expect(await pending()).toEqual([]);
+    expect((await local('c')).mailboxIds).toEqual({ trash: true });
+  });
+
+  it('answers a create per message, so the composer\'s "not saved" path runs (seam for the drafts agent)', async () => {
+    const answer = await set({ create: { draft: { subject: 'x' } } });
+    expect(answer?.methodResponses[0][0]).toBe('Email/set');
+    expect(answer?.methodResponses[0][1].notCreated.draft.type).toBe('serverUnavailable');
+  });
+});
+
+describe('showing changes at once', () => {
+  it('moves a message and keeps the folder counts right', async () => {
+    expect(await boxes()).toMatchObject({ inbox: [2, 1], trash: [1, 0] });
+    await update({ a: { 'mailboxIds/inbox': null, 'mailboxIds/trash': true } });
+    expect(await boxes()).toMatchObject({ inbox: [1, 0], trash: [2, 1] });
+    const answer = await t.engine.answer([['Email/query', { filter: { inMailbox: 'trash' }, sort: [{ property: 'receivedAt', isAscending: false }] }, 'q']]);
+    expect(answer?.methodResponses[0][1].ids).toEqual(['c', 'a']);
+  });
+
+  it('counts a read change once, also after later changes to the same record', async () => {
+    await update({ a: { 'keywords/$seen': true } });
+    expect((await boxes()).inbox).toEqual([2, 0]);
+    await update({ a: { 'keywords/$flagged': true } });
+    expect((await boxes()).inbox).toEqual([2, 0]);
+    await update({ a: { 'keywords/$seen': null } });
+    expect((await boxes()).inbox).toEqual([2, 1]);
+  });
+
+  it('whole-map patches count the same', async () => {
+    await update({ a: { keywords: { $seen: true } } });
+    expect((await boxes()).inbox).toEqual([2, 0]);
+    await update({ b: { mailboxIds: { trash: true } } });
+    expect(await boxes()).toMatchObject({ inbox: [1, 0], trash: [2, 0] });
+  });
+
+  it('deletes for good right away, from lists, threads and counts', async () => {
+    const answer = await set({ destroy: ['a'] });
+    expect(answer?.methodResponses[0][1].destroyed).toEqual(['a']);
+    expect(await boxes()).toMatchObject({ inbox: [1, 0] });
+    const check = await t.engine.answer([
+      ['Email/get', { ids: ['a'], properties: ['id'] }, 'g'],
+      ['Thread/get', { ids: ['t1'] }, 't'],
+    ]);
+    expect(check?.methodResponses[0][1].notFound).toEqual(['a']);
+    expect(check?.methodResponses[1][1].list).toEqual([{ id: 't1', emailIds: ['b'] }]);
+    expect((await pending()).map((row) => row.op)).toEqual(['destroy']);
+  });
+
+  it('empties a folder through the back-reference the client sends', async () => {
+    const answer = await t.engine.answer([
+      ['Email/query', { filter: { inMailbox: 'trash' }, limit: 500 }, '0'],
+      ['Email/set', { '#destroy': { resultOf: '0', name: 'Email/query', path: '/ids' } }, '1'],
+    ]);
+    expect(answer?.methodResponses[1][1].destroyed).toEqual(['c']);
+    expect((await boxes()).trash).toEqual([0, 0]);
+    const again = await t.engine.answer([['Email/query', { filter: { inMailbox: 'trash' } }, '0']]);
+    expect(again?.methodResponses[0][1].ids).toEqual([]);
+    await flush();
+    expect(t.server.emails.has('c')).toBe(false);
+    expect(await pending()).toEqual([]);
+  });
+
+  it('a change to a message waiting to be deleted is not found', async () => {
+    await set({ destroy: ['a'] });
+    const answer = await update({ a: { 'keywords/$seen': true } });
+    expect(answer?.methodResponses[0][1].notUpdated.a.type).toBe('notFound');
+    expect((await pending())[0].op).toBe('destroy');
+  });
+});
+
+describe('sync and waiting changes', () => {
+  it('reapplies a waiting change over what the server sends', async () => {
+    await update({ a: { 'keywords/$flagged': true } });
+    t.server.updateEmail('a', { subject: 'Renamed', keywords: { $seen: true } });
+    await t.engine.requestSync();
+    expect(await local('a')).toMatchObject({ subject: 'Renamed', keywords: { $seen: true, $flagged: true } });
+    expect(await pending()).toHaveLength(1);
+  });
+
+  it('survives a full resync, and keeps a pending delete away', async () => {
+    await update({ a: { 'keywords/$flagged': true } });
+    await set({ destroy: ['b'] });
+    t.server.truncateLog('Email');
+    t.server.addEmail({ id: 'new' });
+    await t.engine.requestSync();
+    expect((await local('a')).keywords).toEqual({ $flagged: true });
+    expect(await local('b')).toBeUndefined();
+    expect(await local('new')).toBeTruthy();
+  });
+
+  it('doesn\'t bring back a message waiting to be deleted when the server changes it', async () => {
+    await set({ destroy: ['a'] });
+    t.server.updateEmail('a', { keywords: { $flagged: true } });
+    await t.engine.requestSync();
+    expect(await local('a')).toBeUndefined();
+  });
+
+  it('follows the server\'s new counts without counting a waiting change twice', async () => {
+    await update({ a: { 'keywords/$seen': true } });
+    expect((await boxes()).inbox).toEqual([2, 0]);
+    t.server.mailboxes.get('inbox')!.totalEmails = 3;
+    t.server.mailboxes.get('inbox')!.unreadEmails = 2;
+    t.server.coll.Mailbox.push('updated', 'inbox');
+    t.server.addEmail({ id: 'new', keywords: {} });
+    await t.engine.requestSync();
+    expect((await boxes()).inbox).toEqual([3, 1]);
+  });
+
+  it('drops the patch once the server took it, and the next run brings the truth', async () => {
+    await update({ a: { 'keywords/$seen': true } });
+    const { outcomes, finished } = await flush();
+    expect(finished).toBe(true);
+    expect(outcomes).toEqual([expect.objectContaining({ recordId: 'a', outcome: 'done' })]);
+    expect(await pending()).toEqual([]);
+    expect((t.server.emails.get('a') as FakeEmail).keywords).toEqual({ $seen: true });
+    t.server.updateEmail('a', { keywords: { $seen: true, $answered: true } });
+    await t.engine.requestSync();
+    expect((await local('a')).keywords).toEqual({ $seen: true, $answered: true });
+  });
+});
+
+describe('conflicts', () => {
+  it('holds back a change to what the server changed since, and shows the server\'s state', async () => {
+    await update({ a: { 'keywords/$flagged': true } });
+    t.server.updateEmail('a', { keywords: { $flagged: true, $seen: true } });
+    // The same outcome as wanted: not a conflict.
+    let run = await flush();
+    expect(run.outcomes[0]).toMatchObject({ outcome: 'done' });
+
+    await update({ b: { 'keywords/$seen': null } });
+    t.server.updateEmail('b', { keywords: { $seen: true, $flagged: true } });
+    // Another keyword moved: this one still stands.
+    run = await flush();
+    expect(run.outcomes[0]).toMatchObject({ outcome: 'done' });
+
+    await update({ c: { 'mailboxIds/trash': null, 'mailboxIds/inbox': true } });
+    t.server.updateEmail('c', { mailboxIds: { sent: true } });
+    run = await flush();
+    expect(run.outcomes[0]).toMatchObject({ outcome: 'conflict', reason: 'changed' });
+    const { conflicts, patches } = await read();
+    expect(patches).toBe(0);
+    expect(conflicts).toEqual([expect.objectContaining({ recordId: 'c', jmap: JMAP_ACCOUNT, summary: { subject: 'Sea', op: 'update', reason: 'changed' } })]);
+    expect((t.server.emails.get('c') as FakeEmail).mailboxIds).toEqual({ sent: true });
+    expect((await local('c')).mailboxIds).toEqual({ sent: true });
+  });
+
+  it('never sends a conflicting change, and sends the rest of the batch', async () => {
+    await update({ a: { 'mailboxIds/inbox': null, 'mailboxIds/trash': true }, b: { 'keywords/$flagged': true } });
+    t.server.updateEmail('a', { mailboxIds: { sent: true } });
+    await flush();
+    expect((t.server.emails.get('a') as FakeEmail).mailboxIds).toEqual({ sent: true });
+    expect((t.server.emails.get('b') as FakeEmail).keywords).toEqual({ $seen: true, $flagged: true });
+  });
+
+  it('shows what the server refused', async () => {
+    await update({ a: { 'keywords/$flagged': true } });
+    t.server.refuse.set('a', { type: 'forbidden', description: 'Read only' });
+    await flush();
+    const { conflicts } = await read();
+    expect(conflicts[0].summary).toEqual({ subject: 'Aye', op: 'update', reason: 'refused', detail: 'Read only' });
+    expect((await local('a')).keywords).toEqual({});
+    await t.engine.areaCall('outbox.dismissConflict', { id: conflicts[0].id });
+    expect((await read()).conflicts).toEqual([]);
+  });
+
+  it('shows a change to a message gone from the server, and removes the local copy', async () => {
+    await update({ a: { 'keywords/$flagged': true } });
+    t.server.destroyEmail('a');
+    await flush();
+    expect((await read()).conflicts[0].summary).toMatchObject({ reason: 'gone', subject: 'Aye' });
+    expect(await local('a')).toBeUndefined();
+  });
+
+  it('a delete of what\'s already gone is simply done', async () => {
+    await set({ destroy: ['a'] });
+    t.server.destroyEmail('a');
+    const { outcomes } = await flush();
+    expect(outcomes[0]).toMatchObject({ outcome: 'done' });
+    expect((await read()).conflicts).toEqual([]);
+  });
+
+  it('holds back a delete of what changed on the server, and the message comes back', async () => {
+    await set({ destroy: ['a'] });
+    t.server.updateEmail('a', { keywords: { $flagged: true } });
+    await t.engine.requestSync();
+    await flush();
+    expect(t.server.emails.has('a')).toBe(true);
+    expect((await read()).conflicts[0].summary).toMatchObject({ op: 'destroy', reason: 'changed' });
+    expect((await local('a')).keywords).toEqual({ $flagged: true });
+  });
+
+  it('shows a refused delete', async () => {
+    await set({ destroy: ['a'] });
+    t.server.refuse.set('a', { type: 'forbidden' });
+    await flush();
+    expect((await read()).conflicts[0].summary).toMatchObject({ op: 'destroy', reason: 'refused', detail: 'forbidden' });
+    expect((await local('a'))?.subject).toBe('Aye');
+  });
+
+  it('compares per property, keywords the way the server does', () => {
+    const base = { keywords: { '$SEEN': true, '$label:A': true }, mailboxIds: { x: true } };
+    // System flags fold.
+    expect(patchConflicts({ 'keywords/$seen': null }, base, { keywords: { $seen: true, '$label:A': true }, mailboxIds: { x: true } })).toBe(false);
+    // Custom keywords are case-sensitive: the server now has another one.
+    expect(patchConflicts({ 'keywords/$label:A': null }, base, { keywords: { '$label:a': true }, mailboxIds: { x: true } })).toBe(false);
+    expect(patchConflicts({ 'keywords/$label:a': true }, { keywords: {}, mailboxIds: {} }, { keywords: { '$label:A': true }, mailboxIds: {} })).toBe(false);
+    expect(patchConflicts({ 'keywords/$label:A': true }, { keywords: { '$label:A': true }, mailboxIds: {} }, { keywords: { '$label:a': true }, mailboxIds: {} })).toBe(true);
+  });
+
+  it('compares per property', () => {
+    const base = { keywords: { '$label:a': true }, mailboxIds: { x: true } };
+    expect(patchConflicts({ 'keywords/$seen': true }, base, { keywords: {}, mailboxIds: { x: true } })).toBe(false);
+    expect(patchConflicts({ keywords: { $seen: true } }, base, { keywords: {}, mailboxIds: { x: true } })).toBe(true);
+    expect(patchConflicts({ keywords: { $seen: true } }, base, { keywords: { $seen: true }, mailboxIds: { x: true } })).toBe(false);
+    expect(patchConflicts({ keywords: { $seen: true } }, null, { keywords: {}, mailboxIds: {} })).toBe(false);
+  });
+});
+
+describe('when the server can\'t be reached during a flush', () => {
+  it('stops and keeps every change, without calling anything a conflict', async () => {
+    await update({ a: { 'keywords/$seen': true } });
+    t.server.offline = true;
+    const { outcomes, finished } = await flush();
+    expect(finished).toBe(false);
+    expect(outcomes).toEqual([]);
+    expect(await pending()).toHaveLength(1);
+    expect((await read()).conflicts).toEqual([]);
+    expect((await local('a')).keywords).toEqual({ $seen: true });
+  });
+
+  it('stops on "not now" from the server too', async () => {
+    await update({ a: { 'keywords/$seen': true } });
+    t.server.failNext.set('Email/set', 'serverUnavailable');
+    const { finished } = await flush();
+    expect(finished).toBe(false);
+    expect(await pending()).toHaveLength(1);
+  });
+
+  /** Refuses the Email/set with this answer, and reads go through. */
+  const refusingSet = (message: string) => ({
+    request: async (calls: MethodCall[]) => {
+      if (calls[0][0] === 'Email/set') throw new Error(message);
+      return t.server.request(calls);
+    },
+  });
+  const PROBLEM = 'Request failed: 400 - {"type":"urn:ietf:params:jmap:error:notRequest","status":400}';
+
+  it('turns a request the server refuses for good into a conflict, and shows what the server has', async () => {
+    await update({ a: { 'keywords/$seen': true } });
+    const { outcomes, finished } = await flush(refusingSet(PROBLEM));
+    expect(finished).toBe(true);
+    expect(outcomes[0]).toMatchObject({ outcome: 'conflict', reason: 'refused' });
+    expect(await pending()).toEqual([]);
+    // The change is gone, and so is its effect here.
+    const answer = await t.engine.answer([['Email/get', { ids: ['a'], properties: ['keywords'] }, 'g']]);
+    expect(answer?.methodResponses[0][1].list[0].keywords).toEqual({});
+    expect((await read()).conflicts).toHaveLength(1);
+  });
+
+  it.each([
+    ['the parallel-request limit', 'Request failed: 400 - {"type":"urn:ietf:params:jmap:error:limit","limit":"maxConcurrentRequests"}'],
+    ['a proxy\'s error page', 'Request failed: 403 - <html>Forbidden</html>'],
+    ['a body that\'s no JMAP problem', 'Request failed: 413 - Payload too large'],
+    ['a server error', 'Request failed: 500 - oops'],
+  ])('keeps the change for later on %s', async (_name, message) => {
+    await update({ a: { 'keywords/$seen': true } });
+    const { outcomes, finished } = await flush(refusingSet(message));
+    expect(finished).toBe(false);
+    expect(outcomes).toEqual([]);
+    expect(await pending()).toHaveLength(1);
+    expect((await read()).conflicts).toEqual([]);
+  });
+
+  it('keeps the change for later when the read after a refusal fails', async () => {
+    await update({ a: { 'keywords/$seen': true } });
+    let calls = 0;
+    const { finished } = await flush({
+      request: async (batch: MethodCall[]) => {
+        calls += 1;
+        if (calls === 1) return t.server.request(batch);
+        if (batch[0][0] === 'Email/set') throw new Error(PROBLEM);
+        throw new TypeError('Failed to fetch');
+      },
+    });
+    expect(finished).toBe(false);
+    expect(await pending()).toHaveLength(1);
+  });
+
+  it('keeps a change made while the flush ran, and doesn\'t compare it with the state the flush caused', async () => {
+    await update({ a: { 'keywords/$seen': true } });
+    const rows = await pending();
+    await update({ a: { 'keywords/$flagged': true } });
+    await flushPatches(io(), rows, async (batch) => { await t.engine.areaCall('outbox.patchResults', { outcomes: batch }); });
+    const left = await pending();
+    expect(left).toHaveLength(1);
+    expect(left[0].base).toBeNull();
+    await flush();
+    expect((t.server.emails.get('a') as FakeEmail).keywords).toEqual({ $seen: true, $flagged: true });
+    expect((await read()).conflicts).toEqual([]);
+  });
+});
+
+describe('sends', () => {
+  const summary = { subject: 'S', to: ['b@example.org'] };
+  const item = { kind: 'email', args: [['b@example.org'], 'S', 'x'] };
+
+  it('takes an entry for sending once: a second claim loses', async () => {
+    const id = await t.engine.areaCall('outbox.queueSend', { summary, item, messageId: 'fixed@example.org' }) as number;
+    expect(await t.engine.areaCall('outbox.claim', { id })).toBe(true);
+    expect(await t.engine.areaCall('outbox.claim', { id })).toBe(false);
+    const entry = (await read()).entries[0];
+    expect(entry).toMatchObject({ status: 'sending', sendingSince: NOW, lastAttemptAt: NOW, messageId: 'fixed@example.org', item });
+  });
+
+  it('marks what a closed tab left behind uncertain', async () => {
+    const id = await t.engine.areaCall('outbox.queueSend', { summary, item }) as number;
+    await t.engine.areaCall('outbox.claim', { id });
+    await t.engine.areaCall('outbox.settleStale', { before: NOW });
+    expect((await read()).entries[0].status).toBe('sending');
+    await t.engine.areaCall('outbox.settleStale', { before: NOW + 1 });
+    expect((await read()).entries[0]).toMatchObject({ status: 'uncertain', firstAttemptAt: NOW });
+  });
+
+  it('keeps the first attempt time across retries, so the lookup covers the first copy', async () => {
+    const id = await t.engine.areaCall('outbox.queueSend', { summary, item }) as number;
+    await t.engine.areaCall('outbox.claim', { id });
+    await t.engine.areaCall('outbox.update', { id, status: 'uncertain' });
+    expect((await read()).entries[0].firstAttemptAt).toBe(NOW);
+    clock = NOW + 60_000;
+    await t.engine.areaCall('outbox.update', { id, status: 'waiting' });
+    await t.engine.areaCall('outbox.claim', { id });
+    await t.engine.areaCall('outbox.update', { id, status: 'uncertain' });
+    const entry = (await read()).entries[0];
+    expect(entry.firstAttemptAt).toBe(NOW);
+    expect(entry.lastAttemptAt).toBe(NOW + 60_000);
+  });
+
+  it('doesn\'t call a try that never started an attempt', async () => {
+    const id = await t.engine.areaCall('outbox.queueSend', { summary, item }) as number;
+    for (let i = 0; i < 2; i += 1) {
+      await t.engine.areaCall('outbox.claim', { id });
+      await t.engine.areaCall('outbox.update', { id, status: 'waiting' });
+    }
+    expect((await read()).entries[0].firstAttemptAt).toBeUndefined();
+  });
+
+  it('keeps order across changes and sends, and a later merge moves a change later', async () => {
+    await update({ a: { 'keywords/$seen': true } });
+    await t.engine.areaCall('outbox.queueSend', { summary, item });
+    await update({ b: { 'keywords/$flagged': true } });
+    const { entries } = await read();
+    const before = await t.engine.areaCall('outbox.pendingPatches', { upToSeq: entries[0].seq }) as PendingPatch[];
+    expect(before.map((row) => row.recordId)).toEqual(['a']);
+    await update({ a: { 'keywords/$flagged': true } });
+    expect(await t.engine.areaCall('outbox.pendingPatches', { upToSeq: entries[0].seq })).toEqual([]);
+  });
+
+  it('removes the files of a removed entry, and keeps an update from bringing a deleted one back', async () => {
+    const data = new TextEncoder().encode('hello');
+    const held = await t.engine.areaCall('outbox.holdFile', { name: 'note.txt', type: 'text/plain', data }) as { blobId: string; size: number };
+    expect(held).toMatchObject({ size: 5, type: 'text/plain' });
+    expect(held.blobId).toMatch(/^bulwark-local-/);
+    const file = await t.engine.areaCall('outbox.heldFile', { blobId: held.blobId }) as { name: string; data: Uint8Array };
+    expect(file.name).toBe('note.txt');
+    expect(new TextDecoder().decode(file.data)).toBe('hello');
+    const id = await t.engine.areaCall('outbox.queueSend', { summary, item: { kind: 'raw', blobId: held.blobId, identityId: 'i' } }) as number;
+    await t.engine.areaCall('outbox.remove', { id });
+    expect(await t.engine.areaCall('outbox.heldFile', { blobId: held.blobId })).toBeNull();
+    await t.engine.areaCall('outbox.update', { id, status: 'failed' });
+    expect((await read()).entries).toEqual([]);
+  });
+
+  it('leaves a file alone that another area holds', async () => {
+    const held = await t.engine.areaCall('outbox.holdFile', { name: 'draft.txt', type: 'text/plain', data: new Uint8Array(1) }) as { blobId: string };
+    const stale = await t.engine.areaCall('outbox.holdFile', { name: 'old.txt', type: 'text/plain', data: new Uint8Array(1) }) as { blobId: string };
+    addHeldFileSource(() => [held.blobId]);
+    expect(await t.engine.areaCall('outbox.dropOrphans', { olderThan: NOW + 1 })).toBe(1);
+    expect(await t.engine.areaCall('outbox.heldFile', { blobId: held.blobId })).not.toBeNull();
+    expect(await t.engine.areaCall('outbox.heldFile', { blobId: stale.blobId })).toBeNull();
+  });
+
+  it('drops old files nothing needs', async () => {
+    const data = new Uint8Array([1]);
+    const orphan = await t.engine.areaCall('outbox.holdFile', { name: 'a', type: '', data }) as { blobId: string };
+    const used = await t.engine.areaCall('outbox.holdFile', { name: 'b', type: '', data }) as { blobId: string };
+    await t.engine.areaCall('outbox.queueSend', { summary, item: { kind: 'email', args: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, [{ blobId: used.blobId }]] } });
+    expect(await t.engine.areaCall('outbox.dropOrphans', { olderThan: NOW })).toBe(0);
+    expect(await t.engine.areaCall('outbox.dropOrphans', { olderThan: NOW + 1 })).toBe(1);
+    expect(await t.engine.areaCall('outbox.heldFile', { blobId: orphan.blobId })).toBeNull();
+    expect(await t.engine.areaCall('outbox.heldFile', { blobId: used.blobId })).not.toBeNull();
+  });
+});
+
+describe('looking a send up before it goes again', () => {
+  const MESSAGE_ID = 'k3x.11111111@example.org';
+  const args = (over: Partial<LookupArgs> = {}): LookupArgs => ({
+    jmap: JMAP_ACCOUNT,
+    submissionJmap: JMAP_ACCOUNT,
+    messageId: MESSAGE_ID,
+    attemptAt: NOW - 60_000,
+    now: NOW,
+    copyKept: true,
+    ...over,
+  });
+
+  function server() {
+    return new FakeJmapMail({ mailboxes: BOXES.map((box) => ({ ...box })) });
+  }
+
+  const inDrafts = (s: FakeJmapMail, over: Partial<FakeEmail> = {}) => s.addEmail({
+    id: 'copy',
+    messageId: [MESSAGE_ID],
+    mailboxIds: { drafts: true },
+    keywords: { $seen: true, $draft: true },
+    receivedAt: new Date(NOW - 30_000).toISOString(),
+    ...over,
+  });
+
+  // The five cases of decision 4.
+  it('request never arrived: send again', async () => {
+    const s = server();
+    // A message from before, and another with its own id.
+    s.addEmail({ id: 'other', messageId: ['other@example.org'], mailboxIds: { sent: true }, receivedAt: new Date(NOW - 10_000).toISOString() });
+    expect(await decideRetry(io(s), args())).toEqual({ action: 'send' });
+  });
+
+  it('draft arrived, submission didn\'t: submit that copy, don\'t create another', async () => {
+    const s = server();
+    inDrafts(s);
+    expect(await decideRetry(io(s), args())).toEqual({ action: 'submit', emailId: 'copy' });
+  });
+
+  it('both arrived: done', async () => {
+    const s = server();
+    inDrafts(s, { mailboxIds: { sent: true }, keywords: { $seen: true } });
+    s.addSubmission('copy', 'final');
+    expect(await decideRetry(io(s), args())).toEqual({ action: 'done', emailId: 'copy', why: 'sent' });
+    // A record Stalwart already removed doesn't change that.
+    s.submissions.clear();
+    expect(await decideRetry(io(s), args())).toEqual({ action: 'done', emailId: 'copy', why: 'sent' });
+  });
+
+  it('scheduled and waiting: done, leave it', async () => {
+    const s = server();
+    inDrafts(s);
+    s.addSubmission('copy', 'pending');
+    expect(await decideRetry(io(s), args())).toEqual({ action: 'done', emailId: 'copy', why: 'scheduled' });
+  });
+
+  it('canceled: someone decided against it, so it doesn\'t go', async () => {
+    const s = server();
+    inDrafts(s);
+    s.addSubmission('copy', 'canceled');
+    expect(await decideRetry(io(s), args())).toEqual({ action: 'done', emailId: 'copy', why: 'canceled' });
+  });
+
+  it('never uses a header or text filter, which find nothing on either version', async () => {
+    const s = server();
+    inDrafts(s, { mailboxIds: { sent: true }, keywords: {} });
+    await decideRetry(io(s), args());
+    const filters = JSON.stringify(s.calls.filter(([name]) => name === 'Email/query').map(([, a]) => a.filter));
+    expect(filters).not.toMatch(/header|text/);
+    expect(filters).toMatch(/inMailbox/);
+  });
+
+  it('finds a copy whose server time is behind this device\'s clock, within the margin', async () => {
+    const s = server();
+    const skew = CLOCK_SKEW_MARGIN_MS - 60_000;
+    inDrafts(s, { receivedAt: new Date(NOW - 60_000 - skew).toISOString() });
+    expect((await decideRetry(io(s), args())).action).toBe('submit');
+  });
+
+  it('matches with or without angle brackets', async () => {
+    const s = server();
+    inDrafts(s);
+    expect((await decideRetry(io(s), args({ messageId: `<${MESSAGE_ID}>` }))).action).toBe('submit');
+  });
+
+  it('can\'t tell without a Message-ID (a send from before they were fixed)', async () => {
+    expect(await decideRetry(io(server()), args({ messageId: undefined }))).toEqual({ action: 'undecided', why: 'no-message-id' });
+  });
+
+  it('can\'t tell without the folders', async () => {
+    const s = new FakeJmapMail();
+    expect(await decideRetry(io(s), args())).toEqual({ action: 'undecided', why: 'no-folders' });
+  });
+
+  it('can\'t tell when nothing stays after a good send, and nothing is found', async () => {
+    expect(await decideRetry(io(server()), args({ copyKept: false }))).toEqual({ action: 'undecided', why: 'no-copy-kept' });
+  });
+
+  it('can\'t tell once the server may have forgotten the submission', async () => {
+    const old = args({ attemptAt: NOW - LOOKUP_TRUSTED_MS - 1000 });
+    expect(await decideRetry(io(server()), old)).toEqual({ action: 'undecided', why: 'too-old' });
+    const s = server();
+    inDrafts(s, { receivedAt: new Date(old.attemptAt).toISOString() });
+    expect(await decideRetry(io(s), old)).toEqual({ action: 'undecided', why: 'too-old' });
+  });
+
+  it('can\'t tell when more mail arrived than it reads, unless the copy is among it', async () => {
+    const s = server();
+    for (let i = 0; i < 2500; i += 1) s.addEmail({ mailboxIds: { sent: true }, receivedAt: new Date(NOW - 1000).toISOString() });
+    expect(await decideRetry(io(s), args())).toEqual({ action: 'undecided', why: 'too-many' });
+  }, 30_000);
+
+  it('lets a failed lookup fail, so the caller leaves the entry alone', async () => {
+    const s = server();
+    s.offline = true;
+    await expect(decideRetry(io(s), args())).rejects.toBeInstanceOf(TransportError);
+  });
+});
+
+describe('moving the old outbox in', () => {
+  const legacy = {
+    entries: [
+      { summary: { subject: 'Old', to: [] }, item: { kind: 'email', args: [] }, status: 'uncertain', createdAt: 5 },
+      { summary: { subject: 'Older file', to: [] }, item: { kind: 'raw', blobId: 'bulwark-local-x', identityId: 'i' }, status: 'waiting', createdAt: 6 },
+    ],
+    patches: [{ jmap: JMAP_ACCOUNT, update: { a: { 'keywords/$seen': true } } }],
+    files: [{ blobId: 'bulwark-local-x', name: 'x.eml', type: 'message/rfc822', data: new Uint8Array([1, 2]) }],
+  };
+
+  it('takes all of it once, keeping stand-in ids and order', async () => {
+    expect(await t.engine.areaCall('outbox.importLegacy', legacy)).toBe(true);
+    expect(await t.engine.areaCall('outbox.importLegacy', legacy)).toBe(false);
+    const { entries, patches } = await read();
+    expect(entries.map((e) => [e.summary.subject, e.status, e.createdAt])).toEqual([['Old', 'uncertain', 5], ['Older file', 'waiting', 6]]);
+    expect(patches).toBe(1);
+    expect(await t.engine.areaCall('outbox.heldFile', { blobId: 'bulwark-local-x' })).toMatchObject({ name: 'x.eml' });
+    expect((await local('a')).keywords).toEqual({ $seen: true });
+  });
+
+  it('takes nothing when a part of it fails, and can run again', async () => {
+    const broken = { ...legacy, files: [{ blobId: 'x', name: null, type: null, data: null }] };
+    await expect(t.engine.areaCall('outbox.importLegacy', broken)).rejects.toThrow();
+    expect((await read()).entries).toEqual([]);
+    expect(await pending()).toEqual([]);
+    expect(await t.engine.areaCall('outbox.importLegacy', legacy)).toBe(true);
+  });
+});
diff --git a/lib/store/__tests__/page-side.test.ts b/lib/store/__tests__/page-side.test.ts
new file mode 100644
index 000000000..fbd336b69
--- /dev/null
+++ b/lib/store/__tests__/page-side.test.ts
@@ -0,0 +1,406 @@
+import 'fake-indexeddb/auto';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import { configureStore, getStore, setStoreBackend, STORE_OPENED_KEY } from '../client/api';
+import { forgetAccountKey, getAccountRecord } from '../client/keys';
+import { purgeStoreFiles } from '../client/purge';
+import { StoreClient, StoreOwnerGoneError } from '../client/store-client';
+import { storeFilesToPrune } from '../worker/host';
+import { FAKE_SESSION } from './helpers/fake-jmap';
+
+/** Everything on one page: a BroadcastChannel that also reaches other objects here, as in a browser. */
+class FakeChannel {
+  static open = new Set<FakeChannel>();
+  onmessage: ((event: MessageEvent) => void) | null = null;
+  constructor(readonly name: string) {
+    FakeChannel.open.add(this);
+  }
+  postMessage(data: unknown): void {
+    for (const channel of FakeChannel.open) {
+      if (channel !== this && channel.name === this.name) channel.onmessage?.({ data } as MessageEvent);
+    }
+  }
+  close(): void {
+    FakeChannel.open.delete(this);
+  }
+}
+
+class FakeWorker {
+  static all: FakeWorker[] = [];
+  static openResult: unknown;
+  onmessage: ((event: MessageEvent) => void) | null = null;
+  posted: Array<Record<string, unknown>> = [];
+  terminated = false;
+  constructor(readonly url: string, readonly options: unknown) {
+    FakeWorker.all.push(this);
+  }
+  postMessage(message: Record<string, unknown>): void {
+    this.posted.push(message);
+    if (message.kind === 'open' || message.kind === 'prune-files') queueMicrotask(() => this.onmessage?.({ data: { kind: 'result', id: message.id, result: message.kind === 'open' ? FakeWorker.openResult : undefined } } as MessageEvent));
+  }
+  terminate(): void {
+    this.terminated = true;
+  }
+  becomeOwner(): void {
+    this.onmessage?.({ data: { kind: 'owner' } } as MessageEvent);
+  }
+}
+
+beforeEach(() => {
+  FakeChannel.open.clear();
+  FakeWorker.all = [];
+  vi.stubGlobal('BroadcastChannel', FakeChannel);
+  vi.stubGlobal('Worker', FakeWorker);
+});
+
+afterEach(() => {
+  vi.unstubAllGlobals();
+  setStoreBackend(null);
+  configureStore(null);
+});
+
+describe('whether the store can run here', () => {
+  afterEach(() => {
+    delete (window.navigator as { storage?: unknown }).storage;
+    delete (window.navigator as { locks?: unknown }).locks;
+  });
+
+  it('doesn’t ask the page for what only exists in a worker', () => {
+    expect(StoreClient.supported()).toBe(false);
+    Object.defineProperty(window.navigator, 'storage', { configurable: true, value: { getDirectory: async () => ({}) } });
+    Object.defineProperty(window.navigator, 'locks', { configurable: true, value: { request: async () => {} } });
+    // As on a real page: the class is there, without createSyncAccessHandle on it.
+    vi.stubGlobal('FileSystemFileHandle', class {});
+    expect(StoreClient.supported()).toBe(true);
+  });
+});
+
+describe('a tab that starts after the owner', () => {
+  it('asks who owns the store, so its calls don\'t wait for an announcement that never comes', async () => {
+    const owner = new FakeChannel('bulwark-store-rpc');
+    const asked: unknown[] = [];
+    owner.onmessage = (event) => {
+      asked.push(event.data);
+      if ((event.data as { kind: string }).kind === 'who-owns') owner.postMessage({ kind: 'owner-changed', owner: 'other-tab' });
+      if ((event.data as { kind: string }).kind === 'rpc') {
+        const { id, from } = event.data as { id: string; from: string };
+        owner.postMessage({ kind: 'reply', id, to: from, result: { answered: true } });
+      }
+    };
+    const client = new StoreClient();
+    client.start();
+    expect(asked).toEqual([{ kind: 'who-owns' }]);
+    await expect(client.area('a', 'x.y')).resolves.toEqual({ answered: true });
+    client.halt();
+  });
+
+  it('passes the error\'s name over the channel, so a caller can wait for the account to open', async () => {
+    const owner = new FakeChannel('bulwark-store-rpc');
+    owner.onmessage = (event) => {
+      if ((event.data as { kind: string }).kind === 'who-owns') owner.postMessage({ kind: 'owner-changed', owner: 'other-tab' });
+      if ((event.data as { kind: string }).kind === 'rpc') {
+        const { id, from } = event.data as { id: string; from: string };
+        owner.postMessage({ kind: 'reply', id, to: from, error: 'Not open', errorName: 'StoreAccountClosedError' });
+      }
+    };
+    const client = new StoreClient();
+    client.start();
+    await expect(client.area('a', 'x.y')).rejects.toMatchObject({ name: 'StoreAccountClosedError' });
+    client.halt();
+  });
+});
+
+describe('an owner that stopped answering', () => {
+  afterEach(() => vi.useRealTimers());
+
+  async function clientWithOwner(answers: () => boolean) {
+    vi.useFakeTimers();
+    const owner = new FakeChannel('bulwark-store-rpc');
+    owner.onmessage = (event) => {
+      const data = event.data as { kind: string };
+      if (data.kind === 'who-owns' && answers()) owner.postMessage({ kind: 'owner-changed', owner: 'elsewhere' });
+    };
+    const client = new StoreClient({ basePath: '' });
+    client.start();
+    await vi.advanceTimersByTimeAsync(0);
+    return client;
+  }
+
+  it('stops its calls waiting, long before their own time limit', async () => {
+    let answering = true;
+    const client = await clientWithOwner(() => answering);
+    const call = client.sync('a@x');
+    const failed = vi.fn();
+    void call.catch(failed);
+    await vi.advanceTimersByTimeAsync(0);
+    answering = false;
+    await vi.advanceTimersByTimeAsync(39_000);
+    expect(failed).not.toHaveBeenCalled();
+    await vi.advanceTimersByTimeAsync(11_000);
+    expect(failed.mock.calls[0][0]).toBeInstanceOf(StoreOwnerGoneError);
+    client.halt();
+  });
+
+  it('leaves calls alone while the owner answers', async () => {
+    const client = await clientWithOwner(() => true);
+    const failed = vi.fn();
+    void client.sync('a@x').catch(failed);
+    await vi.advanceTimersByTimeAsync(10 * 60_000);
+    expect(failed).not.toHaveBeenCalled();
+    client.halt();
+  });
+});
+
+describe('the owner tab calling its own worker', () => {
+  it('waits for the worker on the channel, since a call posted before that is lost', async () => {
+    const worker = new FakeChannel('bulwark-store-rpc');
+    const heard: Array<{ kind: string; id?: string; from?: string }> = [];
+    worker.onmessage = (event) => heard.push(event.data as { kind: string });
+    const client = new StoreClient();
+    client.start();
+    FakeWorker.all[0].becomeOwner();
+    expect(client.ownsStore).toBe(true);
+
+    const call = client.area('a', 'x.y');
+    await new Promise((resolve) => setTimeout(resolve, 5));
+    expect(heard.some(({ kind }) => kind === 'rpc')).toBe(false);
+    // It asked again, for when the first announcement was missed.
+    expect(heard.filter(({ kind }) => kind === 'who-owns')).toHaveLength(2);
+
+    worker.postMessage({ kind: 'owner-changed', owner: client.clientId });
+    await vi.waitFor(() => expect(heard.some(({ kind }) => kind === 'rpc')).toBe(true));
+    const rpc = heard.find(({ kind }) => kind === 'rpc')!;
+    worker.postMessage({ kind: 'reply', id: rpc.id, to: rpc.from, result: 'done' });
+    await expect(call).resolves.toBe('done');
+    client.halt();
+  });
+});
+
+describe('a sign-out in any tab', () => {
+  it('stops this tab\'s worker and rejects what was waiting', async () => {
+    const halted = vi.fn();
+    const client = new StoreClient({ onHalted: halted });
+    client.start();
+    const owner = new FakeChannel('bulwark-store-rpc');
+    owner.postMessage({ kind: 'owner-changed', owner: 'x' });
+    const pending = client.area('a', 'x.y');
+    await Promise.resolve();
+    owner.postMessage({ kind: 'shutdown' });
+    await expect(pending).rejects.toMatchObject({ name: 'StoreOwnerGoneError' });
+    expect(FakeWorker.all[0].terminated).toBe(true);
+    expect(halted).toHaveBeenCalled();
+  });
+});
+
+describe('purgeStoreFiles', () => {
+  function storage(removeEntry: (name: string, options: unknown) => Promise<void>) {
+    Object.defineProperty(window.navigator, 'storage', { configurable: true, value: { getDirectory: async () => ({ removeEntry }) } });
+  }
+
+  afterEach(() => {
+    delete (window.navigator as { storage?: unknown }).storage;
+    delete (window.navigator as { locks?: unknown }).locks;
+  });
+
+  it('forgets the keys first, tells every tab, and deletes the pool holding the owner lock', async () => {
+    const seen: unknown[] = [];
+    const tab = new FakeChannel('bulwark-store-rpc');
+    tab.onmessage = (event) => seen.push(event.data);
+    const order: string[] = [];
+    Object.defineProperty(window.navigator, 'locks', {
+      configurable: true,
+      value: { request: async (name: string, _options: unknown, run: () => Promise<void>) => { order.push(`lock ${name}`); await run(); order.push('unlock'); } },
+    });
+    storage(async (name, options) => {
+      order.push(`remove ${name} ${JSON.stringify(options)}`);
+    });
+    await purgeStoreFiles();
+    expect(seen).toEqual([{ kind: 'shutdown' }]);
+    expect(order).toEqual(['lock bulwark-store-owner', 'remove .bulwark-store {"recursive":true}', 'unlock']);
+    expect((await indexedDB.databases()).map((d) => d.name)).not.toContain('bulwark-store');
+  });
+
+  it('deletes what it can when another tab never lets go of the owner lock', async () => {
+    const remove = vi.fn(async () => {});
+    storage(remove);
+    let waited: AbortSignal | undefined;
+    Object.defineProperty(window.navigator, 'locks', {
+      configurable: true,
+      value: {
+        // The browser gives up when the signal says so.
+        request: async (_name: string, options: { signal: AbortSignal }) => {
+          waited = options.signal;
+          throw new DOMException('Took too long', 'TimeoutError');
+        },
+      },
+    });
+    await purgeStoreFiles();
+    expect(waited).toBeInstanceOf(AbortSignal);
+    expect(remove).toHaveBeenCalledTimes(1);
+  });
+
+  it('waits out a worker that still holds the files, and shrugs at a pool that isn\'t there', async () => {
+    const remove = vi.fn()
+      .mockRejectedValueOnce(Object.assign(new Error('busy'), { name: 'NoModificationAllowedError' }))
+      .mockResolvedValue(undefined);
+    storage(remove);
+    await purgeStoreFiles();
+    expect(remove).toHaveBeenCalledTimes(2);
+
+    storage(async () => { throw Object.assign(new Error('none'), { name: 'NotFoundError' }); });
+    await expect(purgeStoreFiles()).resolves.toBeUndefined();
+  });
+});
+
+describe('which files have no key', () => {
+  it('names store files with no key, and leaves anything else alone', () => {
+    expect(storeFilesToPrune(['/a01.db', '/a02.db', '/a02.db-journal', '/other', '/ab.DB'], ['/a02.db'])).toEqual(['/a01.db']);
+  });
+});
+
+describe('the page\'s store', () => {
+  function allowEngine() {
+    configureStore({
+      inputs: () => ({ session: FAKE_SESSION, auth: 'Basic x', invertedKeywordSort: true }),
+      refreshAuth: async () => 'Bearer fresh',
+      onEvent: () => {},
+    });
+  }
+
+  it('opens an account only as the owner, with the key to its own worker', async () => {
+    allowEngine();
+    const store = getStore();
+    await store.ensureOpen('a@x');
+    const worker = FakeWorker.all[0];
+    expect(worker.posted.some((m) => m.kind === 'open')).toBe(false);
+    worker.becomeOwner();
+    await vi.waitFor(() => expect(worker.posted.some((m) => m.kind === 'open')).toBe(true));
+    const open = worker.posted.find((m) => m.kind === 'open') as { params: { account: string; keyHex: string; file: string; auth: string; invertedKeywordSort: boolean } };
+    expect(open.params).toMatchObject({ account: 'a@x', auth: 'Basic x', invertedKeywordSort: true });
+    expect(open.params.keyHex).toMatch(/^[0-9a-f]{64}$/);
+    expect(open.params.file).toMatch(/^\/a[0-9a-f]+\.db$/);
+    store.stop();
+    expect(worker.terminated).toBe(true);
+  });
+
+  describe('when the key or the file of a store is gone', () => {
+    const lost = vi.fn();
+    const open = async () => {
+      configureStore({
+        inputs: () => ({ session: FAKE_SESSION, auth: 'Basic x', invertedKeywordSort: true }),
+        refreshAuth: async () => null,
+        onEvent: () => {},
+        onStoreLost: lost,
+      });
+      const store = getStore();
+      await store.ensureOpen('lost@x');
+      const worker = FakeWorker.all[FakeWorker.all.length - 1];
+      worker.becomeOwner();
+      await vi.waitFor(() => expect(worker.posted.some((m) => m.kind === 'open')).toBe(true));
+      await vi.waitFor(() => expect(localStorage.getItem(STORE_OPENED_KEY)).toContain('lost@x'));
+      store.stop();
+      return worker;
+    };
+
+    beforeEach(() => {
+      lost.mockClear();
+      localStorage.clear();
+    });
+
+    afterEach(async () => {
+      await forgetAccountKey('lost@x');
+    });
+
+    it('stays quiet about a first open, and removes nothing a key still names', async () => {
+      const worker = await open();
+      expect(lost).not.toHaveBeenCalled();
+      const prune = worker.posted.find((m) => m.kind === 'prune-files') as unknown as { keep: string[] };
+      const record = await getAccountRecord('lost@x');
+      expect(prune.keep).toContain(record!.file);
+    });
+
+    it('deletes the orphan and tells the page when the key went', async () => {
+      await open();
+      const before = await getAccountRecord('lost@x');
+      await forgetAccountKey('lost@x');
+      const worker = await open();
+      const after = await getAccountRecord('lost@x');
+      expect(after!.file).not.toBe(before!.file);
+      const prune = worker.posted.find((m) => m.kind === 'prune-files') as unknown as { keep: string[] };
+      expect(prune.keep).toContain(after!.file);
+      expect(prune.keep).not.toContain(before!.file);
+      expect(lost).toHaveBeenCalledWith('lost@x');
+    });
+
+    it('stays quiet on a normal reopen', async () => {
+      await open();
+      const worker = await open();
+      expect(lost).not.toHaveBeenCalled();
+      expect(worker.posted.some((m) => m.kind === 'prune-files')).toBe(false);
+    });
+
+    it('tells the page when the file went and the key stayed', async () => {
+      await open();
+      FakeWorker.openResult = { created: true };
+      try {
+        await open();
+      } finally {
+        FakeWorker.openResult = undefined;
+      }
+      expect(lost).toHaveBeenCalledWith('lost@x');
+    });
+
+    it('doesn\'t remember an account that was removed', async () => {
+      await open();
+      vi.spyOn(StoreClient.prototype, 'removeAccount').mockResolvedValue(true as never);
+      await getStore().remove('lost@x');
+      getStore().stop();
+      vi.restoreAllMocks();
+      await open();
+      expect(lost).not.toHaveBeenCalled();
+    });
+  });
+
+  it('runs the client\'s refresh when the worker needs auth, and hands the result over', async () => {
+    allowEngine();
+    const store = getStore();
+    await store.ensureOpen('a@x');
+    const worker = FakeWorker.all[0];
+    worker.onmessage?.({ data: { kind: 'need-auth', account: 'a@x' } } as MessageEvent);
+    await vi.waitFor(() => expect(worker.posted).toContainEqual({ kind: 'set-auth', account: 'a@x', auth: 'Bearer fresh' }));
+    store.stop();
+  });
+
+  it('forgets the key when an account is removed, also in a tab that isn\'t the owner', async () => {
+    allowEngine();
+    const store = getStore();
+    await store.ensureOpen('a@x');
+    const worker = FakeWorker.all[0];
+    worker.becomeOwner();
+    await vi.waitFor(() => expect(worker.posted.some((m) => m.kind === 'open')).toBe(true));
+    expect(await getAccountRecord('a@x')).not.toBeNull();
+
+    const owner = new FakeChannel('bulwark-store-rpc');
+    owner.postMessage({ kind: 'owner-changed', owner: 'worker' });
+    const removed: unknown[] = [];
+    owner.onmessage = (event) => {
+      const message = event.data as { kind: string; id: string; from: string; method: string; params: unknown };
+      if (message.kind !== 'rpc') return;
+      removed.push([message.method, message.params]);
+      owner.postMessage({ kind: 'reply', id: message.id, to: message.from, result: true });
+    };
+    const record = await getAccountRecord('a@x');
+    await store.remove('a@x');
+    expect(await getAccountRecord('a@x')).toBeNull();
+    expect(removed).toEqual([['removeAccount', { account: 'a@x', file: record?.file }]]);
+    store.stop();
+  });
+
+  it('stops waiting when the engine couldn\'t start in this browser', async () => {
+    allowEngine();
+    const store = getStore();
+    await store.ensureOpen('a@x');
+    FakeWorker.all[0].onmessage?.({ data: { kind: 'event', event: { type: 'error', account: '', area: 'store', message: 'no wasm' } } } as MessageEvent);
+    await expect(store.answer('a@x', [])).rejects.toThrow('could not start');
+    store.stop();
+  });
+});
diff --git a/lib/store/adapters/wasm.ts b/lib/store/adapters/wasm.ts
index 2af1373fe..d9ec6387d 100644
--- a/lib/store/adapters/wasm.ts
+++ b/lib/store/adapters/wasm.ts
@@ -12,11 +12,11 @@
  */
 
 import { runTransaction, type SqlRow, type SqlValue, type StorageAdapter } from '../storage';
+import { POOL_DIRECTORY } from '../worker/protocol';
 
 const VFS = 'multipleciphers-opfs-sahpool';
 const INIT_TIMEOUT_MS = 30_000;
 const REQUIRED_PAGE_SIZE = 8192;
-const POOL_DIRECTORY = '.bulwark-store';
 const INITIAL_CAPACITY = 16;
 /** A database and its journal, plus room for one more. */
 const SLOTS_PER_DATABASE = 3;
@@ -117,6 +117,10 @@ class WasmAdapter implements StorageAdapter {
   }
 }
 
+export function installMayPass(error: unknown): boolean {
+  return (error as Error)?.name !== 'SecurityError';
+}
+
 /** The module and the pool, once. Only the owner gets here. */
 export class WasmStorage {
   private constructor(private readonly sqlite3: any, private readonly pool: Pool) {}
@@ -141,6 +145,8 @@ export class WasmStorage {
         }) as Pool;
         return new WasmStorage(sqlite3, pool);
       } catch (error) {
+        // The browser won't allow it here at all, a private window: waiting won't help.
+        if (!installMayPass(error)) throw error;
         lastError = error;
         await new Promise((resolve) => setTimeout(resolve, 100 + attempt * 50));
       }
diff --git a/lib/store/area.ts b/lib/store/area.ts
index b73740b5b..c435a4bce 100644
--- a/lib/store/area.ts
+++ b/lib/store/area.ts
@@ -28,6 +28,9 @@ export const DEFAULT_SCOPE: StoreScope = {
   maxTotalBytes: 2 * 1024 * 1024 * 1024,
 };
 
+/** The `area` of an error event for a write that failed: a full disk, the browser's quota. */
+export const STORAGE_ERROR_AREA = 'storage';
+
 export interface SyncStateRow {
   state: string | null;
   /** The newest state the server told us about, to know when a run is caught up. */
@@ -52,8 +55,18 @@ export interface StoreContext {
   scope: StoreScope;
   now(): number;
   emit(event: StoreEvent): void;
+  /** Records of one type as this device shows them: see RecordOverlay. */
+  overlay<T extends { id: string }>(jmap: string, type: string, records: T[]): T[];
 }
 
+/**
+ * What an area changes about records another area stores: the outbox lays
+ * changes that wait for the server over what the server sent. Runs inside the
+ * caller's transaction. Returns the records to use; a record left out is one
+ * this device already treats as gone.
+ */
+export type RecordOverlay = (ctx: Pick<StoreContext, 'db' | 'now'>, jmap: string, type: string, records: Array<{ id: string }>) => Array<{ id: string }>;
+
 export interface SyncContext extends StoreContext {
   transport: JmapTransport;
   /** True once the engine is closing or lost the network: stop at the next batch. */
@@ -107,4 +120,5 @@ export interface StoreArea {
   methods: Readonly<Record<string, MethodHandler>>;
   syncers: readonly Syncer[];
   calls?: Readonly<Record<string, AreaCall>>;
+  overlay?: RecordOverlay;
 }
diff --git a/lib/store/areas.ts b/lib/store/areas.ts
index 30a6541ff..08fe2c607 100644
--- a/lib/store/areas.ts
+++ b/lib/store/areas.ts
@@ -3,5 +3,6 @@
 import type { StoreArea } from './area';
 import { calendarArea } from './calendar';
 import { mailArea } from './mail';
+import { outboxArea } from './outbox';
 
-export const STORE_AREAS: readonly StoreArea[] = [mailArea, calendarArea];
+export const STORE_AREAS: readonly StoreArea[] = [mailArea, outboxArea, calendarArea];
diff --git a/lib/store/calendar/index.ts b/lib/store/calendar/index.ts
index 12d908660..1401c050e 100644
--- a/lib/store/calendar/index.ts
+++ b/lib/store/calendar/index.ts
@@ -11,6 +11,8 @@ export const calendarArea: StoreArea = {
   syncers: [calendarSyncer],
   calls: {
     'calendar.flush': (ctx) => flushCalendar(ctx),
+    /** Edits the server hasn't got, for the question before a sign-out. */
+    'calendar.pending': (ctx) => Number(ctx.db.get<{ n: number }>('SELECT COUNT(*) AS n FROM calendar_pending')?.n ?? 0),
     'calendar.conflicts': (ctx) => listConflicts(ctx.db),
     'calendar.resolveStandIns': (ctx, params: { ids: string[] }) => resolveStandIns(ctx.db, params.ids),
     'calendar.dismissConflict': (ctx, params: { id: number }) => {
diff --git a/lib/store/client/api.ts b/lib/store/client/api.ts
new file mode 100644
index 000000000..83cb83655
--- /dev/null
+++ b/lib/store/client/api.ts
@@ -0,0 +1,246 @@
+/**
+ * The page's way to the local store: one StoreClient per tab, accounts opened
+ * while this tab is the owner, sessions and auth handed over. Knows nothing of
+ * the app's stores: lib/offline/offline-mode.ts wires those in with
+ * configureStore, so the worker bundle stays free of them.
+ */
+
+import { DEFAULT_SCOPE, type StoreEvent, type StoreScope } from '../area';
+import type { JmapResponse, MethodCall, StoreSession } from '../engine/transport';
+import { forgetAccountKey, getAccountRecord, knownStoreFiles, openAccountKey, type WrapLayer } from './keys';
+import { StoreClient } from './store-client';
+
+export interface StoreAccountInputs {
+  session: StoreSession | null;
+  auth: string | null;
+  scope?: StoreScope;
+  invertedKeywordSort: boolean | null;
+}
+
+export interface StorePageHooks {
+  /** What this tab knows about an account right now. */
+  inputs(account: string): StoreAccountInputs;
+  /** Runs the client's refresh path; the fresh Authorization header, or null. */
+  refreshAuth(account: string): Promise<string | null>;
+  onEvent(event: StoreEvent): void;
+  /** Wrap layers on top of the WebCrypto one (desktop keychain, app lock). */
+  keyLayers?(): readonly WrapLayer[];
+  /** An account this device kept mail for has an empty store now: its key or its file went. */
+  onStoreLost?(account: string): void;
+}
+
+/** What lib/offline uses. A seam, so its tests run the real engine on node:sqlite. */
+export interface StoreBackend {
+  supported(): boolean;
+  /** Asks for the account to be open. `session` is for a first open with no client yet. */
+  ensureOpen(account: string, session?: StoreSession | null): Promise<void>;
+  /** Hands the owner what this tab now knows: session, auth, sort polarity. */
+  refresh(account: string): void;
+  answer(account: string, calls: MethodCall[]): Promise<JmapResponse | null>;
+  area<T = unknown>(account: string, name: string, params?: unknown): Promise<T>;
+  sync(account: string): Promise<void>;
+  noteStateChange(account: string, changed: Record<string, Record<string, string>>): Promise<void>;
+  setOnline(online: boolean): Promise<void>;
+  /** Closes the account, forgets its key and deletes its file. */
+  remove(account: string): Promise<void>;
+  /** Stops this tab's worker at once (a sign-out; the files go separately). */
+  stop(): void;
+}
+
+/** How long a call waits for the owner to have opened an account. */
+const OPEN_RETRIES = 25;
+const OPEN_RETRY_MS = 200;
+
+/**
+ * localStorage: accounts that have had a store here. Holds nothing but the
+ * account's id, and it outlives what a browser may clear of the rest.
+ */
+export const STORE_OPENED_KEY = 'bulwark-store-opened';
+
+function readOpenedAccounts(): string[] {
+  try {
+    const parsed = JSON.parse(localStorage.getItem(STORE_OPENED_KEY) ?? '[]') as unknown;
+    return Array.isArray(parsed) ? parsed as string[] : [];
+  } catch {
+    return [];
+  }
+}
+
+function rememberOpened(account: string, opened: boolean): void {
+  try {
+    const others = readOpenedAccounts().filter((id) => id !== account);
+    localStorage.setItem(STORE_OPENED_KEY, JSON.stringify(opened ? [...others, account] : others));
+  } catch {
+    // Without it a lost store goes unnoticed, and the store still works.
+  }
+}
+
+class PageStore implements StoreBackend {
+  private client: StoreClient | null = null;
+  private readonly wanted = new Map<string, StoreSession | null>();
+  private readonly opening = new Map<string, Promise<void>>();
+  /** The engine can't start in this browser: don't keep every caller waiting for an owner. */
+  private broken = false;
+  /** What the owner's engine was last told to keep. */
+  private readonly sentScope = new Map<string, string>();
+
+  constructor(private readonly hooks: () => StorePageHooks | null) {}
+
+  supported(): boolean {
+    return StoreClient.supported();
+  }
+
+  private started(): StoreClient {
+    if (this.client) return this.client;
+    this.broken = false;
+    const client = new StoreClient({
+      basePath: (process.env.NEXT_PUBLIC_BASE_PATH ?? '').replace(/\/+$/, ''),
+      buildId: process.env.NEXT_PUBLIC_BUILD_ID,
+      onEvent: (event) => {
+        if (event.type === 'error' && event.area === 'store' && !event.account) this.broken = true;
+        this.hooks()?.onEvent(event);
+      },
+      onOwner: () => {
+        this.opening.clear();
+        for (const account of this.wanted.keys()) void this.openHere(account).catch(() => {});
+      },
+      onNeedAuth: (account) => {
+        void (this.hooks()?.refreshAuth(account) ?? Promise.resolve(null))
+          .catch(() => null)
+          .then((auth) => this.client?.setAuth(account, auth));
+      },
+      onHalted: () => this.reset(),
+    });
+    client.start();
+    this.client = client;
+    return client;
+  }
+
+  private reset(): void {
+    this.client = null;
+    this.sentScope.clear();
+    this.wanted.clear();
+    this.opening.clear();
+    this.broken = false;
+  }
+
+  /** Only the owner may open: the key goes to this tab's own worker, never over the channel. */
+  private openHere(account: string): Promise<void> {
+    const running = this.opening.get(account);
+    if (running) return running;
+    const run = (async () => {
+      const client = this.started();
+      const { keyHex, record, fresh } = await openAccountKey(account, this.hooks()?.keyLayers?.() ?? []);
+      // The old file, if the key alone went, can never be read again.
+      if (fresh) await client.pruneFiles(await knownStoreFiles()).catch(() => {});
+      const inputs = this.hooks()?.inputs(account) ?? { session: null, auth: null, invertedKeywordSort: null };
+      if (inputs.scope) this.sentScope.set(account, JSON.stringify(inputs.scope));
+      const opened = await client.openAccount({
+        account,
+        file: record.file,
+        keyHex,
+        session: inputs.session ?? this.wanted.get(account) ?? null,
+        scope: inputs.scope ?? DEFAULT_SCOPE,
+        invertedKeywordSort: inputs.invertedKeywordSort,
+        auth: inputs.auth,
+      });
+      if (fresh || opened?.created) {
+        if (readOpenedAccounts().includes(account)) this.hooks()?.onStoreLost?.(account);
+      }
+      rememberOpened(account, true);
+    })();
+    this.opening.set(account, run);
+    run.catch(() => this.opening.delete(account));
+    return run;
+  }
+
+  async ensureOpen(account: string, session?: StoreSession | null): Promise<void> {
+    this.wanted.set(account, session ?? this.wanted.get(account) ?? null);
+    const client = this.started();
+    if (client.ownsStore) await this.openHere(account);
+    // Otherwise the owner opens it: calls below wait for that.
+  }
+
+  refresh(account: string): void {
+    const client = this.client;
+    if (!client?.ownsStore) return;
+    const inputs = this.hooks()?.inputs(account);
+    if (!inputs) return;
+    if (inputs.session) client.setSession(account, inputs.session);
+    client.setAuth(account, inputs.auth);
+    // Only a real change: setting it starts over what a full disk made the store give up on.
+    const scope = inputs.scope ? JSON.stringify(inputs.scope) : null;
+    if (inputs.scope && scope !== this.sentScope.get(account)) {
+      if (this.sentScope.has(account)) client.setScope(account, inputs.scope);
+      this.sentScope.set(account, scope!);
+    }
+    if (inputs.invertedKeywordSort !== null) client.setInvertedKeywordSort(account, inputs.invertedKeywordSort);
+  }
+
+  /** A call for an account: the owner may still be opening it, in this tab or another. */
+  private async whenOpen<T>(account: string, call: (client: StoreClient) => Promise<T>): Promise<T> {
+    if (this.broken) throw new Error('The local store could not start');
+    await this.ensureOpen(account);
+    for (let attempt = 0; ; attempt += 1) {
+      try {
+        return await call(this.started());
+      } catch (error) {
+        if ((error as Error)?.name !== 'StoreAccountClosedError' || attempt >= OPEN_RETRIES) throw error;
+        await new Promise((resolve) => setTimeout(resolve, OPEN_RETRY_MS));
+      }
+    }
+  }
+
+  answer(account: string, calls: MethodCall[]): Promise<JmapResponse | null> {
+    return this.whenOpen(account, (client) => client.answer(account, calls));
+  }
+
+  area<T = unknown>(account: string, name: string, params?: unknown): Promise<T> {
+    return this.whenOpen(account, (client) => client.area<T>(account, name, params));
+  }
+
+  sync(account: string): Promise<void> {
+    return this.whenOpen(account, (client) => client.sync(account));
+  }
+
+  noteStateChange(account: string, changed: Record<string, Record<string, string>>): Promise<void> {
+    return this.whenOpen(account, (client) => client.noteStateChange(account, changed));
+  }
+
+  async setOnline(online: boolean): Promise<void> {
+    if (!this.client || this.broken) return;
+    await this.client.setOnline(online);
+  }
+
+  async remove(account: string): Promise<void> {
+    const record = await getAccountRecord(account);
+    await forgetAccountKey(account);
+    rememberOpened(account, false);
+    this.wanted.delete(account);
+    this.opening.delete(account);
+    if (record && !this.broken) await this.started().removeAccount(account, record.file);
+  }
+
+  stop(): void {
+    this.client?.halt();
+    this.reset();
+  }
+}
+
+let hooks: StorePageHooks | null = null;
+let backend: StoreBackend | null = null;
+
+/** Registers what the store needs from the app. */
+export function configureStore(next: StorePageHooks | null): void {
+  hooks = next;
+}
+
+export function getStore(): StoreBackend {
+  backend ??= new PageStore(() => hooks);
+  return backend;
+}
+
+/** Tests run the real engine in-process. */
+export function setStoreBackend(next: StoreBackend | null): void {
+  backend = next;
+}
diff --git a/lib/store/client/keys.ts b/lib/store/client/keys.ts
index ecd4fe4c2..9723c6710 100644
--- a/lib/store/client/keys.ts
+++ b/lib/store/client/keys.ts
@@ -83,6 +83,14 @@ export function newStoreFileName(): string {
   return `/a${toHex(crypto.getRandomValues(new Uint8Array(8)))}.db`;
 }
 
+/** The file of every account with a key. Any other file in the pool can't be read by anyone. */
+export async function knownStoreFiles(): Promise<string[]> {
+  return withDb(async (db) => {
+    const records = await promisify(db.transaction(ACCOUNTS, 'readonly').objectStore(ACCOUNTS).getAll()) as AccountRecord[];
+    return records.map((record) => record.file);
+  });
+}
+
 export async function getAccountRecord(account: string): Promise<AccountRecord | null> {
   return withDb(async (db) => {
     const found = await promisify(db.transaction(ACCOUNTS, 'readonly').objectStore(ACCOUNTS).get(account)) as AccountRecord | undefined;
@@ -95,7 +103,7 @@ export async function listAccountRecords(): Promise<AccountRecord[]> {
 }
 
 /** The account's key in hex, created on first use. Returns the record too, for the file name. */
-export async function openAccountKey(account: string, layers: readonly WrapLayer[] = []): Promise<{ keyHex: string; record: AccountRecord }> {
+export async function openAccountKey(account: string, layers: readonly WrapLayer[] = []): Promise<{ keyHex: string; record: AccountRecord; fresh: boolean }> {
   return withDb(async (db) => {
     const wrapping = await wrapKey(db);
     const found = await promisify(db.transaction(ACCOUNTS, 'readonly').objectStore(ACCOUNTS).get(account)) as AccountRecord | undefined;
@@ -109,7 +117,7 @@ export async function openAccountKey(account: string, layers: readonly WrapLayer
       const raw = new Uint8Array(await crypto.subtle.decrypt({ name: 'AES-GCM', iv: asBuffer(found.iv) }, wrapping, asBuffer(data)));
       const keyHex = toHex(raw);
       raw.fill(0);
-      return { keyHex, record: found };
+      return { keyHex, record: found, fresh: false };
     }
     const raw = crypto.getRandomValues(new Uint8Array(32));
     const iv = crypto.getRandomValues(new Uint8Array(12));
@@ -126,7 +134,7 @@ export async function openAccountKey(account: string, layers: readonly WrapLayer
     await promisify(db.transaction(ACCOUNTS, 'readwrite').objectStore(ACCOUNTS).put(record));
     const keyHex = toHex(raw);
     raw.fill(0);
-    return { keyHex, record };
+    return { keyHex, record, fresh: true };
   });
 }
 
diff --git a/lib/store/client/purge.ts b/lib/store/client/purge.ts
new file mode 100644
index 000000000..10fb04dfb
--- /dev/null
+++ b/lib/store/client/purge.ts
@@ -0,0 +1,64 @@
+/**
+ * Deletes the local store from the page: the keys and the OPFS pool, with no
+ * worker running and no wasm loaded, also on the sign-in page. Imports nothing
+ * heavy, because lib/sign-out-cleanup.ts is in every page's bundle.
+ */
+
+import { OWNER_LOCK, POOL_DIRECTORY, RPC_CHANNEL, type ChannelMessage } from '../worker/protocol';
+import { deleteKeyDatabase } from './keys';
+
+/** A worker just stopped may hold the files for a moment longer. */
+const REMOVE_TRIES = 10;
+const REMOVE_WAIT_MS = 200;
+/** A sign-out doesn't wait for a tab that never lets go of the owner lock. */
+const POOL_LOCK_WAIT_MS = 5_000;
+
+async function removePool(): Promise<void> {
+  const root = await navigator.storage.getDirectory();
+  for (let attempt = 0; ; attempt += 1) {
+    try {
+      await root.removeEntry(POOL_DIRECTORY, { recursive: true });
+      return;
+    } catch (error) {
+      if ((error as Error)?.name === 'NotFoundError') return;
+      if (attempt >= REMOVE_TRIES) throw error;
+      await new Promise((resolve) => setTimeout(resolve, REMOVE_WAIT_MS));
+    }
+  }
+}
+
+/** Deletes the pool folder, holding the owner lock so no worker can take the files meanwhile. */
+export async function deleteStorePool(): Promise<void> {
+  if (typeof navigator === 'undefined' || typeof navigator.storage?.getDirectory !== 'function') return;
+  if (!navigator.locks) {
+    await removePool();
+    return;
+  }
+  try {
+    await navigator.locks.request(OWNER_LOCK, { signal: AbortSignal.timeout(POOL_LOCK_WAIT_MS) }, removePool);
+  } catch (error) {
+    if ((error as Error)?.name !== 'TimeoutError' && (error as Error)?.name !== 'AbortError') throw error;
+    // A tab that won't let go, stuck or asleep: the key is gone, so what can be
+    // deleted goes now, and what it still holds can't be read anyway.
+    await removePool();
+  }
+}
+
+/**
+ * Forgets every key first, which makes the files unreadable even if deleting
+ * them fails, then has every tab stop its worker and deletes the files.
+ * Started synchronously: the sign-out may navigate away right after.
+ */
+export function purgeStoreFiles(): Promise<void> {
+  deleteKeyDatabase();
+  try {
+    const channel = new BroadcastChannel(RPC_CHANNEL);
+    channel.postMessage({ kind: 'shutdown' } satisfies ChannelMessage);
+    channel.close();
+  } catch {
+    // No BroadcastChannel: no store either.
+  }
+  return deleteStorePool().catch(() => {
+    // The key is gone, so what's left can't be read.
+  });
+}
diff --git a/lib/store/client/store-client.ts b/lib/store/client/store-client.ts
index 5ae621748..66e7c3b92 100644
--- a/lib/store/client/store-client.ts
+++ b/lib/store/client/store-client.ts
@@ -21,6 +21,11 @@ import {
 
 const CALL_TIMEOUT_MS = 60_000;
 const OWNER_WAIT_MS = 15_000;
+/** Calls waiting on the owner ask it this often whether it's still there. */
+const OWNER_PING_MS = 10_000;
+const OWNER_PING_MISSES = 3;
+/** A first sync of a large account runs a long time, and its promise is what ends "syncing". */
+const SYNC_TIMEOUT_MS = 30 * 60_000;
 
 export class StoreOwnerGoneError extends Error {
   constructor() {
@@ -44,6 +49,8 @@ export interface StoreClientOptions {
   onOwner?(): void;
   /** The worker asks for a fresh Authorization header. */
   onNeedAuth?(account: string): void;
+  /** Another tab signed everyone out: this tab's worker is gone. */
+  onHalted?(): void;
 }
 
 export class StoreClient {
@@ -54,6 +61,9 @@ export class StoreClient {
   private isOwner = false;
   private readonly pending = new Map<string, Pending>();
   private readonly ownerWaiters: Array<() => void> = [];
+  private ownerWatch: ReturnType<typeof setInterval> | null = null;
+  private ownerAnswered: (() => void) | null = null;
+  private lifecycleBound = false;
 
   constructor(private readonly options: StoreClientOptions = {}) {}
 
@@ -63,8 +73,10 @@ export class StoreClient {
       && typeof navigator !== 'undefined'
       && Boolean(navigator.locks)
       && typeof navigator.storage?.getDirectory === 'function'
-      && typeof FileSystemFileHandle !== 'undefined'
-      && 'createSyncAccessHandle' in FileSystemFileHandle.prototype;
+      // createSyncAccessHandle itself only exists inside a dedicated worker,
+      // so the page can't check for it. A browser without it fails at the
+      // worker's start, which the page hears as an error event.
+      && typeof FileSystemFileHandle !== 'undefined';
   }
 
   start(): void {
@@ -80,10 +92,14 @@ export class StoreClient {
       clientId: this.clientId,
       moduleUrl: new URL(`${base}/${SQLITE3MC_PUBLIC_DIR}/sqlite3.mjs`, location.origin).href,
     });
+    // An owner from before this tab won't announce itself again.
+    this.channel.postMessage({ kind: 'who-owns' } satisfies ChannelMessage);
     this.bindLifecycle();
   }
 
   private bindLifecycle(): void {
+    if (this.lifecycleBound) return;
+    this.lifecycleBound = true;
     // A clean handover when the tab goes. If this doesn't get to run, the lock
     // and the handles die with the worker and the next owner retries.
     addEventListener('pagehide', (event) => {
@@ -99,8 +115,10 @@ export class StoreClient {
     switch (message.kind) {
       case 'owner':
         this.isOwner = true;
-        this.owner = this.clientId;
-        this.flushOwnerWaiters();
+        // Not an owner to call yet. This message can overtake the worker's
+        // channel getting registered, and a call posted then never reaches it,
+        // so calls wait for the worker's answer on the channel itself.
+        this.channel?.postMessage({ kind: 'who-owns' } satisfies ChannelMessage);
         this.options.onOwner?.();
         break;
       case 'result': {
@@ -137,8 +155,13 @@ export class StoreClient {
         break;
       case 'owner-changed':
         this.owner = message.owner;
+        if (message.owner) this.ownerAnswered?.();
         if (message.owner) this.flushOwnerWaiters();
         break;
+      case 'shutdown':
+        this.halt();
+        this.options.onHalted?.();
+        break;
       default:
         break;
     }
@@ -149,8 +172,48 @@ export class StoreClient {
     if (!pending) return;
     this.pending.delete(message.id);
     clearTimeout(pending.timer);
-    if (message.error) pending.reject(new Error(message.error));
-    else pending.resolve(message.result);
+    if (message.error) {
+      const error = new Error(message.error);
+      if (message.errorName) error.name = message.errorName;
+      pending.reject(error);
+    } else {
+      pending.resolve(message.result);
+    }
+  }
+
+  /**
+   * A tab that's frozen or stuck keeps the lock, and nothing else would tell.
+   * While calls wait, the owner is asked to answer; when it doesn't for a while,
+   * they stop waiting instead of running into their long time limits.
+   */
+  private watchOwner(): void {
+    if (this.ownerWatch) return;
+    let unanswered = 0;
+    this.ownerAnswered = () => { unanswered = 0; };
+    this.ownerWatch = setInterval(() => {
+      if (this.pending.size === 0) {
+        this.stopWatchingOwner();
+        return;
+      }
+      if (unanswered >= OWNER_PING_MISSES) {
+        this.owner = null;
+        this.stopWatchingOwner();
+        for (const [id, pending] of this.pending) {
+          this.pending.delete(id);
+          clearTimeout(pending.timer);
+          pending.reject(new StoreOwnerGoneError());
+        }
+        return;
+      }
+      unanswered += 1;
+      this.channel?.postMessage({ kind: 'who-owns' } satisfies ChannelMessage);
+    }, OWNER_PING_MS);
+  }
+
+  private stopWatchingOwner(): void {
+    if (this.ownerWatch) clearInterval(this.ownerWatch);
+    this.ownerWatch = null;
+    this.ownerAnswered = null;
   }
 
   private flushOwnerWaiters(): void {
@@ -178,10 +241,11 @@ export class StoreClient {
     });
   }
 
-  private async rpc<K extends keyof StoreRpc>(method: K, params: Parameters<StoreRpc[K]>[0]): Promise<ReturnType<StoreRpc[K]>> {
+  private async rpc<K extends keyof StoreRpc>(method: K, params: Parameters<StoreRpc[K]>[0], timeoutMs = CALL_TIMEOUT_MS): Promise<ReturnType<StoreRpc[K]>> {
     await this.waitForOwner();
+    this.watchOwner();
     const id = crypto.randomUUID();
-    const result = this.track<ReturnType<StoreRpc[K]>>(id, CALL_TIMEOUT_MS);
+    const result = this.track<ReturnType<StoreRpc[K]>>(id, timeoutMs);
     this.channel?.postMessage({ kind: 'rpc', id, from: this.clientId, method, params } as ChannelMessage);
     return result;
   }
@@ -198,18 +262,20 @@ export class StoreClient {
     return this.isOwner;
   }
 
-  openAccount(params: OpenAccountParams): Promise<void> {
+  /** `created`: there was no database under this name. */
+  openAccount(params: OpenAccountParams): Promise<{ created?: boolean } | undefined> {
     return this.direct({ kind: 'open', id: crypto.randomUUID(), params });
   }
 
+  /** Deletes every store file but these. */
+  pruneFiles(keep: string[]): Promise<void> {
+    return this.direct({ kind: 'prune-files', id: crypto.randomUUID(), keep });
+  }
+
   closeAccount(account: string): Promise<void> {
     return this.direct({ kind: 'close-account', id: crypto.randomUUID(), account });
   }
 
-  removeAccount(account: string, file: string): Promise<boolean> {
-    return this.direct({ kind: 'remove-account', id: crypto.randomUUID(), account, file });
-  }
-
   setAuth(account: string, auth: string | null): void {
     this.post({ kind: 'set-auth', account, auth });
   }
@@ -222,19 +288,38 @@ export class StoreClient {
     this.post({ kind: 'set-scope', account, scope });
   }
 
+  setInvertedKeywordSort(account: string, inverted: boolean): void {
+    this.post({ kind: 'set-inverted', account, inverted });
+  }
+
   /** Hands the store over: the worker closes everything, then lets go of the lock. */
   async release(): Promise<void> {
     if (!this.worker) return;
-    const worker = this.worker;
     if (this.isOwner) {
       await this.direct({ kind: 'release', id: crypto.randomUUID() });
       this.isOwner = false;
       this.owner = null;
     }
-    worker.terminate();
+    this.halt();
+  }
+
+  /**
+   * Stops at once, with no handover. For a sign-out: the data goes anyway, and
+   * the worker's end frees the lock and the OPFS handles.
+   */
+  halt(): void {
+    this.worker?.terminate();
     this.worker = null;
     this.channel?.close();
     this.channel = null;
+    this.isOwner = false;
+    this.owner = null;
+    this.stopWatchingOwner();
+    for (const [id, pending] of this.pending) {
+      this.pending.delete(id);
+      clearTimeout(pending.timer);
+      pending.reject(new StoreOwnerGoneError());
+    }
   }
 
   // ---- Any tab ----
@@ -244,7 +329,11 @@ export class StoreClient {
   }
 
   sync(account: string): Promise<void> {
-    return this.rpc('sync', { account });
+    return this.rpc('sync', { account }, SYNC_TIMEOUT_MS);
+  }
+
+  removeAccount(account: string, file: string): Promise<boolean> {
+    return this.rpc('removeAccount', { account, file });
   }
 
   noteStateChange(account: string, changed: Record<string, Record<string, string>>): Promise<void> {
diff --git a/lib/store/engine/account-engine.ts b/lib/store/engine/account-engine.ts
index ab3a2b9b5..df9452248 100644
--- a/lib/store/engine/account-engine.ts
+++ b/lib/store/engine/account-engine.ts
@@ -4,8 +4,8 @@
  * the UI. Nothing here touches the DOM, so tests run it on node:sqlite.
  */
 
-import { MethodError, type AreaCall, type MethodHandler, type StoreArea, type StoreContext, type StoreEvent, type StoreScope, type SyncContext, type SyncStateRow, type Syncer } from '../area';
-import { migrate, type StorageAdapter } from '../storage';
+import { MethodError, STORAGE_ERROR_AREA, type AreaCall, type MethodHandler, type RecordOverlay, type StoreArea, type StoreContext, type StoreEvent, type StoreScope, type SyncContext, type SyncStateRow, type Syncer } from '../area';
+import { isStorageFailure, migrate, type StorageAdapter } from '../storage';
 import { answerRequest, buildMethodTable } from './responder';
 import { TransportError, type JmapResponse, type JmapTransport, type MethodCall, type StoreSession } from './transport';
 import { CORE_MIGRATIONS, metaGet, metaSet } from './core-schema';
@@ -26,6 +26,9 @@ export interface AccountEngineOptions {
 
 const RATE_RETRIES = 5;
 const RATE_BACKOFF_MS = 2_000;
+/** After a failed write: the first wait, and the longest. */
+const STORAGE_BACKOFF_MS = 60_000;
+const STORAGE_BACKOFF_MAX_MS = 60 * 60_000;
 
 export class AccountEngine {
   readonly account: string;
@@ -36,6 +39,7 @@ export class AccountEngine {
   private readonly syncers: readonly Syncer[];
   private readonly methods: ReadonlyMap<string, MethodHandler>;
   private readonly calls = new Map<string, AreaCall>();
+  private readonly overlays: readonly RecordOverlay[];
   private readonly emitter: (event: StoreEvent) => void;
   private readonly now: () => number;
   private readonly sleep: (ms: number) => Promise<void>;
@@ -44,6 +48,9 @@ export class AccountEngine {
   private online = true;
   private running: Promise<void> | null = null;
   private again = false;
+  /** A write failed (full disk, quota): no sync before this time, however much the server pushes. */
+  private storageBlockedUntil = 0;
+  private storageFailures = 0;
 
   constructor(options: AccountEngineOptions) {
     this.account = options.account;
@@ -53,6 +60,7 @@ export class AccountEngine {
     this.transport = options.transport;
     this.syncers = options.areas.flatMap((area) => area.syncers);
     this.methods = buildMethodTable(options.areas);
+    this.overlays = options.areas.flatMap((area) => (area.overlay ? [area.overlay] : []));
     for (const area of options.areas) {
       for (const [name, call] of Object.entries(area.calls ?? {})) {
         if (this.calls.has(name)) throw new Error(`Two store areas define ${name}`);
@@ -62,9 +70,11 @@ export class AccountEngine {
     this.emitter = options.emit ?? (() => {});
     this.now = options.now ?? Date.now;
     this.sleep = options.sleep ?? ((ms) => new Promise((resolve) => setTimeout(resolve, ms)));
-    this.invertedKeywordSort = options.invertedKeywordSort ?? false;
     migrate(this.db, [...CORE_MIGRATIONS, ...options.areas.flatMap((area) => area.migrations)]);
     metaSet(this.db, 'session', JSON.stringify(options.session));
+    // An offline start has no way to probe the server, so the last answer stays.
+    this.invertedKeywordSort = options.invertedKeywordSort ?? metaGet(this.db, 'inverted_keyword_sort') === '1';
+    if (options.invertedKeywordSort !== undefined) metaSet(this.db, 'inverted_keyword_sort', options.invertedKeywordSort ? '1' : '0');
   }
 
   /** The session kept from the last time, for a start without a network. */
@@ -81,11 +91,20 @@ export class AccountEngine {
 
   setScope(scope: StoreScope): void {
     this.scope = scope;
+    // The user may just have made room by keeping less.
+    this.storageBlockedUntil = 0;
     metaSet(this.db, 'scope', JSON.stringify(scope));
   }
 
   setInvertedKeywordSort(inverted: boolean): void {
     this.invertedKeywordSort = inverted;
+    metaSet(this.db, 'inverted_keyword_sort', inverted ? '1' : '0');
+  }
+
+  private overlay<T extends { id: string }>(jmap: string, type: string, records: T[]): T[] {
+    let out: Array<{ id: string }> = records;
+    for (const overlay of this.overlays) out = overlay({ db: this.db, now: this.now }, jmap, type, out);
+    return out as T[];
   }
 
   setOnline(online: boolean): void {
@@ -128,7 +147,7 @@ export class AccountEngine {
 
   /** Starts a run, or asks the running one to go again when it's done. */
   requestSync(): Promise<void> {
-    if (this.closed) return Promise.resolve();
+    if (this.closed || this.now() < this.storageBlockedUntil) return Promise.resolve();
     if (this.running) {
       this.again = true;
       return this.running;
@@ -143,7 +162,7 @@ export class AccountEngine {
     do {
       this.again = false;
       await this.runOnce();
-    } while (this.again && !this.closed && this.online);
+    } while (this.again && !this.closed && this.online && this.now() >= this.storageBlockedUntil);
   }
 
   private async runOnce(): Promise<void> {
@@ -158,6 +177,7 @@ export class AccountEngine {
         if (!(await this.runSyncer(ctx, syncer, jmap))) return;
       }
     }
+    this.storageFailures = 0;
     if (!this.closed && this.online) this.emitter({ type: 'synced', account: this.account, at: this.now() });
   }
 
@@ -175,6 +195,11 @@ export class AccountEngine {
             continue;
           }
         }
+        // The others would fail on the same disk: the run ends, and sync waits.
+        if (isStorageFailure(error)) {
+          this.noteStorageFailure(error);
+          return false;
+        }
         // One part failing doesn't hold up the others. It runs again next time.
         this.emitter({
           type: 'error',
@@ -187,6 +212,18 @@ export class AccountEngine {
     }
   }
 
+  private noteStorageFailure(error: unknown): void {
+    this.storageFailures += 1;
+    const wait = Math.min(STORAGE_BACKOFF_MS * 2 ** (this.storageFailures - 1), STORAGE_BACKOFF_MAX_MS);
+    this.storageBlockedUntil = this.now() + wait;
+    this.emitter({
+      type: 'error',
+      account: this.account,
+      area: STORAGE_ERROR_AREA,
+      message: error instanceof Error ? error.message : String(error),
+    });
+  }
+
   private syncContext(): SyncContext {
     return {
       account: this.account,
@@ -199,6 +236,7 @@ export class AccountEngine {
       stopped: () => this.closed || !this.online,
       syncState: (jmap, type) => this.syncState(jmap, type),
       setSyncState: (jmap, type, row) => this.setSyncState(jmap, type, row),
+      overlay: (jmap, type, records) => this.overlay(jmap, type, records),
     };
   }
 
@@ -210,6 +248,7 @@ export class AccountEngine {
       scope: this.scope,
       now: this.now,
       emit: this.emitter,
+      overlay: (jmap, type, records) => this.overlay(jmap, type, records),
     };
   }
 
@@ -217,22 +256,32 @@ export class AccountEngine {
   async areaCall(name: string, params: unknown): Promise<unknown> {
     const call = this.calls.get(name);
     if (!call) throw new Error(`Unknown store call ${name}`);
-    return call(this.syncContext(), params as never);
+    try {
+      return await call(this.syncContext(), params as never);
+    } catch (error) {
+      if (isStorageFailure(error)) this.noteStorageFailure(error);
+      throw error;
+    }
   }
 
   /** An answer from the device. Null when nothing in the request could be answered. */
   async answer(calls: MethodCall[]): Promise<JmapResponse | null> {
     if (this.closed) throw new MethodError('serverUnavailable', 'The local store is closed');
     const primary = this.session.primaryAccounts['urn:ietf:params:jmap:mail'] ?? Object.keys(this.session.accounts)[0];
-    return answerRequest(
-      {
-        ...this.storeContext(),
-        defaultJmap: primary,
-        invertedKeywordSort: this.invertedKeywordSort,
-      },
-      this.methods,
-      calls,
-    );
+    try {
+      return await answerRequest(
+        {
+          ...this.storeContext(),
+          defaultJmap: primary,
+          invertedKeywordSort: this.invertedKeywordSort,
+        },
+        this.methods,
+        calls,
+      );
+    } catch (error) {
+      if (isStorageFailure(error)) this.noteStorageFailure(error);
+      throw error;
+    }
   }
 
   /** Stops syncing and waits for the current batch. The database stays open for the caller to close. */
diff --git a/lib/store/mail/calls.ts b/lib/store/mail/calls.ts
new file mode 100644
index 000000000..713975810
--- /dev/null
+++ b/lib/store/mail/calls.ts
@@ -0,0 +1,65 @@
+/** What the page asks the mail part of the store outside JMAP. */
+
+import type { AreaCall, StoreContext } from '../area';
+import { putBlob, storeBody, upsertEmail, type EmailObject } from './records';
+
+/**
+ * A message the user opened online: kept with its text if the store doesn't
+ * have that yet, for instance because it's older than the window the user
+ * chose. Parts cut short for a list view aren't kept.
+ */
+function recordOpened(ctx: StoreContext, params: { jmap: string; emails: EmailObject[] }): void {
+  ctx.db.transaction(() => {
+    for (const email of ctx.overlay(params.jmap, 'Email', params.emails)) {
+      const values = (email.bodyValues ?? {}) as Record<string, { isTruncated?: boolean }>;
+      if (Object.keys(values).length === 0 || Object.values(values).some((value) => value?.isTruncated)) continue;
+      const kept = ctx.db.get<{ rowid: number; json: string; body_state: number }>(
+        'SELECT rowid, json, body_state FROM email WHERE jmap = ? AND id = ?',
+        [params.jmap, email.id],
+      );
+      if (kept && Number(kept.body_state) === 1) continue;
+      if (kept) {
+        storeBody(ctx.db, Number(kept.rowid), String(kept.json), email);
+        continue;
+      }
+      // A row needs at least what lists sort and filter on.
+      if (typeof email.receivedAt !== 'string' || !email.mailboxIds) continue;
+      const gen = Number(ctx.db.get<{ gen: number | null }>('SELECT MAX(gen) AS gen FROM email WHERE jmap = ?', [params.jmap])?.gen ?? 0);
+      const { bodyValues, textBody, htmlBody, attachments, bodyStructure, headers, bcc, replyTo, messageId, inReplyTo, references, sender, ...list } = email;
+      const rowid = upsertEmail(ctx.db, params.jmap, list as EmailObject, gen);
+      storeBody(ctx.db, rowid, JSON.stringify(list), { bodyValues, textBody, htmlBody, attachments, bodyStructure, headers, bcc, replyTo, messageId, inReplyTo, references, sender });
+    }
+  });
+}
+
+/** A file of a kept message the user opened. Nothing else is kept: not an export, not a stray file. */
+function recordBlob(ctx: StoreContext, params: { jmap: string; blobId: string; type: string | null; data: Uint8Array }): boolean {
+  if (!ctx.scope.attachments || params.data.byteLength > ctx.scope.maxAttachmentBytes) return false;
+  const owner = ctx.db.get<{ received_at: number }>('SELECT received_at FROM email_part WHERE jmap = ? AND blob_id = ?', [params.jmap, params.blobId]);
+  if (!owner) return false;
+  putBlob(ctx.db, params.jmap, params.blobId, params.type, params.data, Number(owner.received_at));
+  return true;
+}
+
+function getBlob(ctx: StoreContext, params: { jmap: string; blobId: string }): { type: string | null; data: Uint8Array } | null {
+  const row = ctx.db.get<{ type: string | null; data: Uint8Array }>('SELECT type, data FROM blob WHERE jmap = ? AND blob_id = ?', [params.jmap, params.blobId]);
+  return row ? { type: row.type, data: row.data } : null;
+}
+
+/** How much of the disk this account's file takes. */
+function usage(ctx: StoreContext): { bytes: number } {
+  const pages = Number(ctx.db.get<{ page_count: number }>('PRAGMA page_count')?.page_count ?? 0);
+  const size = Number(ctx.db.get<{ page_size: number }>('PRAGMA page_size')?.page_size ?? 0);
+  return { bytes: pages * size };
+}
+
+export const MAIL_CALLS: Readonly<Record<string, AreaCall>> = {
+  'mail.recordOpened': recordOpened,
+  'mail.recordBlob': recordBlob,
+  'mail.getBlob': getBlob,
+  'mail.usage': usage,
+  /** The session kept with the account, for a start from the local copy. */
+  'mail.session': (ctx) => ctx.session,
+  /** Whether a start may show the store: it has a folder list from the server. */
+  'mail.hasFolders': (ctx) => ctx.db.get("SELECT 1 AS yes FROM sync_state WHERE type = 'Mailbox' AND state IS NOT NULL") !== undefined,
+};
diff --git a/lib/store/mail/headers.ts b/lib/store/mail/headers.ts
new file mode 100644
index 000000000..a35211cc5
--- /dev/null
+++ b/lib/store/mail/headers.ts
@@ -0,0 +1,181 @@
+/**
+ * The `header:<Name>[:<form>][:all]` properties of Email/get (RFC 8621
+ * section 4.1.2), worked out from the raw `headers` a kept message stores.
+ * Callers read these for mailing list ids, classification labels and rules.
+ */
+
+export interface RawHeader {
+  name: string;
+  value: string;
+}
+
+export interface HeaderForm {
+  name: string;
+  form: 'asRaw' | 'asText' | 'asAddresses' | 'asGroupedAddresses' | 'asMessageIds' | 'asDate' | 'asURLs';
+  all: boolean;
+}
+
+const FORMS = new Set<HeaderForm['form']>(['asRaw', 'asText', 'asAddresses', 'asGroupedAddresses', 'asMessageIds', 'asDate', 'asURLs']);
+
+export function parseHeaderProperty(property: string): HeaderForm | null {
+  if (!property.startsWith('header:')) return null;
+  const parts = property.slice('header:'.length).split(':');
+  const name = parts.shift();
+  if (!name) return null;
+  let all = false;
+  if (parts[parts.length - 1] === 'all') {
+    all = true;
+    parts.pop();
+  }
+  if (parts.length > 1) return null;
+  const form = (parts[0] ?? 'asRaw') as HeaderForm['form'];
+  return FORMS.has(form) ? { name, form, all } : null;
+}
+
+function unfold(value: string): string {
+  return value.replace(/\r?\n(?=[ \t])/g, '').trim();
+}
+
+function decodeBytes(charset: string, bytes: Uint8Array): string {
+  try {
+    return new TextDecoder(charset).decode(bytes);
+  } catch {
+    return new TextDecoder().decode(bytes);
+  }
+}
+
+/** RFC 2047 encoded words. Whitespace between two of them goes. */
+function decodeWords(value: string): string {
+  return value
+    .replace(/(=\?[^?\s]+\?[bBqQ]\?[^?\s]*\?=)\s+(?==\?[^?\s]+\?[bBqQ]\?)/g, '$1')
+    .replace(/=\?([^?\s]+)\?([bBqQ])\?([^?\s]*)\?=/g, (whole, charset: string, encoding: string, text: string) => {
+      try {
+        if (encoding.toUpperCase() === 'B') {
+          return decodeBytes(charset, Uint8Array.from(atob(text), (c) => c.charCodeAt(0)));
+        }
+        const raw = text.replace(/_/g, ' ').replace(/=([0-9A-Fa-f]{2})/g, (_, hex: string) => String.fromCharCode(parseInt(hex, 16)));
+        return decodeBytes(charset, Uint8Array.from(raw, (c) => c.charCodeAt(0)));
+      } catch {
+        return whole;
+      }
+    });
+}
+
+interface Address { name: string | null; email: string }
+interface Group { name: string | null; addresses: Address[] }
+
+/** Splits on a separator outside quotes, comments and angle brackets. */
+function splitOutside(value: string, separators: string): string[] {
+  const parts: string[] = [];
+  let current = '';
+  let quoted = false;
+  let depth = 0;
+  let angle = false;
+  for (let i = 0; i < value.length; i += 1) {
+    const c = value[i];
+    if (quoted) {
+      current += c;
+      if (c === '\\') {
+        current += value[i + 1] ?? '';
+        i += 1;
+      } else if (c === '"') quoted = false;
+      continue;
+    }
+    if (c === '"') quoted = true;
+    else if (c === '(') depth += 1;
+    else if (c === ')') depth = Math.max(0, depth - 1);
+    else if (c === '<') angle = true;
+    else if (c === '>') angle = false;
+    if (depth === 0 && !angle && separators.includes(c)) {
+      parts.push(current);
+      if (c !== ',') parts.push(c);
+      current = '';
+      continue;
+    }
+    current += c;
+  }
+  parts.push(current);
+  return parts;
+}
+
+function parseAddress(text: string): Address | null {
+  const trimmed = text.replace(/\((?:[^()\\]|\\.)*\)/g, ' ').trim();
+  if (!trimmed) return null;
+  const angle = trimmed.match(/^([\s\S]*)<([^<>]*)>\s*$/);
+  const email = (angle ? angle[2] : trimmed).trim();
+  if (!angle && !email.includes('@')) return null;
+  const rawName = angle ? angle[1].trim() : '';
+  const name = rawName.startsWith('"') && rawName.endsWith('"') && rawName.length >= 2
+    ? rawName.slice(1, -1).replace(/\\(.)/g, '$1')
+    : rawName;
+  return { name: name ? decodeWords(name) : null, email };
+}
+
+function parseGroups(value: string): Group[] {
+  const groups: Group[] = [];
+  let current: Group | null = null;
+  let loose: Group | null = null;
+  const tokens = splitOutside(unfold(value), ',:;');
+  for (let i = 0; i < tokens.length; i += 1) {
+    const token = tokens[i];
+    if (tokens[i + 1] === ':') {
+      current = { name: decodeWords(token.trim().replace(/^"|"$/g, '')) || null, addresses: [] };
+      groups.push(current);
+      loose = null;
+      i += 1;
+      continue;
+    }
+    if (token === ';') {
+      current = null;
+      continue;
+    }
+    if (token === ':') continue;
+    const address = parseAddress(token);
+    if (!address) continue;
+    if (current) current.addresses.push(address);
+    else {
+      if (!loose) {
+        loose = { name: null, addresses: [] };
+        groups.push(loose);
+      }
+      loose.addresses.push(address);
+    }
+  }
+  return groups;
+}
+
+function parseMessageIds(value: string): string[] | null {
+  const ids = [...unfold(value).matchAll(/<([^<>\s]+)>/g)].map((match) => match[1]);
+  return ids.length > 0 ? ids : null;
+}
+
+function parseDate(value: string): string | null {
+  const ms = Date.parse(unfold(value).replace(/\((?:[^()\\]|\\.)*\)/g, ' '));
+  return Number.isFinite(ms) ? new Date(ms).toISOString() : null;
+}
+
+function parseUrls(value: string): string[] | null {
+  const urls = [...unfold(value).matchAll(/<([^<>\s]+)>/g)].map((match) => match[1]);
+  return urls.length > 0 ? urls : null;
+}
+
+function convert(value: string, form: HeaderForm['form']): unknown {
+  switch (form) {
+    case 'asRaw': return value;
+    case 'asText': return decodeWords(unfold(value));
+    case 'asAddresses': return parseGroups(value).flatMap((group) => group.addresses);
+    case 'asGroupedAddresses': return parseGroups(value);
+    case 'asMessageIds': return parseMessageIds(value);
+    case 'asDate': return parseDate(value);
+    case 'asURLs': return parseUrls(value);
+  }
+}
+
+/** The value of one header property. Without `:all`, the last header of that name, or null. */
+export function headerValue(form: HeaderForm, headers: readonly RawHeader[]): unknown {
+  const wanted = form.name.toLowerCase();
+  const found = headers.filter((header) => header.name.toLowerCase() === wanted);
+  if (form.all) return found.map((header) => convert(header.value, form.form));
+  const last = found[found.length - 1];
+  return last ? convert(last.value, form.form) : null;
+}
diff --git a/lib/store/mail/index.ts b/lib/store/mail/index.ts
index 0c7749864..aa0ba6e6b 100644
--- a/lib/store/mail/index.ts
+++ b/lib/store/mail/index.ts
@@ -1,12 +1,14 @@
 import type { StoreArea } from '../area';
+import { MAIL_CALLS } from './calls';
 import { MAIL_METHODS } from './methods';
 import { MAIL_MIGRATIONS } from './schema';
 import { SEARCH_MIGRATIONS } from './search-schema';
-import { mailSyncer } from './sync';
+import { identitySyncer, mailSyncer, quotaSyncer } from './sync';
 
 export const mailArea: StoreArea = {
   name: 'mail',
   migrations: [...MAIL_MIGRATIONS, ...SEARCH_MIGRATIONS],
   methods: MAIL_METHODS,
-  syncers: [mailSyncer],
+  syncers: [mailSyncer, identitySyncer, quotaSyncer],
+  calls: MAIL_CALLS,
 };
diff --git a/lib/store/mail/methods.ts b/lib/store/mail/methods.ts
index 1b5c954d9..8462563e4 100644
--- a/lib/store/mail/methods.ts
+++ b/lib/store/mail/methods.ts
@@ -1,8 +1,14 @@
-/** Mail reads answered from the store. */
+/**
+ * Mail reads answered from the store. What an answer must look like is in
+ * local-data/desktop-offline-facts-parts/offline-jmap.md sections 1 and 4: it
+ * follows what the calling method in lib/jmap/client.ts reads.
+ */
 
 import { MethodError, type MethodContext, type MethodHandler, type MethodResult } from '../area';
 import { listObjects } from '../engine/core-schema';
 import type { SqlValue } from '../storage';
+import { headerValue, parseHeaderProperty, type RawHeader } from './headers';
+import { keywordKey } from './records';
 import { limitTextConditions, searchSnippetGet, textCondition, TEXT_FIELDS, type TextField } from './search';
 
 type Filter = Record<string, unknown>;
@@ -13,14 +19,26 @@ function jmapOf(ctx: MethodContext, args: Record<string, unknown>): string {
   return (args.accountId as string | undefined) ?? ctx.defaultJmap;
 }
 
+function lastState(ctx: MethodContext, jmap: string, type: string): string | null {
+  return ctx.db.get<{ state: string | null }>('SELECT state FROM sync_state WHERE jmap = ? AND type = ?', [jmap, type])?.state ?? null;
+}
+
+function likeTerm(value: unknown): string {
+  return `%${String(value).replace(/[\\%_]/g, (c) => `\\${c}`)}%`;
+}
+
 /**
  * `drivenBy` is the folder the query already starts from: repeating that
- * condition would look the membership up again for every row.
+ * condition would look the membership up again for every row. With a folder row
+ * (`d`) at hand, conditions read it instead of the message's own row, which
+ * saves reading the message at all when nothing else needs it.
  */
-function filterSql(filter: Filter, jmap: string, drivenBy: string | null = null): Sql {
+function filterSql(filter: Filter, jmap: string, drivenBy: string | null = null, folderRow = drivenBy !== null): Sql {
+  const rowid = folderRow ? 'd.email_rowid' : 'e.rowid';
+  const receivedAt = folderRow ? 'd.received_at' : 'e.received_at';
   if (typeof filter.operator === 'string') {
     const conditions = Array.isArray(filter.conditions) ? filter.conditions as Filter[] : [];
-    const parts = conditions.map((c) => filterSql(c, jmap, filter.operator === 'AND' ? drivenBy : null));
+    const parts = conditions.map((c) => filterSql(c, jmap, filter.operator === 'AND' ? drivenBy : null, folderRow));
     const params = parts.flatMap((p) => p.params);
     const joined = (joiner: string) => parts.map((p) => `(${p.sql})`).join(joiner);
     if (filter.operator === 'AND') return { sql: parts.length ? joined(' AND ') : '1', params };
@@ -34,29 +52,29 @@ function filterSql(filter: Filter, jmap: string, drivenBy: string | null = null)
     switch (key) {
       case 'inMailbox':
         if (value === drivenBy) break;
-        conditions.push('EXISTS (SELECT 1 FROM email_mailbox m WHERE m.email_rowid = e.rowid AND m.mailbox_id = ?)');
+        conditions.push(`EXISTS (SELECT 1 FROM email_mailbox m WHERE m.email_rowid = ${rowid} AND m.mailbox_id = ?)`);
         params.push(String(value));
         break;
       case 'inMailboxOtherThan': {
         const ids = (value as string[]).map(String);
-        conditions.push(`EXISTS (SELECT 1 FROM email_mailbox m WHERE m.email_rowid = e.rowid AND m.mailbox_id NOT IN (${ids.map(() => '?').join(',') || "''"}))`);
+        conditions.push(`EXISTS (SELECT 1 FROM email_mailbox m WHERE m.email_rowid = ${rowid} AND m.mailbox_id NOT IN (${ids.map(() => '?').join(',') || "''"}))`);
         params.push(...ids);
         break;
       }
       case 'hasKeyword':
-        conditions.push('EXISTS (SELECT 1 FROM email_keyword k WHERE k.email_rowid = e.rowid AND k.keyword = ?)');
-        params.push(String(value).toLowerCase());
+        conditions.push(`EXISTS (SELECT 1 FROM email_keyword k WHERE k.email_rowid = ${rowid} AND k.keyword = ?)`);
+        params.push(keywordKey(String(value)));
         break;
       case 'notKeyword':
-        conditions.push('NOT EXISTS (SELECT 1 FROM email_keyword k WHERE k.email_rowid = e.rowid AND k.keyword = ?)');
-        params.push(String(value).toLowerCase());
+        conditions.push(`NOT EXISTS (SELECT 1 FROM email_keyword k WHERE k.email_rowid = ${rowid} AND k.keyword = ?)`);
+        params.push(keywordKey(String(value)));
         break;
       case 'after':
-        conditions.push('e.received_at >= ?');
+        conditions.push(`${receivedAt} >= ?`);
         params.push(Date.parse(String(value)) || 0);
         break;
       case 'before':
-        conditions.push('e.received_at < ?');
+        conditions.push(`${receivedAt} < ?`);
         params.push(Date.parse(String(value)) || 0);
         break;
       case 'minSize':
@@ -74,6 +92,16 @@ function filterSql(filter: Filter, jmap: string, drivenBy: string | null = null)
         conditions.push(`e.id IN (${(value as string[]).map(() => '?').join(',') || "''"})`);
         params.push(...(value as string[]).map(String));
         break;
+      case 'header': {
+        // Stalwart finds nothing for this on either version, plugins may still
+        // ask. Answered from the raw headers of the messages kept with a body.
+        const [name, wanted] = value as [string, string | undefined];
+        conditions.push(`EXISTS (SELECT 1 FROM email_body b, json_each(b.json, '$.headers') h
+          WHERE b.email_rowid = e.rowid AND lower(json_extract(h.value, '$.name')) = ?${wanted === undefined ? '' : " AND json_extract(h.value, '$.value') LIKE ? ESCAPE '\\'"})`);
+        params.push(String(name).toLowerCase());
+        if (wanted !== undefined) params.push(likeTerm(wanted));
+        break;
+      }
       default:
         if ((TEXT_FIELDS as readonly string[]).includes(key)) {
           const text = textCondition(key as TextField, String(value));
@@ -81,7 +109,7 @@ function filterSql(filter: Filter, jmap: string, drivenBy: string | null = null)
           params.push(...text.params);
           break;
         }
-        // header and the thread keyword filters: the server's job.
+        // The thread keyword filters: nothing in the app sends them.
         throw new MethodError('unsupportedFilter', `${key} isn't available offline`);
     }
   }
@@ -118,7 +146,7 @@ function orderSql(ctx: MethodContext, sort: Comparator[]): Sql {
         // stored answer has to read it the way that server would.
         if (ctx.invertedKeywordSort) ascending = !ascending;
         parts.push(`EXISTS (SELECT 1 FROM email_keyword s WHERE s.email_rowid = e.rowid AND s.keyword = ?) ${ascending ? 'ASC' : 'DESC'}`);
-        params.push(String(level.keyword ?? '').toLowerCase());
+        params.push(keywordKey(String(level.keyword ?? '')));
         break;
       }
       default:
@@ -142,6 +170,121 @@ function drivingMailbox(filter: Filter | undefined): string | null {
   return null;
 }
 
+/** One step of a "pinned first" or "unread first" order. */
+interface KeywordLevel { keyword: string; first: boolean }
+
+/** A keyword this rare is read off its own index, then sorted. Commoner ones are checked along the folder. */
+const RARE_KEYWORD_ROWS = 5000;
+const MAX_KEYWORD_LEVELS = 4;
+
+/**
+ * The keyword comparators of an order that goes on newest first, which is what
+ * the pinned and unread-first lists send. Null for any other order.
+ */
+function keywordLevels(ctx: MethodContext, sort: Comparator[]): KeywordLevel[] | null {
+  const levels: KeywordLevel[] = [];
+  let next = 0;
+  for (; sort[next]?.property === 'hasKeyword'; next += 1) {
+    const ascending = sort[next].isAscending !== false;
+    levels.push({ keyword: keywordKey(String(sort[next].keyword ?? '')), first: ctx.invertedKeywordSort ? ascending : !ascending });
+  }
+  if (levels.length === 0 || levels.length > MAX_KEYWORD_LEVELS) return null;
+  return isNewestFirst(sort.slice(next)) ? levels : null;
+}
+
+/**
+ * A page of an order by keywords and then date, without sorting the folder: the
+ * order splits into groups (pinned, then the rest), and each group is read in
+ * date order off the folder's index until the page is full.
+ */
+function keywordOrderedPage(
+  ctx: MethodContext,
+  jmap: string,
+  box: string | null,
+  where: Sql,
+  levels: readonly KeywordLevel[],
+  position: number,
+  limit: number,
+): string[] {
+  const rowid = box ? 'd.email_rowid' : 'e.rowid';
+  const rows = new Map<string, number>();
+  const rowsOf = (keyword: string): number => {
+    let n = rows.get(keyword);
+    if (n === undefined) {
+      n = Number(ctx.db.get<{ n: number }>('SELECT COUNT(*) AS n FROM email_keyword INDEXED BY email_keyword_lookup WHERE keyword = ?', [keyword])?.n ?? 0);
+      rows.set(keyword, n);
+    }
+    return n;
+  };
+
+  const groupQuery = (group: ReadonlyArray<{ keyword: string; has: boolean }>) => {
+    const rare = group
+      .filter((level) => level.has && rowsOf(level.keyword) <= RARE_KEYWORD_ROWS)
+      .sort((a, b) => rowsOf(a.keyword) - rowsOf(b.keyword))[0];
+    const checked = group.filter((level) => level !== rare);
+    const sql = [
+      `${box ? 'd.jmap = ?' : 'e.jmap = ?'}${box && !rare ? ' AND d.mailbox_id = ?' : ''}`,
+      ...checked.map((level) => `${level.has ? '' : 'NOT '}EXISTS (SELECT 1 FROM email_keyword c WHERE c.email_rowid = ${rowid} AND c.keyword = ?)`),
+      `(${where.sql})`,
+    ].join(' AND ');
+    let head: string;
+    const params: SqlValue[] = [];
+    if (rare) {
+      head = box
+        ? 'email_keyword r INDEXED BY email_keyword_lookup CROSS JOIN email_mailbox d ON d.email_rowid = r.email_rowid AND d.mailbox_id = ?'
+        : 'email_keyword r INDEXED BY email_keyword_lookup';
+      if (box) params.push(box);
+    } else {
+      head = box ? 'email_mailbox d INDEXED BY email_mailbox_list' : '';
+    }
+    const emailJoin = !box
+      ? (rare ? ' CROSS JOIN email e ON e.rowid = r.email_rowid' : 'email e')
+      : ' CROSS JOIN email e ON e.rowid = d.email_rowid';
+    const after: SqlValue[] = [jmap, ...(box && !rare ? [box] : []), ...checked.map((level) => level.keyword), ...where.params];
+    const rareCondition = rare ? 'r.keyword = ? AND ' : '';
+    const allParams = [...params, ...(rare ? [rare.keyword] : []), ...after];
+    return {
+      // The message's own row is read only for what goes out, or if a condition needs it.
+      countFrom: box && !/\be\./.test(where.sql) ? head : `${head}${emailJoin}`,
+      from: `${head}${emailJoin}`,
+      where: `${rareCondition}${sql}`,
+      params: allParams,
+      order: box ? 'd.received_at DESC, d.email_rowid DESC' : 'e.received_at DESC, e.rowid DESC',
+    };
+  };
+
+  const groups = levels.reduce<Array<Array<{ keyword: string; has: boolean }>>>(
+    (all, level) => all.flatMap((group) => [
+      [...group, { keyword: level.keyword, has: level.first }],
+      [...group, { keyword: level.keyword, has: !level.first }],
+    ]),
+    [[]],
+  );
+
+  const ids: string[] = [];
+  let skip = position;
+  let need = limit;
+  for (const group of groups) {
+    if (need === 0) break;
+    const query = groupQuery(group);
+    if (skip > 0) {
+      const inGroup = Number(ctx.db.get<{ n: number }>(`SELECT COUNT(*) AS n FROM ${query.countFrom} WHERE ${query.where}`, query.params)?.n ?? 0);
+      if (inGroup <= skip) {
+        skip -= inGroup;
+        continue;
+      }
+    }
+    const found = ctx.db.all<{ id: string }>(
+      `SELECT e.id FROM ${query.from} WHERE ${query.where} ORDER BY ${query.order} LIMIT ? OFFSET ?`,
+      [...query.params, need, skip],
+    );
+    for (const row of found) ids.push(String(row.id));
+    skip = 0;
+    if (need > 0) need -= found.length;
+  }
+  return ids;
+}
+
 const emailQuery: MethodHandler = (ctx, args) => {
   const jmap = jmapOf(ctx, args);
   const filter = limitTextConditions((args.filter ?? undefined) as Filter | undefined);
@@ -149,7 +292,11 @@ const emailQuery: MethodHandler = (ctx, args) => {
   const box = drivingMailbox(filter);
   const where = filter ? filterSql(filter, jmap, box) : { sql: '1', params: [] };
   const sort = (args.sort as Comparator[]) ?? [];
-  const order: Sql = !isNewestFirst(sort)
+  const collapse = Boolean(args.collapseThreads);
+  const levels = collapse ? null : keywordLevels(ctx, sort);
+  const order: Sql = levels
+    ? { sql: '', params: [] }
+    : !isNewestFirst(sort)
     ? orderSql(ctx, sort)
     : { sql: box ? 'd.received_at DESC, d.email_rowid DESC' : 'e.received_at DESC, e.rowid DESC', params: [] };
   // Starting from the folder's own index keeps small folders fast in a large account.
@@ -161,24 +308,30 @@ const emailQuery: MethodHandler = (ctx, args) => {
     : { sql: 'e.jmap = ?', params: [jmap] as SqlValue[] };
   const position = Math.max(0, Number(args.position ?? 0));
   const limit = typeof args.limit === 'number' && args.limit > 0 ? args.limit : -1;
-  const collapse = Boolean(args.collapseThreads);
   const group = collapse ? 'GROUP BY COALESCE(e.thread_id, e.id)' : '';
-  const ids = ctx.db.all<{ id: string }>(
-    `SELECT e.id FROM ${from} WHERE ${base.sql} AND (${where.sql}) ${group} ORDER BY ${order.sql} LIMIT ? OFFSET ?`,
-    [...base.params, ...where.params, ...order.params, limit, position],
-  ).map((row) => String(row.id));
+  const ids = levels
+    ? keywordOrderedPage(ctx, jmap, box, where, levels, position, limit)
+    : ctx.db.all<{ id: string }>(
+      `SELECT e.id FROM ${from} WHERE ${base.sql} AND (${where.sql}) ${group} ORDER BY ${order.sql} LIMIT ? OFFSET ?`,
+      [...base.params, ...where.params, ...order.params, limit, position],
+    ).map((row) => String(row.id));
+  // Stalwart's queryState is the Email state. Absent until the first sync, as allowed.
+  const queryState = lastState(ctx, jmap, 'Email');
+  // Nothing here doesn't mean nothing there: an empty folder of a first sync
+  // that hasn't finished mustn't paint over what's on screen.
+  if (ids.length === 0 && position === 0 && !queryState) throw new MethodError('serverUnavailable', 'Mail not kept yet');
   const result: MethodResult = {
     accountId: jmap,
     canCalculateChanges: false,
-    // Local answers aren't a position in the server's log, so this is a token only.
-    queryState: 'local',
+    ...(queryState ? { queryState } : {}),
     position,
     ids,
   };
   if (args.calculateTotal) {
     const count = collapse ? 'COUNT(DISTINCT COALESCE(e.thread_id, e.id))' : 'COUNT(*)';
-    // A plain folder counts from its index alone, without reading a message.
-    const countFrom = box && !collapse && where.sql === '1' ? 'email_mailbox d INDEXED BY email_mailbox_list' : from;
+    // In a folder, what needs nothing of the message itself counts off the
+    // folder's index and the keyword rows, without reading a message.
+    const countFrom = box && !collapse && !/\be\./.test(where.sql) ? 'email_mailbox d INDEXED BY email_mailbox_list' : from;
     result.total = Number(ctx.db.get<{ n: number }>(
       `SELECT ${count} AS n FROM ${countFrom} WHERE ${base.sql} AND (${where.sql})`,
       [...base.params, ...where.params],
@@ -187,12 +340,60 @@ const emailQuery: MethodHandler = (ctx, args) => {
   return result;
 };
 
-const BODY_PROPERTIES = new Set(['bodyValues', 'textBody', 'htmlBody', 'bodyStructure', 'headers', 'attachments', 'bcc', 'replyTo', 'messageId', 'inReplyTo', 'references']);
+/** What only the stored body has, past what the list keeps. */
+const BODY_PROPERTIES = new Set(['bodyValues', 'textBody', 'htmlBody', 'bodyStructure', 'headers', 'attachments', 'bcc', 'replyTo', 'messageId', 'inReplyTo', 'references', 'sender']);
 
-function pick(email: Record<string, unknown>, properties: string[] | undefined): Record<string, unknown> {
-  if (!properties) return email;
-  const out: Record<string, unknown> = { id: email.id };
-  for (const property of properties) if (property in email) out[property] = email[property];
+interface BodyPart { partId?: string | null; subParts?: BodyPart[]; [key: string]: unknown }
+
+function partWithProperties(part: BodyPart, wanted: readonly string[]): BodyPart {
+  const out: BodyPart = {};
+  for (const name of wanted) if (name in part) out[name] = part[name];
+  if (part.subParts) out.subParts = part.subParts.map((sub) => partWithProperties(sub, wanted));
+  return out;
+}
+
+/** The body values the call asked for. The whole kept text: never cut to maxBodyValueBytes. */
+function chosenBodyValues(body: Record<string, unknown>, args: Record<string, unknown>): Record<string, unknown> {
+  const values = (body.bodyValues ?? {}) as Record<string, unknown>;
+  if (args.fetchAllBodyValues) return values;
+  const parts = [
+    ...(args.fetchTextBodyValues ? (body.textBody ?? []) as BodyPart[] : []),
+    ...(args.fetchHTMLBodyValues ? (body.htmlBody ?? []) as BodyPart[] : []),
+  ];
+  const out: Record<string, unknown> = {};
+  for (const part of parts) {
+    const id = part.partId ?? '';
+    if (id in values) out[id] = values[id];
+  }
+  return out;
+}
+
+function shapeEmail(
+  list: Record<string, unknown>,
+  body: Record<string, unknown> | null,
+  args: Record<string, unknown>,
+): Record<string, unknown> {
+  const merged: Record<string, unknown> = { ...(body ?? {}), ...list };
+  if (body) merged.bodyValues = chosenBodyValues(body, args);
+  const bodyProperties = args.bodyProperties as string[] | undefined;
+  if (bodyProperties) {
+    for (const key of ['textBody', 'htmlBody', 'attachments']) {
+      if (Array.isArray(merged[key])) merged[key] = (merged[key] as BodyPart[]).map((part) => partWithProperties(part, bodyProperties));
+    }
+    if (merged.bodyStructure) merged.bodyStructure = partWithProperties(merged.bodyStructure as BodyPart, bodyProperties);
+  }
+  const properties = args.properties as string[] | undefined;
+  if (!properties) return merged;
+  const out: Record<string, unknown> = { id: list.id };
+  for (const property of properties) {
+    if (property in merged) {
+      out[property] = merged[property];
+      continue;
+    }
+    // Only a message kept with its text has the raw headers these come from.
+    const form = parseHeaderProperty(property);
+    if (form && body && Array.isArray(body.headers)) out[property] = headerValue(form, body.headers as RawHeader[]);
+  }
   return out;
 }
 
@@ -201,7 +402,7 @@ const emailGet: MethodHandler = (ctx, args) => {
   if (!Array.isArray(args.ids)) throw new MethodError('requestTooLarge', 'ids: null needs the server');
   const properties = args.properties as string[] | undefined;
   const wantsValues = Boolean(args.fetchTextBodyValues || args.fetchHTMLBodyValues || args.fetchAllBodyValues) || Boolean(properties?.includes('bodyValues'));
-  const wantsBody = wantsValues || !properties || properties.some((p) => BODY_PROPERTIES.has(p));
+  const wantsBody = wantsValues || !properties || properties.some((p) => BODY_PROPERTIES.has(p) || p.startsWith('header:'));
   const list: Record<string, unknown>[] = [];
   const notFound: string[] = [];
   for (const id of args.ids as string[]) {
@@ -215,7 +416,7 @@ const emailGet: MethodHandler = (ctx, args) => {
     }
     const email = JSON.parse(row.json) as Record<string, unknown>;
     if (!wantsBody) {
-      list.push(pick(email, properties));
+      list.push(shapeEmail(email, null, args));
       continue;
     }
     const body = ctx.db.get<{ json: string }>('SELECT json FROM email_body WHERE email_rowid = ?', [row.rowid]);
@@ -224,56 +425,73 @@ const emailGet: MethodHandler = (ctx, args) => {
       notFound.push(id);
       continue;
     }
-    list.push(pick({ ...(body ? JSON.parse(body.json) as object : {}), ...email }, properties));
+    list.push(shapeEmail(email, body ? JSON.parse(body.json) as Record<string, unknown> : null, args));
   }
-  const state = ctx.db.get<{ state: string | null }>("SELECT state FROM sync_state WHERE jmap = ? AND type = 'Email'", [jmap])?.state;
+  const state = lastState(ctx, jmap, 'Email');
   return { accountId: jmap, ...(state ? { state } : {}), list, notFound };
 };
 
 const threadGet: MethodHandler = (ctx, args) => {
   const jmap = jmapOf(ctx, args);
   const ids = Array.isArray(args.ids) ? [...new Set(args.ids as string[])] : [];
-  const list: Array<{ id: string; emailIds: string[] }> = [];
-  const notFound: string[] = [];
+  const found: Array<{ id: string; emailIds: string[] }> = [];
   for (const id of ids) {
     const stored = ctx.db.get<{ email_ids: string }>('SELECT email_ids FROM thread WHERE jmap = ? AND id = ?', [jmap, id]);
     if (stored) {
-      list.push({ id, emailIds: JSON.parse(stored.email_ids) as string[] });
+      found.push({ id, emailIds: JSON.parse(stored.email_ids) as string[] });
       continue;
     }
     const rows = ctx.db.all<{ id: string }>('SELECT id FROM email WHERE jmap = ? AND thread_id = ? ORDER BY received_at ASC', [jmap, id]);
-    if (rows.length > 0) list.push({ id, emailIds: rows.map((row) => String(row.id)) });
-    else notFound.push(id);
+    if (rows.length > 0) found.push({ id, emailIds: rows.map((row) => String(row.id)) });
   }
-  return { accountId: jmap, list, notFound };
-};
-
-const mailboxGet: MethodHandler = (ctx, args) => {
-  const jmap = jmapOf(ctx, args);
-  const boxes = listObjects<Record<string, unknown>>(ctx.db, jmap, 'Mailbox');
-  if (boxes.length === 0) throw new MethodError('serverUnavailable', 'Folders not kept yet');
-  const ids = Array.isArray(args.ids) ? new Set(args.ids as string[]) : null;
-  const chosen = ids ? boxes.filter((box) => ids.has(box.id as string)) : boxes;
-  const state = ctx.db.get<{ state: string | null }>("SELECT state FROM sync_state WHERE jmap = ? AND type = 'Mailbox'", [jmap])?.state;
+  const list = ctx.overlay(jmap, 'Thread', found).filter((thread) => thread.emailIds.length > 0);
+  const state = lastState(ctx, jmap, 'Thread');
   return {
     accountId: jmap,
     ...(state ? { state } : {}),
-    list: chosen.map((box) => pick(box, args.properties as string[] | undefined)),
-    notFound: ids ? [...ids].filter((id) => !boxes.some((box) => box.id === id)) : [],
+    list,
+    notFound: ids.filter((id) => !list.some((thread) => thread.id === id)),
   };
 };
 
+function pick(item: Record<string, unknown>, properties: string[] | undefined): Record<string, unknown> {
+  if (!properties) return item;
+  const out: Record<string, unknown> = { id: item.id };
+  for (const property of properties) if (property in item) out[property] = item[property];
+  return out;
+}
+
+/** The answer of a /get over objects the syncers keep. An error until they've run once. */
+function objectGet(ctx: MethodContext, args: Record<string, unknown>, type: string, label: string): MethodResult {
+  const jmap = jmapOf(ctx, args);
+  const state = lastState(ctx, jmap, type);
+  const all = ctx.overlay(jmap, type, listObjects<Record<string, unknown> & { id: string }>(ctx.db, jmap, type));
+  if (all.length === 0 && !state) throw new MethodError('serverUnavailable', `${label} not kept yet`);
+  const ids = Array.isArray(args.ids) ? args.ids as string[] : null;
+  const chosen = ids ? all.filter((item) => ids.includes(item.id)) : all;
+  return {
+    accountId: jmap,
+    ...(state ? { state } : {}),
+    list: chosen.map((item) => pick(item, args.properties as string[] | undefined)),
+    notFound: ids ? ids.filter((id) => !all.some((item) => item.id === id)) : [],
+  };
+}
+
 const mailboxQuery: MethodHandler = (ctx, args) => {
   const jmap = jmapOf(ctx, args);
   const boxes = listObjects<Record<string, unknown>>(ctx.db, jmap, 'Mailbox');
-  if (boxes.length === 0) throw new MethodError('serverUnavailable', 'Folders not kept yet');
-  const filter = (args.filter ?? {}) as { role?: string };
+  const state = lastState(ctx, jmap, 'Mailbox');
+  if (boxes.length === 0 || !state) throw new MethodError('serverUnavailable', 'Folders not kept yet');
+  const filter = (args.filter ?? {}) as Record<string, unknown>;
+  for (const key of Object.keys(filter)) {
+    if (key !== 'role') throw new MethodError('unsupportedFilter', `${key} isn't available offline`);
+  }
   const chosen = filter.role ? boxes.filter((box) => box.role === filter.role) : boxes;
   const position = typeof args.position === 'number' ? args.position : 0;
   const limit = typeof args.limit === 'number' ? args.limit : chosen.length;
   return {
     accountId: jmap,
-    queryState: 'local',
+    queryState: state,
     canCalculateChanges: false,
     position,
     ids: chosen.slice(position, position + limit).map((box) => box.id),
@@ -281,11 +499,44 @@ const mailboxQuery: MethodHandler = (ctx, args) => {
   };
 };
 
+/** The client treats this as "do a full fetch": what it reads next comes from the store anyway. */
+const noChanges: MethodHandler = () => {
+  throw new MethodError('cannotCalculateChanges', 'Changes need the server');
+};
+
+const keywordGet: MethodHandler = (ctx, args) => {
+  const jmap = jmapOf(ctx, args);
+  const rows = ctx.db.all<{ keyword: string; total: number; unread: number }>(
+    `SELECT k.keyword AS keyword, COUNT(*) AS total,
+       SUM(NOT EXISTS (SELECT 1 FROM email_keyword s WHERE s.email_rowid = k.email_rowid AND s.keyword = '$seen')) AS unread
+     FROM email_keyword k JOIN email e ON e.rowid = k.email_rowid
+     WHERE e.jmap = ? GROUP BY k.keyword`,
+    [jmap],
+  );
+  const counts = new Map(rows.map((row) => [String(row.keyword), { id: String(row.keyword), total: Number(row.total), unread: Number(row.unread) }]));
+  const wanted = Array.isArray(args.ids) ? args.ids as string[] : null;
+  const list = wanted
+    ? wanted.map((id) => ({ ...(counts.get(keywordKey(id)) ?? { total: 0, unread: 0 }), id }))
+    : [...counts.values()];
+  return {
+    accountId: jmap,
+    list,
+    notFound: [],
+    totalEmails: Number(ctx.db.get<{ n: number }>('SELECT COUNT(*) AS n FROM email WHERE jmap = ?', [jmap])?.n ?? 0),
+  };
+};
+
 export const MAIL_METHODS: Readonly<Record<string, MethodHandler>> = {
+  'Core/echo': (_ctx, args) => args,
   'Email/query': emailQuery,
   'Email/get': emailGet,
+  'Email/changes': noChanges,
   'Thread/get': threadGet,
-  'Mailbox/get': mailboxGet,
+  'Mailbox/get': (ctx, args) => objectGet(ctx, args, 'Mailbox', 'Folders'),
   'Mailbox/query': mailboxQuery,
+  'Mailbox/changes': noChanges,
+  'Identity/get': (ctx, args) => objectGet(ctx, args, 'Identity', 'Identities'),
+  'Quota/get': (ctx, args) => objectGet(ctx, args, 'Quota', 'Quotas'),
+  'Keyword/get': keywordGet,
   'SearchSnippet/get': searchSnippetGet,
 };
diff --git a/lib/store/mail/records.ts b/lib/store/mail/records.ts
index 72b2397f8..e9d575c44 100644
--- a/lib/store/mail/records.ts
+++ b/lib/store/mail/records.ts
@@ -2,6 +2,18 @@
 
 import type { StorageAdapter } from '../storage';
 
+/**
+ * How keywords compare, measured on both Stalwart versions: the IMAP system
+ * flags fold to lower case, every other keyword is case-sensitive, so `Tag` and
+ * `tag` are two keywords and one message can carry both.
+ */
+const SYSTEM_KEYWORDS = new Set(['$seen', '$flagged', '$answered', '$draft', '$forwarded', '$mdnsent', '$junk', '$notjunk', '$phishing', '$recent', '$deleted']);
+
+export function keywordKey(keyword: string): string {
+  const lower = keyword.toLowerCase();
+  return SYSTEM_KEYWORDS.has(lower) ? lower : keyword;
+}
+
 export const MAIL_USING = ['urn:ietf:params:jmap:core', 'urn:ietf:params:jmap:mail'];
 
 export const EMAIL_LIST_PROPERTIES = [
@@ -80,11 +92,19 @@ export function upsertEmail(db: StorageAdapter, jmap: string, email: EmailObject
     if (on) db.run('INSERT INTO email_mailbox (email_rowid, jmap, mailbox_id, received_at) VALUES (?, ?, ?, ?)', [rowid, jmap, box, receivedAt]);
   }
   for (const [keyword, on] of Object.entries((email.keywords ?? {}) as Record<string, boolean>)) {
-    if (on) db.run('INSERT INTO email_keyword (email_rowid, keyword) VALUES (?, ?)', [rowid, keyword.toLowerCase()]);
+    if (on) db.run('INSERT OR IGNORE INTO email_keyword (email_rowid, keyword) VALUES (?, ?)', [rowid, keywordKey(keyword)]);
   }
   return rowid;
 }
 
+export function putBlob(db: StorageAdapter, jmap: string, blobId: string, type: string | null, data: Uint8Array, at: number): void {
+  db.run(
+    `INSERT INTO blob (jmap, blob_id, type, size, at, data) VALUES (?, ?, ?, ?, ?, ?)
+     ON CONFLICT (jmap, blob_id) DO UPDATE SET type = excluded.type, size = excluded.size, at = excluded.at, data = excluded.data`,
+    [jmap, blobId, type, data.byteLength, at, data],
+  );
+}
+
 export function deleteEmail(db: StorageAdapter, jmap: string, id: string): void {
   const row = db.get<{ rowid: number }>('SELECT rowid FROM email WHERE jmap = ? AND id = ?', [jmap, id]);
   if (!row) return;
@@ -94,6 +114,7 @@ export function deleteEmail(db: StorageAdapter, jmap: string, id: string): void
 export function deleteEmailRow(db: StorageAdapter, rowid: number): void {
   deleteHeadIndex(db, rowid);
   deleteBodyIndex(db, rowid);
+  forgetParts(db, rowid);
   // Explicit rather than ON DELETE CASCADE: foreign keys stay off for bulk speed.
   db.run('DELETE FROM email_mailbox WHERE email_rowid = ?', [rowid]);
   db.run('DELETE FROM email_keyword WHERE email_rowid = ?', [rowid]);
@@ -211,11 +232,37 @@ export function indexEmail(db: StorageAdapter, rowid: number, email: Record<stri
   indexBody(db, rowid, body);
 }
 
+/** A message's files go with it, unless another kept message has the same one. */
+function forgetParts(db: StorageAdapter, rowid: number): void {
+  const parts = db.all<{ jmap: string; blob_id: string }>('SELECT jmap, blob_id FROM email_part WHERE email_rowid = ?', [rowid]);
+  db.run('DELETE FROM email_part WHERE email_rowid = ?', [rowid]);
+  for (const part of parts) {
+    db.run(
+      'DELETE FROM blob WHERE jmap = ? AND blob_id = ? AND NOT EXISTS (SELECT 1 FROM email_part p WHERE p.jmap = ? AND p.blob_id = ?)',
+      [part.jmap, part.blob_id, part.jmap, part.blob_id],
+    );
+  }
+}
+
+function rememberParts(db: StorageAdapter, rowid: number, attachments: unknown): void {
+  const row = db.get<{ jmap: string; received_at: number }>('SELECT jmap, received_at FROM email WHERE rowid = ?', [rowid]);
+  if (!row || !Array.isArray(attachments)) return;
+  for (const part of attachments as Array<{ blobId?: unknown; size?: unknown; type?: unknown; name?: unknown }>) {
+    if (typeof part.blobId !== 'string') continue;
+    db.run(
+      `INSERT INTO email_part (jmap, blob_id, email_rowid, received_at, size, type, name) VALUES (?, ?, ?, ?, ?, ?, ?)
+       ON CONFLICT (jmap, blob_id, email_rowid) DO NOTHING`,
+      [row.jmap, part.blobId, rowid, row.received_at, typeof part.size === 'number' ? part.size : 0, typeof part.type === 'string' ? part.type : null, typeof part.name === 'string' ? part.name : null],
+    );
+  }
+}
+
 export function storeBody(db: StorageAdapter, rowid: number, listJson: string, full: Record<string, unknown>): void {
   const list = JSON.parse(listJson) as Record<string, unknown>;
   const body: Record<string, unknown> = {};
   for (const [key, value] of Object.entries(full)) if (!(key in list)) body[key] = value;
   const hadBody = Number(db.get<{ body_state: number }>('SELECT body_state FROM email WHERE rowid = ?', [rowid])?.body_state) === 1;
+  rememberParts(db, rowid, body.attachments);
   db.run('INSERT INTO email_body (email_rowid, json) VALUES (?, ?) ON CONFLICT (email_rowid) DO UPDATE SET json = excluded.json', [rowid, JSON.stringify(body)]);
   db.run('UPDATE email SET body_state = 1 WHERE rowid = ?', [rowid]);
   // A first body is one insert. Only a body stored again has an old row to replace.
diff --git a/lib/store/mail/schema.ts b/lib/store/mail/schema.ts
index 98f29576d..64def1243 100644
--- a/lib/store/mail/schema.ts
+++ b/lib/store/mail/schema.ts
@@ -62,4 +62,34 @@ export const MAIL_MIGRATIONS: readonly Migration[] = [
       );
     `,
   },
+  {
+    id: 101,
+    name: 'mail attachments',
+    sql: `
+      -- The attachments and inline images of kept messages.
+      CREATE TABLE email_part (
+        jmap TEXT NOT NULL,
+        blob_id TEXT NOT NULL,
+        email_rowid INTEGER NOT NULL,
+        received_at INTEGER NOT NULL,
+        size INTEGER NOT NULL DEFAULT 0,
+        type TEXT,
+        name TEXT,
+        -- 1 when the server wouldn't give it: not asked for again
+        refused INTEGER NOT NULL DEFAULT 0,
+        PRIMARY KEY (jmap, blob_id, email_rowid)
+      ) WITHOUT ROWID;
+      CREATE INDEX email_part_message ON email_part (email_rowid);
+      CREATE INDEX email_part_newest ON email_part (jmap, received_at DESC);
+      CREATE TABLE blob (
+        jmap TEXT NOT NULL,
+        blob_id TEXT NOT NULL,
+        type TEXT,
+        size INTEGER NOT NULL,
+        at INTEGER NOT NULL,
+        data BLOB NOT NULL,
+        PRIMARY KEY (jmap, blob_id)
+      ) WITHOUT ROWID;
+    `,
+  },
 ];
diff --git a/lib/store/mail/sync.ts b/lib/store/mail/sync.ts
index 30b8c7b7b..f3919d1e4 100644
--- a/lib/store/mail/sync.ts
+++ b/lib/store/mail/sync.ts
@@ -10,13 +10,14 @@
 import type { SyncContext, Syncer } from '../area';
 import { deleteObject, putObject } from '../engine/core-schema';
 import { runChangesLoop } from '../engine/changes';
-import { responseFor, type MethodCall } from '../engine/transport';
+import { JmapMethodError, responseFor, TransportError, type MethodCall } from '../engine/transport';
 import {
   deleteEmail,
   deleteEmailRow,
   EMAIL_BODY_PROPERTIES,
   EMAIL_LIST_PROPERTIES,
   MAIL_USING,
+  putBlob,
   storeBody,
   upsertEmail,
   type EmailObject,
@@ -83,7 +84,12 @@ async function syncMailboxes(ctx: SyncContext, jmap: string): Promise<void> {
 
 // ---- Email list ----
 
-interface ListCursor { position: number; gen: number; captured: string }
+/**
+ * `anchor` is the last id a pass saw. A pass can be paused for days, and a
+ * position would shift with every deletion before it: a message would be
+ * skipped, and no /changes after the captured state would ever mention it.
+ */
+interface ListCursor { position: number; gen: number; captured: string; anchor?: string | null }
 
 /** The generation of the last full listing. One row is enough: every row of a pass has it or an older one. */
 function currentGen(ctx: SyncContext, jmap: string): number {
@@ -98,19 +104,50 @@ async function startFullList(ctx: SyncContext, jmap: string): Promise<ListCursor
   return cursor;
 }
 
+/**
+ * What the pass didn't see isn't necessarily gone: paging can miss a message
+ * when the anchor was lost. So the server is asked about each. Only what it says
+ * is gone, or what left the chosen window, is dropped. One batch to a
+ * transaction, so a reload picks up what's left.
+ */
+async function sweepUnseen(ctx: SyncContext, jmap: string, gen: number): Promise<boolean> {
+  for (;;) {
+    if (ctx.stopped()) return false;
+    const unseen = ctx.db.all<{ rowid: number; id: string }>('SELECT rowid, id FROM email WHERE jmap = ? AND gen < ? LIMIT ?', [jmap, gen, PAGE]);
+    if (unseen.length === 0) return true;
+    const response = await ctx.transport.request([['Email/get', {
+      accountId: jmap,
+      ids: unseen.map((row) => String(row.id)),
+      properties: EMAIL_LIST_PROPERTIES,
+    }, 'g']], MAIL_USING);
+    const found = responseFor(response, 'g')[1].list as EmailObject[];
+    ctx.db.transaction(() => {
+      const kept = new Set<string>();
+      for (const email of ctx.overlay(jmap, 'Email', found.filter((candidate) => inWindow(ctx, candidate)))) {
+        upsertEmail(ctx.db, jmap, email, gen);
+        kept.add(email.id);
+      }
+      for (const row of unseen) if (!kept.has(String(row.id))) deleteEmailRow(ctx.db, Number(row.rowid));
+    });
+  }
+}
+
 async function runFullList(ctx: SyncContext, jmap: string, start: ListCursor): Promise<boolean> {
   const cursor = { ...start };
   const filter = windowFilter(ctx);
   let total: number | null = null;
   for (;;) {
     if (ctx.stopped()) return false;
+    const pageArgs = (i: number): Record<string, unknown> => (cursor.anchor
+      ? { anchor: cursor.anchor, anchorOffset: 1 + i * PAGE }
+      : { position: cursor.position + i * PAGE });
     const calls: MethodCall[] = [];
     for (let i = 0; i < PAIRS_PER_REQUEST; i += 1) {
       calls.push(['Email/query', {
         accountId: jmap,
         ...(filter ? { filter } : {}),
         sort: [{ property: 'receivedAt', isAscending: false }],
-        position: cursor.position + i * PAGE,
+        ...pageArgs(i),
         limit: PAGE,
         calculateTotal: i === 0,
       }, `q${i}`]);
@@ -124,30 +161,36 @@ async function runFullList(ctx: SyncContext, jmap: string, start: ListCursor): P
     let done = false;
     let got = 0;
     const lists: EmailObject[][] = [];
-    for (let i = 0; i < PAIRS_PER_REQUEST; i += 1) {
-      const [, query] = responseFor(response, `q${i}`);
-      if (i === 0 && typeof query.total === 'number') total = query.total;
-      lists.push(responseFor(response, `g${i}`)[1].list as EmailObject[]);
-      got += (query.ids as string[]).length;
-      if ((query.ids as string[]).length < PAGE) {
-        done = true;
-        break;
+    try {
+      for (let i = 0; i < PAIRS_PER_REQUEST; i += 1) {
+        const [, query] = responseFor(response, `q${i}`);
+        if (i === 0 && typeof query.total === 'number') total = query.total;
+        lists.push(responseFor(response, `g${i}`)[1].list as EmailObject[]);
+        const ids = query.ids as string[];
+        got += ids.length;
+        if (ids.length > 0) cursor.anchor = ids[ids.length - 1];
+        if (ids.length < PAGE) {
+          done = true;
+          break;
+        }
       }
+    } catch (error) {
+      if (!(error instanceof JmapMethodError) || error.type !== 'anchorNotFound' || !cursor.anchor) throw error;
+      // The anchor was deleted, or left the window. Back to positions, a page
+      // earlier, since deletions before the cursor have shifted them.
+      cursor.anchor = null;
+      cursor.position = Math.max(0, cursor.position - PAGE);
+      continue;
     }
     cursor.position += got;
     ctx.db.transaction(() => {
-      for (const list of lists) for (const email of list) upsertEmail(ctx.db, jmap, email, cursor.gen);
-      if (done) {
-        // Whatever this pass didn't see is gone from the server or the window.
-        const stale = ctx.db.all<{ rowid: number }>('SELECT rowid FROM email WHERE jmap = ? AND gen < ?', [jmap, cursor.gen]);
-        for (const row of stale) deleteEmailRow(ctx.db, Number(row.rowid));
-        ctx.setSyncState(jmap, 'Email', { state: cursor.captured, phase: null, cursor: null });
-      } else {
-        ctx.setSyncState(jmap, 'Email', { cursor: { ...cursor } });
-      }
+      for (const list of lists) for (const email of ctx.overlay(jmap, 'Email', list)) upsertEmail(ctx.db, jmap, email, cursor.gen);
+      ctx.setSyncState(jmap, 'Email', { cursor: { ...cursor } });
     });
     ctx.emit({ type: 'progress', account: ctx.account, area: 'mail', phase: 'list', done: cursor.position, total });
     if (done) {
+      if (!(await sweepUnseen(ctx, jmap, cursor.gen))) return false;
+      ctx.db.transaction(() => ctx.setSyncState(jmap, 'Email', { state: cursor.captured, phase: null, cursor: null }));
       ctx.emit({ type: 'changed', account: ctx.account, collections: ['Email'] });
       return true;
     }
@@ -178,7 +221,7 @@ async function syncEmailDelta(ctx: SyncContext, jmap: string, since: string, tar
       const newIds: string[] = [];
       ctx.db.transaction(() => {
         const gen = fetched.length > 0 ? currentGen(ctx, jmap) : 0;
-        for (const email of fetched) {
+        for (const email of ctx.overlay(jmap, 'Email', fetched)) {
           const known = ctx.db.get('SELECT 1 AS x FROM email WHERE jmap = ? AND id = ?', [jmap, email.id]);
           // An old message changing doesn't pull it into the window.
           if (!known && !inWindow(ctx, email)) continue;
@@ -306,6 +349,110 @@ async function backfillBodies(ctx: SyncContext, jmap: string): Promise<void> {
   }
 }
 
+// ---- Attachments ----
+
+/**
+ * The files of kept messages, newest first, within what the user chose: one
+ * at a time, each in its own transaction, so a reload loses at most one.
+ */
+async function fetchAttachments(ctx: SyncContext, jmap: string): Promise<void> {
+  if (!ctx.scope.attachments) return;
+  let used = Number(ctx.db.get<{ n: number | null }>('SELECT SUM(size) AS n FROM blob')?.n ?? 0);
+  for (;;) {
+    if (ctx.stopped()) return;
+    const parts = ctx.db.all<{ blob_id: string; size: number; type: string | null; name: string | null; received_at: number }>(
+      `SELECT p.blob_id, p.size, p.type, p.name, p.received_at FROM email_part p
+       WHERE p.jmap = ? AND p.refused = 0 AND p.size <= ?
+         AND NOT EXISTS (SELECT 1 FROM blob b WHERE b.jmap = p.jmap AND b.blob_id = p.blob_id)
+       ORDER BY p.received_at DESC LIMIT 20`,
+      [jmap, ctx.scope.maxAttachmentBytes],
+    );
+    if (parts.length === 0) return;
+    for (const part of parts) {
+      if (ctx.stopped()) return;
+      const blobId = String(part.blob_id);
+      if (used + Number(part.size) > ctx.scope.maxTotalBytes) return;
+      let data: Uint8Array;
+      try {
+        data = await ctx.transport.download(jmap, blobId, part.type ?? 'application/octet-stream', part.name ?? 'attachment');
+      } catch (error) {
+        // Only what says this file won't come. Anything else, like a 500 or a 429, is tried at the next sync.
+        if (error instanceof TransportError && error.kind === 'http' && PERMANENT_DOWNLOAD_STATUSES.has(error.status ?? 0)) {
+          ctx.db.run('UPDATE email_part SET refused = 1 WHERE jmap = ? AND blob_id = ?', [jmap, blobId]);
+          continue;
+        }
+        if (error instanceof TransportError && error.kind === 'http') return;
+        throw error;
+      }
+      putBlob(ctx.db, jmap, blobId, part.type, data, Number(part.received_at));
+      used += data.byteLength;
+    }
+  }
+}
+
+const PERMANENT_DOWNLOAD_STATUSES = new Set([403, 404, 410]);
+
+// ---- Identities and quotas ----
+
+const IDENTITY_USING = ['urn:ietf:params:jmap:core', 'urn:ietf:params:jmap:mail', 'urn:ietf:params:jmap:submission'];
+const QUOTA_USING = ['urn:ietf:params:jmap:core', 'urn:ietf:params:jmap:quota'];
+
+async function fullIdentities(ctx: SyncContext, jmap: string): Promise<void> {
+  const response = await ctx.transport.request([['Identity/get', { accountId: jmap, ids: null }, 'i']], IDENTITY_USING);
+  const [, result] = responseFor(response, 'i');
+  ctx.db.transaction(() => {
+    ctx.db.run("DELETE FROM object WHERE jmap = ? AND type = 'Identity'", [jmap]);
+    for (const identity of result.list as Array<{ id: string }>) putObject(ctx.db, jmap, 'Identity', identity.id, identity);
+    ctx.setSyncState(jmap, 'Identity', { state: String(result.state), phase: null, cursor: null });
+  });
+}
+
+export const identitySyncer: Syncer = {
+  name: 'identities',
+  capability: 'urn:ietf:params:jmap:submission',
+  async run(ctx, jmap) {
+    const { state, target } = ctx.syncState(jmap, 'Identity');
+    if (!state) return fullIdentities(ctx, jmap);
+    const outcome = await runChangesLoop({
+      transport: ctx.transport,
+      type: 'Identity',
+      jmap,
+      using: IDENTITY_USING,
+      since: state,
+      target,
+      stopped: ctx.stopped,
+      apply: async (page) => {
+        const ids = [...page.created, ...page.updated];
+        const response = ids.length > 0
+          ? await ctx.transport.request([['Identity/get', { accountId: jmap, ids }, 'i']], IDENTITY_USING)
+          : null;
+        const list = response ? responseFor(response, 'i')[1].list as Array<{ id: string }> : [];
+        ctx.db.transaction(() => {
+          for (const identity of list) putObject(ctx.db, jmap, 'Identity', identity.id, identity);
+          for (const id of page.destroyed) deleteObject(ctx.db, jmap, 'Identity', id);
+          ctx.setSyncState(jmap, 'Identity', { state: page.newState });
+        });
+      },
+    });
+    if (outcome.outcome === 'resync') await fullIdentities(ctx, jmap);
+  },
+};
+
+/** Only the last value: Quota/changes always refuses on Stalwart 1.0. */
+export const quotaSyncer: Syncer = {
+  name: 'quota',
+  capability: 'urn:ietf:params:jmap:quota',
+  async run(ctx, jmap) {
+    const response = await ctx.transport.request([['Quota/get', { accountId: jmap, ids: null }, 'q']], QUOTA_USING);
+    const [, result] = responseFor(response, 'q');
+    ctx.db.transaction(() => {
+      ctx.db.run("DELETE FROM object WHERE jmap = ? AND type = 'Quota'", [jmap]);
+      for (const quota of result.list as Array<{ id: string }>) putObject(ctx.db, jmap, 'Quota', quota.id, quota);
+      ctx.setSyncState(jmap, 'Quota', { state: typeof result.state === 'string' ? result.state : null, phase: null, cursor: null });
+    });
+  },
+};
+
 // ---- The whole pass ----
 
 export const mailSyncer: Syncer = {
@@ -334,5 +481,7 @@ export const mailSyncer: Syncer = {
     await syncThreads(ctx, jmap);
     if (ctx.stopped()) return;
     await backfillBodies(ctx, jmap);
+    if (ctx.stopped()) return;
+    await fetchAttachments(ctx, jmap);
   },
 };
diff --git a/lib/store/outbox/calls.ts b/lib/store/outbox/calls.ts
new file mode 100644
index 000000000..33b1f7228
--- /dev/null
+++ b/lib/store/outbox/calls.ts
@@ -0,0 +1,297 @@
+/** What the page asks the outbox. Each call is one SQLite transaction, so two tabs can't interleave. */
+
+import type { AreaCall, StoreContext } from '../area';
+import { metaGet, metaSet } from '../engine/core-schema';
+import { deleteEmail, upsertEmail, type EmailObject } from '../mail/records';
+import { nextSeq, queueUpdate, type PatchRow } from './email-set';
+import type { PatchOutcome, PendingPatch } from './flush-patches';
+import {
+  heldBlobIds,
+  LOCAL_BLOB_PREFIX,
+  type ConflictSummary,
+  type OutboxError,
+  type OutboxStatus,
+  type OutboxSummary,
+  type PolicyFingerprint,
+  type SendItem,
+  type StoredConflict,
+  type StoredOutboxEntry,
+} from './items';
+import type { Patch, RecordState } from './patches';
+
+interface OutboxRow {
+  id: number;
+  seq: number;
+  kind: string;
+  created_at: number;
+  status: string;
+  sending_since: number | null;
+  first_attempt_at: number | null;
+  last_attempt_at: number | null;
+  payload: string;
+  summary: string;
+  message_id: string | null;
+  copy_id: string | null;
+  error: string | null;
+}
+
+function toEntry(row: OutboxRow): StoredOutboxEntry {
+  const payload = JSON.parse(row.payload) as { item: SendItem; fingerprint?: PolicyFingerprint };
+  return {
+    id: Number(row.id),
+    seq: Number(row.seq),
+    createdAt: Number(row.created_at),
+    status: row.status as OutboxStatus,
+    summary: JSON.parse(row.summary) as OutboxSummary,
+    item: payload.item,
+    ...(payload.fingerprint ? { fingerprint: payload.fingerprint } : {}),
+    ...(row.sending_since ? { sendingSince: Number(row.sending_since) } : {}),
+    ...(row.first_attempt_at ? { firstAttemptAt: Number(row.first_attempt_at) } : {}),
+    ...(row.last_attempt_at ? { lastAttemptAt: Number(row.last_attempt_at) } : {}),
+    ...(row.error ? { error: JSON.parse(row.error) as OutboxError } : {}),
+    ...(row.message_id ? { messageId: row.message_id } : {}),
+    ...(row.copy_id ? { copyId: row.copy_id } : {}),
+  };
+}
+
+interface QueueParams {
+  summary: OutboxSummary;
+  item: SendItem;
+  fingerprint?: PolicyFingerprint;
+  messageId?: string;
+  status?: OutboxStatus;
+  createdAt?: number;
+  error?: OutboxError;
+}
+
+function insertEntry(ctx: StoreContext, params: QueueParams): number {
+  return ctx.db.run(
+    `INSERT INTO outbox (seq, kind, created_at, status, payload, summary, message_id, error) VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
+    [
+      nextSeq(ctx.db),
+      params.item.kind,
+      params.createdAt ?? ctx.now(),
+      params.status ?? 'waiting',
+      JSON.stringify({ item: params.item, fingerprint: params.fingerprint }),
+      JSON.stringify(params.summary),
+      params.messageId ?? null,
+      params.error ? JSON.stringify(params.error) : null,
+    ],
+  ).lastInsertRowid;
+}
+
+function queueSend(ctx: StoreContext, params: QueueParams): number {
+  return ctx.db.transaction(() => insertEntry(ctx, params));
+}
+
+function read(ctx: StoreContext): { patches: number; entries: StoredOutboxEntry[]; conflicts: StoredConflict[] } {
+  const patches = Number(ctx.db.get<{ n: number }>('SELECT COUNT(*) AS n FROM outbox_patch')?.n ?? 0);
+  const entries = ctx.db.all<OutboxRow>('SELECT * FROM outbox ORDER BY seq ASC').map(toEntry);
+  const conflicts = ctx.db.all<{ id: number; jmap: string; record_id: string; summary: string; created_at: number }>(
+    'SELECT id, jmap, record_id, summary, created_at FROM conflict ORDER BY id ASC',
+  ).map((row) => ({
+    id: Number(row.id),
+    jmap: row.jmap,
+    recordId: row.record_id,
+    createdAt: Number(row.created_at),
+    summary: JSON.parse(row.summary) as ConflictSummary,
+  }));
+  return { patches, entries, conflicts };
+}
+
+/** Takes a waiting entry for sending: false when it isn't waiting any more (another tab took it, the user deleted it). */
+function claim(ctx: StoreContext, params: { id: number }): boolean {
+  const now = ctx.now();
+  return ctx.db.run(
+    `UPDATE outbox SET status = 'sending', sending_since = ?, last_attempt_at = ? WHERE id = ? AND status = 'waiting'`,
+    [now, now, params.id],
+  ).changes === 1;
+}
+
+/** Deleted meanwhile stays deleted: there's no row to update. */
+function update(ctx: StoreContext, params: { id: number; status: OutboxStatus; error?: OutboxError; copyId?: string | null }): void {
+  ctx.db.run(
+    `UPDATE outbox SET status = ?, error = ?, sending_since = NULL,
+       first_attempt_at = CASE WHEN ? THEN COALESCE(first_attempt_at, last_attempt_at) ELSE first_attempt_at END,
+       copy_id = CASE WHEN ? THEN ? ELSE copy_id END
+     WHERE id = ?`,
+    [
+      params.status,
+      params.error ? JSON.stringify(params.error) : null,
+      // A try that may have reached the server is what a later lookup has to cover.
+      params.status === 'uncertain' ? 1 : 0,
+      params.copyId === undefined ? 0 : 1,
+      params.copyId ?? null,
+      params.id,
+    ],
+  );
+}
+
+/** A send a closed tab left behind may have gone out. */
+function settleStale(ctx: StoreContext, params: { before: number }): number {
+  return ctx.db.run(
+    `UPDATE outbox SET status = 'uncertain', sending_since = NULL, first_attempt_at = COALESCE(first_attempt_at, last_attempt_at)
+     WHERE status = 'sending' AND COALESCE(sending_since, 0) < ?`,
+    [params.before],
+  ).changes;
+}
+
+/** Removes an entry and the files it held. */
+function remove(ctx: StoreContext, params: { id: number }): void {
+  ctx.db.transaction(() => {
+    const row = ctx.db.get<OutboxRow>('SELECT * FROM outbox WHERE id = ?', [params.id]);
+    if (!row) return;
+    for (const blobId of heldBlobIds(toEntry(row).item)) ctx.db.run('DELETE FROM upload WHERE local_id = ?', [blobId]);
+    ctx.db.run('DELETE FROM outbox WHERE id = ?', [params.id]);
+  });
+}
+
+// ---- Files attached offline ----
+
+function holdFile(ctx: StoreContext, params: { jmap?: string; name: string; type: string; data: Uint8Array; localId?: string }): { blobId: string; size: number; type: string } {
+  const blobId = params.localId ?? `${LOCAL_BLOB_PREFIX}${crypto.randomUUID()}`;
+  ctx.db.run(
+    'INSERT OR REPLACE INTO upload (local_id, jmap, type, name, size, data, created_at) VALUES (?, ?, ?, ?, ?, ?, ?)',
+    [blobId, params.jmap ?? null, params.type, params.name, params.data.byteLength, params.data, ctx.now()],
+  );
+  return { blobId, size: params.data.byteLength, type: params.type || 'application/octet-stream' };
+}
+
+function heldFile(ctx: StoreContext, params: { blobId: string }): { name: string; type: string; data: Uint8Array } | null {
+  const row = ctx.db.get<{ name: string | null; type: string | null; data: Uint8Array }>('SELECT name, type, data FROM upload WHERE local_id = ?', [params.blobId]);
+  return row ? { name: row.name ?? 'attachment', type: row.type ?? 'application/octet-stream', data: row.data } : null;
+}
+
+const heldFileSources: Array<(ctx: StoreContext) => Iterable<string>> = [];
+
+/** Another area's records that hold files by their local id, which dropOrphans must leave alone. */
+export function addHeldFileSource(source: (ctx: StoreContext) => Iterable<string>): void {
+  heldFileSources.push(source);
+}
+
+/** Files held for no entry (attached offline to a message that was then discarded). SEAM: the drafts agent keeps its drafts' files here too. */
+function dropOrphans(ctx: StoreContext, params: { olderThan: number }): number {
+  return ctx.db.transaction(() => {
+    const needed = new Set(ctx.db.all<OutboxRow>('SELECT * FROM outbox').flatMap((row) => heldBlobIds(toEntry(row).item)));
+    for (const source of heldFileSources) for (const id of source(ctx)) needed.add(id);
+    let dropped = 0;
+    for (const row of ctx.db.all<{ local_id: string }>('SELECT local_id FROM upload WHERE created_at < ?', [params.olderThan])) {
+      if (needed.has(String(row.local_id))) continue;
+      ctx.db.run('DELETE FROM upload WHERE local_id = ?', [row.local_id]);
+      dropped += 1;
+    }
+    return dropped;
+  });
+}
+
+// ---- Changes ----
+
+function pendingPatches(ctx: StoreContext, params: { upToSeq?: number | null }): PendingPatch[] {
+  const rows = ctx.db.all<PatchRow>(
+    params.upToSeq === undefined || params.upToSeq === null
+      ? 'SELECT * FROM outbox_patch ORDER BY seq ASC'
+      : 'SELECT * FROM outbox_patch WHERE seq < ? ORDER BY seq ASC',
+    params.upToSeq === undefined || params.upToSeq === null ? [] : [params.upToSeq],
+  );
+  return rows.map((row) => ({
+    jmap: row.jmap,
+    type: row.type,
+    recordId: row.record_id,
+    op: row.op,
+    patch: JSON.parse(row.patch) as Patch,
+    base: row.base ? JSON.parse(row.base) as RecordState : null,
+    subject: row.subject,
+    seq: Number(row.seq),
+  }));
+}
+
+function subjectFor(row: PatchRow, server: EmailObject | null | undefined): string {
+  if (typeof server?.subject === 'string') return server.subject;
+  return row.subject ?? '';
+}
+
+/**
+ * What came of a flush. A change made while it ran stays and goes next time,
+ * without comparing against a state this flush itself just moved. After a
+ * conflict the local copy is the server's again: nothing else will correct it
+ * if sync already passed that point.
+ */
+function patchResults(ctx: StoreContext, params: { outcomes: PatchOutcome[] }): number {
+  let conflicts = 0;
+  ctx.db.transaction(() => {
+    for (const outcome of params.outcomes) {
+      const key = [outcome.jmap, outcome.type, outcome.recordId];
+      const row = ctx.db.get<PatchRow>('SELECT * FROM outbox_patch WHERE jmap = ? AND type = ? AND record_id = ?', key);
+      if (!row) continue;
+      if (outcome.outcome === 'done' && Number(row.seq) !== outcome.seq) {
+        ctx.db.run('UPDATE outbox_patch SET base = NULL WHERE jmap = ? AND type = ? AND record_id = ?', key);
+        continue;
+      }
+      ctx.db.run('DELETE FROM outbox_patch WHERE jmap = ? AND type = ? AND record_id = ?', key);
+      if (outcome.outcome === 'done') continue;
+      conflicts += 1;
+      const summary: ConflictSummary = {
+        subject: subjectFor(row, outcome.server),
+        op: row.op,
+        reason: outcome.reason,
+        ...(outcome.detail ? { detail: outcome.detail } : {}),
+      };
+      ctx.db.run(
+        'INSERT INTO conflict (jmap, type, record_id, summary, local, created_at) VALUES (?, ?, ?, ?, ?, ?)',
+        [outcome.jmap, outcome.type, outcome.recordId, JSON.stringify(summary), JSON.stringify({ op: row.op, patch: JSON.parse(row.patch) }), ctx.now()],
+      );
+      if (outcome.server === null) {
+        deleteEmail(ctx.db, outcome.jmap, outcome.recordId);
+      } else if (outcome.server) {
+        const gen = Number(ctx.db.get<{ gen: number | null }>('SELECT MAX(gen) AS gen FROM email WHERE jmap = ?', [outcome.jmap])?.gen ?? 0);
+        upsertEmail(ctx.db, outcome.jmap, outcome.server, gen);
+      }
+    }
+  });
+  if (conflicts > 0) ctx.emit({ type: 'changed', account: ctx.account, collections: ['Email', 'Mailbox', 'Thread'] });
+  return conflicts;
+}
+
+function dismissConflict(ctx: StoreContext, params: { id: number }): void {
+  ctx.db.run('DELETE FROM conflict WHERE id = ?', [params.id]);
+}
+
+// ---- What the old offline database held ----
+
+export interface LegacyImport {
+  entries: QueueParams[];
+  patches: Array<{ jmap: string; update: Record<string, Patch> }>;
+  files: Array<{ blobId: string; name: string; type: string; data: Uint8Array }>;
+}
+
+const LEGACY_DONE = 'legacy_outbox_moved';
+
+/** One transaction: all of it or none. A second run after a partial failure elsewhere adds nothing. */
+function importLegacy(ctx: StoreContext, params: LegacyImport): boolean {
+  return ctx.db.transaction(() => {
+    if (metaGet(ctx.db, LEGACY_DONE)) return false;
+    for (const file of params.files) holdFile(ctx, { name: file.name, type: file.type, data: file.data, localId: file.blobId });
+    for (const entry of params.entries) insertEntry(ctx, entry);
+    for (const { jmap, update: changes } of params.patches) {
+      for (const [id, patch] of Object.entries(changes)) queueUpdate(ctx.db, jmap, id, patch, ctx.now());
+    }
+    metaSet(ctx.db, LEGACY_DONE, '1');
+    return true;
+  });
+}
+
+export const OUTBOX_CALLS: Readonly<Record<string, AreaCall>> = {
+  'outbox.queueSend': queueSend,
+  'outbox.read': read,
+  'outbox.claim': claim,
+  'outbox.update': update,
+  'outbox.settleStale': settleStale,
+  'outbox.remove': remove,
+  'outbox.holdFile': holdFile,
+  'outbox.heldFile': heldFile,
+  'outbox.dropOrphans': dropOrphans,
+  'outbox.pendingPatches': pendingPatches,
+  'outbox.patchResults': patchResults,
+  'outbox.dismissConflict': dismissConflict,
+  'outbox.importLegacy': importLegacy,
+};
diff --git a/lib/store/outbox/dedupe.ts b/lib/store/outbox/dedupe.ts
new file mode 100644
index 000000000..ca50ca900
--- /dev/null
+++ b/lib/store/outbox/dedupe.ts
@@ -0,0 +1,149 @@
+/**
+ * Before a send whose response got lost goes out again: did it reach the
+ * server? JMAP has no idempotency key and a second create or submission is
+ * simply accepted, so this looks. The `header` and `text` filters find no
+ * Message-ID on either Stalwart, so it reads the recent Drafts and Sent and
+ * matches on the client (stalwart-changes-prf.md section 1, decision 4).
+ *
+ * | Lookup                            | Decision                             |
+ * | no match                          | send it again                        |
+ * | in Drafts, no submission          | submit the copy that's there         |
+ * | in Sent                           | done                                 |
+ * | in Drafts, a submission waiting   | done, it's scheduled                 |
+ * | in Drafts, a canceled submission  | done, someone decided against it     |
+ *
+ * It answers "undecided" when it can't tell, and the entry stays with the user.
+ */
+
+import { responseFor, type JmapResponse, type MethodCall } from '../engine/transport';
+import { MAIL_USING } from '../mail/records';
+
+/**
+ * `after` compares the server's receivedAt with this device's clock, so it
+ * looks a day further back than the attempt. Only an exact Message-ID matches,
+ * so looking further costs nothing but a page or two.
+ */
+export const CLOCK_SKEW_MARGIN_MS = 24 * 60 * 60 * 1000;
+/**
+ * Stalwart drops submissions after 3 days (`expungeSubmissionsAfter`). Past
+ * this, "no submission" and "not found" no longer say the send never happened.
+ */
+export const LOOKUP_TRUSTED_MS = 2 * 24 * 60 * 60 * 1000;
+const PAGE = 500;
+const MAX_PAGES = 5;
+const SUBMISSION_USING = [...MAIL_USING, 'urn:ietf:params:jmap:submission'];
+
+export type RetryDecision =
+  | { action: 'send' }
+  | { action: 'submit'; emailId: string }
+  | { action: 'done'; emailId: string; why: 'sent' | 'scheduled' | 'canceled' }
+  | { action: 'undecided'; why: 'no-message-id' | 'no-folders' | 'too-many' | 'too-old' | 'no-copy-kept' | 'unexpected' };
+
+export interface LookupIo {
+  request(calls: MethodCall[], using: string[]): Promise<JmapResponse>;
+}
+
+export interface LookupArgs {
+  /** The JMAP account the send creates its copy in. */
+  jmap: string;
+  submissionJmap: string;
+  messageId: string | undefined;
+  /** When the first attempt was handed to the server. */
+  attemptAt: number;
+  now: number;
+  /**
+   * False when a successful send leaves no copy (no copy in Sent, a submit-only
+   * raw send): then finding nothing doesn't mean it never arrived.
+   */
+  copyKept: boolean;
+}
+
+interface FoundEmail {
+  id: string;
+  messageId?: string[] | null;
+  mailboxIds?: Record<string, boolean>;
+  keywords?: Record<string, boolean>;
+}
+
+function bare(id: string): string {
+  return id.trim().replace(/^<|>$/g, '');
+}
+
+async function findCopies(io: LookupIo, args: LookupArgs, folders: { drafts?: string; sent?: string }): Promise<FoundEmail[] | 'too-many'> {
+  const boxes = [folders.drafts, folders.sent].filter((box): box is string => Boolean(box));
+  const wanted = bare(args.messageId as string);
+  const filter = {
+    operator: 'AND',
+    conditions: [
+      { operator: 'OR', conditions: boxes.map((inMailbox) => ({ inMailbox })) },
+      { after: new Date(args.attemptAt - CLOCK_SKEW_MARGIN_MS).toISOString() },
+    ],
+  };
+  const found: FoundEmail[] = [];
+  for (let page = 0; page < MAX_PAGES; page += 1) {
+    const response = await io.request([
+      ['Email/query', {
+        accountId: args.jmap,
+        filter,
+        sort: [{ property: 'receivedAt', isAscending: false }],
+        position: page * PAGE,
+        limit: PAGE,
+      }, 'q'],
+      ['Email/get', {
+        accountId: args.jmap,
+        '#ids': { resultOf: 'q', name: 'Email/query', path: '/ids' },
+        properties: ['id', 'messageId', 'mailboxIds', 'keywords'],
+      }, 'g'],
+    ], MAIL_USING);
+    const ids = responseFor(response, 'q')[1].ids as string[];
+    const list = responseFor(response, 'g')[1].list as FoundEmail[];
+    found.push(...list.filter((email) => (email.messageId ?? []).some((id) => bare(id) === wanted)));
+    if (ids.length < PAGE) return found;
+  }
+  // More than this since the attempt, and nothing matched so far: it may be further on.
+  return found.length > 0 ? found : 'too-many';
+}
+
+async function submissionsOf(io: LookupIo, jmap: string, emailId: string): Promise<Array<{ undoStatus?: string }>> {
+  const response = await io.request([
+    ['EmailSubmission/query', { accountId: jmap, filter: { emailIds: [emailId] } }, 'q'],
+    ['EmailSubmission/get', {
+      accountId: jmap,
+      '#ids': { resultOf: 'q', name: 'EmailSubmission/query', path: '/ids' },
+      properties: ['id', 'undoStatus'],
+    }, 'g'],
+  ], SUBMISSION_USING);
+  return responseFor(response, 'g')[1].list as Array<{ undoStatus?: string }>;
+}
+
+/** What to do with a send that may have reached the server. Throws when the lookup itself fails. */
+export async function decideRetry(io: LookupIo, args: LookupArgs): Promise<RetryDecision> {
+  if (!args.messageId) return { action: 'undecided', why: 'no-message-id' };
+  const boxesResponse = await io.request([['Mailbox/get', { accountId: args.jmap, properties: ['id', 'role'] }, 'm']], MAIL_USING);
+  const boxes = responseFor(boxesResponse, 'm')[1].list as Array<{ id: string; role?: string | null }>;
+  const folders = { drafts: boxes.find((box) => box.role === 'drafts')?.id, sent: boxes.find((box) => box.role === 'sent')?.id };
+  if (!folders.drafts && !folders.sent) return { action: 'undecided', why: 'no-folders' };
+
+  const copies = await findCopies(io, args, folders);
+  if (copies === 'too-many') return { action: 'undecided', why: 'too-many' };
+  const trusted = args.now - args.attemptAt <= LOOKUP_TRUSTED_MS;
+
+  const inSent = copies.find((email) => folders.sent && email.mailboxIds?.[folders.sent]);
+  if (inSent) return { action: 'done', emailId: inSent.id, why: 'sent' };
+
+  const inDrafts = copies.find((email) => folders.drafts && email.mailboxIds?.[folders.drafts]);
+  if (inDrafts) {
+    const submissions = await submissionsOf(io, args.submissionJmap, inDrafts.id);
+    if (submissions.length > 0) {
+      const live = submissions.some((submission) => submission.undoStatus !== 'canceled');
+      return { action: 'done', emailId: inDrafts.id, why: live ? 'scheduled' : 'canceled' };
+    }
+    if (!trusted) return { action: 'undecided', why: 'too-old' };
+    if (!inDrafts.keywords?.$draft) return { action: 'undecided', why: 'unexpected' };
+    return { action: 'submit', emailId: inDrafts.id };
+  }
+
+  if (!args.copyKept) return { action: 'undecided', why: 'no-copy-kept' };
+  if (!trusted) return { action: 'undecided', why: 'too-old' };
+  return { action: 'send' };
+}
diff --git a/lib/store/outbox/email-set.ts b/lib/store/outbox/email-set.ts
new file mode 100644
index 000000000..5451e1c21
--- /dev/null
+++ b/lib/store/outbox/email-set.ts
@@ -0,0 +1,213 @@
+/**
+ * Email/set answered from the store: changes wait in outbox_patch, merged per
+ * record, and show at once. Deleting for good and emptying a folder wait the
+ * same way. Answers carry no state: a made-up one would reach the server later.
+ */
+
+import { MethodError, type MethodContext, type MethodHandler, type RecordOverlay } from '../area';
+import { metaGet, metaSet } from '../engine/core-schema';
+import { deleteEmail, upsertEmail, type EmailObject } from '../mail/records';
+import type { StorageAdapter } from '../storage';
+import { applyPatch, mergePatches, normalizePatch, patchProblem, stateOf, type Patch, type RecordState } from './patches';
+
+export interface PatchRow {
+  jmap: string;
+  type: string;
+  record_id: string;
+  op: 'update' | 'destroy';
+  patch: string;
+  base: string | null;
+  server: string | null;
+  subject: string | null;
+  seq: number;
+  queued_at: number;
+}
+
+const EMAIL = 'Email';
+
+/** The next place in the order changes and sends were made. */
+export function nextSeq(db: StorageAdapter): number {
+  const next = Number(metaGet(db, 'outbox_seq') ?? 0) + 1;
+  metaSet(db, 'outbox_seq', String(next));
+  return next;
+}
+
+function pendingRow(db: StorageAdapter, jmap: string, id: string): PatchRow | undefined {
+  return db.get<PatchRow>('SELECT * FROM outbox_patch WHERE jmap = ? AND type = ? AND record_id = ?', [jmap, EMAIL, id]);
+}
+
+function savePatch(db: StorageAdapter, row: Omit<PatchRow, 'seq' | 'queued_at' | 'type'>, now: number): void {
+  db.run(
+    `INSERT INTO outbox_patch (jmap, type, record_id, op, patch, base, server, subject, seq, queued_at)
+     VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+     ON CONFLICT (jmap, type, record_id) DO UPDATE SET op = excluded.op, patch = excluded.patch, seq = excluded.seq`,
+    [row.jmap, EMAIL, row.record_id, row.op, row.patch, row.base, row.server, row.subject, nextSeq(db), now],
+  );
+}
+
+function localEmail(db: StorageAdapter, jmap: string, id: string): { email: EmailObject; gen: number } | null {
+  const row = db.get<{ json: string; gen: number }>('SELECT json, gen FROM email WHERE jmap = ? AND id = ?', [jmap, id]);
+  return row ? { email: JSON.parse(row.json) as EmailObject, gen: Number(row.gen) } : null;
+}
+
+function subjectOf(email: EmailObject | undefined): string | null {
+  return typeof email?.subject === 'string' ? email.subject : null;
+}
+
+/** Queues one change and shows it. The error for `notUpdated`, or null. */
+export function queueUpdate(db: StorageAdapter, jmap: string, id: string, rawPatch: Patch, now: number): { type: string; description?: string } | null {
+  const problem = patchProblem(rawPatch);
+  if (problem) return problem;
+  const patch = normalizePatch(rawPatch);
+  const existing = pendingRow(db, jmap, id);
+  if (existing?.op === 'destroy') return { type: 'notFound' };
+  const local = localEmail(db, jmap, id);
+  const after = applyPatch(local?.email ?? ({} as EmailObject), patch);
+  // JMAP has no message outside every folder. Deleting is a destroy.
+  if ((local || 'mailboxIds' in patch) && Object.keys(after.mailboxIds ?? {}).length === 0) {
+    return { type: 'invalidProperties', description: 'A message has to stay in a folder' };
+  }
+  const state = local ? JSON.stringify(stateOf(local.email)) : null;
+  savePatch(db, {
+    jmap,
+    record_id: id,
+    op: 'update',
+    patch: JSON.stringify(existing ? mergePatches(JSON.parse(existing.patch) as Patch, patch) : patch),
+    base: state,
+    server: state,
+    subject: subjectOf(local?.email),
+  }, now);
+  if (local) upsertEmail(db, jmap, after as EmailObject, local.gen);
+  return null;
+}
+
+/** Queues a delete and shows it. */
+export function queueDestroy(db: StorageAdapter, jmap: string, id: string, now: number): void {
+  const local = localEmail(db, jmap, id);
+  const state = local ? JSON.stringify(stateOf(local.email)) : null;
+  savePatch(db, { jmap, record_id: id, op: 'destroy', patch: '{}', base: state, server: state, subject: subjectOf(local?.email) }, now);
+  // savePatch keeps base and server of a row already there; only the op changes.
+  if (local) deleteEmail(db, jmap, id);
+}
+
+/**
+ * SEAM for the drafts agent: Email/set create is theirs. Until it lands every
+ * create is refused per message, so createDraft throws and the composer shows
+ * its "draft not saved" state, as it does today.
+ */
+function createEmails(_ctx: MethodContext, _jmap: string, create: Record<string, unknown>): Record<string, { type: string; description: string }> {
+  return Object.fromEntries(Object.keys(create).map((id) => [id, { type: 'serverUnavailable', description: 'Saving a draft needs the server' }]));
+}
+
+export const emailSet: MethodHandler = (ctx, args) => {
+  const jmap = (args.accountId as string | undefined) ?? ctx.defaultJmap;
+  if (args.destroy !== undefined && args.destroy !== null && !Array.isArray(args.destroy)) {
+    throw new MethodError('invalidArguments', 'destroy has to be a list');
+  }
+  const result: Record<string, unknown> = { accountId: jmap };
+  ctx.db.transaction(() => {
+    if (args.create && Object.keys(args.create as object).length > 0) {
+      result.created = {};
+      result.notCreated = createEmails(ctx, jmap, args.create as Record<string, unknown>);
+    }
+    if (args.update) {
+      const updated: Record<string, null> = {};
+      const notUpdated: Record<string, unknown> = {};
+      for (const [id, patch] of Object.entries(args.update as Record<string, Patch>)) {
+        const problem = queueUpdate(ctx.db, jmap, id, patch, ctx.now());
+        if (problem) notUpdated[id] = problem;
+        else updated[id] = null;
+      }
+      result.updated = updated;
+      if (Object.keys(notUpdated).length > 0) result.notUpdated = notUpdated;
+    }
+    if (Array.isArray(args.destroy)) {
+      for (const id of args.destroy as string[]) queueDestroy(ctx.db, jmap, id, ctx.now());
+      result.destroyed = args.destroy;
+    }
+  });
+  ctx.emit({ type: 'changed', account: ctx.account, collections: ['Email', 'Mailbox', 'Thread'] });
+  return result;
+};
+
+/** What waiting changes do to the folder counts: from the server's copy to what the change makes of it. */
+function countDeltas(db: StorageAdapter, jmap: string): Map<string, { total: number; unread: number }> {
+  const rows = db.all<{ op: string; patch: string; server: string | null }>('SELECT op, patch, server FROM outbox_patch WHERE jmap = ? AND type = ?', [jmap, EMAIL]);
+  const deltas = new Map<string, { total: number; unread: number }>();
+  const bump = (box: string, total: number, unread: number) => {
+    const delta = deltas.get(box) ?? { total: 0, unread: 0 };
+    delta.total += total;
+    delta.unread += unread;
+    deltas.set(box, delta);
+  };
+  for (const row of rows) {
+    if (!row.server) continue;
+    const before = JSON.parse(row.server) as RecordState;
+    const wasUnread = before.keywords?.$seen ? 0 : 1;
+    const boxesBefore = Object.keys(before.mailboxIds ?? {}).filter((box) => before.mailboxIds?.[box]);
+    if (row.op === 'destroy') {
+      for (const box of boxesBefore) bump(box, -1, -wasUnread);
+      continue;
+    }
+    const after = applyPatch(before, JSON.parse(row.patch) as Patch);
+    const isUnread = after.keywords?.$seen ? 0 : 1;
+    const boxesAfter = Object.keys(after.mailboxIds ?? {});
+    for (const box of boxesBefore) if (!after.mailboxIds?.[box]) bump(box, -1, -wasUnread);
+    for (const box of boxesAfter) {
+      if (!before.mailboxIds?.[box]) bump(box, 1, isUnread);
+      else if (wasUnread !== isUnread) bump(box, 0, isUnread - wasUnread);
+    }
+  }
+  return deltas;
+}
+
+/**
+ * Sync must not lose a change that waits: what the server sends goes under it.
+ * A record waiting to be deleted stays away. The folder counts stay the
+ * server's, with what waits added when they're read, so a sync can't count a
+ * change twice or forget it.
+ */
+export const outboxOverlay: RecordOverlay = (ctx, jmap, type, records) => {
+  if (!ctx.db.get('SELECT 1 AS x FROM outbox_patch WHERE jmap = ? LIMIT 1', [jmap])) return records;
+  switch (type) {
+    case EMAIL: {
+      const out: Array<{ id: string }> = [];
+      for (const record of records) {
+        const row = pendingRow(ctx.db, jmap, record.id);
+        if (!row) {
+          out.push(record);
+          continue;
+        }
+        const email = record as EmailObject;
+        ctx.db.run('UPDATE outbox_patch SET server = ?, subject = COALESCE(subject, ?) WHERE jmap = ? AND type = ? AND record_id = ?', [
+          JSON.stringify(stateOf(email)), subjectOf(email), jmap, EMAIL, record.id,
+        ]);
+        if (row.op === 'update') out.push(applyPatch(email, JSON.parse(row.patch) as Patch) as EmailObject);
+      }
+      return out;
+    }
+    case 'Thread': {
+      const gone = new Set(ctx.db.all<{ record_id: string }>(
+        "SELECT record_id FROM outbox_patch WHERE jmap = ? AND type = ? AND op = 'destroy'",
+        [jmap, EMAIL],
+      ).map((row) => String(row.record_id)));
+      return (records as Array<{ id: string; emailIds: string[] }>).map((thread) => ({
+        ...thread,
+        emailIds: thread.emailIds.filter((id) => !gone.has(id)),
+      }));
+    }
+    case 'Mailbox': {
+      const deltas = countDeltas(ctx.db, jmap);
+      if (deltas.size === 0) return records;
+      return (records as Array<{ id: string; totalEmails?: unknown; unreadEmails?: unknown }>).map((box) => {
+        const delta = deltas.get(box.id);
+        if (!delta) return box;
+        const count = (value: unknown, by: number) => (typeof value === 'number' ? Math.max(0, value + by) : value);
+        // Messages only: how the conversations change can't be told from here.
+        return { ...box, totalEmails: count(box.totalEmails, delta.total), unreadEmails: count(box.unreadEmails, delta.unread) };
+      });
+    }
+    default:
+      return records;
+  }
+};
diff --git a/lib/store/outbox/flush-patches.ts b/lib/store/outbox/flush-patches.ts
new file mode 100644
index 000000000..ae0901828
--- /dev/null
+++ b/lib/store/outbox/flush-patches.ts
@@ -0,0 +1,175 @@
+/**
+ * Sends the changes that waited. Written against a small `request`, so the page
+ * can run it through the JMAP client (its auth, its retries) while the logic
+ * stays testable next to the store.
+ *
+ * Per batch: read what the server has now, keep back what it changed since the
+ * change was queued, send the rest, and report per record. A change the server
+ * took is dropped and the next /changes run brings the truth. A change it
+ * refused, or that met a record changed since, goes to the user as a conflict.
+ * Anything that looks like an outage stops the run: the changes wait.
+ */
+
+import { JmapMethodError, responseFor, type JmapResponse, type MethodCall } from '../engine/transport';
+import { EMAIL_LIST_PROPERTIES, MAIL_USING, type EmailObject } from '../mail/records';
+import type { ConflictReason } from './items';
+import { destroyConflicts, patchConflicts, type Patch, type RecordState } from './patches';
+
+export interface PendingPatch {
+  jmap: string;
+  type: string;
+  recordId: string;
+  op: 'update' | 'destroy';
+  patch: Patch;
+  base: RecordState | null;
+  subject: string | null;
+  seq: number;
+}
+
+export type PatchOutcome =
+  | { jmap: string; type: string; recordId: string; seq: number; outcome: 'done' }
+  | {
+    jmap: string;
+    type: string;
+    recordId: string;
+    seq: number;
+    outcome: 'conflict';
+    reason: ConflictReason;
+    detail?: string;
+    /** The record as the server has it, or null when it's gone there. Undefined when unknown. */
+    server?: EmailObject | null;
+  };
+
+export interface PatchIo {
+  request(calls: MethodCall[], using: string[]): Promise<JmapResponse>;
+}
+
+const BATCH = 200;
+/** Method errors that mean "not now" rather than "no". */
+const RETRY_LATER = new Set(['serverUnavailable', 'serverFail', 'serverPartialFail', 'rateLimit', 'requestTooLarge']);
+
+/**
+ * The server refused the request itself, for good: a JMAP problem document with
+ * a status that says so. `limit` is the parallel-request ceiling, which passes,
+ * and an error page says something about a proxy, not about this request.
+ */
+export function isRequestRefusal(error: unknown): boolean {
+  if (!(error instanceof Error)) return false;
+  const problem = /^Request failed: (?:400|403|404|413|422)\b[\s\S]*?"type"\s*:\s*"urn:ietf:params:jmap:error:([A-Za-z]+)"/.exec(error.message);
+  return !!problem && problem[1] !== 'limit';
+}
+
+function isLater(error: unknown): boolean {
+  if (error instanceof JmapMethodError) return RETRY_LATER.has(error.type);
+  return !isRequestRefusal(error);
+}
+
+function conflict(row: PendingPatch, reason: ConflictReason, server?: EmailObject | null, detail?: string): PatchOutcome {
+  return { jmap: row.jmap, type: row.type, recordId: row.recordId, seq: row.seq, outcome: 'conflict', reason, detail, server };
+}
+
+function done(row: PendingPatch): PatchOutcome {
+  return { jmap: row.jmap, type: row.type, recordId: row.recordId, seq: row.seq, outcome: 'done' };
+}
+
+function errorText(error: unknown): string {
+  return error instanceof Error ? error.message : String(error);
+}
+
+async function readRecords(io: PatchIo, jmap: string, rows: PendingPatch[]): Promise<Map<string, EmailObject>> {
+  const read = await io.request([['Email/get', {
+    accountId: jmap,
+    ids: rows.map((row) => row.recordId),
+    properties: EMAIL_LIST_PROPERTIES,
+  }, 'g']], MAIL_USING);
+  const [, got] = responseFor(read, 'g');
+  return new Map((got.list as EmailObject[]).map((email) => [email.id, email]));
+}
+
+/**
+ * The whole batch was refused. The server's copy of each record goes with the
+ * conflict so that this device shows what's true again. When even that read is
+ * refused the record stays as it is here until the next sync.
+ */
+async function refusedOutcomes(io: PatchIo, jmap: string, rows: PendingPatch[], refusal: unknown): Promise<PatchOutcome[] | null> {
+  let current: Map<string, EmailObject> | null = null;
+  try {
+    current = await readRecords(io, jmap, rows);
+  } catch (error) {
+    if (isLater(error)) return null;
+  }
+  return rows.map((row) => {
+    if (current && !current.has(row.recordId)) return row.op === 'destroy' ? done(row) : conflict(row, 'gone', null);
+    return conflict(row, 'refused', current?.get(row.recordId), errorText(refusal));
+  });
+}
+
+async function flushBatch(io: PatchIo, jmap: string, rows: PendingPatch[]): Promise<PatchOutcome[]> {
+  const current = await readRecords(io, jmap, rows);
+
+  const outcomes: PatchOutcome[] = [];
+  const update: Record<string, Patch> = {};
+  const destroy: string[] = [];
+  const sent = new Map<string, PendingPatch>();
+  for (const row of rows) {
+    const server = current.get(row.recordId);
+    if (!server) {
+      // Asked to delete what's already gone: that's the same result.
+      outcomes.push(row.op === 'destroy' ? done(row) : conflict(row, 'gone', null));
+      continue;
+    }
+    const changed = row.op === 'destroy' ? destroyConflicts(row.base, server) : patchConflicts(row.patch, row.base, server);
+    if (changed) {
+      outcomes.push(conflict(row, 'changed', server));
+      continue;
+    }
+    sent.set(row.recordId, row);
+    if (row.op === 'destroy') destroy.push(row.recordId);
+    else update[row.recordId] = row.patch;
+  }
+  if (sent.size === 0) return outcomes;
+
+  const response = await io.request([['Email/set', {
+    accountId: jmap,
+    ...(Object.keys(update).length > 0 ? { update } : {}),
+    ...(destroy.length > 0 ? { destroy } : {}),
+  }, 's']], MAIL_USING);
+  const [, result] = responseFor(response, 's');
+  const refused: Record<string, { type?: string; description?: string }> = { ...(result.notUpdated ?? {}), ...(result.notDestroyed ?? {}) };
+  for (const [id, row] of sent) {
+    const refusal = refused[id];
+    if (!refusal) {
+      outcomes.push(done(row));
+    } else if (refusal.type === 'notFound') {
+      outcomes.push(row.op === 'destroy' ? done(row) : conflict(row, 'gone', null));
+    } else {
+      outcomes.push(conflict(row, 'refused', current.get(id), refusal.description ?? refusal.type));
+    }
+  }
+  return outcomes;
+}
+
+/** True when all went through to an answer, false when the run stopped on an outage. */
+export async function flushPatches(
+  io: PatchIo,
+  pending: readonly PendingPatch[],
+  report: (outcomes: PatchOutcome[]) => Promise<void>,
+): Promise<boolean> {
+  const byAccount = new Map<string, PendingPatch[]>();
+  for (const row of pending) byAccount.set(row.jmap, [...(byAccount.get(row.jmap) ?? []), row]);
+  for (const [jmap, rows] of byAccount) {
+    for (let i = 0; i < rows.length; i += BATCH) {
+      const batch = rows.slice(i, i + BATCH);
+      let outcomes: PatchOutcome[] | null;
+      try {
+        outcomes = await flushBatch(io, jmap, batch);
+      } catch (error) {
+        if (isLater(error)) return false;
+        outcomes = await refusedOutcomes(io, jmap, batch, error);
+        if (!outcomes) return false;
+      }
+      await report(outcomes);
+    }
+  }
+  return true;
+}
diff --git a/lib/store/outbox/index.ts b/lib/store/outbox/index.ts
new file mode 100644
index 000000000..4d65885cb
--- /dev/null
+++ b/lib/store/outbox/index.ts
@@ -0,0 +1,13 @@
+import type { StoreArea } from '../area';
+import { OUTBOX_CALLS } from './calls';
+import { emailSet, outboxOverlay } from './email-set';
+import { OUTBOX_MIGRATIONS } from './schema';
+
+export const outboxArea: StoreArea = {
+  name: 'outbox',
+  migrations: OUTBOX_MIGRATIONS,
+  methods: { 'Email/set': emailSet },
+  syncers: [],
+  calls: OUTBOX_CALLS,
+  overlay: outboxOverlay,
+};
diff --git a/lib/store/outbox/items.ts b/lib/store/outbox/items.ts
new file mode 100644
index 000000000..e802090ee
--- /dev/null
+++ b/lib/store/outbox/items.ts
@@ -0,0 +1,106 @@
+/**
+ * What a finished send looks like when it waits. An outbox entry is a finished
+ * message: everything a send does up to the transport ran when the user clicked
+ * Send (the organisation's checks, the label, signatures, plugin send checks,
+ * S/MIME or PGP with the user present). What is kept is the arguments of the
+ * final send, or the finished raw message of a plugin's send. Sending it later
+ * can't skip any of that.
+ */
+
+/** The arguments of useEmailStore.sendEmail after the client (positional, as the client takes them). */
+export interface EmailSendItem {
+  kind: 'email';
+  args: unknown[];
+}
+
+export interface RawSendItem {
+  kind: 'raw';
+  /** The finished message, kept as an upload until it is sent. */
+  blobId: string;
+  identityId: string;
+  delayedUntil?: string;
+  envelopeRecipients?: string[];
+  /** submitRaw: no copy in Sent. */
+  submitOnly?: boolean;
+}
+
+export type SendItem = EmailSendItem | RawSendItem;
+
+export interface OutboxSummary {
+  subject: string;
+  to: string[];
+}
+
+/**
+ * - waiting: goes out by itself when the server answers;
+ * - sending: on its way (a tab took it);
+ * - failed: the server refused it; the error says why;
+ * - uncertain: the connection broke after it may have reached the server.
+ *   Looked up when the server is back; stays this way only when the lookup
+ *   can't tell, and then it's the user's to send again or delete;
+ * - held: the organisation's rules got stricter while it waited.
+ */
+export type OutboxStatus = 'waiting' | 'sending' | 'failed' | 'uncertain' | 'held';
+
+/** Why an entry failed: one of ours (a code the UI translates) or the server's own words. */
+export interface OutboxError {
+  code?: 'file_missing' | 'no_sent_mailbox' | 'no_drafts_mailbox';
+  text?: string;
+}
+
+/** What the organisation required when the message was finished. */
+export interface PolicyFingerprint {
+  labelRequired: boolean;
+  hasLabel: boolean;
+  guards: string[];
+}
+
+export interface StoredOutboxEntry {
+  id: number;
+  seq: number;
+  createdAt: number;
+  summary: OutboxSummary;
+  status: OutboxStatus;
+  sendingSince?: number;
+  /** When the first try that may have reached the server began. */
+  firstAttemptAt?: number;
+  lastAttemptAt?: number;
+  error?: OutboxError;
+  item: SendItem;
+  fingerprint?: PolicyFingerprint;
+  messageId?: string;
+  copyId?: string;
+}
+
+/** Stand-in blob ids of files kept on this device start with this. */
+export const LOCAL_BLOB_PREFIX = 'bulwark-local-';
+
+export function isLocalBlobId(blobId: unknown): blobId is string {
+  return typeof blobId === 'string' && blobId.startsWith(LOCAL_BLOB_PREFIX);
+}
+
+/** The stand-in blob ids an outbox entry needs uploaded first. */
+export function heldBlobIds(item: SendItem): string[] {
+  if (item.kind === 'raw') return isLocalBlobId(item.blobId) ? [item.blobId] : [];
+  const attachments = item.args[10];
+  if (!Array.isArray(attachments)) return [];
+  return attachments.map((a) => (a as { blobId?: unknown }).blobId).filter(isLocalBlobId);
+}
+
+export type ConflictReason = 'changed' | 'gone' | 'refused';
+
+export interface ConflictSummary {
+  subject: string;
+  op: 'update' | 'destroy';
+  reason: ConflictReason;
+  /** The server's word when it refused. */
+  detail?: string;
+}
+
+export interface StoredConflict {
+  id: number;
+  jmap: string;
+  recordId: string;
+  createdAt: number;
+  summary: ConflictSummary;
+}
diff --git a/lib/store/outbox/patches.ts b/lib/store/outbox/patches.ts
new file mode 100644
index 000000000..e055ae7b9
--- /dev/null
+++ b/lib/store/outbox/patches.ts
@@ -0,0 +1,157 @@
+/**
+ * JMAP PatchObjects for the two properties that can change offline, keywords
+ * and mailboxIds, in both forms the client sends: `keywords/$seen` paths and
+ * the whole map.
+ */
+
+import { keywordKey } from '../mail/records';
+
+export type Patch = Record<string, unknown>;
+
+export interface RecordState {
+  keywords?: Record<string, boolean>;
+  mailboxIds?: Record<string, boolean>;
+}
+
+const MAPS = ['keywords', 'mailboxIds'] as const;
+type MapName = (typeof MAPS)[number];
+
+function unescapeToken(token: string): string {
+  return token.replace(/~1/g, '/').replace(/~0/g, '~');
+}
+
+/** The map and the key a path changes, or null when it isn't one of ours. */
+function parsePath(path: string): { map: MapName; key: string | null } | null {
+  const slash = path.indexOf('/');
+  const name = slash < 0 ? path : path.slice(0, slash);
+  if (!(MAPS as readonly string[]).includes(name)) return null;
+  return { map: name as MapName, key: slash < 0 ? null : unescapeToken(path.slice(slash + 1)) };
+}
+
+/** Why this patch can't wait offline, or null when it can. */
+export function patchProblem(patch: Patch): { type: string; description: string } | null {
+  const paths = Object.keys(patch);
+  if (paths.length === 0) return { type: 'invalidPatch', description: 'An empty change' };
+  for (const path of paths) {
+    const parsed = parsePath(path);
+    if (!parsed) return { type: 'forbidden', description: `Changing ${path} needs the server` };
+    // A folder made in the same request: that part needs the server, so this does too.
+    if (parsed.map === 'mailboxIds') {
+      const keys = parsed.key !== null ? [parsed.key] : Object.keys((patch[path] ?? {}) as object);
+      if (keys.some((key) => key.startsWith('#'))) return { type: 'forbidden', description: 'A new folder needs the server' };
+    }
+  }
+  return null;
+}
+
+/** `false` means removal to the client's code; on the wire only null does. */
+export function normalizePatch(patch: Patch): Patch {
+  const out: Patch = {};
+  for (const [path, value] of Object.entries(patch)) out[path] = path.includes('/') && !value ? null : value;
+  return out;
+}
+
+export function applyPatch<T extends object>(record: T, patch: Patch): T & RecordState {
+  const state = record as RecordState;
+  const next: T & RecordState = {
+    ...record,
+    keywords: { ...(state.keywords ?? {}) },
+    mailboxIds: { ...(state.mailboxIds ?? {}) },
+  };
+  for (const [path, value] of Object.entries(patch)) {
+    const parsed = parsePath(path);
+    if (!parsed) continue;
+    if (parsed.key === null) {
+      next[parsed.map] = { ...((value ?? {}) as Record<string, boolean>) };
+      continue;
+    }
+    const map = next[parsed.map] as Record<string, boolean>;
+    if (value) map[parsed.key] = true;
+    else delete map[parsed.key];
+  }
+  return next;
+}
+
+/**
+ * A later change to the same record on top of an earlier one. A whole map
+ * replaces every earlier change to that map; a path into a map the earlier
+ * change replaced goes into that map, since the whole map is what gets sent.
+ */
+export function mergePatches(earlier: Patch, later: Patch): Patch {
+  const out: Patch = { ...earlier };
+  for (const [path, value] of Object.entries(later)) {
+    const parsed = parsePath(path);
+    if (!parsed) {
+      out[path] = value;
+      continue;
+    }
+    if (parsed.key === null) {
+      for (const existing of Object.keys(out)) {
+        if (existing === parsed.map || existing.startsWith(`${parsed.map}/`)) delete out[existing];
+      }
+      out[path] = value;
+      continue;
+    }
+    if (parsed.map in out) {
+      const map = { ...(out[parsed.map] as Record<string, boolean>) };
+      if (value) map[parsed.key] = true;
+      else delete map[parsed.key];
+      out[parsed.map] = map;
+      continue;
+    }
+    out[path] = value;
+  }
+  return out;
+}
+
+function sameMap(a: Record<string, boolean> | undefined, b: Record<string, boolean> | undefined): boolean {
+  const left = Object.keys(a ?? {}).filter((key) => a?.[key]).map(keywordKey).sort();
+  const right = Object.keys(b ?? {}).filter((key) => b?.[key]).map(keywordKey).sort();
+  return left.length === right.length && left.every((key, i) => key === right[i]);
+}
+
+function has(map: Record<string, boolean> | undefined, key: string): boolean {
+  const wanted = keywordKey(key);
+  return Object.keys(map ?? {}).some((name) => keywordKey(name) === wanted && map?.[name]);
+}
+
+/**
+ * Whether the server changed what this patch touches since it was queued. A
+ * change elsewhere on the record isn't a conflict, and neither is the server
+ * already having what the patch wants. Folders count as a whole: a move here
+ * after a move on another device would leave the message in both places.
+ * Keywords stand alone.
+ */
+export function patchConflicts(patch: Patch, base: RecordState | null, serverRecord: object): boolean {
+  if (!base) return false;
+  const server = serverRecord as RecordState;
+  const paths = Object.keys(patch).map((path) => parsePath(path));
+  if (paths.some((parsed) => parsed?.map === 'mailboxIds')
+    && !sameMap(base.mailboxIds, server.mailboxIds)
+    && !sameMap(applyPatch(base, patch).mailboxIds, server.mailboxIds)) return true;
+  for (const [path, value] of Object.entries(patch)) {
+    const parsed = parsePath(path);
+    if (!parsed || parsed.map === 'mailboxIds') continue;
+    if (parsed.key === null) {
+      const wanted = value as Record<string, boolean>;
+      if (!sameMap(base[parsed.map], server[parsed.map]) && !sameMap(wanted, server[parsed.map])) return true;
+      continue;
+    }
+    const before = has(base[parsed.map], parsed.key);
+    const now = has(server[parsed.map], parsed.key);
+    if (before !== now && now !== Boolean(value)) return true;
+  }
+  return false;
+}
+
+/** Deleting a record the server changed since: the user should see that. */
+export function destroyConflicts(base: RecordState | null, serverRecord: object): boolean {
+  if (!base) return false;
+  const server = serverRecord as RecordState;
+  return !sameMap(base.keywords, server.keywords) || !sameMap(base.mailboxIds, server.mailboxIds);
+}
+
+export function stateOf(record: object): RecordState {
+  const state = record as RecordState;
+  return { keywords: state.keywords ?? {}, mailboxIds: state.mailboxIds ?? {} };
+}
diff --git a/lib/store/outbox/schema.ts b/lib/store/outbox/schema.ts
new file mode 100644
index 000000000..2f9ed83e5
--- /dev/null
+++ b/lib/store/outbox/schema.ts
@@ -0,0 +1,73 @@
+import type { Migration } from '../storage';
+
+export const OUTBOX_MIGRATIONS: readonly Migration[] = [
+  {
+    id: 201,
+    name: 'outbox_last_attempt',
+    sql: `
+      -- When the latest try began. It becomes first_attempt_at only once a try
+      -- may have reached the server.
+      ALTER TABLE outbox ADD COLUMN last_attempt_at INTEGER;
+    `,
+  },
+  {
+    id: 200,
+    name: 'outbox',
+    sql: `
+      -- Finished messages waiting for the server. seq is shared with
+      -- outbox_patch, so changes and sends go out in the order they were made.
+      CREATE TABLE outbox (
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        seq INTEGER NOT NULL,
+        kind TEXT NOT NULL,
+        created_at INTEGER NOT NULL,
+        status TEXT NOT NULL,
+        sending_since INTEGER,
+        -- When it was first handed to the server: where a retry's lookup starts.
+        first_attempt_at INTEGER,
+        payload TEXT NOT NULL,
+        summary TEXT NOT NULL,
+        message_id TEXT,
+        -- The copy already on the server that only needs submitting.
+        copy_id TEXT,
+        error TEXT
+      );
+      -- One row per record, later changes merged in. base is the record's state
+      -- when first queued, to tell whether the server changed it since; server
+      -- is the newest state the server sent, for the folder counts.
+      CREATE TABLE outbox_patch (
+        jmap TEXT NOT NULL,
+        type TEXT NOT NULL,
+        record_id TEXT NOT NULL,
+        op TEXT NOT NULL,
+        patch TEXT NOT NULL,
+        base TEXT,
+        server TEXT,
+        subject TEXT,
+        seq INTEGER NOT NULL,
+        queued_at INTEGER NOT NULL,
+        PRIMARY KEY (jmap, type, record_id)
+      ) WITHOUT ROWID;
+      CREATE INDEX outbox_patch_seq ON outbox_patch (seq);
+      CREATE TABLE conflict (
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        jmap TEXT NOT NULL,
+        type TEXT NOT NULL,
+        record_id TEXT NOT NULL,
+        summary TEXT NOT NULL,
+        local TEXT NOT NULL,
+        created_at INTEGER NOT NULL
+      );
+      -- Files attached offline, under a stand-in blob id.
+      CREATE TABLE upload (
+        local_id TEXT PRIMARY KEY,
+        jmap TEXT,
+        type TEXT,
+        name TEXT,
+        size INTEGER NOT NULL,
+        data BLOB NOT NULL,
+        created_at INTEGER NOT NULL
+      ) WITHOUT ROWID;
+    `,
+  },
+];
diff --git a/lib/store/storage.ts b/lib/store/storage.ts
index 5ca4c29af..d59a1b4c6 100644
--- a/lib/store/storage.ts
+++ b/lib/store/storage.ts
@@ -52,6 +52,16 @@ export function runTransaction<T>(
   }
 }
 
+/**
+ * The disk is full, the browser's quota ran out, the file can't be written.
+ * Trying again right away can't help, and each try costs network and power.
+ */
+export function isStorageFailure(error: unknown): boolean {
+  if (!(error instanceof Error)) return false;
+  if (error.name === 'QuotaExceededError') return true;
+  return /SQLITE_FULL|SQLITE_IOERR|SQLITE_CANTOPEN|disk is full|disk I\/O error|QuotaExceeded|No space left/i.test(error.message);
+}
+
 export interface Migration {
   /** Unique, ascending. Ranges per area are listed in lib/store/area.ts. */
   id: number;
diff --git a/lib/store/worker/host.ts b/lib/store/worker/host.ts
index 636c231c9..3a2a7036f 100644
--- a/lib/store/worker/host.ts
+++ b/lib/store/worker/host.ts
@@ -9,6 +9,11 @@ import { FetchTransport, type StoreSession } from '../engine/transport';
 import type { StorageAdapter } from '../storage';
 import type { OpenAccountParams, StoreRpc, StoreStatus } from './protocol';
 
+/** Files in the pool that belong to no key. A name that isn't a store file's is left alone. */
+export function storeFilesToPrune(files: readonly string[], keep: readonly string[]): string[] {
+  return files.filter((file) => /^\/a[0-9a-f]+\.db$/.test(file) && !keep.includes(file));
+}
+
 export interface HostStorage {
   open(file: string, keyHex: string): Promise<StorageAdapter>;
   remove(file: string): boolean;
@@ -30,6 +35,13 @@ export interface StoreHostOptions {
   needAuth(account: string): void;
 }
 
+/** The owner hasn't opened this account yet. The caller may try again shortly. */
+function accountClosed(): Error {
+  const error = new Error('The local store is not open for this account');
+  error.name = 'StoreAccountClosedError';
+  return error;
+}
+
 export class StoreHost {
   private readonly accounts = new Map<string, OpenAccount>();
   private online = true;
@@ -37,17 +49,18 @@ export class StoreHost {
 
   constructor(private readonly options: StoreHostOptions) {}
 
-  async openAccount(params: OpenAccountParams): Promise<void> {
+  async openAccount(params: OpenAccountParams): Promise<{ created: boolean }> {
     const existing = this.accounts.get(params.account);
     if (existing) {
       if (params.session) this.setSession(params.account, params.session);
       this.setAuth(params.account, params.auth);
       existing.engine.setScope(params.scope);
-      existing.engine.setInvertedKeywordSort(params.invertedKeywordSort);
+      if (params.invertedKeywordSort !== null) existing.engine.setInvertedKeywordSort(params.invertedKeywordSort);
       void existing.engine.requestSync();
-      return;
+      return { created: false };
     }
     const db = await this.options.storage.open(params.file, params.keyHex);
+    const created = !db.get("SELECT 1 AS yes FROM sqlite_master WHERE name = 'schema_migration'");
     const session = params.session ?? AccountEngine.storedSession(db);
     if (!session) {
       db.close();
@@ -69,7 +82,7 @@ export class StoreHost {
       transport,
       areas: this.options.areas,
       scope: params.scope,
-      invertedKeywordSort: params.invertedKeywordSort,
+      invertedKeywordSort: params.invertedKeywordSort ?? undefined,
       emit: (event) => {
         if (event.type === 'synced') this.synced.set(event.account, event.at);
         this.options.emit(event);
@@ -78,6 +91,7 @@ export class StoreHost {
     account.engine.setOnline(this.online);
     this.accounts.set(params.account, account);
     void account.engine.requestSync();
+    return { created };
   }
 
   setAuth(account: string, auth: string | null): void {
@@ -101,6 +115,10 @@ export class StoreHost {
     void open.engine.requestSync();
   }
 
+  setInvertedKeywordSort(account: string, inverted: boolean): void {
+    this.accounts.get(account)?.engine.setInvertedKeywordSort(inverted);
+  }
+
   async closeAccount(account: string): Promise<void> {
     const open = this.accounts.get(account);
     if (!open) return;
@@ -126,7 +144,7 @@ export class StoreHost {
       case 'answer': {
         const { account, calls } = params as Parameters<StoreRpc['answer']>[0];
         const open = this.accounts.get(account);
-        if (!open) throw new Error('The local store is not open for this account');
+        if (!open) throw accountClosed();
         return open.engine.answer(calls);
       }
       case 'sync': {
@@ -152,9 +170,13 @@ export class StoreHost {
       case 'area': {
         const { account, name, params: callParams } = params as Parameters<StoreRpc['area']>[0];
         const open = this.accounts.get(account);
-        if (!open) throw new Error('The local store is not open for this account');
+        if (!open) throw accountClosed();
         return open.engine.areaCall(name, callParams);
       }
+      case 'removeAccount': {
+        const { account, file } = params as Parameters<StoreRpc['removeAccount']>[0];
+        return this.removeAccount(account, file);
+      }
       default:
         throw new Error(`Unknown store call ${String(method)}`);
     }
diff --git a/lib/store/worker/protocol.ts b/lib/store/worker/protocol.ts
index ed5a08f96..5fefc7e0f 100644
--- a/lib/store/worker/protocol.ts
+++ b/lib/store/worker/protocol.ts
@@ -5,6 +5,8 @@ import type { JmapResponse, MethodCall, StoreSession } from '../engine/transport
 
 export const RPC_CHANNEL = 'bulwark-store-rpc';
 export const OWNER_LOCK = 'bulwark-store-owner';
+/** The OPFS folder of the database pool. The page can delete it without loading wasm. */
+export const POOL_DIRECTORY = '.bulwark-store';
 
 export interface OpenAccountParams {
   account: string;
@@ -14,7 +16,8 @@ export interface OpenAccountParams {
   keyHex: string;
   session: StoreSession | null;
   scope: StoreScope;
-  invertedKeywordSort: boolean;
+  /** Null when this tab's client hasn't probed it: the stored answer stays. */
+  invertedKeywordSort: boolean | null;
   /** The page's current Authorization header. */
   auth: string | null;
 }
@@ -28,6 +31,8 @@ export interface StoreRpc {
   status(params: { account: string }): StoreStatus | null;
   /** A non-JMAP call into an area of the store. */
   area(params: { account: string; name: string; params: unknown }): unknown;
+  /** Closes an account and deletes its file. The name holds no account data. */
+  removeAccount(params: { account: string; file: string }): boolean;
 }
 
 export interface StoreStatus {
@@ -52,21 +57,27 @@ export type RpcReply = {
   to: string;
   result?: unknown;
   error?: string;
+  errorName?: string;
 };
 
 export type ChannelMessage =
   | RpcRequest
   | RpcReply
   | { kind: 'event'; event: StoreEvent }
-  | { kind: 'owner-changed'; owner: string | null };
+  | { kind: 'owner-changed'; owner: string | null }
+  // A tab started after the owner announced itself asks.
+  | { kind: 'who-owns' }
+  // Everyone signed out: every tab stops its worker, so the pool can go.
+  | { kind: 'shutdown' };
 
 /** From this tab's page to its own worker, never on the channel. */
 export type PageToWorker =
   | { kind: 'init'; clientId: string; moduleUrl: string }
   | { kind: 'open'; id: string; params: OpenAccountParams }
   | { kind: 'close-account'; id: string; account: string }
-  | { kind: 'remove-account'; id: string; account: string; file: string }
+  | { kind: 'prune-files'; id: string; keep: string[] }
   | { kind: 'set-auth'; account: string; auth: string | null }
+  | { kind: 'set-inverted'; account: string; inverted: boolean }
   | { kind: 'set-session'; account: string; session: StoreSession }
   | { kind: 'set-scope'; account: string; scope: StoreScope }
   | { kind: 'release'; id: string };
diff --git a/lib/store/worker/worker.ts b/lib/store/worker/worker.ts
index 003340c82..a41ee1405 100644
--- a/lib/store/worker/worker.ts
+++ b/lib/store/worker/worker.ts
@@ -9,7 +9,7 @@
 import { WasmStorage } from '../adapters/wasm';
 import { STORE_AREAS } from '../areas';
 import { RPC_CHANNEL, OWNER_LOCK, type ChannelMessage, type PageToWorker, type WorkerToPage } from './protocol';
-import { StoreHost } from './host';
+import { StoreHost, storeFilesToPrune } from './host';
 
 const scope = self as unknown as {
   postMessage(message: WorkerToPage): void;
@@ -56,6 +56,10 @@ async function becomeOwner(): Promise<void> {
   channel = new BroadcastChannel(RPC_CHANNEL);
   channel.onmessage = async (event: MessageEvent<ChannelMessage>) => {
     const message = event.data;
+    if (message.kind === 'who-owns') {
+      channel?.postMessage({ kind: 'owner-changed', owner: clientId } satisfies ChannelMessage);
+      return;
+    }
     if (message.kind !== 'rpc') return;
     try {
       const result = await requireHost().call(message.method, message.params);
@@ -66,6 +70,7 @@ async function becomeOwner(): Promise<void> {
         id: message.id,
         to: message.from,
         error: error instanceof Error ? error.message : String(error),
+        errorName: error instanceof Error ? error.name : undefined,
       } satisfies ChannelMessage);
     }
   };
@@ -105,7 +110,14 @@ scope.addEventListener('message', async (event) => {
       break;
     case 'open':
       try {
-        await requireHost().openAccount(message.params);
+        reply(message.id, await requireHost().openAccount(message.params));
+      } catch (error) {
+        replyError(message.id, error);
+      }
+      break;
+    case 'prune-files':
+      try {
+        for (const file of storeFilesToPrune(storage?.files() ?? [], message.keep)) storage?.remove(file);
         reply(message.id);
       } catch (error) {
         replyError(message.id, error);
@@ -119,13 +131,6 @@ scope.addEventListener('message', async (event) => {
         replyError(message.id, error);
       }
       break;
-    case 'remove-account':
-      try {
-        reply(message.id, await requireHost().removeAccount(message.account, message.file));
-      } catch (error) {
-        replyError(message.id, error);
-      }
-      break;
     case 'set-auth':
       host?.setAuth(message.account, message.auth);
       break;
@@ -135,6 +140,9 @@ scope.addEventListener('message', async (event) => {
     case 'set-scope':
       host?.setScope(message.account, message.scope);
       break;
+    case 'set-inverted':
+      host?.setInvertedKeywordSort(message.account, message.inverted);
+      break;
     case 'release':
       try {
         await release();
diff --git a/locales/ar/common.json b/locales/ar/common.json
index 91db0f8ea..4ddf9d120 100644
--- a/locales/ar/common.json
+++ b/locales/ar/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "تعذّر العثور على مجلد المسودات."
     }
   },
+  "offlineConflicts": {
+    "title": "تغييرات لم تُطبَّق",
+    "description": "أجريت هذه التغييرات دون اتصال. لم تُطبَّق وتبقى الرسالة كما هي على الخادم.",
+    "changed": "تم التغيير على جهاز آخر، لذا لم يُطبَّق تغييرك",
+    "changed_delete": "تم التغيير على جهاز آخر، لذا لم تُحذف",
+    "gone": "لم تعد على الخادم، لذا لم يُطبَّق تغييرك",
+    "refused": "رفض الخادم هذا التغيير: {reason}",
+    "dismiss": "إغلاق",
+    "dismiss_label": "إغلاق الملاحظة حول {subject}",
+    "banner": "تغييرات لم تُطبَّق: {count}",
+    "toast": "تغييرات أُجريت دون اتصال ولم تُطبَّق: {count}. يوضح صندوق الصادر أيها.",
+    "storage_failed": "لم تعد هناك مساحة على هذا الجهاز للبريد دون اتصال. أفرغ مساحة أو احتفظ بأقل من الإعدادات.",
+    "signout_changes_title": "هل تريد تسجيل الخروج مع تغييرات غير محفوظة؟",
+    "signout_changes": "تغييرات لم تصل إلى الخادم بعد: {count}. يؤدي تسجيل الخروج إلى حذفها.",
+    "store_unavailable": "لا يمكن فتح البريد دون اتصال على هذا الجهاز الآن. يبقى البريد غير المرسل هنا ويواصل التطبيق المحاولة.",
+    "store_reset": "تعذرت قراءة البريد دون اتصال على هذا الجهاز، لذا يجري تنزيله من جديد. ما لم يُرسل قد فُقد.",
+    "legacy_stranded": "لا يمكن لهذا المتصفح فتح البريد غير المرسل المحفوظ من إصدار سابق. قد يعيده تحديث المتصفح.",
+    "store_private": "لا يمكن للنوافذ الخاصة الاحتفاظ بالبريد للاستخدام دون اتصال.",
+    "server_not_answering": "خادم البريد لا يستجيب. حاول مرة أخرى بعد قليل."
+  },
   "deep_link": {
     "message_not_found": "لم تعد هذه الرسالة متاحة.",
     "thread_not_found": "لم تعد هذه المحادثة متاحة.",
diff --git a/locales/ca/common.json b/locales/ca/common.json
index d2e062a69..d878d3899 100644
--- a/locales/ca/common.json
+++ b/locales/ca/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "No s'ha trobat la carpeta Esborranys."
     }
   },
+  "offlineConflicts": {
+    "title": "Canvis no aplicats",
+    "description": "Heu fet aquests canvis sense connexió. No s'han aplicat i el missatge queda tal com és al servidor.",
+    "changed": "Canviat en un altre dispositiu, el vostre canvi no s'ha aplicat",
+    "changed_delete": "Canviat en un altre dispositiu, no s'ha suprimit",
+    "gone": "Ja no és al servidor, el vostre canvi no s'ha aplicat",
+    "refused": "El servidor ha rebutjat aquest canvi: {reason}",
+    "dismiss": "Descarta",
+    "dismiss_label": "Descarta la nota sobre {subject}",
+    "banner": "Canvis no aplicats: {count}",
+    "toast": "Canvis fets sense connexió que no s'han aplicat: {count}. La safata de sortida indica quins.",
+    "storage_failed": "Aquest dispositiu no té més espai per al correu sense connexió. Allibereu espai o conserveu-ne menys a la configuració.",
+    "signout_changes_title": "Voleu tancar la sessió amb canvis sense desar?",
+    "signout_changes": "Canvis que encara no són al servidor: {count}. En tancar la sessió s'eliminen.",
+    "store_unavailable": "El correu sense connexió d'aquest dispositiu no es pot obrir ara. El correu no enviat es queda aquí i l'aplicació ho continua provant.",
+    "store_reset": "No s'ha pogut llegir el correu sense connexió d'aquest dispositiu, així que es torna a baixar. El que no s'havia enviat s'ha perdut.",
+    "legacy_stranded": "Aquest navegador no pot obrir el correu no enviat desat per una versió anterior. Actualitzar el navegador el pot recuperar.",
+    "store_private": "Les finestres privades no poden desar correu per fer-lo servir sense connexió.",
+    "server_not_answering": "El servidor de correu no respon. Torneu-ho a provar d'aquí a un moment."
+  },
   "deep_link": {
     "message_not_found": "Aquest missatge ja no està disponible.",
     "thread_not_found": "Aquesta conversa ja no està disponible.",
diff --git a/locales/cs/common.json b/locales/cs/common.json
index 6b1e41754..a07558c21 100644
--- a/locales/cs/common.json
+++ b/locales/cs/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Složka Koncepty nebyla nalezena."
     }
   },
+  "offlineConflicts": {
+    "title": "Nepoužité změny",
+    "description": "Tyto změny jste provedli offline. Nebyly použity a zpráva zůstává tak, jak je na serveru.",
+    "changed": "Změněno na jiném zařízení, vaše změna nebyla použita",
+    "changed_delete": "Změněno na jiném zařízení, zpráva nebyla smazána",
+    "gone": "Už není na serveru, vaše změna nebyla použita",
+    "refused": "Server tuto změnu odmítl: {reason}",
+    "dismiss": "Zavřít",
+    "dismiss_label": "Zavřít poznámku o {subject}",
+    "banner": "Nepoužité změny: {count}",
+    "toast": "Nepoužité změny provedené offline: {count}. Které to jsou, ukazuje pošta k odeslání.",
+    "storage_failed": "Na tomto zařízení už není místo pro poštu offline. Uvolněte místo nebo v nastavení ponechte méně.",
+    "signout_changes_title": "Odhlásit se s neuloženými změnami?",
+    "signout_changes": "Změny, které ještě nejsou na serveru: {count}. Odhlášení je smaže.",
+    "store_unavailable": "Poštu offline na tomto zařízení teď nelze otevřít. Neodeslaná pošta tu zůstává a aplikace to dál zkouší.",
+    "store_reset": "Poštu offline na tomto zařízení se nepodařilo přečíst, proto se stahuje znovu. Co nebylo odesláno, je pryč.",
+    "legacy_stranded": "Tento prohlížeč neotevře neodeslanou poštu uloženou starší verzí. Aktualizace prohlížeče ji může vrátit.",
+    "store_private": "Soukromá okna nemohou uchovávat poštu pro použití offline.",
+    "server_not_answering": "Poštovní server neodpovídá. Zkuste to za chvíli znovu."
+  },
   "deep_link": {
     "message_not_found": "Tato zpráva už není dostupná.",
     "thread_not_found": "Tato konverzace už není dostupná.",
diff --git a/locales/da/common.json b/locales/da/common.json
index 61d6a1412..368d343bf 100644
--- a/locales/da/common.json
+++ b/locales/da/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Mappen Kladder blev ikke fundet."
     }
   },
+  "offlineConflicts": {
+    "title": "Ændringer, der ikke blev gennemført",
+    "description": "Du lavede disse ændringer offline. De blev ikke gennemført, og beskeden forbliver, som den er på serveren.",
+    "changed": "Ændret på en anden enhed, din ændring blev ikke gennemført",
+    "changed_delete": "Ændret på en anden enhed, den blev ikke slettet",
+    "gone": "Findes ikke længere på serveren, din ændring blev ikke gennemført",
+    "refused": "Serveren afviste denne ændring: {reason}",
+    "dismiss": "Afvis",
+    "dismiss_label": "Afvis noten om {subject}",
+    "banner": "Ændringer, der ikke blev gennemført: {count}",
+    "toast": "Ændringer lavet offline, der ikke blev gennemført: {count}. Udbakken viser hvilke.",
+    "storage_failed": "Denne enhed har ikke mere plads til offlinemail. Frigør plads, eller behold mindre i indstillingerne.",
+    "signout_changes_title": "Log ud med ændringer, der ikke er gemt?",
+    "signout_changes": "Ændringer, der endnu ikke er på serveren: {count}. Når du logger ud, slettes de.",
+    "store_unavailable": "Offlinemail på denne enhed kan ikke åbnes lige nu. Ikke-sendt mail bliver her, og appen bliver ved med at prøve.",
+    "store_reset": "Offlinemail på denne enhed kunne ikke læses og hentes derfor igen. Det, der ikke var sendt, er væk.",
+    "legacy_stranded": "Denne browser kan ikke åbne ikke-sendt mail fra en tidligere version. En opdatering af browseren kan hente den tilbage.",
+    "store_private": "Private vinduer kan ikke gemme mail til brug offline.",
+    "server_not_answering": "Mailserveren svarer ikke. Prøv igen om lidt."
+  },
   "deep_link": {
     "message_not_found": "Denne besked er ikke længere tilgængelig.",
     "thread_not_found": "Denne samtale er ikke længere tilgængelig.",
diff --git a/locales/de/common.json b/locales/de/common.json
index eb1ec9a29..a815148d2 100644
--- a/locales/de/common.json
+++ b/locales/de/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Ihr Ordner „Entwürfe“ wurde nicht gefunden."
     }
   },
+  "offlineConflicts": {
+    "title": "Nicht übernommene Änderungen",
+    "description": "Sie haben diese Änderungen offline gemacht. Sie wurden nicht übernommen, die Nachricht bleibt wie auf dem Server.",
+    "changed": "Auf einem anderen Gerät geändert, Ihre Änderung wurde nicht übernommen",
+    "changed_delete": "Auf einem anderen Gerät geändert, die Nachricht wurde nicht gelöscht",
+    "gone": "Nicht mehr auf dem Server, Ihre Änderung wurde nicht übernommen",
+    "refused": "Der Server hat diese Änderung abgelehnt: {reason}",
+    "dismiss": "Ausblenden",
+    "dismiss_label": "Hinweis zu {subject} ausblenden",
+    "banner": "Nicht übernommene Änderungen: {count}",
+    "toast": "Offline gemachte Änderungen wurden nicht übernommen: {count}. Welche, steht im Postausgang.",
+    "storage_failed": "Auf diesem Gerät ist kein Platz mehr für Offline-E-Mails. Geben Sie Speicher frei oder behalten Sie in den Einstellungen weniger.",
+    "signout_changes_title": "Mit nicht gespeicherten Änderungen abmelden?",
+    "signout_changes": "Änderungen, die noch nicht auf dem Server sind: {count}. Beim Abmelden werden sie gelöscht.",
+    "store_unavailable": "Die Offline-E-Mails auf diesem Gerät lassen sich gerade nicht öffnen. Nicht gesendete E-Mails bleiben hier, und die App versucht es weiter.",
+    "store_reset": "Die Offline-E-Mails auf diesem Gerät konnten nicht gelesen werden und werden neu heruntergeladen. Was hier noch nicht gesendet war, ist verloren.",
+    "legacy_stranded": "Dieser Browser kann nicht gesendete E-Mails einer früheren Version nicht öffnen. Ein Browser-Update kann sie zurückholen.",
+    "store_private": "Private Fenster können keine E-Mails für die Offline-Nutzung behalten.",
+    "server_not_answering": "Der Mailserver antwortet nicht. Versuchen Sie es gleich noch einmal."
+  },
   "deep_link": {
     "message_not_found": "Diese Nachricht ist nicht mehr verfügbar.",
     "thread_not_found": "Diese Unterhaltung ist nicht mehr verfügbar.",
diff --git a/locales/en/common.json b/locales/en/common.json
index 0af0e143f..177ba38b4 100644
--- a/locales/en/common.json
+++ b/locales/en/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Your Drafts folder couldn't be found."
     }
   },
+  "offlineConflicts": {
+    "title": "Changes that didn't go through",
+    "description": "You made these changes offline. They weren't applied, and the message stays as it is on the server.",
+    "changed": "Changed on another device, so your change wasn't applied",
+    "changed_delete": "Changed on another device, so it wasn't deleted",
+    "gone": "No longer on the server, so your change wasn't applied",
+    "refused": "The server refused this change: {reason}",
+    "dismiss": "Dismiss",
+    "dismiss_label": "Dismiss the note about {subject}",
+    "banner": "Changes that didn't go through: {count}",
+    "toast": "Changes you made offline weren't applied: {count}. The outbox shows which.",
+    "storage_failed": "This device has no room left for offline mail. Free up space, or keep less in Settings.",
+    "signout_changes_title": "Sign out with unsaved changes?",
+    "signout_changes": "Changes not yet on the server: {count}. Signing out deletes them.",
+    "store_unavailable": "Offline mail on this device can't be opened right now. Unsent mail stays here, and the app keeps trying.",
+    "store_reset": "Offline mail on this device couldn't be read, so it's being downloaded again. Anything unsent that was kept here is gone.",
+    "legacy_stranded": "This browser can't open unsent mail kept by an earlier version. Updating the browser may bring it back.",
+    "store_private": "Private windows can't keep mail for offline use.",
+    "server_not_answering": "The mail server isn't answering. Try again in a moment."
+  },
   "deep_link": {
     "message_not_found": "This message is no longer available.",
     "thread_not_found": "This conversation is no longer available.",
diff --git a/locales/es/common.json b/locales/es/common.json
index 83aeead77..3061c636f 100644
--- a/locales/es/common.json
+++ b/locales/es/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "No se encontró tu carpeta Borradores."
     }
   },
+  "offlineConflicts": {
+    "title": "Cambios no aplicados",
+    "description": "Hiciste estos cambios sin conexión. No se aplicaron y el mensaje queda como está en el servidor.",
+    "changed": "Cambiado en otro dispositivo, tu cambio no se aplicó",
+    "changed_delete": "Cambiado en otro dispositivo, no se eliminó",
+    "gone": "Ya no está en el servidor, tu cambio no se aplicó",
+    "refused": "El servidor rechazó este cambio: {reason}",
+    "dismiss": "Descartar",
+    "dismiss_label": "Descartar la nota sobre {subject}",
+    "banner": "Cambios no aplicados: {count}",
+    "toast": "Cambios hechos sin conexión que no se aplicaron: {count}. La bandeja de salida indica cuáles.",
+    "storage_failed": "Este dispositivo no tiene espacio para el correo sin conexión. Libera espacio o guarda menos en Ajustes.",
+    "signout_changes_title": "¿Cerrar sesión con cambios sin guardar?",
+    "signout_changes": "Cambios que aún no están en el servidor: {count}. Al cerrar sesión se eliminan.",
+    "store_unavailable": "El correo sin conexión de este dispositivo no se puede abrir ahora. El correo sin enviar sigue aquí y la aplicación sigue intentándolo.",
+    "store_reset": "No se pudo leer el correo sin conexión de este dispositivo, así que se está descargando de nuevo. Lo que estaba sin enviar se ha perdido.",
+    "legacy_stranded": "Este navegador no puede abrir el correo sin enviar guardado por una versión anterior. Actualizar el navegador puede recuperarlo.",
+    "store_private": "Las ventanas privadas no pueden guardar correo para usarlo sin conexión.",
+    "server_not_answering": "El servidor de correo no responde. Inténtalo de nuevo en un momento."
+  },
   "deep_link": {
     "message_not_found": "Este mensaje ya no está disponible.",
     "thread_not_found": "Esta conversación ya no está disponible.",
diff --git a/locales/et/common.json b/locales/et/common.json
index 788fb5171..f26b001c5 100644
--- a/locales/et/common.json
+++ b/locales/et/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Kausta Mustandid ei leitud."
     }
   },
+  "offlineConflicts": {
+    "title": "Rakendamata muudatused",
+    "description": "Tegite need muudatused võrguühenduseta. Neid ei rakendatud ja kiri jääb selliseks, nagu see on serveris.",
+    "changed": "Muudetud teises seadmes, teie muudatust ei rakendatud",
+    "changed_delete": "Muudetud teises seadmes, seda ei kustutatud",
+    "gone": "Pole enam serveris, teie muudatust ei rakendatud",
+    "refused": "Server keeldus sellest muudatusest: {reason}",
+    "dismiss": "Sulge",
+    "dismiss_label": "Sulge märkus teemal {subject}",
+    "banner": "Rakendamata muudatused: {count}",
+    "toast": "Võrguühenduseta tehtud rakendamata muudatused: {count}. Väljundkaust näitab, millised.",
+    "storage_failed": "Selles seadmes pole enam ruumi võrguühenduseta kirjade jaoks. Vabastage ruumi või hoidke seadetes vähem.",
+    "signout_changes_title": "Kas logida välja salvestamata muudatustega?",
+    "signout_changes": "Muudatused, mida serveris veel pole: {count}. Väljalogimine kustutab need.",
+    "store_unavailable": "Selle seadme võrguühenduseta kirju ei saa praegu avada. Saatmata kirjad jäävad siia ja rakendus proovib edasi.",
+    "store_reset": "Selle seadme võrguühenduseta kirju ei õnnestunud lugeda, seega laaditakse need uuesti alla. Mis oli saatmata, on kadunud.",
+    "legacy_stranded": "See brauser ei saa avada varasema versiooni hoitud saatmata kirju. Brauseri uuendamine võib need tagasi tuua.",
+    "store_private": "Privaatsed aknad ei saa kirju võrguühenduseta kasutamiseks hoida.",
+    "server_not_answering": "Meiliserver ei vasta. Proovige kohe uuesti."
+  },
   "deep_link": {
     "message_not_found": "See sõnum ei ole enam saadaval.",
     "thread_not_found": "See vestlus ei ole enam saadaval.",
diff --git a/locales/fa/common.json b/locales/fa/common.json
index 9eadf3199..8e39bcc95 100644
--- a/locales/fa/common.json
+++ b/locales/fa/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "پوشهٔ پیش‌نویس‌ها پیدا نشد."
     }
   },
+  "offlineConflicts": {
+    "title": "تغییراتی که اعمال نشدند",
+    "description": "این تغییرات را در حالت آفلاین انجام دادید. اعمال نشدند و پیام همان‌طور که روی سرور است می‌ماند.",
+    "changed": "در دستگاه دیگری تغییر کرده، پس تغییر شما اعمال نشد",
+    "changed_delete": "در دستگاه دیگری تغییر کرده، پس حذف نشد",
+    "gone": "دیگر روی سرور نیست، پس تغییر شما اعمال نشد",
+    "refused": "سرور این تغییر را رد کرد: {reason}",
+    "dismiss": "بستن",
+    "dismiss_label": "بستن یادداشت درباره {subject}",
+    "banner": "تغییراتی که اعمال نشدند: {count}",
+    "toast": "تغییرات آفلاین که اعمال نشدند: {count}. صندوق خروجی نشان می‌دهد کدام‌ها.",
+    "storage_failed": "در این دستگاه جایی برای ایمیل آفلاین نمانده است. فضا را آزاد کنید یا در تنظیمات مقدار کمتری نگه دارید.",
+    "signout_changes_title": "با تغییرات ذخیره‌نشده از حساب خارج می‌شوید؟",
+    "signout_changes": "تغییراتی که هنوز روی سرور نیستند: {count}. خروج از حساب آن‌ها را حذف می‌کند.",
+    "store_unavailable": "ایمیل آفلاین این دستگاه اکنون باز نمی‌شود. ایمیل ارسال‌نشده اینجا می‌ماند و برنامه همچنان تلاش می‌کند.",
+    "store_reset": "ایمیل آفلاین این دستگاه خوانده نشد و دوباره بارگیری می‌شود. آنچه ارسال نشده بود از بین رفته است.",
+    "legacy_stranded": "این مرورگر نمی‌تواند ایمیل ارسال‌نشدهٔ نگه‌داشته‌شده از نسخهٔ قبلی را باز کند. به‌روزرسانی مرورگر ممکن است آن را برگرداند.",
+    "store_private": "پنجره‌های خصوصی نمی‌توانند ایمیل را برای استفادهٔ آفلاین نگه دارند.",
+    "server_not_answering": "سرور ایمیل پاسخ نمی‌دهد. کمی بعد دوباره امتحان کنید."
+  },
   "deep_link": {
     "message_not_found": "این پیام دیگر در دسترس نیست.",
     "thread_not_found": "این گفتگو دیگر در دسترس نیست.",
diff --git a/locales/fr/common.json b/locales/fr/common.json
index a44af9dbe..a7def2938 100644
--- a/locales/fr/common.json
+++ b/locales/fr/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Votre dossier Brouillons est introuvable."
     }
   },
+  "offlineConflicts": {
+    "title": "Modifications non appliquées",
+    "description": "Vous avez fait ces modifications hors ligne. Elles n'ont pas été appliquées et le message reste tel qu'il est sur le serveur.",
+    "changed": "Modifié sur un autre appareil, votre modification n'a pas été appliquée",
+    "changed_delete": "Modifié sur un autre appareil, le message n'a pas été supprimé",
+    "gone": "N'est plus sur le serveur, votre modification n'a pas été appliquée",
+    "refused": "Le serveur a refusé cette modification : {reason}",
+    "dismiss": "Ignorer",
+    "dismiss_label": "Ignorer la note sur {subject}",
+    "banner": "Modifications non appliquées : {count}",
+    "toast": "Des modifications faites hors ligne n'ont pas été appliquées : {count}. La boîte d'envoi indique lesquelles.",
+    "storage_failed": "Cet appareil n'a plus de place pour le courrier hors ligne. Libérez de l'espace ou conservez moins dans les paramètres.",
+    "signout_changes_title": "Se déconnecter avec des modifications non enregistrées ?",
+    "signout_changes": "Modifications pas encore sur le serveur : {count}. La déconnexion les supprime.",
+    "store_unavailable": "Le courrier hors ligne de cet appareil ne peut pas être ouvert pour le moment. Les messages non envoyés restent ici et l'application continue d'essayer.",
+    "store_reset": "Le courrier hors ligne de cet appareil n'a pas pu être lu : il est de nouveau téléchargé. Ce qui n'était pas envoyé est perdu.",
+    "legacy_stranded": "Ce navigateur ne peut pas ouvrir les messages non envoyés conservés par une version précédente. Le mettre à jour peut les récupérer.",
+    "store_private": "Les fenêtres privées ne peuvent pas conserver le courrier pour une utilisation hors ligne.",
+    "server_not_answering": "Le serveur de messagerie ne répond pas. Réessayez dans un instant."
+  },
   "deep_link": {
     "message_not_found": "Ce message n'est plus disponible.",
     "thread_not_found": "Cette conversation n'est plus disponible.",
diff --git a/locales/he/common.json b/locales/he/common.json
index 17580b9a8..ce9459e20 100644
--- a/locales/he/common.json
+++ b/locales/he/common.json
@@ -5744,6 +5744,26 @@
       "no_drafts_mailbox": "התיקייה 'טיוטות' לא נמצאה."
     }
   },
+  "offlineConflicts": {
+    "title": "שינויים שלא הוחלו",
+    "description": "ביצעת את השינויים האלה במצב לא מקוון. הם לא הוחלו וההודעה נשארת כפי שהיא בשרת.",
+    "changed": "שונה במכשיר אחר, ולכן השינוי שלך לא הוחל",
+    "changed_delete": "שונה במכשיר אחר, ולכן לא נמחק",
+    "gone": "כבר לא בשרת, ולכן השינוי שלך לא הוחל",
+    "refused": "השרת דחה את השינוי הזה: {reason}",
+    "dismiss": "סגירה",
+    "dismiss_label": "סגירת ההערה על {subject}",
+    "banner": "שינויים שלא הוחלו: {count}",
+    "toast": "שינויים במצב לא מקוון שלא הוחלו: {count}. דואר יוצא מראה אילו.",
+    "storage_failed": "אין יותר מקום במכשיר הזה לדואר לא מקוון. יש לפנות מקום או לשמור פחות בהגדרות.",
+    "signout_changes_title": "לצאת מהחשבון עם שינויים שלא נשמרו?",
+    "signout_changes": "שינויים שעדיין לא בשרת: {count}. היציאה מהחשבון מוחקת אותם.",
+    "store_unavailable": "אי אפשר לפתוח כרגע את הדואר הלא מקוון במכשיר הזה. דואר שלא נשלח נשאר כאן, והאפליקציה ממשיכה לנסות.",
+    "store_reset": "לא ניתן היה לקרוא את הדואר הלא מקוון במכשיר הזה, ולכן הוא יורד מחדש. מה שלא נשלח אבד.",
+    "legacy_stranded": "הדפדפן הזה לא יכול לפתוח דואר שלא נשלח שנשמר בגרסה קודמת. עדכון הדפדפן עשוי להחזיר אותו.",
+    "store_private": "חלונות פרטיים לא יכולים לשמור דואר לשימוש לא מקוון.",
+    "server_not_answering": "שרת הדואר לא עונה. אפשר לנסות שוב בעוד רגע."
+  },
   "deep_link": {
     "message_not_found": "הודעה זו אינה זמינה עוד.",
     "thread_not_found": "שיחה זו אינה זמינה עוד.",
diff --git a/locales/hu/common.json b/locales/hu/common.json
index 474772591..f82879100 100644
--- a/locales/hu/common.json
+++ b/locales/hu/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "A Piszkozatok mappa nem található."
     }
   },
+  "offlineConflicts": {
+    "title": "Nem alkalmazott módosítások",
+    "description": "Ezeket a módosításokat offline végezte. Nem lettek alkalmazva, és az üzenet úgy marad, ahogy a szerveren van.",
+    "changed": "Másik eszközön módosult, az Ön módosítása nem lett alkalmazva",
+    "changed_delete": "Másik eszközön módosult, nem lett törölve",
+    "gone": "Már nincs a szerveren, az Ön módosítása nem lett alkalmazva",
+    "refused": "A szerver elutasította ezt a módosítást: {reason}",
+    "dismiss": "Bezárás",
+    "dismiss_label": "A(z) {subject} megjegyzésének bezárása",
+    "banner": "Nem alkalmazott módosítások: {count}",
+    "toast": "Offline végzett, nem alkalmazott módosítások: {count}. A postázandók mappa mutatja, melyek.",
+    "storage_failed": "Ezen az eszközön nincs több hely az offline leveleknek. Szabadítson fel helyet, vagy tartson meg kevesebbet a beállításokban.",
+    "signout_changes_title": "Kijelentkezik a nem mentett módosításokkal?",
+    "signout_changes": "Még nem a szerveren lévő módosítások: {count}. A kijelentkezés törli őket.",
+    "store_unavailable": "Az eszközön lévő offline levelek most nem nyithatók meg. Az el nem küldött levelek itt maradnak, az alkalmazás pedig tovább próbálkozik.",
+    "store_reset": "Az eszközön lévő offline leveleket nem sikerült beolvasni, ezért újra letöltődnek. Ami nem lett elküldve, elveszett.",
+    "legacy_stranded": "Ez a böngésző nem tudja megnyitni egy korábbi verzió által megőrzött, el nem küldött leveleket. A böngésző frissítése visszahozhatja őket.",
+    "store_private": "A privát ablakok nem tudnak leveleket megőrizni offline használatra.",
+    "server_not_answering": "A levelezőszerver nem válaszol. Próbálja újra egy pillanat múlva."
+  },
   "deep_link": {
     "message_not_found": "Ez az üzenet már nem érhető el.",
     "thread_not_found": "Ez a beszélgetés már nem érhető el.",
diff --git a/locales/it/common.json b/locales/it/common.json
index 8cc39c364..2b4c6afbe 100644
--- a/locales/it/common.json
+++ b/locales/it/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Impossibile trovare la cartella Bozze."
     }
   },
+  "offlineConflicts": {
+    "title": "Modifiche non applicate",
+    "description": "Hai fatto queste modifiche offline. Non sono state applicate e il messaggio resta com'è sul server.",
+    "changed": "Modificato su un altro dispositivo, la tua modifica non è stata applicata",
+    "changed_delete": "Modificato su un altro dispositivo, non è stato eliminato",
+    "gone": "Non è più sul server, la tua modifica non è stata applicata",
+    "refused": "Il server ha rifiutato questa modifica: {reason}",
+    "dismiss": "Ignora",
+    "dismiss_label": "Ignora la nota su {subject}",
+    "banner": "Modifiche non applicate: {count}",
+    "toast": "Modifiche fatte offline non applicate: {count}. La posta in uscita indica quali.",
+    "storage_failed": "Questo dispositivo non ha più spazio per la posta offline. Libera spazio o conservane meno nelle impostazioni.",
+    "signout_changes_title": "Uscire con modifiche non salvate?",
+    "signout_changes": "Modifiche non ancora sul server: {count}. Uscendo vengono eliminate.",
+    "store_unavailable": "La posta offline di questo dispositivo non si può aprire ora. La posta non inviata resta qui e l'app continua a provare.",
+    "store_reset": "Non è stato possibile leggere la posta offline di questo dispositivo, quindi viene scaricata di nuovo. Ciò che non era stato inviato è perso.",
+    "legacy_stranded": "Questo browser non può aprire la posta non inviata conservata da una versione precedente. Aggiornare il browser può recuperarla.",
+    "store_private": "Le finestre private non possono conservare la posta per l'uso offline.",
+    "server_not_answering": "Il server di posta non risponde. Riprova tra un momento."
+  },
   "deep_link": {
     "message_not_found": "Questo messaggio non è più disponibile.",
     "thread_not_found": "Questa conversazione non è più disponibile.",
diff --git a/locales/ja/common.json b/locales/ja/common.json
index e051ceb66..d0e59ab1e 100644
--- a/locales/ja/common.json
+++ b/locales/ja/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "下書きフォルダーが見つかりません。"
     }
   },
+  "offlineConflicts": {
+    "title": "適用されなかった変更",
+    "description": "これらの変更はオフライン中に行われました。適用されず、メッセージはサーバー上の状態のままです。",
+    "changed": "別のデバイスで変更されたため、変更は適用されませんでした",
+    "changed_delete": "別のデバイスで変更されたため、削除されませんでした",
+    "gone": "サーバーにもうないため、変更は適用されませんでした",
+    "refused": "サーバーがこの変更を拒否しました: {reason}",
+    "dismiss": "閉じる",
+    "dismiss_label": "{subject} のメモを閉じる",
+    "banner": "適用されなかった変更: {count}",
+    "toast": "オフライン中の変更で適用されなかったもの: {count} 件。送信トレイで確認できます。",
+    "storage_failed": "このデバイスにはオフラインメール用の空き容量がありません。空き容量を増やすか、設定で保存する量を減らしてください。",
+    "signout_changes_title": "未保存の変更があるままサインアウトしますか？",
+    "signout_changes": "サーバーにまだ届いていない変更: {count} 件。サインアウトすると削除されます。",
+    "store_unavailable": "このデバイスのオフラインメールを今は開けません。未送信のメールはここに残り、アプリは再試行を続けます。",
+    "store_reset": "このデバイスのオフラインメールを読み取れなかったため、再ダウンロードしています。未送信だったものは失われました。",
+    "legacy_stranded": "このブラウザーでは、以前のバージョンが保存した未送信メールを開けません。ブラウザーを更新すると戻る場合があります。",
+    "store_private": "プライベートウィンドウではオフライン用にメールを保存できません。",
+    "server_not_answering": "メールサーバーが応答していません。少ししてからもう一度お試しください。"
+  },
   "deep_link": {
     "message_not_found": "このメッセージは利用できなくなりました。",
     "thread_not_found": "この会話は利用できなくなりました。",
diff --git a/locales/ko/common.json b/locales/ko/common.json
index e7f7be907..b9e4bdd72 100644
--- a/locales/ko/common.json
+++ b/locales/ko/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "임시보관함 폴더를 찾을 수 없습니다."
     }
   },
+  "offlineConflicts": {
+    "title": "적용되지 않은 변경 사항",
+    "description": "오프라인 상태에서 변경한 내용입니다. 적용되지 않았으며 메시지는 서버에 있는 그대로 유지됩니다.",
+    "changed": "다른 기기에서 변경되어 변경 사항이 적용되지 않았습니다",
+    "changed_delete": "다른 기기에서 변경되어 삭제되지 않았습니다",
+    "gone": "서버에 더 이상 없어 변경 사항이 적용되지 않았습니다",
+    "refused": "서버가 이 변경을 거부했습니다: {reason}",
+    "dismiss": "닫기",
+    "dismiss_label": "{subject} 관련 메모 닫기",
+    "banner": "적용되지 않은 변경 사항: {count}",
+    "toast": "오프라인에서 변경했지만 적용되지 않은 항목: {count}개. 보낼 편지함에서 확인할 수 있습니다.",
+    "storage_failed": "이 기기에 오프라인 메일을 저장할 공간이 없습니다. 공간을 확보하거나 설정에서 보관량을 줄이세요.",
+    "signout_changes_title": "저장하지 않은 변경 사항이 있는 채로 로그아웃할까요?",
+    "signout_changes": "아직 서버에 없는 변경 사항: {count}개. 로그아웃하면 삭제됩니다.",
+    "store_unavailable": "지금은 이 기기의 오프라인 메일을 열 수 없습니다. 보내지 않은 메일은 여기에 남아 있고 앱이 계속 시도합니다.",
+    "store_reset": "이 기기의 오프라인 메일을 읽을 수 없어 다시 내려받는 중입니다. 보내지 않은 내용은 사라졌습니다.",
+    "legacy_stranded": "이 브라우저에서는 이전 버전이 보관한 보내지 않은 메일을 열 수 없습니다. 브라우저를 업데이트하면 되찾을 수 있습니다.",
+    "store_private": "개인 정보 보호 창에서는 오프라인용 메일을 보관할 수 없습니다.",
+    "server_not_answering": "메일 서버가 응답하지 않습니다. 잠시 후 다시 시도하세요."
+  },
   "deep_link": {
     "message_not_found": "이 메시지를 더 이상 사용할 수 없습니다.",
     "thread_not_found": "이 대화를 더 이상 사용할 수 없습니다.",
diff --git a/locales/lv/common.json b/locales/lv/common.json
index c07fe9c31..ed0da4a56 100644
--- a/locales/lv/common.json
+++ b/locales/lv/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Mape Melnraksti netika atrasta."
     }
   },
+  "offlineConflicts": {
+    "title": "Nepiemērotās izmaiņas",
+    "description": "Šīs izmaiņas veicāt bezsaistē. Tās netika piemērotas, un ziņojums paliek tāds, kāds tas ir serverī.",
+    "changed": "Mainīts citā ierīcē, jūsu izmaiņas netika piemērotas",
+    "changed_delete": "Mainīts citā ierīcē, tas netika izdzēsts",
+    "gone": "Vairs nav serverī, jūsu izmaiņas netika piemērotas",
+    "refused": "Serveris noraidīja šīs izmaiņas: {reason}",
+    "dismiss": "Aizvērt",
+    "dismiss_label": "Aizvērt piezīmi par {subject}",
+    "banner": "Nepiemērotās izmaiņas: {count}",
+    "toast": "Bezsaistē veiktās nepiemērotās izmaiņas: {count}. Izsūtne parāda, kuras.",
+    "storage_failed": "Šajā ierīcē vairs nav vietas bezsaistes pastam. Atbrīvojiet vietu vai iestatījumos glabājiet mazāk.",
+    "signout_changes_title": "Vai izrakstīties ar nesaglabātām izmaiņām?",
+    "signout_changes": "Izmaiņas, kas vēl nav serverī: {count}. Izrakstoties tās tiks izdzēstas.",
+    "store_unavailable": "Bezsaistes pastu šajā ierīcē pašlaik nevar atvērt. Nenosūtītais pasts paliek šeit, un lietotne turpina mēģināt.",
+    "store_reset": "Bezsaistes pastu šajā ierīcē neizdevās nolasīt, tāpēc tas tiek lejupielādēts vēlreiz. Tas, kas nebija nosūtīts, ir zudis.",
+    "legacy_stranded": "Šī pārlūkprogramma nevar atvērt iepriekšējās versijas saglabāto nenosūtīto pastu. Pārlūkprogrammas atjaunināšana var to atgūt.",
+    "store_private": "Privātie logi nevar glabāt pastu lietošanai bezsaistē.",
+    "server_not_answering": "Pasta serveris neatbild. Mēģiniet vēlreiz pēc brīža."
+  },
   "deep_link": {
     "message_not_found": "Šī ziņa vairs nav pieejama.",
     "thread_not_found": "Šī sarakste vairs nav pieejama.",
diff --git a/locales/mn/common.json b/locales/mn/common.json
index 4633a5d6d..79d8fdfc1 100644
--- a/locales/mn/common.json
+++ b/locales/mn/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Ноорог хавтас олдсонгүй."
     }
   },
+  "offlineConflicts": {
+    "title": "Хэрэгжээгүй өөрчлөлтүүд",
+    "description": "Та эдгээр өөрчлөлтийг офлайн хийсэн. Тэдгээр нь хэрэгжээгүй бөгөөд захидал серверт байгаа хэвээрээ үлдэнэ.",
+    "changed": "Өөр төхөөрөмж дээр өөрчлөгдсөн тул таны өөрчлөлт хэрэгжээгүй",
+    "changed_delete": "Өөр төхөөрөмж дээр өөрчлөгдсөн тул устгагдаагүй",
+    "gone": "Серверт байхгүй болсон тул таны өөрчлөлт хэрэгжээгүй",
+    "refused": "Сервер энэ өөрчлөлтөөс татгалзлаа: {reason}",
+    "dismiss": "Хаах",
+    "dismiss_label": "{subject}-ийн тэмдэглэлийг хаах",
+    "banner": "Хэрэгжээгүй өөрчлөлтүүд: {count}",
+    "toast": "Офлайн хийсэн, хэрэгжээгүй өөрчлөлтүүд: {count}. Аль нь болохыг Илгээх хайрцгаас харна уу.",
+    "storage_failed": "Энэ төхөөрөмжид офлайн захидалд зай үлдсэнгүй. Зай чөлөөлөх эсвэл тохиргооноос цөөнийг хадгална уу.",
+    "signout_changes_title": "Хадгалаагүй өөрчлөлттэй гарах уу?",
+    "signout_changes": "Сервер дээр хараахан ороогүй өөрчлөлт: {count}. Гарвал устгагдана.",
+    "store_unavailable": "Энэ төхөөрөмжийн офлайн захидлыг одоо нээж чадахгүй байна. Илгээгээгүй захидал энд үлдэх бөгөөд апп үргэлжлүүлэн оролдоно.",
+    "store_reset": "Энэ төхөөрөмжийн офлайн захидлыг уншиж чадсангүй тул дахин татаж байна. Илгээгээгүй зүйл алга болсон.",
+    "legacy_stranded": "Энэ хөтөч өмнөх хувилбарын хадгалсан илгээгээгүй захидлыг нээж чадахгүй. Хөтчөө шинэчилбэл буцаж магадгүй.",
+    "store_private": "Хувийн цонх офлайн ашиглах захидал хадгалж чадахгүй.",
+    "server_not_answering": "Шуудангийн сервер хариу өгөхгүй байна. Хэсэг хугацааны дараа дахин оролдоно уу."
+  },
   "deep_link": {
     "message_not_found": "Энэ зурвас дахин ашиглах боломжгүй болсон.",
     "thread_not_found": "Энэ харилцан яриа дахин ашиглах боломжгүй болсон.",
diff --git a/locales/nb/common.json b/locales/nb/common.json
index d2e1a518e..c500ca8b8 100644
--- a/locales/nb/common.json
+++ b/locales/nb/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Fant ikke mappen Utkast."
     }
   },
+  "offlineConflicts": {
+    "title": "Endringer som ikke ble utført",
+    "description": "Du gjorde disse endringene uten nett. De ble ikke utført, og meldingen forblir som den er på serveren.",
+    "changed": "Endret på en annen enhet, endringen din ble ikke utført",
+    "changed_delete": "Endret på en annen enhet, den ble ikke slettet",
+    "gone": "Finnes ikke lenger på serveren, endringen din ble ikke utført",
+    "refused": "Serveren avviste denne endringen: {reason}",
+    "dismiss": "Lukk",
+    "dismiss_label": "Lukk merknaden om {subject}",
+    "banner": "Endringer som ikke ble utført: {count}",
+    "toast": "Endringer gjort uten nett som ikke ble utført: {count}. Utboksen viser hvilke.",
+    "storage_failed": "Denne enheten har ikke mer plass til e-post uten nett. Frigjør plass, eller behold mindre i innstillingene.",
+    "signout_changes_title": "Logge ut med endringer som ikke er lagret?",
+    "signout_changes": "Endringer som ennå ikke er på serveren: {count}. Når du logger ut, slettes de.",
+    "store_unavailable": "E-post uten nett på denne enheten kan ikke åpnes nå. Usendt e-post blir her, og appen fortsetter å prøve.",
+    "store_reset": "E-post uten nett på denne enheten kunne ikke leses og lastes derfor ned på nytt. Det som ikke var sendt, er borte.",
+    "legacy_stranded": "Denne nettleseren kan ikke åpne usendt e-post fra en tidligere versjon. En oppdatering av nettleseren kan hente den tilbake.",
+    "store_private": "Private vinduer kan ikke beholde e-post for bruk uten nett.",
+    "server_not_answering": "E-postserveren svarer ikke. Prøv igjen om litt."
+  },
   "deep_link": {
     "message_not_found": "Denne meldingen er ikke lenger tilgjengelig.",
     "thread_not_found": "Denne samtalen er ikke lenger tilgjengelig.",
diff --git a/locales/nl/common.json b/locales/nl/common.json
index b704a66fc..9fa70a38d 100644
--- a/locales/nl/common.json
+++ b/locales/nl/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Je map Concepten is niet gevonden."
     }
   },
+  "offlineConflicts": {
+    "title": "Niet doorgevoerde wijzigingen",
+    "description": "Je hebt deze wijzigingen offline gemaakt. Ze zijn niet doorgevoerd en het bericht blijft zoals het op de server staat.",
+    "changed": "Gewijzigd op een ander apparaat, je wijziging is niet doorgevoerd",
+    "changed_delete": "Gewijzigd op een ander apparaat, niet verwijderd",
+    "gone": "Staat niet meer op de server, je wijziging is niet doorgevoerd",
+    "refused": "De server heeft deze wijziging geweigerd: {reason}",
+    "dismiss": "Sluiten",
+    "dismiss_label": "Melding over {subject} sluiten",
+    "banner": "Niet doorgevoerde wijzigingen: {count}",
+    "toast": "Offline gemaakte wijzigingen niet doorgevoerd: {count}. Het Postvak UIT laat zien welke.",
+    "storage_failed": "Dit apparaat heeft geen ruimte meer voor offline mail. Maak ruimte vrij of bewaar minder via Instellingen.",
+    "signout_changes_title": "Afmelden met niet-opgeslagen wijzigingen?",
+    "signout_changes": "Wijzigingen die nog niet op de server staan: {count}. Afmelden verwijdert ze.",
+    "store_unavailable": "De offline mail op dit apparaat kan nu niet worden geopend. Niet-verzonden mail blijft hier en de app blijft het proberen.",
+    "store_reset": "De offline mail op dit apparaat kon niet worden gelezen en wordt opnieuw gedownload. Wat hier nog niet verzonden was, is weg.",
+    "legacy_stranded": "Deze browser kan niet-verzonden mail van een eerdere versie niet openen. De browser bijwerken kan die terughalen.",
+    "store_private": "Privévensters kunnen geen mail bewaren voor offline gebruik.",
+    "server_not_answering": "De mailserver antwoordt niet. Probeer het zo meteen opnieuw."
+  },
   "deep_link": {
     "message_not_found": "Dit bericht is niet meer beschikbaar.",
     "thread_not_found": "Dit gesprek is niet meer beschikbaar.",
diff --git a/locales/pl/common.json b/locales/pl/common.json
index 8ccc30784..4608b20df 100644
--- a/locales/pl/common.json
+++ b/locales/pl/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Nie znaleziono folderu Wersje robocze."
     }
   },
+  "offlineConflicts": {
+    "title": "Niezastosowane zmiany",
+    "description": "Te zmiany wprowadzono w trybie offline. Nie zostały zastosowane, a wiadomość pozostaje taka jak na serwerze.",
+    "changed": "Zmieniono na innym urządzeniu, Twoja zmiana nie została zastosowana",
+    "changed_delete": "Zmieniono na innym urządzeniu, wiadomość nie została usunięta",
+    "gone": "Nie ma już na serwerze, Twoja zmiana nie została zastosowana",
+    "refused": "Serwer odrzucił tę zmianę: {reason}",
+    "dismiss": "Odrzuć",
+    "dismiss_label": "Odrzuć uwagę o {subject}",
+    "banner": "Niezastosowane zmiany: {count}",
+    "toast": "Niezastosowane zmiany wprowadzone offline: {count}. Skrzynka nadawcza pokazuje które.",
+    "storage_failed": "Na tym urządzeniu nie ma już miejsca na pocztę offline. Zwolnij miejsce lub zachowuj mniej w ustawieniach.",
+    "signout_changes_title": "Wylogować z niezapisanymi zmianami?",
+    "signout_changes": "Zmiany, których jeszcze nie ma na serwerze: {count}. Wylogowanie je usunie.",
+    "store_unavailable": "Nie można teraz otworzyć poczty offline na tym urządzeniu. Niewysłane wiadomości zostają tutaj, a aplikacja próbuje dalej.",
+    "store_reset": "Nie udało się odczytać poczty offline na tym urządzeniu, więc jest pobierana ponownie. To, co nie zostało wysłane, przepadło.",
+    "legacy_stranded": "Ta przeglądarka nie może otworzyć niewysłanych wiadomości z wcześniejszej wersji. Aktualizacja przeglądarki może je przywrócić.",
+    "store_private": "Okna prywatne nie mogą przechowywać poczty do użytku offline.",
+    "server_not_answering": "Serwer poczty nie odpowiada. Spróbuj ponownie za chwilę."
+  },
   "deep_link": {
     "message_not_found": "Ta wiadomość nie jest już dostępna.",
     "thread_not_found": "Ta rozmowa nie jest już dostępna.",
diff --git a/locales/pt/common.json b/locales/pt/common.json
index 188b256f8..cca6bb8e2 100644
--- a/locales/pt/common.json
+++ b/locales/pt/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Não foi possível encontrar a pasta Rascunhos."
     }
   },
+  "offlineConflicts": {
+    "title": "Alterações não aplicadas",
+    "description": "Fez estas alterações offline. Não foram aplicadas e a mensagem fica como está no servidor.",
+    "changed": "Alterada noutro dispositivo, a sua alteração não foi aplicada",
+    "changed_delete": "Alterada noutro dispositivo, não foi eliminada",
+    "gone": "Já não está no servidor, a sua alteração não foi aplicada",
+    "refused": "O servidor recusou esta alteração: {reason}",
+    "dismiss": "Dispensar",
+    "dismiss_label": "Dispensar a nota sobre {subject}",
+    "banner": "Alterações não aplicadas: {count}",
+    "toast": "Alterações feitas offline não aplicadas: {count}. A caixa de saída mostra quais.",
+    "storage_failed": "Este dispositivo não tem espaço para o correio offline. Liberte espaço ou guarde menos nas definições.",
+    "signout_changes_title": "Terminar sessão com alterações não guardadas?",
+    "signout_changes": "Alterações ainda não enviadas para o servidor: {count}. Terminar sessão elimina-as.",
+    "store_unavailable": "O correio offline deste dispositivo não pode ser aberto agora. O correio por enviar fica aqui e a aplicação continua a tentar.",
+    "store_reset": "Não foi possível ler o correio offline deste dispositivo, por isso está a ser transferido de novo. O que estava por enviar perdeu-se.",
+    "legacy_stranded": "Este navegador não consegue abrir o correio por enviar guardado por uma versão anterior. Atualizar o navegador pode recuperá-lo.",
+    "store_private": "As janelas privadas não podem guardar correio para uso offline.",
+    "server_not_answering": "O servidor de correio não está a responder. Tente novamente daqui a pouco."
+  },
   "deep_link": {
     "message_not_found": "Esta mensagem não está mais disponível.",
     "thread_not_found": "Esta conversa não está mais disponível.",
diff --git a/locales/ro/common.json b/locales/ro/common.json
index ae31839c2..1f04eda3a 100644
--- a/locales/ro/common.json
+++ b/locales/ro/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Dosarul Ciorne nu a fost găsit."
     }
   },
+  "offlineConflicts": {
+    "title": "Modificări neaplicate",
+    "description": "Ați făcut aceste modificări offline. Nu au fost aplicate, iar mesajul rămâne așa cum este pe server.",
+    "changed": "Modificat pe alt dispozitiv, modificarea dvs. nu a fost aplicată",
+    "changed_delete": "Modificat pe alt dispozitiv, nu a fost șters",
+    "gone": "Nu mai este pe server, modificarea dvs. nu a fost aplicată",
+    "refused": "Serverul a refuzat această modificare: {reason}",
+    "dismiss": "Închide",
+    "dismiss_label": "Închide nota despre {subject}",
+    "banner": "Modificări neaplicate: {count}",
+    "toast": "Modificări făcute offline care nu au fost aplicate: {count}. Căsuța de trimitere arată care.",
+    "storage_failed": "Acest dispozitiv nu mai are loc pentru e-mailul offline. Eliberați spațiu sau păstrați mai puțin din setări.",
+    "signout_changes_title": "Vă deconectați cu modificări nesalvate?",
+    "signout_changes": "Modificări care nu sunt încă pe server: {count}. Deconectarea le șterge.",
+    "store_unavailable": "E-mailul offline de pe acest dispozitiv nu poate fi deschis acum. E-mailul netrimis rămâne aici, iar aplicația continuă să încerce.",
+    "store_reset": "E-mailul offline de pe acest dispozitiv nu a putut fi citit, așa că se descarcă din nou. Ce nu fusese trimis s-a pierdut.",
+    "legacy_stranded": "Acest browser nu poate deschide e-mailul netrimis păstrat de o versiune anterioară. Actualizarea browserului îl poate recupera.",
+    "store_private": "Ferestrele private nu pot păstra e-mailuri pentru utilizare offline.",
+    "server_not_answering": "Serverul de e-mail nu răspunde. Încercați din nou imediat."
+  },
   "deep_link": {
     "message_not_found": "Acest mesaj nu mai este disponibil.",
     "thread_not_found": "Această conversație nu mai este disponibilă.",
diff --git a/locales/ru/common.json b/locales/ru/common.json
index a9ee1c65c..4a11da8b0 100644
--- a/locales/ru/common.json
+++ b/locales/ru/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Папка «Черновики» не найдена."
     }
   },
+  "offlineConflicts": {
+    "title": "Неприменённые изменения",
+    "description": "Вы внесли эти изменения офлайн. Они не применены, письмо остаётся таким, как на сервере.",
+    "changed": "Изменено на другом устройстве, ваше изменение не применено",
+    "changed_delete": "Изменено на другом устройстве, письмо не удалено",
+    "gone": "Больше нет на сервере, ваше изменение не применено",
+    "refused": "Сервер отклонил это изменение: {reason}",
+    "dismiss": "Закрыть",
+    "dismiss_label": "Закрыть заметку о {subject}",
+    "banner": "Неприменённые изменения: {count}",
+    "toast": "Изменения, внесённые офлайн и не применённые: {count}. Какие именно, видно в исходящих.",
+    "storage_failed": "На этом устройстве не осталось места для офлайн-почты. Освободите место или храните меньше в настройках.",
+    "signout_changes_title": "Выйти с несохранёнными изменениями?",
+    "signout_changes": "Изменения, которых ещё нет на сервере: {count}. При выходе они удалятся.",
+    "store_unavailable": "Офлайн-почту на этом устройстве сейчас не удаётся открыть. Неотправленные письма остаются здесь, а приложение продолжает попытки.",
+    "store_reset": "Офлайн-почту на этом устройстве не удалось прочитать, поэтому она загружается заново. Всё, что не было отправлено, потеряно.",
+    "legacy_stranded": "Этот браузер не может открыть неотправленные письма, сохранённые предыдущей версией. Обновление браузера может их вернуть.",
+    "store_private": "Приватные окна не могут хранить почту для работы офлайн.",
+    "server_not_answering": "Почтовый сервер не отвечает. Повторите попытку через минуту."
+  },
   "deep_link": {
     "message_not_found": "Это письмо больше недоступно.",
     "thread_not_found": "Эта переписка больше недоступна.",
diff --git a/locales/sk/common.json b/locales/sk/common.json
index a018ba55a..004c61727 100644
--- a/locales/sk/common.json
+++ b/locales/sk/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Priečinok Koncepty sa nenašiel."
     }
   },
+  "offlineConflicts": {
+    "title": "Nepoužité zmeny",
+    "description": "Tieto zmeny ste urobili offline. Neboli použité a správa zostáva tak, ako je na serveri.",
+    "changed": "Zmenené na inom zariadení, vaša zmena nebola použitá",
+    "changed_delete": "Zmenené na inom zariadení, správa nebola odstránená",
+    "gone": "Už nie je na serveri, vaša zmena nebola použitá",
+    "refused": "Server túto zmenu odmietol: {reason}",
+    "dismiss": "Zavrieť",
+    "dismiss_label": "Zavrieť poznámku o {subject}",
+    "banner": "Nepoužité zmeny: {count}",
+    "toast": "Nepoužité zmeny urobené offline: {count}. Ktoré to sú, ukazuje pošta na odoslanie.",
+    "storage_failed": "V tomto zariadení už nie je miesto na poštu offline. Uvoľnite miesto alebo v nastaveniach ponechajte menej.",
+    "signout_changes_title": "Odhlásiť sa s neuloženými zmenami?",
+    "signout_changes": "Zmeny, ktoré ešte nie sú na serveri: {count}. Odhlásenie ich odstráni.",
+    "store_unavailable": "Poštu offline v tomto zariadení teraz nemožno otvoriť. Neodoslaná pošta tu zostáva a aplikácia to skúša ďalej.",
+    "store_reset": "Poštu offline v tomto zariadení sa nepodarilo prečítať, preto sa sťahuje znova. Čo nebolo odoslané, je preč.",
+    "legacy_stranded": "Tento prehliadač neotvorí neodoslanú poštu uloženú staršou verziou. Aktualizácia prehliadača ju môže vrátiť.",
+    "store_private": "Súkromné okná nemôžu uchovávať poštu na používanie offline.",
+    "server_not_answering": "Poštový server neodpovedá. Skúste to o chvíľu znova."
+  },
   "deep_link": {
     "message_not_found": "Táto správa už nie je dostupná.",
     "thread_not_found": "Táto konverzácia už nie je dostupná.",
diff --git a/locales/th/common.json b/locales/th/common.json
index 065a7afbc..4e87f1d6d 100644
--- a/locales/th/common.json
+++ b/locales/th/common.json
@@ -2088,6 +2088,26 @@
       "no_drafts_mailbox": "ไม่พบโฟลเดอร์แบบร่าง"
     }
   },
+  "offlineConflicts": {
+    "title": "การเปลี่ยนแปลงที่ไม่ได้นำไปใช้",
+    "description": "คุณทำการเปลี่ยนแปลงเหล่านี้ขณะออฟไลน์ การเปลี่ยนแปลงไม่ได้ถูกนำไปใช้ และข้อความยังคงเหมือนบนเซิร์ฟเวอร์",
+    "changed": "มีการเปลี่ยนแปลงบนอุปกรณ์อื่น การเปลี่ยนแปลงของคุณจึงไม่ถูกนำไปใช้",
+    "changed_delete": "มีการเปลี่ยนแปลงบนอุปกรณ์อื่น จึงไม่ถูกลบ",
+    "gone": "ไม่มีบนเซิร์ฟเวอร์แล้ว การเปลี่ยนแปลงของคุณจึงไม่ถูกนำไปใช้",
+    "refused": "เซิร์ฟเวอร์ปฏิเสธการเปลี่ยนแปลงนี้: {reason}",
+    "dismiss": "ปิด",
+    "dismiss_label": "ปิดหมายเหตุเกี่ยวกับ {subject}",
+    "banner": "การเปลี่ยนแปลงที่ไม่ได้นำไปใช้: {count}",
+    "toast": "การเปลี่ยนแปลงขณะออฟไลน์ที่ไม่ได้นำไปใช้: {count} ดูรายการได้ในกล่องขาออก",
+    "storage_failed": "อุปกรณ์นี้ไม่มีที่ว่างสำหรับอีเมลออฟไลน์แล้ว โปรดเพิ่มพื้นที่ว่างหรือเก็บให้น้อยลงในการตั้งค่า",
+    "signout_changes_title": "ออกจากระบบทั้งที่มีการเปลี่ยนแปลงที่ยังไม่บันทึกหรือไม่",
+    "signout_changes": "การเปลี่ยนแปลงที่ยังไม่อยู่บนเซิร์ฟเวอร์: {count} การออกจากระบบจะลบรายการเหล่านี้",
+    "store_unavailable": "ตอนนี้เปิดอีเมลออฟไลน์บนอุปกรณ์นี้ไม่ได้ อีเมลที่ยังไม่ส่งยังอยู่ที่นี่ และแอปจะลองต่อไป",
+    "store_reset": "อ่านอีเมลออฟไลน์บนอุปกรณ์นี้ไม่ได้ จึงกำลังดาวน์โหลดใหม่ สิ่งที่ยังไม่ได้ส่งหายไปแล้ว",
+    "legacy_stranded": "เบราว์เซอร์นี้เปิดอีเมลที่ยังไม่ส่งซึ่งเวอร์ชันก่อนหน้าเก็บไว้ไม่ได้ การอัปเดตเบราว์เซอร์อาจนำกลับมาได้",
+    "store_private": "หน้าต่างส่วนตัวเก็บอีเมลไว้ใช้แบบออฟไลน์ไม่ได้",
+    "server_not_answering": "เซิร์ฟเวอร์อีเมลไม่ตอบสนอง โปรดลองอีกครั้งในอีกสักครู่"
+  },
   "plugin_pages": {
     "loading": "กำลังโหลดหน้าเว็บ...",
     "not_available_title": "หน้านี้ไม่พร้อมใช้งาน",
diff --git a/locales/tr/common.json b/locales/tr/common.json
index 81acedbf7..2fe4bf8f1 100644
--- a/locales/tr/common.json
+++ b/locales/tr/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Taslaklar klasörü bulunamadı."
     }
   },
+  "offlineConflicts": {
+    "title": "Uygulanmayan değişiklikler",
+    "description": "Bu değişiklikleri çevrimdışıyken yaptınız. Uygulanmadı ve ileti sunucudaki haliyle kalıyor.",
+    "changed": "Başka bir cihazda değiştirildi, değişikliğiniz uygulanmadı",
+    "changed_delete": "Başka bir cihazda değiştirildi, silinmedi",
+    "gone": "Artık sunucuda yok, değişikliğiniz uygulanmadı",
+    "refused": "Sunucu bu değişikliği reddetti: {reason}",
+    "dismiss": "Kapat",
+    "dismiss_label": "{subject} ile ilgili notu kapat",
+    "banner": "Uygulanmayan değişiklikler: {count}",
+    "toast": "Çevrimdışı yapılan ve uygulanmayan değişiklikler: {count}. Giden kutusu hangileri olduğunu gösterir.",
+    "storage_failed": "Bu cihazda çevrimdışı e-posta için yer kalmadı. Yer açın veya Ayarlar'dan daha azını saklayın.",
+    "signout_changes_title": "Kaydedilmemiş değişikliklerle oturum kapatılsın mı?",
+    "signout_changes": "Henüz sunucuda olmayan değişiklikler: {count}. Oturumu kapatmak bunları siler.",
+    "store_unavailable": "Bu cihazdaki çevrimdışı e-postalar şu anda açılamıyor. Gönderilmemiş e-postalar burada kalır ve uygulama denemeye devam eder.",
+    "store_reset": "Bu cihazdaki çevrimdışı e-postalar okunamadı, bu yüzden yeniden indiriliyor. Gönderilmemiş olanlar kayboldu.",
+    "legacy_stranded": "Bu tarayıcı, önceki bir sürümün sakladığı gönderilmemiş e-postaları açamıyor. Tarayıcıyı güncellemek bunları geri getirebilir.",
+    "store_private": "Gizli pencereler e-postaları çevrimdışı kullanım için saklayamaz.",
+    "server_not_answering": "E-posta sunucusu yanıt vermiyor. Birazdan yeniden deneyin."
+  },
   "deep_link": {
     "message_not_found": "Bu ileti artık kullanılamıyor.",
     "thread_not_found": "Bu sohbet artık kullanılamıyor.",
diff --git a/locales/uk/common.json b/locales/uk/common.json
index 42dbd1aba..88c17f3ef 100644
--- a/locales/uk/common.json
+++ b/locales/uk/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "Теку «Чернетки» не знайдено."
     }
   },
+  "offlineConflicts": {
+    "title": "Незастосовані зміни",
+    "description": "Ви внесли ці зміни офлайн. Їх не застосовано, і лист залишається таким, як на сервері.",
+    "changed": "Змінено на іншому пристрої, вашу зміну не застосовано",
+    "changed_delete": "Змінено на іншому пристрої, лист не видалено",
+    "gone": "Більше немає на сервері, вашу зміну не застосовано",
+    "refused": "Сервер відхилив цю зміну: {reason}",
+    "dismiss": "Закрити",
+    "dismiss_label": "Закрити примітку про {subject}",
+    "banner": "Незастосовані зміни: {count}",
+    "toast": "Зміни, внесені офлайн і не застосовані: {count}. Які саме, видно у вихідних.",
+    "storage_failed": "На цьому пристрої не залишилося місця для офлайн-пошти. Звільніть місце або зберігайте менше в налаштуваннях.",
+    "signout_changes_title": "Вийти з незбереженими змінами?",
+    "signout_changes": "Зміни, яких ще немає на сервері: {count}. Під час виходу вони видаляться.",
+    "store_unavailable": "Офлайн-пошту на цьому пристрої зараз не вдається відкрити. Ненадіслані листи залишаються тут, а застосунок продовжує спроби.",
+    "store_reset": "Офлайн-пошту на цьому пристрої не вдалося прочитати, тому вона завантажується знову. Усе, що не було надіслано, втрачено.",
+    "legacy_stranded": "Цей браузер не може відкрити ненадіслані листи, збережені попередньою версією. Оновлення браузера може їх повернути.",
+    "store_private": "Приватні вікна не можуть зберігати пошту для роботи офлайн.",
+    "server_not_answering": "Поштовий сервер не відповідає. Спробуйте ще раз за хвилину."
+  },
   "deep_link": {
     "message_not_found": "Цей лист більше недоступний.",
     "thread_not_found": "Ця розмова більше недоступна.",
diff --git a/locales/vi/common.json b/locales/vi/common.json
index 9cbcd8bd3..6fd6e2c04 100644
--- a/locales/vi/common.json
+++ b/locales/vi/common.json
@@ -5755,6 +5755,26 @@
       "no_drafts_mailbox": "Không tìm thấy thư mục Thư nháp."
     }
   },
+  "offlineConflicts": {
+    "title": "Các thay đổi chưa được áp dụng",
+    "description": "Bạn đã thực hiện các thay đổi này khi ngoại tuyến. Chúng chưa được áp dụng và thư vẫn giữ nguyên như trên máy chủ.",
+    "changed": "Đã thay đổi trên thiết bị khác nên thay đổi của bạn chưa được áp dụng",
+    "changed_delete": "Đã thay đổi trên thiết bị khác nên chưa bị xóa",
+    "gone": "Không còn trên máy chủ nên thay đổi của bạn chưa được áp dụng",
+    "refused": "Máy chủ đã từ chối thay đổi này: {reason}",
+    "dismiss": "Đóng",
+    "dismiss_label": "Đóng ghi chú về {subject}",
+    "banner": "Các thay đổi chưa được áp dụng: {count}",
+    "toast": "Thay đổi khi ngoại tuyến chưa được áp dụng: {count}. Hộp thư đi cho biết là những thay đổi nào.",
+    "storage_failed": "Thiết bị này không còn chỗ cho thư ngoại tuyến. Hãy giải phóng dung lượng hoặc giữ ít hơn trong Cài đặt.",
+    "signout_changes_title": "Đăng xuất khi còn thay đổi chưa lưu?",
+    "signout_changes": "Thay đổi chưa có trên máy chủ: {count}. Đăng xuất sẽ xóa chúng.",
+    "store_unavailable": "Hiện không mở được thư ngoại tuyến trên thiết bị này. Thư chưa gửi vẫn ở đây và ứng dụng tiếp tục thử.",
+    "store_reset": "Không đọc được thư ngoại tuyến trên thiết bị này nên đang tải lại. Những gì chưa gửi đã mất.",
+    "legacy_stranded": "Trình duyệt này không mở được thư chưa gửi do phiên bản trước lưu. Cập nhật trình duyệt có thể lấy lại chúng.",
+    "store_private": "Cửa sổ riêng tư không thể giữ thư để dùng ngoại tuyến.",
+    "server_not_answering": "Máy chủ thư không phản hồi. Hãy thử lại sau giây lát."
+  },
   "deep_link": {
     "message_not_found": "Thư này không còn nữa.",
     "thread_not_found": "Cuộc trò chuyện này không còn tồn tại nữa.",
diff --git a/locales/zh-TW/common.json b/locales/zh-TW/common.json
index 5ba44316f..ead0cce96 100644
--- a/locales/zh-TW/common.json
+++ b/locales/zh-TW/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "找不到「草稿」資料夾。"
     }
   },
+  "offlineConflicts": {
+    "title": "未套用的變更",
+    "description": "這些變更是您離線時做的。它們沒有被套用，郵件維持伺服器上的狀態。",
+    "changed": "已在其他裝置上變更，您的變更未被套用",
+    "changed_delete": "已在其他裝置上變更，未被刪除",
+    "gone": "伺服器上已沒有此郵件，您的變更未被套用",
+    "refused": "伺服器拒絕了此變更：{reason}",
+    "dismiss": "關閉",
+    "dismiss_label": "關閉關於 {subject} 的提示",
+    "banner": "未套用的變更：{count}",
+    "toast": "離線時的變更未被套用：{count} 項。可在寄件匣中查看。",
+    "storage_failed": "此裝置已沒有空間存放離線郵件。請釋出空間，或在設定中減少保留的內容。",
+    "signout_changes_title": "要在有未儲存變更時登出嗎？",
+    "signout_changes": "尚未到達伺服器的變更：{count} 項。登出會刪除它們。",
+    "store_unavailable": "目前無法開啟此裝置上的離線郵件。未傳送的郵件仍保留在這裡，應用程式會繼續嘗試。",
+    "store_reset": "無法讀取此裝置上的離線郵件，正在重新下載。未傳送的內容已遺失。",
+    "legacy_stranded": "此瀏覽器無法開啟舊版本保存的未傳送郵件。更新瀏覽器可能會找回它們。",
+    "store_private": "私密視窗無法保留供離線使用的郵件。",
+    "server_not_answering": "郵件伺服器沒有回應。請稍後再試。"
+  },
   "deep_link": {
     "message_not_found": "已無法使用此郵件。",
     "thread_not_found": "已無法使用此對話串。",
diff --git a/locales/zh/common.json b/locales/zh/common.json
index f53c82da4..47e79990b 100644
--- a/locales/zh/common.json
+++ b/locales/zh/common.json
@@ -5743,6 +5743,26 @@
       "no_drafts_mailbox": "找不到“草稿”文件夹。"
     }
   },
+  "offlineConflicts": {
+    "title": "未应用的更改",
+    "description": "这些更改是您离线时做的。它们没有被应用，邮件保持服务器上的状态。",
+    "changed": "已在其他设备上更改，您的更改未被应用",
+    "changed_delete": "已在其他设备上更改，未被删除",
+    "gone": "服务器上已没有此邮件，您的更改未被应用",
+    "refused": "服务器拒绝了此更改：{reason}",
+    "dismiss": "关闭",
+    "dismiss_label": "关闭关于 {subject} 的提示",
+    "banner": "未应用的更改：{count}",
+    "toast": "离线时的更改未被应用：{count} 项。可在发件箱中查看。",
+    "storage_failed": "此设备已没有空间存放离线邮件。请释放空间，或在设置中减少保留的内容。",
+    "signout_changes_title": "要在有未保存更改时退出登录吗？",
+    "signout_changes": "尚未到达服务器的更改：{count} 项。退出登录会删除它们。",
+    "store_unavailable": "现在无法打开此设备上的离线邮件。未发送的邮件仍保留在这里，应用会继续尝试。",
+    "store_reset": "无法读取此设备上的离线邮件，正在重新下载。未发送的内容已丢失。",
+    "legacy_stranded": "此浏览器无法打开早期版本保存的未发送邮件。更新浏览器可能会找回它们。",
+    "store_private": "隐私窗口无法保留供离线使用的邮件。",
+    "server_not_answering": "邮件服务器没有响应。请稍后再试。"
+  },
   "deep_link": {
     "message_not_found": "此邮件已不可用。",
     "thread_not_found": "此会话已不可用。",
diff --git a/public/sw.js b/public/sw.js
index f46f5fee7..22e4174ba 100644
--- a/public/sw.js
+++ b/public/sw.js
@@ -126,7 +126,10 @@ function appPagePath(url) {
 
 function staticPath(url) {
   if (url.origin !== self.location.origin) return false;
-  return url.pathname.startsWith(BASE_PATH + "/_next/static/");
+  if (url.pathname.startsWith(BASE_PATH + "/_next/static/")) return true;
+  // The local store's engine: named by build (?v=) and by version, so it can be
+  // kept like a hashed file, and an offline start needs it.
+  return url.pathname === BASE_PATH + "/store-worker.js" || url.pathname.startsWith(BASE_PATH + "/sqlite3mc/");
 }
 
 /** Where a page of the app is kept: its address without the query. */
diff --git a/scripts/lite/lib.mjs b/scripts/lite/lib.mjs
index 3760b208a..9396192d3 100644
--- a/scripts/lite/lib.mjs
+++ b/scripts/lite/lib.mjs
@@ -49,6 +49,13 @@ export const LITE_REMOVED_PATHS = [
   "public/sqlite3mc",
 ];
 
+/** The local store's engine in an export: Lite has no offline mode, and must not ship or load it. */
+export function unexpectedEngineFiles(files) {
+  return files
+    .map((file) => file.replace(/\\/g, "/"))
+    .filter((file) => /(^|\/)store-worker\.js$/.test(file) || /(^|\/)sqlite3mc\//.test(file) || /(^|\/)sqlite3\.(wasm|mjs)$/.test(file));
+}
+
 /** Test trees are pruned too: they import the routes removed above. */
 export const LITE_TEST_DIR_NAME = "__tests__";
 export const LITE_TEST_FILE_PATTERN = /\.test\.[cm]?[jt]sx?$/;
diff --git a/scripts/lite/verify.mjs b/scripts/lite/verify.mjs
index 3e2800168..4a19c6e30 100644
--- a/scripts/lite/verify.mjs
+++ b/scripts/lite/verify.mjs
@@ -10,7 +10,7 @@ import { existsSync, readFileSync, statSync } from "node:fs";
 import { join } from "node:path";
 import {
   LITE_PENDING_PATH_KEY, STALWART_EXCLUDED_FILES, STALWART_MAX_BUNDLE_BYTES, STALWART_SAFE_BUNDLE_BYTES, STALWART_ZIP_NAME,
-  collectApiStrings, collectZipEntries, discoverBuiltLocales, flightTextRowsWithNeedles, inlineScriptHashes, isMainModule, listZipEntries, parseLiteTarget, resolveRepoRoot, stalwartEntryProblems, stalwartZipEntryProblems, unexpectedApiStrings,
+  collectApiStrings, collectZipEntries, discoverBuiltLocales, flightTextRowsWithNeedles, inlineScriptHashes, isMainModule, listZipEntries, parseLiteTarget, resolveRepoRoot, stalwartEntryProblems, stalwartZipEntryProblems, unexpectedApiStrings, unexpectedEngineFiles,
 } from "./lib.mjs";
 
 const repoRoot = resolveRepoRoot(import.meta.url);
@@ -83,6 +83,10 @@ export function verifyExport({ root = repoRoot, target, safeBundleBytes = STALWA
   const unexpected = unexpectedApiStrings(apiStrings);
   for (const s of unexpected) problems.push(`client chunk references undocumented server endpoint ${s} (add an IS_LITE gate or document it in scripts/lite/lib.mjs)`);
 
+  if (existsSync(outDir)) {
+    for (const file of unexpectedEngineFiles(collectZipEntries(outDir).map(({ name }) => name))) problems.push(`out/${file} is the local store's engine, which Lite must not ship`);
+  }
+
   let zipBytes = 0;
   if (resolvedTarget === "stalwart") {
     const entry = join(outDir, "index.html");
diff --git a/stores/__tests__/auth-store-keep-local.test.ts b/stores/__tests__/auth-store-keep-local.test.ts
new file mode 100644
index 000000000..99ba77f90
--- /dev/null
+++ b/stores/__tests__/auth-store-keep-local.test.ts
@@ -0,0 +1,225 @@
+import 'fake-indexeddb/auto';
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+// What an automatic sign-out does to the mail on this device. A real refusal of
+// the login wipes it, like a sign-out. An outage, or a refusal that says nothing
+// about the login, keeps it for the next sign-in.
+
+const purge = vi.hoisted(() => ({ files: 0 }));
+vi.mock('@/lib/store/client/purge', () => ({ purgeStoreFiles: async () => { purge.files += 1; }, deleteStorePool: async () => {} }));
+vi.mock('@/lib/compose-flush-registry', () => ({ flushComposers: vi.fn(async () => ({ total: 0, settled: 0, failed: 0, timedOut: false })) }));
+
+let useAuthStore: typeof import('../auth-store').useAuthStore;
+let useAccountStore: typeof import('../account-store').useAccountStore;
+let state: typeof import('@/lib/offline/state');
+let offline: typeof import('@/lib/offline/offline-mode');
+let queue: typeof import('@/lib/offline/queue');
+let lost: typeof import('@/lib/offline/lost');
+let store: import('@/lib/store/__tests__/helpers/in-process-store').InProcessStore;
+
+const ALICE = 'alice@mail.example.test';
+
+function entry(id: string, cookieSlot: number) {
+  return {
+    id, label: id, serverUrl: 'https://mail.example.test', username: id.split('@mail')[0], authMode: 'oauth', rememberMe: true,
+    displayName: id, email: id, lastLoginAt: Date.now(), isConnected: true, hasError: false, isDefault: cookieSlot === 0, cookieSlot, avatarColor: '#000',
+  };
+}
+
+function answer(status: number, body: unknown = {}): Response {
+  return new Response(typeof body === 'string' ? body : JSON.stringify(body), { status, headers: { 'Content-Type': 'application/json' } });
+}
+
+function tokenAnswers(next: () => Response): void {
+  vi.stubGlobal('fetch', vi.fn(async (input: unknown) => (String(input).includes('/api/auth/token') ? next() : answer(200))));
+}
+
+/** `times`: as often as the retry timer would run it. */
+async function refresh(times = 1): Promise<void> {
+  for (let i = 0; i < times; i += 1) await useAuthStore.getState().refreshAccessToken({ accountId: ALICE });
+  await vi.waitFor(() => expect(useAuthStore.getState().isAuthenticated).toBe(false));
+}
+
+beforeEach(async () => {
+  vi.resetModules();
+  purge.files = 0;
+  localStorage.clear();
+  sessionStorage.clear();
+  ({ useAuthStore } = await import('../auth-store'));
+  ({ useAccountStore } = await import('../account-store'));
+  state = await import('@/lib/offline/state');
+  offline = await import('@/lib/offline/offline-mode');
+  queue = await import('@/lib/offline/queue');
+  lost = await import('@/lib/offline/lost');
+  const browserNavigation = await import('@/lib/browser-navigation');
+  vi.spyOn(browserNavigation, 'replaceWindowLocation').mockImplementation(() => {});
+  const { InProcessStore } = await import('@/lib/store/__tests__/helpers/in-process-store');
+  const { setStoreBackend } = await import('@/lib/store/client/api');
+  store = new InProcessStore();
+  setStoreBackend(store);
+  useAccountStore.setState({ accounts: [entry(ALICE, 0)], activeAccountId: ALICE, defaultAccountId: ALICE } as never);
+  useAuthStore.setState({ isAuthenticated: true, activeAccountId: ALICE, authMode: 'oauth', serverUrl: 'https://mail.example.test', username: 'alice' });
+  state.writeEnabled([ALICE]);
+  await queue.queueSend(ALICE, { subject: 'Unsent', to: [] }, { kind: 'email', args: [] });
+}, 60_000);
+
+function expectKept(): void {
+  expect(purge.files).toBe(0);
+  expect(state.useOfflineStore.getState().enabled).toEqual([ALICE]);
+  expect(localStorage.getItem(state.OFFLINE_ACCOUNTS_KEY)).toContain(ALICE);
+  expect(state.isEvicted(ALICE)).toBe(true);
+  expect(store.removed).toEqual([]);
+  expect(store.stopped).toBe(0);
+  // Nothing was lost, so nothing is named at the sign-in page.
+  expect(lost.consumeLost()).toEqual([]);
+}
+
+describe('an automatic sign-out of the active account', () => {
+  it('keeps the data through a run of 502s from a proxy', async () => {
+    tokenAnswers(() => answer(502, '<html>Bad Gateway</html>'));
+    await refresh(5);
+    expectKept();
+  });
+
+  it('keeps the data through a run of the route\'s own 500s', async () => {
+    tokenAnswers(() => answer(500, { error: 'Internal server error' }));
+    await refresh(5);
+    expectKept();
+  });
+
+  it('keeps the data on a refusal that says nothing about the login', async () => {
+    tokenAnswers(() => answer(401, { error: 'Refresh failed' }));
+    await refresh();
+    expectKept();
+  });
+
+  it('keeps the data on a refusal it can\'t read', async () => {
+    tokenAnswers(() => answer(401, 'nope'));
+    await refresh();
+    expectKept();
+  });
+
+  it('wipes on a real invalid_grant, and names the lost mail', async () => {
+    tokenAnswers(() => answer(401, { error: 'invalid_grant' }));
+    offline.startOfflineMode();
+    await refresh();
+    await vi.waitFor(() => expect(purge.files).toBeGreaterThan(0));
+    expect(localStorage.getItem(state.OFFLINE_ACCOUNTS_KEY)).toBeNull();
+    expect(lost.consumeLost()).toEqual(['Unsent']);
+  });
+
+  it('wipes at the organisation\'s session limit', async () => {
+    const { SESSION_TOO_OLD } = await import('@/lib/session-policy/constants');
+    tokenAnswers(() => answer(401, { error: SESSION_TOO_OLD, maxHours: 8 }));
+    await refresh();
+    await vi.waitFor(() => expect(purge.files).toBeGreaterThan(0));
+  });
+});
+
+describe('a background account', () => {
+  const BOB = 'bob@mail.example.test';
+  const token = async () => useAuthStore.getState().refreshAccessToken({ accountId: BOB });
+
+  beforeEach(() => {
+    useAccountStore.setState({ accounts: [entry(ALICE, 0), entry(BOB, 1)] } as never);
+    state.writeEnabled([ALICE, BOB]);
+    offline.startOfflineMode();
+  });
+
+  it('keeps its data on an unknown refusal', async () => {
+    tokenAnswers(() => answer(401, { error: 'Refresh failed' }));
+    await token();
+    await vi.waitFor(() => expect(useAccountStore.getState().getAccountById(BOB)).toBeUndefined());
+    expect(state.isEvicted(BOB)).toBe(true);
+    expect(store.removed).toEqual([]);
+  });
+
+  it('wipes on a real invalid_grant', async () => {
+    tokenAnswers(() => answer(401, { error: 'invalid_grant' }));
+    await token();
+    await vi.waitFor(() => expect(store.removed).toEqual([BOB]));
+    expect(state.isEvicted(BOB)).toBe(false);
+  });
+});
+
+describe('data waiting for a sign-in', () => {
+  const BOB = 'bob@mail.example.test';
+
+  beforeEach(async () => {
+    state.writeEnabled([ALICE, BOB]);
+    await queue.queueSend(BOB, { subject: 'Bob\'s', to: [] }, { kind: 'email', args: [] });
+    useAccountStore.setState({ accounts: [entry(ALICE, 0), entry(BOB, 1)] } as never);
+    useAccountStore.getState().removeAccount(BOB, 'evicted');
+  });
+
+  it('is hidden from anyone else, in every list', async () => {
+    await offline.refreshQueueState();
+    expect(state.useOfflineStore.getState().outbox.map((row) => row.subject)).toEqual(['Unsent']);
+    expect((await queue.readQueue()).outbox.map((row) => row.account)).toEqual([ALICE]);
+    await offline.refreshUsage();
+    expect(state.visibleAccounts()).toEqual([ALICE]);
+  });
+
+  it('shows again when the account signs in', async () => {
+    useAccountStore.getState().addAccount({ username: 'bob', serverUrl: 'https://mail.example.test', authMode: 'oauth', rememberMe: true, label: 'bob', displayName: 'bob', email: 'bob', lastLoginAt: 1, isConnected: true, hasError: false, isDefault: false } as never);
+    expect(state.isEvicted(BOB)).toBe(false);
+    await offline.refreshQueueState();
+    expect(state.useOfflineStore.getState().outbox.map((row) => row.subject).sort()).toEqual(['Bob\'s', 'Unsent']);
+  });
+
+  it('goes after 30 days', async () => {
+    localStorage.setItem(state.OFFLINE_EVICTED_KEY, JSON.stringify({ [BOB]: Date.now() - state.EVICTED_KEEP_MS - 1000 }));
+    offline.startOfflineMode();
+    await vi.waitFor(() => expect(store.removed).toEqual([BOB]));
+    expect(state.isEvicted(BOB)).toBe(false);
+    expect(state.useOfflineStore.getState().enabled).toEqual([ALICE]);
+  });
+
+  it('stays before that', async () => {
+    offline.startOfflineMode();
+    await new Promise((resolve) => setTimeout(resolve, 20));
+    expect(store.removed).toEqual([]);
+    expect(state.useOfflineStore.getState().enabled).toEqual([ALICE, BOB]);
+  });
+
+  it('survives someone else\'s full sign-out, whose own data goes', async () => {
+    offline.startOfflineMode();
+    await useAuthStore.getState().logout({ endProviderSession: false });
+    await vi.waitFor(() => expect(store.removed).toEqual([ALICE]));
+    expect(purge.files).toBe(0);
+    expect(state.useOfflineStore.getState().enabled).toEqual([BOB]);
+    expect(state.isEvicted(BOB)).toBe(true);
+  });
+});
+
+describe('a sign-out that has to drop another account', () => {
+  const BOB = 'bob@mail.example.test';
+
+  it('keeps that account\'s data for its next sign-in, since nobody asked it', async () => {
+    useAccountStore.setState({ accounts: [entry(ALICE, 0), { ...entry(BOB, 1), hasError: true }] } as never);
+    state.writeEnabled([ALICE, BOB]);
+    await queue.queueSend(BOB, { subject: 'Bob\'s', to: [] }, { kind: 'email', args: [] });
+    offline.startOfflineMode();
+    tokenAnswers(() => answer(200));
+    await useAuthStore.getState().logout({ endProviderSession: false });
+    await vi.waitFor(() => expect(useAccountStore.getState().accounts).toEqual([]));
+    await vi.waitFor(() => expect(store.removed).toEqual([ALICE]));
+    expect(purge.files).toBe(0);
+    expect(state.isEvicted(BOB)).toBe(true);
+    expect(state.useOfflineStore.getState().enabled).toEqual([BOB]);
+    expect(lost.consumeLost()).not.toContain('Bob\'s');
+  });
+});
+
+describe('a login without "remember me"', () => {
+  it('ends with its data at a reload, naming lost mail, even before the host runs', async () => {
+    useAccountStore.setState({ accounts: [{ ...entry(ALICE, 0), rememberMe: false }] } as never);
+    tokenAnswers(() => answer(200));
+    await useAuthStore.getState().checkAuth();
+    expect(useAccountStore.getState().getAccountById(ALICE)).toBeUndefined();
+    expect(state.isEvicted(ALICE)).toBe(false);
+    offline.startOfflineMode();
+    await vi.waitFor(() => expect(purge.files).toBeGreaterThan(0));
+    expect(lost.consumeLost()).toEqual(['Unsent']);
+  });
+});
diff --git a/stores/__tests__/auth-store-local-copy.test.ts b/stores/__tests__/auth-store-local-copy.test.ts
new file mode 100644
index 000000000..ee514fb01
--- /dev/null
+++ b/stores/__tests__/auth-store-local-copy.test.ts
@@ -0,0 +1,212 @@
+import { beforeAll, beforeEach, expect, it, vi } from 'vitest';
+import { createConfig } from '@/lib/__tests__/fixtures/config';
+
+// With the local store on, a start paints from the local copy at once, then
+// connects and swaps. The hooks are there before the first request.
+const offline = vi.hoisted(() => ({
+  order: [] as string[],
+  session: { apiUrl: 'x' } as unknown,
+  gone: false,
+  ready: true,
+  // A local copy with no identities kept answers an empty list.
+  localIdentities: Promise.resolve([]) as Promise<unknown[]>,
+  releaseLocal: () => {},
+}));
+
+vi.mock('@/lib/offline/offline-mode', () => ({
+  registerOfflineHooks: () => { offline.order.push('hooks'); },
+  offlineSessionFor: async (_account: string, options?: { withFolders?: boolean }) => (options?.withFolders && !offline.ready ? null : offline.session),
+  serverUnreachable: async () => offline.gone,
+  markStartedOffline: () => { offline.order.push('startedOffline'); },
+}));
+
+let connectGate: Promise<void> = Promise.resolve();
+
+vi.mock('@/lib/jmap/client', () => {
+  class JMAPClient {
+    offlineOnly = false;
+    constructor(public serverUrl: string, public username: string, public password: string) {}
+    static withBearer() { throw new Error('not used'); }
+    static fromOfflineSession(serverUrl: string, username: string) {
+      offline.order.push('local client');
+      const client = new JMAPClient(serverUrl, username, '');
+      client.offlineOnly = true;
+      return client;
+    }
+    isOfflineOnly() { return this.offlineOnly; }
+    async connect() { offline.order.push('connect'); await connectGate; }
+    getSessionUsername() { return this.username; }
+    getUsername() { return this.username; }
+    async getIdentities() {
+      return this.offlineOnly ? offline.localIdentities : [{ id: 'a', email: this.username, name: this.username, mayDelete: false }];
+    }
+    getAuthHeader() { return 'Basic eA=='; }
+    onConnectionChange() {}
+    onRateLimit() {}
+    getRateLimitRemainingMs() { return 0; }
+    supportsContacts() { return false; }
+    supportsPrincipals() { return false; }
+    supportsVacationResponse() { return false; }
+    supportsCalendars() { return false; }
+    supportsSieve() { return false; }
+    disconnect() {}
+    getAccountId() { return 'acct'; }
+  }
+  class RateLimitError extends Error {}
+  class RequestTimeoutError extends Error {}
+  return { JMAPClient, RateLimitError, RequestTimeoutError };
+});
+vi.mock('@/lib/stalwart/principal', () => ({ fetchPrincipalDisplayName: async () => null }));
+
+import { useAuthStore } from '@/stores/auth-store';
+import { useAccountStore } from '@/stores/account-store';
+import { useOfflineStore } from '@/lib/offline/state';
+
+// The auth store keeps its clients for good, so each test gets an account of its own.
+let run = 0;
+let ACCOUNT = makeAccount();
+
+function makeAccount() {
+  run += 1;
+  const username = `bob${run}@x.test`;
+  return {
+    id: `${username}@mail.x.test`, label: 'Bob', serverUrl: 'https://mail.x.test', username, authMode: 'basic' as const,
+    rememberMe: true, cookieSlot: 0, displayName: 'Bob', email: username, isConnected: false, hasError: false,
+    lastLoginAt: 1, avatarColor: '#000000', isDefault: true,
+  };
+}
+
+let sessionAnswer: () => Response;
+
+beforeAll(() => {
+  vi.stubGlobal('fetch', vi.fn(async (input: unknown) => {
+    const url = String(input);
+    if (url.includes('/api/auth/session')) return sessionAnswer();
+    if (url.includes('/api/config')) return new Response(JSON.stringify(createConfig()), { status: 200 });
+    return new Response('{}', { status: 200 });
+  }));
+});
+
+const goodSession = () => new Response(JSON.stringify({ serverUrl: ACCOUNT.serverUrl, username: ACCOUNT.username, password: 'x' }), { status: 200 });
+
+beforeEach(async () => {
+  ACCOUNT = makeAccount();
+  offline.order.length = 0;
+  offline.session = { apiUrl: 'x' };
+  offline.gone = false;
+  offline.ready = true;
+  offline.localIdentities = Promise.resolve([]);
+  connectGate = Promise.resolve();
+  sessionAnswer = goodSession;
+  useAccountStore.setState({ accounts: [ACCOUNT] as never, activeAccountId: ACCOUNT.id, defaultAccountId: ACCOUNT.id });
+  useOfflineStore.setState({ enabled: [ACCOUNT.id], startedOffline: false });
+  useAuthStore.setState({ client: null, isAuthenticated: false, activeAccountId: ACCOUNT.id, identities: [], primaryIdentity: null });
+});
+
+type ClientLike = { isOfflineOnly(): boolean };
+const current = () => useAuthStore.getState().client as unknown as ClientLike | null;
+
+it('registers the hooks first, shows the local copy before connecting, then swaps', async () => {
+  let open: () => void = () => {};
+  connectGate = new Promise((resolve) => { open = resolve; });
+  await useAuthStore.getState().checkAuth();
+
+  // The real connect hasn't finished, and the app is up on the local copy.
+  expect(useAuthStore.getState().isAuthenticated).toBe(true);
+  expect(useAuthStore.getState().isLoading).toBe(false);
+  expect(current()?.isOfflineOnly()).toBe(true);
+  expect(offline.order[0]).toBe('hooks');
+  expect(offline.order).toContain('local client');
+  // No "you're offline" while the server is simply being asked.
+  expect(offline.order).not.toContain('startedOffline');
+
+  open();
+  await vi.waitFor(() => expect(current()?.isOfflineOnly()).toBe(false));
+  expect(useAuthStore.getState().isAuthenticated).toBe(true);
+  expect(useAuthStore.getState().getClientForAccount(ACCOUNT.id)).toBe(useAuthStore.getState().client);
+});
+
+it('stays on the local copy when the server can\'t be reached', async () => {
+  sessionAnswer = () => new Response('{}', { status: 503 });
+  offline.gone = true;
+  await useAuthStore.getState().checkAuth();
+  await vi.waitFor(() => expect(offline.order).toContain('startedOffline'));
+  expect(useAuthStore.getState().isAuthenticated).toBe(true);
+  expect(current()?.isOfflineOnly()).toBe(true);
+  expect(useAccountStore.getState().getAccountById(ACCOUNT.id)).toBeTruthy();
+});
+
+it('stays on the local copy, and says so, when the server answers a start with a 5xx or 429', async () => {
+  for (const status of [502, 429]) {
+    ACCOUNT = makeAccount();
+    offline.order.length = 0;
+    useAccountStore.setState({ accounts: [ACCOUNT] as never, activeAccountId: ACCOUNT.id, defaultAccountId: ACCOUNT.id });
+    useOfflineStore.setState({ enabled: [ACCOUNT.id] });
+    useAuthStore.setState({ client: null, isAuthenticated: false, activeAccountId: ACCOUNT.id });
+    sessionAnswer = () => new Response('{}', { status });
+    // The probe passes: the server itself is there.
+    offline.gone = false;
+    await useAuthStore.getState().checkAuth();
+    await vi.waitFor(() => expect(offline.order).toContain('startedOffline'));
+    expect(current()?.isOfflineOnly()).toBe(true);
+    expect(useAccountStore.getState().getAccountById(ACCOUNT.id)).toBeTruthy();
+  }
+});
+
+it('goes the usual way when the store has no copy', async () => {
+  offline.session = null;
+  await useAuthStore.getState().checkAuth();
+  expect(offline.order).not.toContain('local client');
+  expect(current()?.isOfflineOnly()).toBe(false);
+});
+
+it('doesn\'t touch the store for an account without it', async () => {
+  useOfflineStore.setState({ enabled: [] });
+  await useAuthStore.getState().checkAuth();
+  expect(offline.order).toEqual(['connect']);
+  expect(current()?.isOfflineOnly()).toBe(false);
+});
+
+it('goes the usual way while the store has no folders yet', async () => {
+  offline.ready = false;
+  await useAuthStore.getState().checkAuth();
+  expect(offline.order).not.toContain('local client');
+  expect(current()?.isOfflineOnly()).toBe(false);
+});
+
+it('still starts on an empty store when the server can\'t be reached', async () => {
+  offline.ready = false;
+  offline.gone = true;
+  sessionAnswer = () => new Response('{}', { status: 503 });
+  await useAuthStore.getState().checkAuth();
+  await vi.waitFor(() => expect(current()?.isOfflineOnly()).toBe(true));
+});
+
+it('fills the From list from the server after the swap, when the local copy had none', async () => {
+  let open: () => void = () => {};
+  connectGate = new Promise((resolve) => { open = resolve; });
+  await useAuthStore.getState().checkAuth();
+  await vi.waitFor(() => expect(current()?.isOfflineOnly()).toBe(true));
+  expect(useAuthStore.getState().identities).toEqual([]);
+  open();
+  await vi.waitFor(() => expect(useAuthStore.getState().identities.map((identity) => identity.email)).toEqual([ACCOUNT.username]));
+  expect(useAuthStore.getState().primaryIdentity?.email).toBe(ACCOUNT.username);
+});
+
+it('doesn\'t let a late local answer overwrite the server\'s From list', async () => {
+  offline.localIdentities = new Promise((resolve) => { offline.releaseLocal = () => resolve([{ id: 'old', email: 'stale@x.test', name: 'Stale', mayDelete: false }]); });
+  await useAuthStore.getState().checkAuth();
+  await vi.waitFor(() => expect(useAuthStore.getState().identities.map((identity) => identity.email)).toEqual([ACCOUNT.username]));
+  offline.releaseLocal();
+  await new Promise((resolve) => setTimeout(resolve, 10));
+  expect(useAuthStore.getState().identities.map((identity) => identity.email)).toEqual([ACCOUNT.username]);
+});
+
+it('leaves the login path to a refused account, and keeps its data', async () => {
+  sessionAnswer = () => new Response('{}', { status: 401 });
+  await useAuthStore.getState().checkAuth();
+  await vi.waitFor(() => expect(useAccountStore.getState().getAccountById(ACCOUNT.id)).toBeUndefined());
+  await vi.waitFor(() => expect(useAuthStore.getState().isAuthenticated).toBe(false));
+  expect(useAuthStore.getState().client).toBeNull();
+  expect(useOfflineStore.getState().enabled).toEqual([ACCOUNT.id]);
+});
diff --git a/stores/__tests__/email-snapshot-account.test.ts b/stores/__tests__/email-snapshot-account.test.ts
index a7d2c4e4f..c2ee1933d 100644
--- a/stores/__tests__/email-snapshot-account.test.ts
+++ b/stores/__tests__/email-snapshot-account.test.ts
@@ -38,6 +38,72 @@ describe('email boot snapshot', { timeout: 30_000 }, () => {
   });
 });
 
+// With the local store on, mail doesn't go to localStorage in plain text too.
+describe('email boot snapshot for an account in the local store', { timeout: 30_000 }, () => {
+  const STATE = { mailboxes: MAILBOXES, selectedMailbox: 'inbox', emails: [{ id: 'e1', mailboxIds: { inbox: true } }] };
+
+  async function fresh(account: string) {
+    vi.useFakeTimers();
+    persistSession(account);
+    vi.resetModules();
+    const { useEmailStore } = await import('@/stores/email-store');
+    const offline = await import('@/lib/offline/state');
+    return { useEmailStore, offline };
+  }
+
+  afterEach(() => vi.useRealTimers());
+
+  it('isn\'t written', async () => {
+    const { useEmailStore, offline } = await fresh('alice@mail.example');
+    offline.useOfflineStore.setState({ enabled: ['alice@mail.example'] });
+    useEmailStore.setState(STATE as never);
+    await vi.advanceTimersByTimeAsync(1500);
+    expect(localStorage.getItem('email-snapshot')).toBeNull();
+  });
+
+  it('is written for an account outside it', async () => {
+    const { useEmailStore, offline } = await fresh('alice@mail.example');
+    offline.useOfflineStore.setState({ enabled: ['bob@mail.example'] });
+    useEmailStore.setState(STATE as never);
+    await vi.advanceTimersByTimeAsync(1500);
+    expect(JSON.parse(localStorage.getItem('email-snapshot') ?? '{}').account).toBe('alice@mail.example');
+  });
+
+  it('goes only when that account\'s store can take over', async () => {
+    const { offline } = await fresh('alice@mail.example');
+    localStorage.setItem('email-snapshot', JSON.stringify({ v: 3, account: 'alice@mail.example', mailboxes: MAILBOXES }));
+    offline.forgetMailSnapshot('bob@mail.example');
+    expect(localStorage.getItem('email-snapshot')).not.toBeNull();
+    offline.forgetMailSnapshot('alice@mail.example');
+    expect(localStorage.getItem('email-snapshot')).toBeNull();
+  });
+});
+
+// A client's late answer doesn't land on the client that replaced it.
+describe('a list answer from a client that was replaced', { timeout: 30_000 }, () => {
+  it('is dropped', async () => {
+    persistSession('alice@mail.example');
+    vi.resetModules();
+    const { useEmailStore } = await import('@/stores/email-store');
+    const { useAuthStore } = await import('@/stores/auth-store');
+    const rows = [{ id: 'stale', mailboxIds: { inbox: true } }];
+    let answer: (value: unknown) => void = () => {};
+    const local = {
+      getAccountId: () => 'acc',
+      getEmails: vi.fn(() => new Promise((resolve) => { answer = resolve; })),
+      getThreadEmailCounts: vi.fn(async () => ({})),
+    };
+    useAuthStore.setState({ client: local as never, activeAccountId: 'alice@mail.example' });
+    useEmailStore.setState({ mailboxes: MAILBOXES as never, selectedMailbox: 'inbox', emails: [] });
+    const fetching = useEmailStore.getState().fetchEmails(local as never, 'inbox');
+    await vi.waitFor(() => expect(local.getEmails).toHaveBeenCalled());
+    useAuthStore.setState({ client: { getAccountId: () => 'acc' } as never });
+    answer({ emails: rows, hasMore: false, total: 1, state: 's1' });
+    await fetching;
+    expect(useEmailStore.getState().emails).toEqual([]);
+  });
+});
+
 // The snapshot keeps the last plain folder that was open; a session that
 // ended in a unified view left Trash there, and every visit to "/" opened it.
 describe('email boot snapshot folder', { timeout: 30_000 }, () => {
diff --git a/stores/account-store.ts b/stores/account-store.ts
index ebaf2b6dc..836dada92 100644
--- a/stores/account-store.ts
+++ b/stores/account-store.ts
@@ -5,6 +5,17 @@ import { IS_DESKTOP_BUILD } from '@/lib/desktop/flag';
 import { forgetDesktopServer } from '@/lib/desktop/bridge';
 import { generateAccountId, generateAvatarColor, getMaxAccounts } from '@/lib/account-utils';
 import { authHooks } from '@/lib/plugin-hooks';
+import { clearEvicted, markEvicted } from '@/lib/offline/state';
+
+export type AccountRemovalReason = 'explicit' | 'evicted';
+
+const removalListeners = new Set<(accountId: string, reason: AccountRemovalReason) => void>();
+
+/** Told before an account leaves the registry, and why. */
+export function onAccountRemoved(listener: (accountId: string, reason: AccountRemovalReason) => void): () => void {
+  removalListeners.add(listener);
+  return () => removalListeners.delete(listener);
+}
 
 function sameServerOrigin(a: string, b: string): boolean {
   try {
@@ -85,7 +96,11 @@ interface AccountState {
   defaultAccountId: string | null;
 
   addAccount: (entry: Omit<AccountEntry, 'id' | 'cookieSlot' | 'avatarColor'>) => string;
-  removeAccount: (accountId: string) => void;
+  /**
+   * `reason`: 'explicit' when someone signed the account out or removed it, its
+   * offline data goes with it; 'evicted' when the app dropped it by itself.
+   */
+  removeAccount: (accountId: string, reason?: AccountRemovalReason) => void;
   setActiveAccount: (accountId: string) => void;
   setDefaultAccount: (accountId: string) => void;
   getDefaultAccount: () => AccountEntry | null;
@@ -108,6 +123,7 @@ export const useAccountStore = create<AccountState>()(
         const state = get();
 
         const id = generateAccountId(entry.username, entry.serverUrl);
+        clearEvicted(id);
         if (state.accounts.some((a) => a.id === id)) {
           // Already exists - update mutable fields and return existing id
           set((s) => ({
@@ -158,9 +174,11 @@ export const useAccountStore = create<AccountState>()(
         return id;
       },
 
-      removeAccount: (accountId) => {
+      removeAccount: (accountId, reason = 'explicit') => {
         if (!get().accounts.some((a) => a.id === accountId)) return;
         const leaving = get().accounts.find((a) => a.id === accountId);
+        if (reason === 'evicted') markEvicted(accountId);
+        for (const listener of [...removalListeners]) listener(accountId, reason);
         set((s) => {
           const remaining = s.accounts.filter((a) => a.id !== accountId);
           const wasDefault = s.defaultAccountId === accountId;
diff --git a/stores/auth-store.ts b/stores/auth-store.ts
index 9f6579916..9fc0c7ca3 100644
--- a/stores/auth-store.ts
+++ b/stores/auth-store.ts
@@ -9,7 +9,7 @@ import { useVacationStore } from './vacation-store';
 import { subscriptionOwner, useCalendarStore } from './calendar-store';
 import { useFilterStore } from './filter-store';
 import { useSettingsStore } from './settings-store';
-import { useAccountStore, type AccountEntry } from './account-store';
+import { useAccountStore, type AccountEntry, type AccountRemovalReason } from './account-store';
 import { fetchPrincipalDisplayName } from '@/lib/stalwart/principal';
 import { fetchConfig, getCachedConfig } from '@/hooks/use-config';
 import { debug } from '@/lib/debug';
@@ -22,7 +22,7 @@ import { DESKTOP_CLIENT_ID_KEY } from '@/lib/desktop/browser-sign-in';
 import { isEmbedded, notifyParent } from '@/lib/iframe-bridge';
 import { snapshotAccount, restoreAccount, clearAllStores, evictAccount, evictAll, forgetAccountRows } from '@/lib/account-state-manager';
 import { clearAllPluginStorage, clearPluginStorageForAccount } from '@/lib/plugin-sandbox/storage-scope';
-import { broadcastSignOut, onSignedOutElsewhere, passSignOutGates, purgeSignedOutData, runBeforeSignOut } from '@/lib/sign-out-cleanup';
+import { broadcastSignOut, onSignedOutElsewhere, passSignOutGates, purgeSignedOutData, runBeforeSignOut, type SignOutCleanupOptions } from '@/lib/sign-out-cleanup';
 import { forgetPrincipals } from '@/lib/delegation/known-principals';
 import { useSearchHistoryStore } from './search-history-store';
 import { useCalendarNotificationStore } from './calendar-notification-store';
@@ -36,6 +36,8 @@ import { IS_LITE, IS_LITE_STALWART } from '@/lib/lite';
 import { withTokenLock } from '@/lib/auth/token-lock';
 import { requestWindowSession, type SharedAccountSession } from '@/lib/popout/channel';
 import { closePopoutWindow, isPopoutWindow, mainWindowStorage } from '@/lib/popout/window-role';
+import { noteCredentialsRejected } from '@/lib/offline/credentials-rejected';
+import { readEvicted, useOfflineStore } from '@/lib/offline/state';
 import { toAsciiEmail } from '@/lib/idn';
 import { flushComposers } from '@/lib/compose-flush-registry';
 import { sortIdentities } from '@/lib/identity-order';
@@ -122,7 +124,7 @@ interface AuthState {
    * (the organisation's session limits, which sign out without asking).
    */
   logoutAll: (options?: LogoutOptions) => Promise<void>;
-  removeAccount: (accountId: string) => void;
+  removeAccount: (accountId: string, reason?: AccountRemovalReason) => void;
   switchAccount: (accountId: string) => Promise<void>;
   checkAuth: () => Promise<void>;
   /**
@@ -164,6 +166,12 @@ export interface LogoutOptions {
    * provider, and signing in again should stay a single click.
    */
   endProviderSession?: boolean;
+  /**
+   * The app, not the user, ends this login, and nothing says the login itself
+   * is over (an outage, an unknown refusal): local mail and the outbox stay,
+   * hidden, for the next sign-in or 30 days.
+   */
+  keepLocalData?: boolean;
 }
 
 const ERROR_PATTERNS: Array<{ key: string; matches: string[] }> = [
@@ -1241,6 +1249,20 @@ function recordPermanentRefreshFailure(status: number, accountId?: string): bool
   return true;
 }
 
+/**
+ * Whether a refused renewal ends the login for real, which wipes the account's
+ * local data: the server said invalid_grant, or the organisation's session limit
+ * was reached. Anything else, including a body we can't read, keeps the data.
+ */
+async function loginReallyOver(res: Response): Promise<boolean> {
+  try {
+    const { error } = await res.clone().json() as { error?: unknown };
+    return error === 'invalid_grant' || error === SESSION_TOO_OLD;
+  } catch {
+    return false;
+  }
+}
+
 function notifySignInAgain(): void {
   void import('@/stores/toast-store').then(({ toast }) => {
     toast.error('Your session could not be renewed', 'Sign in again to continue.');
@@ -1417,7 +1439,27 @@ async function startOfflineClient(accountId: string, serverUrl: string, username
   }
 }
 
-function performFullLogout(set: (state: Partial<AuthState>) => void): void {
+/**
+ * The account's local copy, to show right away while the real connect runs. A
+ * client that answers from the device only; null without the local store for
+ * that account, and the start goes the usual way.
+ */
+async function startLocalCopyClient(accountId: string, serverUrl: string, username: string): Promise<JMAPClient | null> {
+  if (IS_LITE || skipLocalCopy || !useOfflineStore.getState().enabled.includes(accountId)) return null;
+  try {
+    const offline = await import('@/lib/offline/offline-mode');
+    // A store that has no folders yet has nothing to show: the snapshot stays up.
+    const session = await offline.offlineSessionFor(accountId, { withFolders: true });
+    return session ? JMAPClient.fromOfflineSession(serverUrl, username, session) : null;
+  } catch {
+    return null;
+  }
+}
+
+// While device-only clients get replaced, restoring goes straight to the server.
+let skipLocalCopy = false;
+
+function performFullLogout(set: (state: Partial<AuthState>) => void, options: SignOutCleanupOptions = {}): void {
   useSettingsStore.getState().disableSync();
   // With settings sync on, the local settings and templates are a copy of the
   // signed-out account's server file. Left in place, the next account to sign
@@ -1456,7 +1498,9 @@ function performFullLogout(set: (state: Partial<AuthState>) => void): void {
   // doesn't re-write stale values.
   try { localStorage.removeItem('auth-storage'); } catch { /* noop */ }
   try { localStorage.removeItem('account-registry'); } catch { /* noop */ }
-  purgeSignedOutData();
+  // A dropped account's data outlives anyone else's sign-out. The account that
+  // signed out takes its own along when it leaves the registry.
+  purgeSignedOutData({ keepLocalStore: options.keepLocalStore || Object.keys(readEvicted()).length > 0 });
   // Other tabs still hold the accounts' mail in memory.
   broadcastSignOut();
 }
@@ -1477,9 +1521,9 @@ function notifySignedIn(state: { activeAccountId: string | null; username: strin
   void authHooks.onLogin.emit({ accountId: state.activeAccountId, username: state.username ?? '' });
 }
 
-function beforeLogoutHooks(accountId: string): Promise<void> {
+function beforeLogoutHooks(accountId: string, options: SignOutCleanupOptions = {}): Promise<void> {
   return Promise.race([
-    Promise.all([authHooks.onBeforeLogout.emit({ accountId }), runBeforeSignOut(accountId)]).then(() => {}),
+    Promise.all([authHooks.onBeforeLogout.emit({ accountId }), runBeforeSignOut(accountId, options)]).then(() => {}),
     new Promise<void>((resolve) => setTimeout(resolve, LOGOUT_HOOK_BUDGET_MS)),
   ]);
 }
@@ -2288,15 +2332,17 @@ export const useAuthStore = create<AuthState>()(
               // maintenance windows and offline spells.
               if (res.status === 401) {
                 resetRefreshBackoff(accountId ?? undefined);
+                const over = await loginReallyOver(res);
+                if (over && accountId) noteCredentialsRejected(accountId);
                 // Only this login's refresh token was refused.
                 if (accountId && !isActive) {
-                  get().removeAccount(accountId);
+                  get().removeAccount(accountId, over ? 'explicit' : 'evicted');
                   return null;
                 }
                 await saveDraftsBeforeExpiry(slot);
                 notifyParent('sso:session-expired');
                 markSessionExpired();
-                get().logout({ endProviderSession: false });
+                get().logout({ endProviderSession: false, keepLocalData: !over });
                 return null;
               }
               // A Bulwark-side failure (500/502) that keeps repeating will not
@@ -2308,10 +2354,11 @@ export const useAuthStore = create<AuthState>()(
                 notifyParent('sso:session-expired');
                 markSessionExpired();
                 // removeAccount() on the active account would sign out as if the user asked to.
-                if (accountId && accountId !== get().activeAccountId) get().removeAccount(accountId);
+                if (accountId && accountId !== get().activeAccountId) get().removeAccount(accountId, 'evicted');
                 else {
                   await saveDraftsBeforeExpiry(slot);
-                  get().logout({ endProviderSession: false });
+                  // An outage on our side says nothing against the mail on this device.
+                  get().logout({ endProviderSession: false, keepLocalData: true });
                 }
                 return null;
               }
@@ -2381,13 +2428,14 @@ export const useAuthStore = create<AuthState>()(
         const slot = account?.cookieSlot ?? 0;
         // `options` can be a click event when the action is wired straight to onClick.
         const userInitiated = options?.endProviderSession !== false;
+        const keepLocalData = options?.keepLocalData === true;
         const endProviderSession = userInitiated && !wasDemoMode && shouldEndProviderSession(account);
 
         // Signing out on purpose may be stopped by the user (unsent mail in
         // the offline outbox would be lost); an automatic one may not.
         if (userInitiated && !(await passSignOutGates(accountId ?? 'all'))) return;
 
-        await beforeLogoutHooks(accountId ?? 'all');
+        await beforeLogoutHooks(accountId ?? 'all', { keepLocalStore: keepLocalData });
 
         // From here on nothing may renew this slot's session; the cleanup
         // below reopens it once the credentials are gone.
@@ -2405,7 +2453,7 @@ export const useAuthStore = create<AuthState>()(
         if (accountId) {
           clients.delete(accountId);
           evictAccount(accountId);
-          accountStore.removeAccount(accountId);
+          accountStore.removeAccount(accountId, keepLocalData ? 'evicted' : 'explicit');
           forgetPrincipals(accountId);
           if (!wasDemoMode) clearPluginStorageForAccount(accountId);
         }
@@ -2499,7 +2547,9 @@ export const useAuthStore = create<AuthState>()(
             clients.get(remaining.id)?.disconnect();
             clients.delete(remaining.id);
             evictAccount(remaining.id);
-            accountStore.removeAccount(remaining.id);
+            // Dropped by this sign-out, not signed out by anyone: their unsent
+            // mail never passed a question, so it waits for their next sign-in.
+            accountStore.removeAccount(remaining.id, 'evicted');
           }
         }
 
@@ -2513,7 +2563,7 @@ export const useAuthStore = create<AuthState>()(
           ...droppedAccounts.map((dropped) => clearSlotCredentials(dropped.cookieSlot ?? 0, dropped.authMode === 'oauth')),
         ]);
 
-        performFullLogout(set);
+        performFullLogout(set, { keepLocalStore: keepLocalData });
 
         notifyParent('sso:logout');
 
@@ -2524,7 +2574,7 @@ export const useAuthStore = create<AuthState>()(
       // drop it from the registry, and clear its per-slot cookies. If asked to
       // remove the active account, defer to logout() which handles switching
       // away or redirecting.
-      removeAccount: (accountId: string) => {
+      removeAccount: (accountId: string, reason = 'explicit') => {
         if (accountId === get().activeAccountId) { void get().logout(); return; }
         const accountStore = useAccountStore.getState();
         const account = accountStore.getAccountById(accountId);
@@ -2544,7 +2594,7 @@ export const useAuthStore = create<AuthState>()(
         clients.delete(accountId);
         evictAccount(accountId);
         forgetAccountRows(accountId, get().client);
-        accountStore.removeAccount(accountId);
+        accountStore.removeAccount(accountId, reason);
         forgetPrincipals(accountId);
         clearPluginStorageForAccount(accountId);
       },
@@ -2704,7 +2754,7 @@ export const useAuthStore = create<AuthState>()(
 
           // Cannot restore - remove the stale account and redirect to login
           evictAccount(accountId);
-          accountStore.removeAccount(accountId);
+          accountStore.removeAccount(accountId, 'evicted');
           void clearSlotCredentials(targetAccount.cookieSlot, targetAccount.authMode === 'oauth');
 
           // Restore the previous account if still available
@@ -2882,6 +2932,12 @@ export const useAuthStore = create<AuthState>()(
           // with a stale client reference while we're restoring accounts.
           set({ isLoading: true, client: null });
 
+          // The offline hooks have to be there before the first request, or a
+          // start without the server has nothing to paint from.
+          if (!IS_LITE && useOfflineStore.getState().enabled.length > 0) {
+            await import('@/lib/offline/offline-mode').then((offline) => offline.registerOfflineHooks()).catch(() => {});
+          }
+
           // Determine which account to activate first
           const defaultAccount = accountStore.getDefaultAccount();
           const activeId = get().activeAccountId;
@@ -2910,7 +2966,8 @@ export const useAuthStore = create<AuthState>()(
             if (!account.rememberMe && !IS_LITE) {
               forgottenAccounts += 1;
               evictAccount(account.id);
-              accountStore.removeAccount(account.id);
+              // The user's choice on what may be a shared computer: its local data goes too.
+              accountStore.removeAccount(account.id, 'explicit');
               if (account.authMode === 'oauth') void clearSlotCredentials(account.cookieSlot, true);
               return;
             }
@@ -2935,7 +2992,7 @@ export const useAuthStore = create<AuthState>()(
                   // Repeated 500/502 (see recordPermanentRefreshFailure) falls
                   // through here and evicts the account like a rejection. (#972)
                   if (res.status >= 500) notifySignInAgain();
-                  throw new Error(`Token refresh failed: ${res.status}`);
+                  throw Object.assign(new Error(`Token refresh failed: ${res.status}`), { loginOver: await loginReallyOver(res) });
                 }
               } else {
                 const res = await fetchSlotSession(account.cookieSlot);
@@ -2953,7 +3010,7 @@ export const useAuthStore = create<AuthState>()(
                     impersonated: session.impersonated === true,
                   });
                   void syncAccountDisplayName(account.id, client);
-                } else if (res.status >= 500) {
+                } else if (res.status >= 500 || res.status === 429) {
                   throw new TransientAuthError('Session restore failed', res.status);
                 } else {
                   throw new Error(`Session cookie missing: ${res.status}`);
@@ -2992,9 +3049,10 @@ export const useAuthStore = create<AuthState>()(
               }
               // Remove unrestorable accounts so the user is prompted to log in
               // again rather than seeing a stale error entry forever. Its
-              // refresh token goes with it: nothing would use or revoke it.
+              // refresh token goes with it: nothing would use or revoke it. Its
+              // local data waits, unless the server really ended the login.
               evictAccount(account.id);
-              accountStore.removeAccount(account.id);
+              accountStore.removeAccount(account.id, (err as { loginOver?: boolean }).loginOver ? 'explicit' : 'evicted');
               void clearSlotCredentials(account.cookieSlot, account.authMode === 'oauth');
             }
           };
@@ -3005,7 +3063,56 @@ export const useAuthStore = create<AuthState>()(
           // bump re-runs per-client effects (push binding) over the full set.
           const targetEntry = accounts.find((account) => account.id === targetId);
           const otherAccounts = accounts.filter((account) => account.id !== targetId);
-          if (targetEntry) await restoreAccount(targetEntry);
+          // With the local store on, the local copy shows at once and the real
+          // connect takes over when it's done (swapInRealClient below).
+          const localCopy = targetEntry && !targetEntry.awaitingSignIn && targetEntry.rememberMe
+            ? await startLocalCopyClient(targetEntry.id, targetEntry.serverUrl, targetEntry.username)
+            : null;
+          if (localCopy && targetEntry) {
+            clients.set(targetEntry.id, localCopy);
+            accountStore.updateAccount(targetEntry.id, { isConnected: true, hasError: false });
+          } else if (targetEntry) {
+            await restoreAccount(targetEntry);
+          }
+
+          /**
+           * The real connect behind a local copy on screen. No reload and no
+           * loading state: the client in the store changes and the pages
+           * refetch from the server. A refused account goes through the usual
+           * restore path, an unreachable server keeps the local copy.
+           */
+          const swapInRealClient = async (entry: (typeof accounts)[number], local: JMAPClient) => {
+            clients.delete(entry.id);
+            await restoreAccount(entry);
+            const real = clients.get(entry.id);
+            if (!real) {
+              if (useAccountStore.getState().getAccountById(entry.id)) {
+                clients.set(entry.id, local);
+                // A 5xx or a rate limit, with the server up otherwise. The app stays
+                // on the local copy, and says so, and leaves it when the server answers.
+                void import('@/lib/offline/offline-mode').then((offline) => offline.markStartedOffline()).catch(() => {});
+                return;
+              }
+              if (get().activeAccountId !== entry.id) return;
+              // Refused, and evicted by the restore. Whoever is left, or the login page.
+              set({ client: null, isAuthenticated: false, activeAccountId: null });
+              if (useAccountStore.getState().accounts.length > 0) await get().checkAuth();
+              else markSessionExpired();
+              return;
+            }
+            if (get().activeAccountId !== entry.id) return;
+            initializeFeatureStores(real);
+            set({ client: real, ...getClientRateLimitState(real), connectionLost: false, error: null });
+            // The local copy may have had none yet, and the server's are newer.
+            void real.getIdentities()
+              .then((raw) => {
+                if (get().client !== real) return;
+                const { identities, primaryIdentity } = loadIdentities(raw, entry.username);
+                set({ identities, primaryIdentity });
+                applyPreferredIdentity(entry.id);
+              })
+              .catch((err) => debug.error('Failed to load identities after the local copy:', err));
+          };
 
           // A few at a time rather than one after the other: with many logins
           // the serial walk left the last of them - and with it a complete
@@ -3049,6 +3156,8 @@ export const useAuthStore = create<AuthState>()(
             // spending a serial round trip before the UI unblocks.
             const identitiesLoaded = targetClient.getIdentities()
               .then((raw) => {
+                // The real client took over meanwhile, and asks for itself.
+                if (localCopy && get().client !== null && get().client !== targetClient) return;
                 const { identities, primaryIdentity } = loadIdentities(raw, targetAccount.username);
                 set({ identities, primaryIdentity });
               })
@@ -3067,6 +3176,7 @@ export const useAuthStore = create<AuthState>()(
               error: null,
               activeAccountId: targetId,
             });
+            if (localCopy && targetEntry) void swapInRealClient(targetEntry, localCopy);
 
             fetchConfig().then(config => {
               if (!config.settingsSyncEnabled) return;
@@ -3484,7 +3594,12 @@ export const useAuthStore = create<AuthState>()(
         const offline = [...clients.entries()].filter(([, c]) => c.isOfflineOnly());
         if (offline.length === 0) return true;
         for (const [id] of offline) clients.delete(id);
-        await get().checkAuth();
+        skipLocalCopy = true;
+        try {
+          await get().checkAuth();
+        } finally {
+          skipLocalCopy = false;
+        }
         return offline.every(([id]) => {
           const client = clients.get(id);
           return !!client && !client.isOfflineOnly();
diff --git a/stores/email-store.ts b/stores/email-store.ts
index 0f1b60161..8bff6f55d 100644
--- a/stores/email-store.ts
+++ b/stores/email-store.ts
@@ -38,6 +38,7 @@ import { SendCancelledCleanupError } from "@/lib/send-failure-message";
 import type { StorageQuota } from "@/lib/quota";
 import { isArchiveActionEnabled } from "@/lib/archive-gate";
 import { getOutboxHooks } from "@/lib/offline/outbox-hooks";
+import { useOfflineStore } from "@/lib/offline/state";
 import {
   READ_FILTER, UNREAD_FILTER, UNREAD_SECTION_SIZE, andFilters, isUnreadFirstView, mergeUnreadSection,
   openSectionRows, sectionFromUnreadRows, unreadSectionRowCount, withoutReached, type UnreadSection,
@@ -1626,10 +1627,13 @@ function threadCountsPatch(
 function captureEmailListView(): () => boolean {
   const view = useEmailStore.getState();
   const activeAccountId = useAuthStore.getState().activeAccountId;
+  // A local copy's late answer must not overwrite what the real client loaded.
+  const authClient = useAuthStore.getState().client;
   const epoch = currentStoreEpoch();
   return () => {
     const current = useEmailStore.getState();
     return currentStoreEpoch() === epoch
+      && useAuthStore.getState().client === authClient
       && current.selectedMailbox === view.selectedMailbox
       && current.selectedKeyword === view.selectedKeyword
       && current.viewingAccountId === view.viewingAccountId
@@ -8728,6 +8732,8 @@ if (typeof window !== 'undefined') {
       if (s.searchQuery || s.selectedKeyword || s.isScheduledView || s.viewingAccountId || s.isUnifiedView) return;
       const account = persistedAuthState()?.activeAccountId;
       if (typeof account !== 'string' || !account) return;
+      // Its mail lives encrypted in the store, and not in plain localStorage too.
+      if (useOfflineStore.getState().enabled.includes(account)) return;
       try {
         window.localStorage.setItem(EMAIL_SNAPSHOT_KEY, JSON.stringify({
           v: EMAIL_SNAPSHOT_VERSION,
diff --git a/stores/file-store.ts b/stores/file-store.ts
index f9ec1a6b5..190c37264 100644
--- a/stores/file-store.ts
+++ b/stores/file-store.ts
@@ -1,3 +1,4 @@
+import { getOfflineHooks, type OfflineClientRef } from '@/lib/jmap/offline-hooks';
 import { create } from 'zustand';
 import type { FileNodeListings, IJMAPClient } from '@/lib/jmap/client-interface';
 import type { FileNode, FileNodeRights } from '@/lib/jmap/types';
@@ -1688,7 +1689,8 @@ export const useFileStore = create<FileState>((set, get) => ({
   },
 
   addRecentFile: (name: string, id: string) => {
-    const { recentFiles } = get();
+    const { recentFiles, client } = get();
+    if (client && id) getOfflineHooks()?.fileOpened?.(client as OfflineClientRef, client.getFilesAccountId(), id);
     const entry = { name, id, timestamp: Date.now() };
     const filtered = recentFiles.filter(r => r.id !== id);
     const next = [entry, ...filtered].slice(0, 20);