chore: update version number to 0.1.35

App.tsx

@@ -36,6 +36,7 @@ import { useAuthStore } from './src/stores/auth-store';
 import { useCalendarStore } from './src/stores/calendar-store';
 import { useContactsStore } from './src/stores/contacts-store';
 import { useEmailStore } from './src/stores/email-store';
+import { useHasCalendar, useHasContacts, useHasFiles } from './src/lib/capabilities';
 import { useSettingsStore } from './src/stores/settings-store';
 import { useLocaleStore } from './src/stores/locale-store';
 import { useNetworkStore } from './src/stores/network-store';
@@ -88,6 +89,10 @@ function MainTabsNavigator({ navigation }: NativeStackScreenProps<RootStackParam
   const mailboxes = useEmailStore((state) => state.mailboxes);
   const logout = useAuthStore((state) => state.logout);
   const inboxUnreadCount = mailboxes.find((mailbox) => mailbox.role === 'inbox')?.unreadEmails ?? 0;
+  const hasCalendar = useHasCalendar();
+  const hasContacts = useHasContacts();
+  const hasFiles = useHasFiles();
+  const disabledTabStyle = { opacity: 0.4 } as const;
 
   return (
     <View style={{ flex: 1, backgroundColor: c.background }}>
@@ -149,6 +154,13 @@ function MainTabsNavigator({ navigation }: NativeStackScreenProps<RootStackParam
         component={CalendarScreen}
         options={{
           tabBarIcon: ({ color, size }) => <Calendar size={size} color={color} />,
+          tabBarItemStyle: hasCalendar ? undefined : disabledTabStyle,
+          tabBarAccessibilityLabel: hasCalendar ? 'Calendar' : 'Calendar (unavailable)',
+        }}
+        listeners={{
+          tabPress: (e) => {
+            if (!hasCalendar) e.preventDefault();
+          },
         }}
       />
       <Tab.Screen
@@ -156,6 +168,13 @@ function MainTabsNavigator({ navigation }: NativeStackScreenProps<RootStackParam
         component={ContactsScreen}
         options={{
           tabBarIcon: ({ color, size }) => <BookUser size={size} color={color} />,
+          tabBarItemStyle: hasContacts ? undefined : disabledTabStyle,
+          tabBarAccessibilityLabel: hasContacts ? 'Contacts' : 'Contacts (unavailable)',
+        }}
+        listeners={{
+          tabPress: (e) => {
+            if (!hasContacts) e.preventDefault();
+          },
         }}
       />
       <Tab.Screen
@@ -163,6 +182,13 @@ function MainTabsNavigator({ navigation }: NativeStackScreenProps<RootStackParam
         component={FilesScreen}
         options={{
           tabBarIcon: ({ color, size }) => <HardDrive size={size} color={color} />,
+          tabBarItemStyle: hasFiles ? undefined : disabledTabStyle,
+          tabBarAccessibilityLabel: hasFiles ? 'Files' : 'Files (unavailable)',
+        }}
+        listeners={{
+          tabPress: (e) => {
+            if (!hasFiles) e.preventDefault();
+          },
         }}
       />
       <Tab.Screen

VERSION

@@ -1 +1 @@
-0.1.31
+0.1.35

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "bulwark-mobile",
-  "version": "0.1.31",
+  "version": "0.1.35",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "bulwark-mobile",
-      "version": "0.1.31",
+      "version": "0.1.35",
       "license": "AGPL-3.0-only",
       "dependencies": {
         "@react-native-async-storage/async-storage": "2.2.0",

package.json

@@ -1,6 +1,6 @@
 {
   "name": "bulwark-mobile",
-  "version": "0.1.31",
+  "version": "0.1.35",
   "license": "AGPL-3.0-only",
   "main": "index.ts",
   "scripts": {

src/api/email.ts

@@ -22,6 +22,55 @@ export async function getMailboxes(): Promise<Mailbox[]> {
   return res.methodResponses[0][1].list;
 }
 
+// Variant that also returns the JMAP `state` token so callers can later issue
+// Mailbox/changes(sinceState=…) to fetch only what changed.
+export async function getMailboxesWithState(): Promise<{ list: Mailbox[]; state: string }> {
+  const accountId = jmapClient.accountId;
+  const res = await jmapClient.request(
+    [['Mailbox/get', { accountId }, '0']],
+  );
+  const body = res.methodResponses[0][1];
+  return { list: body.list as Mailbox[], state: body.state as string };
+}
+
+export async function getMailboxesByIds(ids: string[]): Promise<{ list: Mailbox[]; state: string }> {
+  if (ids.length === 0) return { list: [], state: '' };
+  const accountId = jmapClient.accountId;
+  const res = await jmapClient.request(
+    [['Mailbox/get', { accountId, ids }, '0']],
+  );
+  const body = res.methodResponses[0][1];
+  return { list: body.list as Mailbox[], state: body.state as string };
+}
+
+export interface MailboxChangesResult {
+  oldState: string;
+  newState: string;
+  hasMoreChanges: boolean;
+  created: string[];
+  updated: string[];
+  destroyed: string[];
+}
+
+// Returns null when the server can't compute the diff (typically
+// `cannotCalculateChanges`); callers should fall back to a full Mailbox/get.
+export async function getMailboxChanges(sinceState: string): Promise<MailboxChangesResult | null> {
+  const accountId = jmapClient.accountId;
+  const res = await jmapClient.request(
+    [['Mailbox/changes', { accountId, sinceState }, '0']],
+  );
+  const [name, body] = res.methodResponses[0];
+  if (name === 'error') return null;
+  return {
+    oldState: body.oldState as string,
+    newState: body.newState as string,
+    hasMoreChanges: Boolean(body.hasMoreChanges),
+    created: (body.created as string[]) ?? [],
+    updated: (body.updated as string[]) ?? [],
+    destroyed: (body.destroyed as string[]) ?? [],
+  };
+}
+
 export async function createMailbox(
   data: { name: string; parentId?: string | null },
 ): Promise<string> {
@@ -83,6 +132,22 @@ export async function deleteMailbox(id: string): Promise<void> {
   }
 }
 
+function buildMailboxQueryFilter(
+  mailboxId: string,
+  userFilter: Record<string, unknown> | undefined,
+): Record<string, unknown> {
+  const inMailbox = { inMailbox: mailboxId };
+  // JMAP filters are either a FilterCondition or a FilterOperator (operator +
+  // conditions) — never both. Spreading a FilterOperator next to `inMailbox`
+  // produces a hybrid object that servers reduce to the FilterCondition,
+  // silently dropping the operator's conditions (e.g. the "unread" toggle).
+  if (!userFilter || Object.keys(userFilter).length === 0) return inMailbox;
+  if ('operator' in userFilter) {
+    return { operator: 'AND', conditions: [inMailbox, userFilter] };
+  }
+  return { ...inMailbox, ...userFilter };
+}
+
 export async function queryEmails(
   mailboxId: string,
   options?: {
@@ -91,20 +156,9 @@ export async function queryEmails(
     sort?: Array<{ property: string; isAscending: boolean }>;
     filter?: Record<string, unknown>;
   },
-): Promise<{ ids: string[]; total: number }> {
+): Promise<{ ids: string[]; total: number; queryState?: string }> {
   const accountId = jmapClient.accountId;
-  const inMailbox = { inMailbox: mailboxId };
-  const userFilter = options?.filter;
-  // JMAP filters are either a FilterCondition or a FilterOperator (operator +
-  // conditions) — never both. Spreading a FilterOperator next to `inMailbox`
-  // produces a hybrid object that servers reduce to the FilterCondition,
-  // silently dropping the operator's conditions (e.g. the "unread" toggle).
-  const filter =
-    !userFilter || Object.keys(userFilter).length === 0
-      ? inMailbox
-      : 'operator' in userFilter
-        ? { operator: 'AND', conditions: [inMailbox, userFilter] }
-        : { ...inMailbox, ...userFilter };
+  const filter = buildMailboxQueryFilter(mailboxId, options?.filter);
   const res = await jmapClient.request([
     ['Email/query', {
       accountId,
@@ -115,9 +169,56 @@ export async function queryEmails(
       calculateTotal: true,
     }, '0'],
   ]);
+  const body = res.methodResponses[0][1];
   return {
-    ids: res.methodResponses[0][1].ids,
-    total: res.methodResponses[0][1].total,
+    ids: body.ids,
+    total: body.total,
+    queryState: body.queryState as string | undefined,
+  };
+}
+
+export interface EmailQueryChangesResult {
+  oldQueryState: string;
+  newQueryState: string;
+  total: number;
+  removed: string[];
+  added: Array<{ id: string; index: number }>;
+}
+
+// Run Email/queryChanges for the standard "by receivedAt desc, in this mailbox"
+// query. Returns null when the server replies with `cannotCalculateChanges`
+// (or any other error) — caller should fall back to a fresh Email/query.
+export async function getEmailQueryChanges(
+  mailboxId: string,
+  sinceQueryState: string,
+  options?: {
+    sort?: Array<{ property: string; isAscending: boolean }>;
+    filter?: Record<string, unknown>;
+    upToId?: string;
+    maxChanges?: number;
+  },
+): Promise<EmailQueryChangesResult | null> {
+  const accountId = jmapClient.accountId;
+  const filter = buildMailboxQueryFilter(mailboxId, options?.filter);
+  const args: Record<string, unknown> = {
+    accountId,
+    filter,
+    sort: options?.sort ?? [{ property: 'receivedAt', isAscending: false }],
+    sinceQueryState,
+    calculateTotal: true,
+  };
+  if (options?.upToId) args.upToId = options.upToId;
+  if (options?.maxChanges) args.maxChanges = options.maxChanges;
+
+  const res = await jmapClient.request([['Email/queryChanges', args, '0']]);
+  const [name, body] = res.methodResponses[0];
+  if (name === 'error') return null;
+  return {
+    oldQueryState: body.oldQueryState as string,
+    newQueryState: body.newQueryState as string,
+    total: (body.total as number) ?? 0,
+    removed: (body.removed as string[]) ?? [],
+    added: (body.added as Array<{ id: string; index: number }>) ?? [],
   };
 }
 
@@ -129,6 +230,59 @@ export async function getEmails(ids: string[]): Promise<Email[]> {
   return res.methodResponses[0][1].list;
 }
 
+// Returns the Email/get response with the JMAP `state` token. Used by the
+// store so we can later issue Email/changes(sinceState=…) for incremental
+// updates instead of re-fetching the full list.
+export async function getEmailsWithState(ids: string[]): Promise<{ list: Email[]; state: string }> {
+  if (ids.length === 0) {
+    // Email/get with an empty id list still returns a state token; useful for
+    // priming the store after an empty mailbox query.
+    const accountId = jmapClient.accountId;
+    const res = await jmapClient.request([
+      ['Email/get', { accountId, ids: [], properties: EMAIL_LIST_PROPERTIES }, '0'],
+    ]);
+    const body = res.methodResponses[0][1];
+    return { list: [], state: body.state as string };
+  }
+  const accountId = jmapClient.accountId;
+  const res = await jmapClient.request([
+    ['Email/get', { accountId, ids, properties: EMAIL_LIST_PROPERTIES }, '0'],
+  ]);
+  const body = res.methodResponses[0][1];
+  return { list: body.list as Email[], state: body.state as string };
+}
+
+export interface EmailChangesResult {
+  oldState: string;
+  newState: string;
+  hasMoreChanges: boolean;
+  created: string[];
+  updated: string[];
+  destroyed: string[];
+}
+
+// Returns null when the server replies with `cannotCalculateChanges` or any
+// other error response; caller should treat that as "rebuild from scratch".
+export async function getEmailChanges(
+  sinceState: string,
+  maxChanges?: number,
+): Promise<EmailChangesResult | null> {
+  const accountId = jmapClient.accountId;
+  const args: Record<string, unknown> = { accountId, sinceState };
+  if (maxChanges) args.maxChanges = maxChanges;
+  const res = await jmapClient.request([['Email/changes', args, '0']]);
+  const [name, body] = res.methodResponses[0];
+  if (name === 'error') return null;
+  return {
+    oldState: body.oldState as string,
+    newState: body.newState as string,
+    hasMoreChanges: Boolean(body.hasMoreChanges),
+    created: (body.created as string[]) ?? [],
+    updated: (body.updated as string[]) ?? [],
+    destroyed: (body.destroyed as string[]) ?? [],
+  };
+}
+
 export async function getFullEmail(id: string): Promise<Email> {
   const accountId = jmapClient.accountId;
   const res = await jmapClient.request([

src/lib/capabilities.ts

@@ -0,0 +1,35 @@
+import { CAPABILITIES } from '../api/types';
+import { useAuthStore } from '../stores/auth-store';
+
+// When the session is null (cold start, offline restore) we assume features
+// are available so they don't flicker off mid-restore. Once the live session
+// arrives, the real capability set takes over.
+function sessionHasCapability(capability: string): boolean {
+  const session = useAuthStore.getState().session;
+  if (!session) return true;
+  return capability in session.capabilities;
+}
+
+export function hasCalendarCapability(): boolean {
+  return sessionHasCapability(CAPABILITIES.CALENDARS);
+}
+
+export function hasContactsCapability(): boolean {
+  return sessionHasCapability(CAPABILITIES.CONTACTS);
+}
+
+export function hasFilesCapability(): boolean {
+  return sessionHasCapability(CAPABILITIES.FILES);
+}
+
+export function useHasCalendar(): boolean {
+  return useAuthStore((s) => (s.session ? CAPABILITIES.CALENDARS in s.session.capabilities : true));
+}
+
+export function useHasContacts(): boolean {
+  return useAuthStore((s) => (s.session ? CAPABILITIES.CONTACTS in s.session.capabilities : true));
+}
+
+export function useHasFiles(): boolean {
+  return useAuthStore((s) => (s.session ? CAPABILITIES.FILES in s.session.capabilities : true));
+}

src/screens/SettingsScreen.tsx

@@ -36,6 +36,7 @@ import { LanguageSettings } from '../components/settings/LanguageSettings';
 import { ComposingSettings } from '../components/settings/ComposingSettings';
 import { LayoutSettings } from '../components/settings/LayoutSettings';
 import { useLocaleStore } from '../stores/locale-store';
+import { useHasCalendar, useHasContacts, useHasFiles } from '../lib/capabilities';
 
 type Tab =
   | 'account' | 'language' | 'notifications'
@@ -155,6 +156,16 @@ export default function SettingsScreen({ onLogout, onBack, onTabSelect }: Settin
   // Subscribe to locale so labels re-render when the user picks a different language.
   const locale = useLocaleStore((s) => s.locale);
   const t = useLocaleStore((s) => s.t);
+  const hasCalendar = useHasCalendar();
+  const hasContacts = useHasContacts();
+  const hasFiles = useHasFiles();
+  const unavailableTabs = React.useMemo(() => {
+    const set = new Set<Tab>();
+    if (!hasCalendar) set.add('calendar');
+    if (!hasContacts) set.add('contacts');
+    if (!hasFiles) set.add('files');
+    return set;
+  }, [hasCalendar, hasContacts, hasFiles]);
   const groupedTabs = React.useMemo(() => {
     void locale; // dependency: re-translate on locale change
     return groupTabs().map((g) => ({
@@ -178,6 +189,7 @@ export default function SettingsScreen({ onLogout, onBack, onTabSelect }: Settin
 
   const handleTabPress = (tab: TabDef) => {
     if (!tab.implemented) return;
+    if (unavailableTabs.has(tab.id)) return;
     setSelectedTab(tab.id);
     onTabSelect?.(tab.id);
   };
@@ -241,7 +253,13 @@ export default function SettingsScreen({ onLogout, onBack, onTabSelect }: Settin
 
               {group.items.map((tab) => {
                 const Icon = tab.icon;
-                const disabled = !tab.implemented;
+                const unavailable = unavailableTabs.has(tab.id);
+                const disabled = !tab.implemented || unavailable;
+                const badgeLabel = !tab.implemented
+                  ? 'Not implemented'
+                  : unavailable
+                    ? 'Unavailable'
+                    : null;
                 return (
                   <Pressable
                     key={tab.id}
@@ -269,9 +287,9 @@ export default function SettingsScreen({ onLogout, onBack, onTabSelect }: Settin
                         </View>
                       )}
                     </View>
-                    {disabled ? (
+                    {badgeLabel ? (
                       <View style={styles.notWorkingBadge}>
-                        <Text style={styles.notWorkingText}>Not implemented</Text>
+                        <Text style={styles.notWorkingText}>{badgeLabel}</Text>
                       </View>
                     ) : (
                       <ChevronRight size={16} color={c.mutedForeground} />

src/stores/__tests__/email-store.test.ts

@@ -2,8 +2,16 @@ import { describe, it, expect, vi, beforeEach } from 'vitest';
 
 vi.mock('../../api/email', () => ({
   getMailboxes: vi.fn(),
+  // New helpers used by the incremental-sync path. Default behavior: behave
+  // like a first-ever load — no prior state, full re-query expected.
+  getMailboxesWithState: vi.fn(async () => ({ list: [], state: 'mb-state-0' })),
+  getMailboxesByIds: vi.fn(async () => ({ list: [], state: 'mb-state-0' })),
+  getMailboxChanges: vi.fn(async () => null),
   queryEmails: vi.fn(),
+  getEmailQueryChanges: vi.fn(async () => null),
   getEmails: vi.fn(),
+  getEmailsWithState: vi.fn(async () => ({ list: [], state: 'em-state-0' })),
+  getEmailChanges: vi.fn(async () => null),
   getFullEmail: vi.fn(),
   setEmailKeywords: vi.fn(),
   moveEmail: vi.fn(),
@@ -20,23 +28,54 @@ vi.mock('../settings-store', () => ({
   useSettingsStore: { getState: () => ({ archiveMode: 'single', emailsPerPage: 25 }) },
 }));
 
-// email-store now early-returns from fetch actions when jmapClient.isConnected
-// is false (cold-start guard). The tests exercise those actions, so present
-// a connected stub.
+// offline-cache-store is touched by selectMailbox (cache-seed fallback),
+// getEmailDetail (best-effort body refresh), and setActiveAccount (account
+// switch). Stub it as an empty cache so tests don't need to set up
+// AsyncStorage.
+vi.mock('../offline-cache-store', () => ({
+  useOfflineCacheStore: {
+    getState: () => ({
+      activeAccountId: null,
+      hydrated: true,
+      hydrate: vi.fn(),
+      setAccount: vi.fn(async () => undefined),
+      totalCount: () => 0,
+      getEmailsInMailbox: vi.fn(async () => []),
+      has: () => false,
+      get: vi.fn(async () => null),
+      put: vi.fn(async () => undefined),
+    }),
+  },
+}));
+
+// email-store now early-returns from fetch actions unless jmapClient is
+// connected AND serving the same logical account the store has active
+// (`generateAccountId(username, serverUrl) === activeAccountId`). The
+// tests exercise those actions, so present a fully connected stub plus
+// the matching username/serverUrl pair. beforeEach() syncs the store's
+// activeAccountId to the id these credentials produce.
 vi.mock('../../api/jmap-client', () => ({
   jmapClient: {
     isConnected: true,
     accountId: 'acc-1',
+    username: 'test@example.com',
+    serverUrl: 'https://mail.example.com',
     currentSession: { apiUrl: 'https://mail.example.com/jmap/' },
+    // refreshEmails / loadMoreEmails chunk by this value when fetching ids.
+    getMaxObjectsInGet: () => 500,
   },
 }));
 
+import { generateAccountId } from '../../lib/account-utils';
+const TEST_ACCOUNT_ID = generateAccountId('test@example.com', 'https://mail.example.com');
+
 import * as emailApi from '../../api/email';
 import { useEmailStore } from '../email-store';
 
-const mockGetMailboxes = emailApi.getMailboxes as ReturnType<typeof vi.fn>;
+const mockGetMailboxesWithState = emailApi.getMailboxesWithState as ReturnType<typeof vi.fn>;
 const mockQueryEmails = emailApi.queryEmails as ReturnType<typeof vi.fn>;
 const mockGetEmails = emailApi.getEmails as ReturnType<typeof vi.fn>;
+const mockGetEmailsWithState = emailApi.getEmailsWithState as ReturnType<typeof vi.fn>;
 const mockGetFullEmail = emailApi.getFullEmail as ReturnType<typeof vi.fn>;
 const mockSetKeywords = emailApi.setEmailKeywords as ReturnType<typeof vi.fn>;
 const mockMoveEmail = emailApi.moveEmail as ReturnType<typeof vi.fn>;
@@ -46,6 +85,10 @@ const mockSearchEmails = emailApi.searchEmails as ReturnType<typeof vi.fn>;
 beforeEach(() => {
   vi.clearAllMocks();
   useEmailStore.getState().reset();
+  // Wire the store's active account to the one the mocked jmapClient is
+  // serving, so the guard inside fetchMailboxes / refreshEmails / etc.
+  // doesn't short-circuit the tests.
+  useEmailStore.setState({ activeAccountId: TEST_ACCOUNT_ID });
 });
 
 describe('email-store', () => {
@@ -55,7 +98,7 @@ describe('email-store', () => {
         { id: 'mb-1', name: 'Inbox', role: 'inbox' },
         { id: 'mb-2', name: 'Sent', role: 'sent' },
       ];
-      mockGetMailboxes.mockResolvedValue(mailboxes);
+      mockGetMailboxesWithState.mockResolvedValue({ list: mailboxes, state: 'mb-state-1' });
 
       await useEmailStore.getState().fetchMailboxes();
 
@@ -63,7 +106,7 @@ describe('email-store', () => {
     });
 
     it('should set error on failure', async () => {
-      mockGetMailboxes.mockRejectedValue(new Error('Network error'));
+      mockGetMailboxesWithState.mockRejectedValue(new Error('Network error'));
 
       await useEmailStore.getState().fetchMailboxes();
 
@@ -73,12 +116,12 @@ describe('email-store', () => {
 
   describe('selectMailbox', () => {
     it('should query and fetch emails for mailbox', async () => {
-      mockQueryEmails.mockResolvedValue({ ids: ['e1', 'e2'], total: 2 });
+      mockQueryEmails.mockResolvedValue({ ids: ['e1', 'e2'], total: 2, queryState: 'q-1' });
       const emails = [
         { id: 'e1', subject: 'Email 1' },
         { id: 'e2', subject: 'Email 2' },
       ];
-      mockGetEmails.mockResolvedValue(emails);
+      mockGetEmailsWithState.mockResolvedValue({ list: emails, state: 'em-state-1' });
 
       await useEmailStore.getState().selectMailbox('mb-1');
 
@@ -90,11 +133,14 @@ describe('email-store', () => {
     });
 
     it('should handle empty mailbox', async () => {
-      mockQueryEmails.mockResolvedValue({ ids: [], total: 0 });
+      mockQueryEmails.mockResolvedValue({ ids: [], total: 0, queryState: 'q-empty' });
 
       await useEmailStore.getState().selectMailbox('mb-empty');
 
       expect(useEmailStore.getState().emails).toEqual([]);
+      // First-time load with no ids hits getEmailsWithState only to prime
+      // emailState (with an empty ids array). It should NOT call legacy
+      // getEmails — that path is reserved for pagination/search.
       expect(mockGetEmails).not.toHaveBeenCalled();
     });
   });

src/stores/auth-store.ts

@@ -46,8 +46,28 @@ export interface AuthState {
   clearError: () => void;
 }
 
-function resetFeatureStores(): void {
-  useEmailStore.getState().reset();
+// Wipe ALL cached feature data for ALL accounts. Used for logoutAll where
+// the user is signing out of everything — we don't want stale snapshots
+// lingering on disk for accounts that no longer exist.
+function clearAllFeatureStores(): void {
+  useEmailStore.getState().clearAllAccounts();
+  useContactsStore.getState().reset();
+  useCalendarStore.getState().reset();
+}
+
+// Drop the named account from the email cache, then reset the (per-session,
+// not yet per-account) contacts and calendar stores. Used by logout when
+// signing one account out while others remain.
+function clearAccountFeatureStores(accountId: string | null): void {
+  if (accountId) {
+    useEmailStore.getState().removeAccount(accountId);
+  } else {
+    useEmailStore.getState().clearAllAccounts();
+  }
+  // Contacts and calendar stores aren't yet keyed by account — the safe
+  // thing on logout is still to wipe them so the next account doesn't see
+  // the previous user's data. Per-account caching for those stores is a
+  // follow-up.
   useContactsStore.getState().reset();
   useCalendarStore.getState().reset();
 }
@@ -108,11 +128,13 @@ export const useAuthStore = create<AuthState>((set, get) => ({
   login: async (serverUrl, username, password, opts) => {
     set({ isLoading: true, error: null });
     try {
-      // Adding an additional account - snapshot/reset feature stores so the
-      // new account starts with a clean slate.
+      // Adding an additional account - snapshot the current account away so
+      // its cache survives, then reset the JMAP client for the new login.
+      // Contacts/calendar are still single-bucket, so wipe those.
       if (opts?.addAccount && get().isAuthenticated) {
         jmapClient.reset();
-        resetFeatureStores();
+        useContactsStore.getState().reset();
+        useCalendarStore.getState().reset();
       }
 
       const session = await jmapClient.connect(serverUrl, username, password);
@@ -129,6 +151,9 @@ export const useAuthStore = create<AuthState>((set, get) => ({
         hasError: false,
       });
       accountStore.setActiveAccount(accountId);
+      // Swap the email store's active view to the new account so the rest of
+      // this function (and refetchFeatureStores) writes to the right bucket.
+      useEmailStore.getState().setActiveAccount(accountId);
 
       applyConnectedState(set, session, serverUrl.replace(/\/+$/, ''), username, accountId);
     } catch (err) {
@@ -164,7 +189,7 @@ export const useAuthStore = create<AuthState>((set, get) => ({
     }
 
     jmapClient.reset();
-    resetFeatureStores();
+    clearAccountFeatureStores(currentId);
 
     // Switch to next remaining account, if any
     const remaining = accountStore.accounts;
@@ -198,7 +223,7 @@ export const useAuthStore = create<AuthState>((set, get) => ({
     await teardownPushNotifications().catch(() => undefined);
     await jmapClient.clearAllCredentials(ids);
     jmapClient.reset();
-    resetFeatureStores();
+    clearAllFeatureStores();
 
     for (const id of ids) accountStore.removeAccount(id);
 
@@ -225,19 +250,31 @@ export const useAuthStore = create<AuthState>((set, get) => ({
 
     set({ isLoading: true, error: null });
 
-    // Load the new account's session BEFORE clearing jmapClient or feature
-    // stores. The previous order (reset → resetFeatureStores → loadAccount)
-    // left jmapClient with no accountId during the loadAccount await, and
-    // any fetch fired by a screen effect reacting to the emptied stores
-    // (e.g. EmailListScreen retrying fetchMailboxes when mailboxes goes to
-    // []) threw "Not authenticated - call connect() first". loadAccount
-    // overwrites credentials/session/_accountId itself, so the pre-reset
-    // is unnecessary.
+    // Swap the email-store view to the new account *before* the network
+    // round-trip. The previous account's data is tucked into its snapshot;
+    // the new account's data (if previously cached) is restored to the
+    // top-level fields so the EmailListScreen immediately shows the new
+    // account's last-known mail instead of flashing empty. The network
+    // refresh below applies incremental updates on top.
+    useEmailStore.getState().setActiveAccount(accountId);
+
+    // Contacts and calendar stores aren't yet per-account, so they still
+    // need a reset to avoid showing the previous account's data.
+    useContactsStore.getState().reset();
+    useCalendarStore.getState().reset();
+
+    // Load the new account's session. loadAccount overwrites
+    // credentials/session/_accountId itself, so we don't need to reset
+    // jmapClient first. If it fails, restore the previous active account
+    // so we don't leave the user stranded on a half-switched state.
+    const previousActive = get().activeAccountId;
     try {
       const ok = await jmapClient.loadAccount(accountId);
       if (!ok) {
         // Credentials missing - evict stale entry and surface error
         accountStore.removeAccount(accountId);
+        useEmailStore.getState().removeAccount(accountId);
+        if (previousActive) useEmailStore.getState().setActiveAccount(previousActive);
         set({ isLoading: false, error: 'Session expired for this account' });
         return;
       }
@@ -245,11 +282,14 @@ export const useAuthStore = create<AuthState>((set, get) => ({
       if (err instanceof AuthenticationError) {
         await jmapClient.clearAccountCredentials(accountId).catch(() => undefined);
         accountStore.removeAccount(accountId);
+        useEmailStore.getState().removeAccount(accountId);
+        if (previousActive) useEmailStore.getState().setActiveAccount(previousActive);
         set({ isLoading: false, error: 'Session expired for this account' });
         return;
       }
       // NetworkError or anything else - keep the previous active account
       // intact instead of stranding the user on a half-switched state.
+      if (previousActive) useEmailStore.getState().setActiveAccount(previousActive);
       set({
         isLoading: false,
         error: err instanceof Error ? err.message : 'Failed to switch account',
@@ -257,10 +297,6 @@ export const useAuthStore = create<AuthState>((set, get) => ({
       return;
     }
 
-    // Session is in place under the new account. Safe now to wipe the
-    // previous account's cached feature data; the refetch below repopulates.
-    resetFeatureStores();
-
     accountStore.setActiveAccount(accountId);
     accountStore.updateAccount(accountId, {
       isConnected: true,
@@ -320,11 +356,18 @@ export const useAuthStore = create<AuthState>((set, get) => ({
         return false;
       }
 
+      // Point the email store at the target account before any await — so
+      // the EmailListScreen, which re-renders the moment the persisted state
+      // hydrates, sees the right account's cached emails instead of stale
+      // data from a previous session.
+      useEmailStore.getState().setActiveAccount(target.id);
+
       try {
         const ok = await jmapClient.loadAccount(target.id);
         if (!ok) {
           // No stored credentials (or corrupt) — genuine logout.
           accountStore.removeAccount(target.id);
+          useEmailStore.getState().removeAccount(target.id);
           set({ isLoading: false, hasRestoredSession: true });
           return false;
         }
@@ -358,6 +401,7 @@ export const useAuthStore = create<AuthState>((set, get) => ({
           // Server reachable but credentials rejected — drop them.
           await jmapClient.clearAccountCredentials(target.id).catch(() => undefined);
           accountStore.removeAccount(target.id);
+          useEmailStore.getState().removeAccount(target.id);
           set({ isLoading: false, hasRestoredSession: true, error: 'Session expired' });
           return false;
         }

src/stores/email-store.ts

@@ -5,8 +5,14 @@ import type { Email, Mailbox, StateChange } from '../api/types';
 import { jmapClient } from '../api/jmap-client';
 import {
   getMailboxes as fetchMailboxes,
+  getMailboxesWithState,
+  getMailboxesByIds,
+  getMailboxChanges,
   queryEmails,
+  getEmailQueryChanges,
   getEmails as fetchEmails,
+  getEmailsWithState,
+  getEmailChanges,
   getFullEmail,
   setEmailKeywords,
   moveEmail,
@@ -16,9 +22,27 @@ import {
   searchEmails as apiSearchEmails,
 } from '../api/email';
 import { toWildcardQuery } from '../lib/search-utils';
+import { generateAccountId } from '../lib/account-utils';
 import { useSettingsStore } from './settings-store';
 import { useOfflineCacheStore } from './offline-cache-store';
 
+// True only when the JMAP client is actually serving the email-store's active
+// account. During an account switch there's a window between
+// setActiveAccount() (which swaps the email-store view immediately) and
+// jmapClient.loadAccount() resolving, when the client is still on the
+// *previous* account. Without this guard, any fetchMailboxes/refreshEmails
+// fired in that window (e.g. by an EmailListScreen useEffect reacting to
+// the empty new-account view) would return the previous account's data and
+// stamp it into the new account's snapshot.
+function jmapClientServesActiveAccount(activeAccountId: string | null): boolean {
+  if (!activeAccountId) return false;
+  if (!jmapClient.isConnected) return false;
+  const username = jmapClient.username;
+  const serverUrl = jmapClient.serverUrl;
+  if (!username || !serverUrl) return false;
+  return generateAccountId(username, serverUrl) === activeAccountId;
+}
+
 export interface EmailFilters {
   from?: string;
   to?: string;
@@ -43,17 +67,56 @@ export interface UndoEntry {
   items: Array<{ email: Email; originalMailboxIds: Record<string, boolean> }>;
 }
 
-export interface EmailState {
+// Cached emails for one mailbox (the base view: no search query, no filters).
+// `queryState` is the JMAP queryState for the matching Email/query, used to
+// drive Email/queryChanges on the next refresh.
+interface MailboxSnapshot {
+  emails: Email[];
+  total: number;
+  queryState?: string;
+}
+
+// Everything we cache for one account so switching accounts can restore the
+// previous view instantly instead of going through a network round-trip.
+interface AccountSnapshot {
   mailboxes: Mailbox[];
+  mailboxState?: string;       // JMAP Mailbox state (drives Mailbox/changes)
+  emailState?: string;         // JMAP Email state (drives Email/changes)
   currentMailboxId: string | null;
+  mailboxSnapshots: Record<string, MailboxSnapshot>;
+}
+
+export interface EmailState {
+  // ── Per-account persisted caches ──────────────────────────────
+  // accountSnapshots is the source of truth for accounts the user is *not*
+  // currently viewing. The active account's data lives in the top-level
+  // fields below (`mailboxes`, `mailboxSnapshots`, `mailboxState`, `emailState`,
+  // `currentMailboxId`, `emails`, `totalEmails`, `queryState`) so consumers
+  // keep reading the same shape they always have.
+  accountSnapshots: Record<string, AccountSnapshot>;
+  activeAccountId: string | null;
+
+  // ── Active view (the currently-shown account/mailbox) ─────────
+  mailboxes: Mailbox[];
+  mailboxState?: string;
+  emailState?: string;
+  currentMailboxId: string | null;
+  mailboxSnapshots: Record<string, MailboxSnapshot>;
   emails: Email[];
   totalEmails: number;
+  queryState?: string;          // queryState for the currently-shown mailbox
+
+  // ── UI state (not persisted, not per-account) ─────────────────
   loading: boolean;
   error: string | null;
   searchQuery: string;
   filters: EmailFilters;
   pendingUndo: UndoEntry | null;
 
+  // ── Actions ────────────────────────────────────────────────────
+  setActiveAccount: (accountId: string | null) => void;
+  removeAccount: (accountId: string) => void;
+  clearAllAccounts: () => void;
   fetchMailboxes: () => Promise<void>;
   selectMailbox: (mailboxId: string) => Promise<void>;
   loadMoreEmails: () => Promise<void>;
@@ -115,103 +178,360 @@ function buildJmapFilter(
   return { operator: 'AND', conditions };
 }
 
+// True when the user has no search/filters active. Only in this case do we
+// touch the per-mailbox snapshot cache or use Email/queryChanges — once a
+// filter is in play, the queryState belongs to a different query and the
+// cached list no longer represents what's on screen.
+function isBaseView(searchQuery: string, filters: EmailFilters): boolean {
+  return !searchQuery.trim() && Object.keys(filters).length === 0;
+}
+
+function snapshotFromActive(state: EmailState): AccountSnapshot {
+  // Persist the currently-visible mailbox into its snapshot before tucking
+  // the whole account away.
+  let mailboxSnapshots = state.mailboxSnapshots;
+  if (state.currentMailboxId && isBaseView(state.searchQuery, state.filters)) {
+    mailboxSnapshots = {
+      ...mailboxSnapshots,
+      [state.currentMailboxId]: {
+        emails: state.emails,
+        total: state.totalEmails,
+        queryState: state.queryState,
+      },
+    };
+  }
+  return {
+    mailboxes: state.mailboxes,
+    mailboxState: state.mailboxState,
+    emailState: state.emailState,
+    currentMailboxId: state.currentMailboxId,
+    mailboxSnapshots,
+  };
+}
+
+function viewFromSnapshot(snap: AccountSnapshot | null): {
+  mailboxes: Mailbox[];
+  mailboxState?: string;
+  emailState?: string;
+  currentMailboxId: string | null;
+  mailboxSnapshots: Record<string, MailboxSnapshot>;
+  emails: Email[];
+  totalEmails: number;
+  queryState?: string;
+} {
+  if (!snap) {
+    return {
+      mailboxes: [],
+      mailboxState: undefined,
+      emailState: undefined,
+      currentMailboxId: null,
+      mailboxSnapshots: {},
+      emails: [],
+      totalEmails: 0,
+      queryState: undefined,
+    };
+  }
+  const mailboxSnap = snap.currentMailboxId
+    ? snap.mailboxSnapshots[snap.currentMailboxId]
+    : undefined;
+  return {
+    mailboxes: snap.mailboxes,
+    mailboxState: snap.mailboxState,
+    emailState: snap.emailState,
+    currentMailboxId: snap.currentMailboxId,
+    mailboxSnapshots: snap.mailboxSnapshots,
+    emails: mailboxSnap?.emails ?? [],
+    totalEmails: mailboxSnap?.total ?? 0,
+    queryState: mailboxSnap?.queryState,
+  };
+}
+
+// JMAP's maxObjectsInGet bounds how many ids we can pull in one Email/get.
+// Chunk to that ceiling (with a small safety fallback) so large change sets
+// don't trip 429/413 responses.
+async function fetchEmailsChunked(ids: string[]): Promise<Email[]> {
+  if (ids.length === 0) return [];
+  const cap = Math.max(1, jmapClient.getMaxObjectsInGet());
+  const chunk = Math.min(cap, 200);
+  if (ids.length <= chunk) return fetchEmails(ids);
+  const out: Email[] = [];
+  for (let i = 0; i < ids.length; i += chunk) {
+    const slice = await fetchEmails(ids.slice(i, i + chunk));
+    out.push(...slice);
+  }
+  return out;
+}
+
+// Merge a fresh batch of emails into an existing list keyed by id. New entries
+// replace stale ones (keywords/mailboxIds may have changed); destroyed ids are
+// dropped. Order is preserved according to the supplied id order — pass the
+// authoritative id list from Email/query when re-syncing.
+function applyEmailDiff(
+  current: Email[],
+  orderedIds: string[],
+  fetched: Email[],
+  destroyed: Set<string>,
+): Email[] {
+  const byId = new Map<string, Email>();
+  for (const e of current) byId.set(e.id, e);
+  for (const e of fetched) byId.set(e.id, e);
+  const out: Email[] = [];
+  for (const id of orderedIds) {
+    if (destroyed.has(id)) continue;
+    const e = byId.get(id);
+    if (e) out.push(e);
+  }
+  return out;
+}
+
 export const useEmailStore = create<EmailState>()(
   persist(
     (set, get) => ({
+  accountSnapshots: {},
+  activeAccountId: null,
+
   mailboxes: [],
+  mailboxState: undefined,
+  emailState: undefined,
   currentMailboxId: null,
+  mailboxSnapshots: {},
   emails: [],
   totalEmails: 0,
+  queryState: undefined,
+
   loading: false,
   error: null,
   searchQuery: '',
   filters: {},
   pendingUndo: null,
 
+  // Swap which account's data is currently visible. The previous account's
+  // view is tucked into accountSnapshots so a return-trip can restore it
+  // without a network call; the new account's view is pulled from its
+  // snapshot (or empty defaults if we've never seen it). Callers (auth-store)
+  // run the network refresh afterwards.
+  setActiveAccount: (accountId) => {
+    const state = get();
+    if (state.activeAccountId === accountId) return;
+
+    const nextSnapshots = { ...state.accountSnapshots };
+    if (state.activeAccountId) {
+      nextSnapshots[state.activeAccountId] = snapshotFromActive(state);
+    }
+    const incoming = accountId ? nextSnapshots[accountId] ?? null : null;
+    const view = viewFromSnapshot(incoming);
+
+    set({
+      accountSnapshots: nextSnapshots,
+      activeAccountId: accountId,
+      ...view,
+      // UI state is reset on switch — search/filters and pending undo belong
+      // to the previous account's intent.
+      searchQuery: '',
+      filters: {},
+      pendingUndo: null,
+      error: null,
+      loading: false,
+    });
+
+    // Point the offline body cache at the same account so getEmailDetail's
+    // fallback and selectMailbox's seed read from the right bucket. Fire-
+    // and-forget — the cache returns empty until hydration completes,
+    // which is the correct degraded behaviour.
+    void useOfflineCacheStore.getState().setAccount(accountId);
+  },
+
+  removeAccount: (accountId) => {
+    const state = get();
+    const { [accountId]: _drop, ...rest } = state.accountSnapshots;
+    if (state.activeAccountId === accountId) {
+      set({
+        accountSnapshots: rest,
+        activeAccountId: null,
+        mailboxes: [],
+        mailboxState: undefined,
+        emailState: undefined,
+        currentMailboxId: null,
+        mailboxSnapshots: {},
+        emails: [],
+        totalEmails: 0,
+        queryState: undefined,
+        searchQuery: '',
+        filters: {},
+        pendingUndo: null,
+      });
+      void useOfflineCacheStore.getState().setAccount(null);
+    } else {
+      set({ accountSnapshots: rest });
+    }
+  },
+
+  clearAllAccounts: () => {
+    set({
+      accountSnapshots: {},
+      activeAccountId: null,
+      mailboxes: [],
+      mailboxState: undefined,
+      emailState: undefined,
+      currentMailboxId: null,
+      mailboxSnapshots: {},
+      emails: [],
+      totalEmails: 0,
+      queryState: undefined,
+      searchQuery: '',
+      filters: {},
+      pendingUndo: null,
+      error: null,
+      loading: false,
+    });
+    void useOfflineCacheStore.getState().setAccount(null);
+  },
+
   fetchMailboxes: async () => {
-    // Skip silently when there's no live session. Screens fire this from
-    // mount-time useEffects, and on cold start App.tsx renders MainTabs
-    // before restoreSession() finishes; without this guard the underlying
-    // API call would throw "Not authenticated - call connect() first" and
-    // surface as a user-visible error before the real fetch (kicked off by
-    // refetchFeatureStores() once the session is live) replaces it.
-    if (!jmapClient.isConnected) return;
+    // Skip silently when there's no live session, or when jmapClient is
+    // mid-transition to a different account (see jmapClientServesActiveAccount).
+    // Screens fire this from mount-time useEffects, and on cold start
+    // App.tsx renders MainTabs before restoreSession() finishes; without
+    // this guard the underlying API call would either throw "Not
+    // authenticated - call connect() first" or — worse, during an account
+    // switch — return the *previous* account's mailboxes and stamp them
+    // into the new account's snapshot.
+    const activeAccountId = get().activeAccountId;
+    if (!jmapClientServesActiveAccount(activeAccountId)) return;
+
+    const prevState = get().mailboxState;
     try {
-      const mailboxes = await fetchMailboxes();
-      set({ mailboxes });
+      // Incremental path: ask for just what changed since last time. Fall
+      // through to a full refetch when the server can't compute the diff or
+      // we have no previous state to compare against.
+      if (prevState) {
+        const changes = await getMailboxChanges(prevState);
+        // Bail if the user switched accounts during the await — anything we
+        // set() now would land in the wrong account's bucket.
+        if (get().activeAccountId !== activeAccountId) return;
+        if (changes) {
+          // No changes at all — keep the cached list, just bump the state.
+          if (
+            changes.created.length === 0 &&
+            changes.updated.length === 0 &&
+            changes.destroyed.length === 0
+          ) {
+            set({ mailboxState: changes.newState });
+            return;
+          }
+          const toFetch = [...changes.created, ...changes.updated];
+          const fetched = toFetch.length > 0
+            ? (await getMailboxesByIds(toFetch)).list
+            : [];
+          if (get().activeAccountId !== activeAccountId) return;
+          const destroyed = new Set(changes.destroyed);
+          const byId = new Map<string, Mailbox>();
+          for (const m of get().mailboxes) byId.set(m.id, m);
+          for (const m of fetched) byId.set(m.id, m);
+          for (const id of destroyed) byId.delete(id);
+          set({
+            mailboxes: Array.from(byId.values()),
+            mailboxState: changes.hasMoreChanges ? prevState : changes.newState,
+          });
+          // hasMoreChanges = there are still pending changes past the
+          // server's response cap. Run the same path again to drain.
+          if (changes.hasMoreChanges) {
+            void get().fetchMailboxes();
+          }
+          return;
+        }
+        // changes === null → cannotCalculateChanges. Fall through to full.
+      }
+
+      const { list, state } = await getMailboxesWithState();
+      if (get().activeAccountId !== activeAccountId) return;
+      set({ mailboxes: list, mailboxState: state });
     } catch (err) {
       console.warn('[email-store] fetchMailboxes failed:', err);
-      set({ error: err instanceof Error ? err.message : 'Failed to load mailboxes' });
+      if (get().activeAccountId !== activeAccountId) return;
+      // Don't overwrite the cached list on a transient failure — the user
+      // can still navigate folders. Only surface the error when we have no
+      // mailboxes at all to show.
+      if (get().mailboxes.length === 0) {
+        set({ error: err instanceof Error ? err.message : 'Failed to load mailboxes' });
+      }
     }
   },
 
   selectMailbox: async (mailboxId) => {
-    // Reset search/filters when switching mailbox - matches webmail behavior.
-    // Switching mailboxes invalidates any pending undo: the snackbar would be
-    // stale and the restored email would re-appear in a different view.
+    const state = get();
+    // Tuck the previously-visible mailbox into its snapshot so a return-trip
+    // can restore it without a network call. Only do this for the base view —
+    // a filter or search makes the visible list unrepresentative of the
+    // cached "no-filter" snapshot.
+    let mailboxSnapshots = state.mailboxSnapshots;
+    if (
+      state.currentMailboxId &&
+      state.currentMailboxId !== mailboxId &&
+      isBaseView(state.searchQuery, state.filters)
+    ) {
+      mailboxSnapshots = {
+        ...mailboxSnapshots,
+        [state.currentMailboxId]: {
+          emails: state.emails,
+          total: state.totalEmails,
+          queryState: state.queryState,
+        },
+      };
+    }
+
+    const incoming = mailboxSnapshots[mailboxId];
+    // Swap to the new mailbox's cached view immediately. If there's no
+    // snapshot, fall through to the offline cache as a second-best seed;
+    // if that's also empty we render the empty-state, not a spinner over
+    // a blank list — better than the previous flash to "Loading…".
+    let seededEmails: Email[] = incoming?.emails ?? [];
+    let seededTotal = incoming?.total ?? 0;
+    let seededQueryState = incoming?.queryState;
+
+    if (seededEmails.length === 0) {
+      const cacheStore = useOfflineCacheStore.getState();
+      if (!cacheStore.hydrated) await cacheStore.hydrate();
+      if (cacheStore.totalCount() > 0) {
+        try {
+          const limit = useSettingsStore.getState().emailsPerPage;
+          seededEmails = await cacheStore.getEmailsInMailbox(mailboxId, Math.max(limit, 50));
+          seededTotal = seededEmails.length;
+        } catch (err) {
+          console.warn('[email-store] cache seed failed:', err);
+        }
+      }
+    }
+
     set({
       currentMailboxId: mailboxId,
+      emails: seededEmails,
+      totalEmails: seededTotal,
+      queryState: seededQueryState,
+      mailboxSnapshots,
       loading: true,
       error: null,
-      emails: [],
-      totalEmails: 0,
       searchQuery: '',
       filters: {},
       pendingUndo: null,
     });
 
-    // Seed from the offline cache immediately so changing folders shows
-    // something even before the network responds — and is the fallback
-    // when offline. The network result will replace this once it arrives.
-    const cacheStore = useOfflineCacheStore.getState();
-    if (!cacheStore.hydrated) await cacheStore.hydrate();
-    const limit = useSettingsStore.getState().emailsPerPage;
-    let cached: Email[] = [];
-    if (cacheStore.totalCount() > 0) {
-      try {
-        cached = await cacheStore.getEmailsInMailbox(mailboxId, Math.max(limit, 50));
-        if (cached.length > 0 && get().currentMailboxId === mailboxId) {
-          set({ emails: cached, totalEmails: cached.length });
-        }
-      } catch (err) {
-        console.warn('[email-store] cache seed failed:', err);
-      }
-    }
-
-    // Stop here if there's no live session yet — the cached seed already
-    // gave the user something to look at, and the refetch driven by
-    // restoreSession() / switchAccount will run the network half once the
-    // client is connected.
-    if (!jmapClient.isConnected) {
+    // Stop here if there's no live session OR jmapClient is mid-transition
+    // to a different account. The cached seed already gave the user
+    // something to look at, and the refetch driven by restoreSession() /
+    // switchAccount will run the network half once the client catches up.
+    if (!jmapClientServesActiveAccount(get().activeAccountId)) {
       set({ loading: false });
       return;
     }
 
-    try {
-      const filter = buildJmapFilter(mailboxId, '', {});
-      const { ids, total } = await queryEmails(mailboxId, { limit, filter });
-      const emails = ids.length > 0 ? await fetchEmails(ids) : [];
-      // Race guard: don't overwrite if the user already moved to a different
-      // mailbox while this request was in flight.
-      if (get().currentMailboxId !== mailboxId) return;
-      set({ emails, totalEmails: total, loading: false });
-    } catch (err) {
-      console.warn('[email-store] selectMailbox failed:', err);
-      if (get().currentMailboxId !== mailboxId) return;
-      // Keep whatever the cache seeded with; only surface the error when the
-      // cache is empty. With cached emails visible the OfflineBanner already
-      // tells the user the data is stale.
-      set({
-        loading: false,
-        error: cached.length > 0 ? null : (err instanceof Error ? err.message : 'Failed to load emails'),
-      });
-    }
+    await get().refreshEmails();
   },
 
   loadMoreEmails: async () => {
-    const { currentMailboxId, emails, totalEmails, loading, searchQuery, filters } = get();
+    const { currentMailboxId, emails, totalEmails, loading, searchQuery, filters, activeAccountId } = get();
     if (!currentMailboxId || loading || emails.length >= totalEmails) return;
-    if (!jmapClient.isConnected) return;
+    if (!jmapClientServesActiveAccount(activeAccountId)) return;
 
     set({ loading: true });
     try {
@@ -222,42 +542,186 @@ export const useEmailStore = create<EmailState>()(
         limit,
         filter,
       });
-      const newEmails = ids.length > 0 ? await fetchEmails(ids) : [];
-      set({ emails: [...emails, ...newEmails], loading: false });
+      if (get().activeAccountId !== activeAccountId || get().currentMailboxId !== currentMailboxId) return;
+      const newEmails = ids.length > 0 ? await fetchEmailsChunked(ids) : [];
+      if (get().activeAccountId !== activeAccountId || get().currentMailboxId !== currentMailboxId) return;
+      const merged = [...emails, ...newEmails];
+      const updates: Partial<EmailState> = { emails: merged, loading: false };
+      if (isBaseView(searchQuery, filters)) {
+        updates.mailboxSnapshots = {
+          ...get().mailboxSnapshots,
+          [currentMailboxId]: {
+            emails: merged,
+            total: get().totalEmails,
+            queryState: get().queryState,
+          },
+        };
+      }
+      set(updates);
     } catch (err) {
+      if (get().activeAccountId !== activeAccountId) return;
       set({ loading: false, error: err instanceof Error ? err.message : 'Failed to load more' });
     }
   },
 
   refreshEmails: async () => {
-    const { currentMailboxId, searchQuery, filters, emails: existing } = get();
+    const state = get();
+    const { currentMailboxId, searchQuery, filters, emails: existing, queryState, emailState, activeAccountId } = state;
     if (!currentMailboxId) return;
-    if (!jmapClient.isConnected) return;
-    // Keep existing emails visible while refreshing - swap atomically once
-    // the new list is ready so pull-to-refresh doesn't flash an empty list.
+    if (!jmapClientServesActiveAccount(activeAccountId)) return;
     set({ loading: true, error: null });
+
+    const filter = buildJmapFilter(currentMailboxId, searchQuery, filters);
+    const limit = useSettingsStore.getState().emailsPerPage;
+    const baseView = isBaseView(searchQuery, filters);
+
     try {
-      const filter = buildJmapFilter(currentMailboxId, searchQuery, filters);
-      const limit = useSettingsStore.getState().emailsPerPage;
-      const { ids, total } = await queryEmails(currentMailboxId, { limit, filter });
-      const emails = ids.length > 0 ? await fetchEmails(ids) : [];
-      set({ emails, totalEmails: total, loading: false });
+      // Incremental sync path: requires the base unfiltered view AND a known
+      // queryState (so Email/queryChanges has something to diff against).
+      // Anything else — search, filter active, first-ever load — falls
+      // through to a full re-query.
+      if (baseView && queryState) {
+        const queryChanges = await getEmailQueryChanges(currentMailboxId, queryState, {
+          filter: undefined,
+        });
+        if (queryChanges) {
+          // What's in the visible window now: drop removed ids, then apply
+          // added (id, index) entries. Newly added ids need bodies fetched.
+          const removed = new Set(queryChanges.removed);
+          const addedIds = queryChanges.added.map((a) => a.id);
+
+          // Email/changes catches updates to messages already in our list
+          // (e.g. another device toggled $seen) that queryChanges wouldn't
+          // report. Skipped when we have no emailState yet — first refresh
+          // after a cold start primes it from the Email/get below.
+          let updatedIds: string[] = [];
+          let destroyedExtra: string[] = [];
+          let nextEmailState: string | undefined = emailState;
+          if (emailState) {
+            const ec = await getEmailChanges(emailState);
+            if (ec) {
+              updatedIds = ec.updated;
+              destroyedExtra = ec.destroyed;
+              nextEmailState = ec.newState;
+            } else {
+              // cannotCalculateChanges → forget the state and rely on the
+              // next full re-sync to repopulate it.
+              nextEmailState = undefined;
+            }
+          }
+
+          // Fetch only what we don't already have. `addedIds` are new to the
+          // window; `updatedIds` may already be in `existing` but their
+          // keywords/mailboxIds need refreshing.
+          const existingById = new Map(existing.map((e) => [e.id, e]));
+          const idsToFetch = [
+            ...addedIds.filter((id) => !existingById.has(id)),
+            ...updatedIds.filter((id) => existingById.has(id)),
+          ];
+          let fetchState: string | undefined;
+          let fetched: Email[] = [];
+          if (idsToFetch.length > 0) {
+            const res = await getEmailsWithState(idsToFetch);
+            fetched = res.list;
+            fetchState = res.state;
+          }
+
+          // Rebuild the visible window order: start with existing emails,
+          // drop removed/destroyed, then splice added at their indices.
+          const allDestroyed = new Set([...destroyedExtra, ...removed]);
+          const kept = existing.filter((e) => !allDestroyed.has(e.id));
+          // Map updated entries onto kept array
+          const fetchedById = new Map(fetched.map((e) => [e.id, e]));
+          const updatedKept = kept.map((e) => fetchedById.get(e.id) ?? e);
+
+          // Insert added entries at the indices the server gave us. Sort
+          // ascending by index so each splice lands at the right offset.
+          const sortedAdded = [...queryChanges.added].sort((a, b) => a.index - b.index);
+          const out = [...updatedKept];
+          for (const entry of sortedAdded) {
+            const email = fetchedById.get(entry.id);
+            if (!email) continue;
+            const idx = Math.min(entry.index, out.length);
+            out.splice(idx, 0, email);
+          }
+          // Cap the visible list to the user's page size — Email/queryChanges
+          // can push entries past the original window if many were added.
+          const trimmed = out.slice(0, Math.max(limit, out.length));
+
+          const nextQueryState = queryChanges.newQueryState;
+          const nextTotal = queryChanges.total;
+
+          if (get().activeAccountId !== activeAccountId || get().currentMailboxId !== currentMailboxId) return;
+
+          set({
+            emails: trimmed,
+            totalEmails: nextTotal,
+            queryState: nextQueryState,
+            emailState: nextEmailState ?? fetchState ?? emailState,
+            loading: false,
+            mailboxSnapshots: {
+              ...get().mailboxSnapshots,
+              [currentMailboxId]: {
+                emails: trimmed,
+                total: nextTotal,
+                queryState: nextQueryState,
+              },
+            },
+          });
+          return;
+        }
+        // queryChanges === null → cannotCalculateChanges. Drop our queryState
+        // and fall through to a full re-query, which will repopulate it.
+      }
+
+      // Full re-query path. Used when there's no prior queryState, when the
+      // user has search/filters active (queryState only tracks the base
+      // query), or when the server returned cannotCalculateChanges above.
+      const queryRes = await queryEmails(currentMailboxId, { limit, filter });
+      const fetched = queryRes.ids.length > 0
+        ? await getEmailsWithState(queryRes.ids)
+        : { list: [], state: undefined as string | undefined };
+
+      if (get().currentMailboxId !== currentMailboxId) return;
+
+      const updates: Partial<EmailState> = {
+        emails: fetched.list,
+        totalEmails: queryRes.total,
+        loading: false,
+      };
+      if (baseView) {
+        updates.queryState = queryRes.queryState;
+        updates.emailState = fetched.state;
+        updates.mailboxSnapshots = {
+          ...get().mailboxSnapshots,
+          [currentMailboxId]: {
+            emails: fetched.list,
+            total: queryRes.total,
+            queryState: queryRes.queryState,
+          },
+        };
+      }
+      set(updates);
     } catch (err) {
       console.warn('[email-store] refreshEmails failed:', err);
-      // If the list was empty before the refresh attempt, fall back to the
-      // offline cache so the user still sees something. Otherwise keep what
-      // they had visible and let the OfflineBanner explain.
+      if (get().activeAccountId !== activeAccountId || get().currentMailboxId !== currentMailboxId) return;
+      // Keep whatever's visible; only surface the error when the list is
+      // empty. With cached emails on screen the OfflineBanner already
+      // tells the user the data is stale.
       if (existing.length === 0) {
         try {
           const cacheStore = useOfflineCacheStore.getState();
           if (!cacheStore.hydrated) await cacheStore.hydrate();
           if (cacheStore.totalCount() > 0) {
-            const limit = useSettingsStore.getState().emailsPerPage;
             const cached = await cacheStore.getEmailsInMailbox(
               currentMailboxId,
               Math.max(limit, 50),
             );
-            if (get().currentMailboxId === currentMailboxId && cached.length > 0) {
+            if (
+              get().activeAccountId === activeAccountId &&
+              get().currentMailboxId === currentMailboxId &&
+              cached.length > 0
+            ) {
               set({ emails: cached, totalEmails: cached.length, loading: false, error: null });
               return;
             }
@@ -266,12 +730,19 @@ export const useEmailStore = create<EmailState>()(
           console.warn('[email-store] refresh cache fallback failed:', cacheErr);
         }
       }
-      set({ loading: false, error: err instanceof Error ? err.message : 'Failed to load emails' });
+      set({
+        loading: false,
+        error: existing.length > 0 ? null : (err instanceof Error ? err.message : 'Failed to load emails'),
+      });
     }
   },
 
   handleStateChange: async (change) => {
     if (!jmapClient.currentSession) return;
+    // Drop changes that arrived for a different account than the one we're
+    // currently showing (e.g. push notifications received during/just after
+    // an account switch).
+    if (!jmapClientServesActiveAccount(get().activeAccountId)) return;
     const accountId = jmapClient.accountId;
     const accountChanges = change.changed?.[accountId];
     if (!accountChanges) return;
@@ -527,9 +998,13 @@ export const useEmailStore = create<EmailState>()(
 
   reset: () => set({
     mailboxes: [],
+    mailboxState: undefined,
+    emailState: undefined,
     currentMailboxId: null,
+    mailboxSnapshots: {},
     emails: [],
     totalEmails: 0,
+    queryState: undefined,
     loading: false,
     error: null,
     searchQuery: '',
@@ -537,16 +1012,23 @@ export const useEmailStore = create<EmailState>()(
   }),
     }),
     {
-      // Persist the mail list so the UI can render instantly on re-open,
-      // before the JMAP session has finished restoring. auth-store triggers
-      // a background refresh once the session is ready.
+      // Persist the per-account caches and the active view so the UI can
+      // render instantly on re-open / account switch, before the JMAP
+      // session has finished restoring. auth-store triggers a background
+      // refresh once the session is ready.
       name: 'email-cache',
       storage: createJSONStorage(() => AsyncStorage),
       partialize: (state) => ({
+        accountSnapshots: state.accountSnapshots,
+        activeAccountId: state.activeAccountId,
         mailboxes: state.mailboxes,
+        mailboxState: state.mailboxState,
+        emailState: state.emailState,
         currentMailboxId: state.currentMailboxId,
+        mailboxSnapshots: state.mailboxSnapshots,
         emails: state.emails,
         totalEmails: state.totalEmails,
+        queryState: state.queryState,
       }),
     },
   ),

src/stores/offline-cache-store.ts

@@ -3,16 +3,25 @@
 // AsyncStorage; attachment blobs go to expo-file-system under
 // `Paths.document/offline-attachments/`. The store also exposes the live
 // progress state the OfflineCacheBanner reads from.
+//
+// Storage is keyed by the email-store's `activeAccountId` so logged-in
+// accounts don't leak cached bodies into each other. The store loads one
+// account's bucket at a time (the active one); switching accounts via
+// setAccount() persists the current bucket then hydrates the new one.
 
 import { create } from 'zustand';
 import AsyncStorage from '@react-native-async-storage/async-storage';
 import type { Email } from '../api/types';
 
-const INDEX_KEY = 'webmail:offline-cache:index:v1';
-const ENTRY_KEY_PREFIX = 'webmail:offline-cache:entry:v1:';
+const INDEX_KEY_PREFIX = 'webmail:offline-cache:index:v2:';
+const ENTRY_KEY_PREFIX = 'webmail:offline-cache:entry:v2:';
 
-function entryKey(id: string): string {
-  return `${ENTRY_KEY_PREFIX}${id}`;
+function indexKey(accountId: string): string {
+  return `${INDEX_KEY_PREFIX}${accountId}`;
+}
+
+function entryKey(accountId: string, emailId: string): string {
+  return `${ENTRY_KEY_PREFIX}${accountId}:${emailId}`;
 }
 
 export interface OfflineCacheIndexEntry {
@@ -23,8 +32,6 @@ export interface OfflineCacheIndexEntry {
 }
 
 interface CacheIndex {
-  // Per-account is keyed at the storage layer (one app session = one account
-  // active at a time). Cross-account separation is left to a future change.
   entries: Record<string, OfflineCacheIndexEntry>;
 }
 
@@ -42,8 +49,11 @@ export interface SyncState {
 }
 
 const IDLE: SyncState = { phase: 'idle', total: 0, completed: 0, fetched: 0, bytes: 0 };
+const EMPTY_INDEX: CacheIndex = { entries: {} };
 
 interface OfflineCacheState {
+  // Currently-loaded bucket. null = no account active (no reads/writes).
+  activeAccountId: string | null;
   index: CacheIndex;
   hydrated: boolean;
   sync: SyncState;
@@ -52,6 +62,9 @@ interface OfflineCacheState {
   // AbortControllers need to survive across the function boundary.
   abortRequested: boolean;
 
+  // Point the store at the given account, hydrating its bucket from
+  // AsyncStorage. Pass null to detach (no reads/writes will hit storage).
+  setAccount: (accountId: string | null) => Promise<void>;
   hydrate: () => Promise<void>;
   has: (id: string) => boolean;
   get: (id: string) => Promise<Email | null>;
@@ -74,41 +87,83 @@ interface OfflineCacheState {
   consumeAbort: () => boolean;
 }
 
-function persistIndex(index: CacheIndex): void {
-  void AsyncStorage.setItem(INDEX_KEY, JSON.stringify(index)).catch((err) => {
+function persistIndex(accountId: string, index: CacheIndex): void {
+  void AsyncStorage.setItem(indexKey(accountId), JSON.stringify(index)).catch((err) => {
     console.warn('[offline-cache] persist index failed', err);
   });
 }
 
+async function loadIndex(accountId: string): Promise<CacheIndex> {
+  try {
+    const raw = await AsyncStorage.getItem(indexKey(accountId));
+    if (raw) {
+      const parsed = JSON.parse(raw) as CacheIndex;
+      if (parsed && typeof parsed === 'object' && parsed.entries) {
+        return parsed;
+      }
+    }
+  } catch (err) {
+    console.warn('[offline-cache] hydrate failed', err);
+  }
+  return { entries: {} };
+}
+
 export const useOfflineCacheStore = create<OfflineCacheState>((set, get) => ({
+  activeAccountId: null,
   index: { entries: {} },
   hydrated: false,
   sync: { ...IDLE },
   abortRequested: false,
 
-  hydrate: async () => {
-    if (get().hydrated) return;
-    try {
-      const raw = await AsyncStorage.getItem(INDEX_KEY);
-      if (raw) {
-        const parsed = JSON.parse(raw) as CacheIndex;
-        if (parsed && typeof parsed === 'object' && parsed.entries) {
-          set({ index: parsed, hydrated: true });
-          return;
-        }
-      }
-    } catch (err) {
-      console.warn('[offline-cache] hydrate failed', err);
+  setAccount: async (accountId) => {
+    const state = get();
+    if (state.activeAccountId === accountId) {
+      // Same account — make sure we've hydrated.
+      if (!state.hydrated) await get().hydrate();
+      return;
     }
-    set({ hydrated: true });
+    // Drop any in-flight sync state from the previous account; the abort flag
+    // makes runOfflineSync stop on its next chunk boundary.
+    set({
+      activeAccountId: accountId,
+      index: { ...EMPTY_INDEX },
+      hydrated: false,
+      sync: { ...IDLE },
+      abortRequested: true,
+    });
+    if (accountId) {
+      const index = await loadIndex(accountId);
+      // Re-check in case another setAccount call raced past us.
+      if (get().activeAccountId !== accountId) return;
+      set({ index, hydrated: true, abortRequested: false });
+    } else {
+      set({ hydrated: true, abortRequested: false });
+    }
+  },
+
+  hydrate: async () => {
+    const state = get();
+    if (state.hydrated) return;
+    const accountId = state.activeAccountId;
+    if (!accountId) {
+      // No active account yet — mark hydrated so callers that block on this
+      // (selectMailbox cache-seed path) don't spin. Reads will return empty.
+      set({ hydrated: true });
+      return;
+    }
+    const index = await loadIndex(accountId);
+    if (get().activeAccountId !== accountId) return;
+    set({ index, hydrated: true });
   },
 
   has: (id) => Boolean(get().index.entries[id]),
 
   get: async (id) => {
-    if (!get().index.entries[id]) return null;
+    const state = get();
+    if (!state.activeAccountId) return null;
+    if (!state.index.entries[id]) return null;
     try {
-      const raw = await AsyncStorage.getItem(entryKey(id));
+      const raw = await AsyncStorage.getItem(entryKey(state.activeAccountId, id));
       if (!raw) return null;
       return JSON.parse(raw) as Email;
     } catch (err) {
@@ -118,12 +173,19 @@ export const useOfflineCacheStore = create<OfflineCacheState>((set, get) => ({
   },
 
   put: async (email, approxBytes) => {
+    const state = get();
+    const accountId = state.activeAccountId;
+    if (!accountId) return;
     try {
-      await AsyncStorage.setItem(entryKey(email.id), JSON.stringify(email));
+      await AsyncStorage.setItem(entryKey(accountId, email.id), JSON.stringify(email));
     } catch (err) {
       console.warn('[offline-cache] put failed', email.id, err);
       return;
     }
+    // Re-read the active account in case it changed while we were awaiting
+    // AsyncStorage — don't stamp the new account's index with the old
+    // account's entry.
+    if (get().activeAccountId !== accountId) return;
     const nextEntries = {
       ...get().index.entries,
       [email.id]: {
@@ -135,35 +197,44 @@ export const useOfflineCacheStore = create<OfflineCacheState>((set, get) => ({
     };
     const index = { entries: nextEntries };
     set({ index });
-    persistIndex(index);
+    persistIndex(accountId, index);
   },
 
   remove: async (ids) => {
     if (ids.length === 0) return;
+    const accountId = get().activeAccountId;
+    if (!accountId) return;
     await Promise.all(
-      ids.map((id) => AsyncStorage.removeItem(entryKey(id)).catch(() => undefined)),
+      ids.map((id) => AsyncStorage.removeItem(entryKey(accountId, id)).catch(() => undefined)),
     );
+    if (get().activeAccountId !== accountId) return;
     const next = { ...get().index.entries };
     for (const id of ids) delete next[id];
     const index = { entries: next };
     set({ index });
-    persistIndex(index);
+    persistIndex(accountId, index);
   },
 
   clearAll: async () => {
+    const accountId = get().activeAccountId;
+    if (!accountId) return;
     const ids = Object.keys(get().index.entries);
     await Promise.all(
-      ids.map((id) => AsyncStorage.removeItem(entryKey(id)).catch(() => undefined)),
+      ids.map((id) => AsyncStorage.removeItem(entryKey(accountId, id)).catch(() => undefined)),
     );
+    if (get().activeAccountId !== accountId) return;
     const index = { entries: {} };
     set({ index, sync: { ...IDLE } });
-    persistIndex(index);
+    persistIndex(accountId, index);
   },
 
   getEmailsInMailbox: async (mailboxId, limit = 200) => {
+    const state = get();
+    const accountId = state.activeAccountId;
+    if (!accountId) return [];
     // Sort the index by receivedAt descending first so we don't have to read
     // entries we won't return — the index already carries receivedAt.
-    const sorted = Object.values(get().index.entries).sort((a, b) => {
+    const sorted = Object.values(state.index.entries).sort((a, b) => {
       const at = a.receivedAt ? new Date(a.receivedAt).getTime() : 0;
       const bt = b.receivedAt ? new Date(b.receivedAt).getTime() : 0;
       return bt - at;
@@ -172,7 +243,7 @@ export const useOfflineCacheStore = create<OfflineCacheState>((set, get) => ({
     for (const entry of sorted) {
       if (matches.length >= limit) break;
       try {
-        const raw = await AsyncStorage.getItem(entryKey(entry.id));
+        const raw = await AsyncStorage.getItem(entryKey(accountId, entry.id));
         if (!raw) continue;
         const email = JSON.parse(raw) as Email;
         if (email.mailboxIds?.[mailboxId]) {