diff --git a/lib/plugin-sandbox/assistant/c.batch.ts b/lib/plugin-sandbox/assistant/c.batch.ts
index 5ed3b0c8c..b8bc70d5c 100644
--- a/lib/plugin-sandbox/assistant/c.batch.ts
+++ b/lib/plugin-sandbox/assistant/c.batch.ts
@@ -13,7 +13,7 @@ import { recordUndo, runUndo } from '../../undo-history';
 import { KEYWORD_PREFIX, KEYWORD_PREFIX_LEGACY } from '../../thread-utils';
 import { readId, readObject, readString, sessionClient, withinRate } from '../host-api-input';
 import { MAX_PLUGIN_MOVES_PER_MINUTE } from '../host-api-mail';
-import { issueUndoToken, redeemUndoToken } from './c.undo';
+import { issueUndoToken, redeemUndoToken, undoAccount } from './c.undo';
 import type { MailBatchAction, MailBatchResult } from './c.types';
 
 /** Most messages one email.batch call changes. */
@@ -134,7 +134,7 @@ export async function doEmailBatch(pluginId: string, input: unknown): Promise<Ma
   const run = once(undo);
   // One entry in the app's undo history: Ctrl+Z reaches it too.
   const entry = recordUndo(`Plugin ${pluginId}: ${label} messages`, () => { void run().catch(() => { /* the plugin's undo reports it */ }); });
-  const token = issueUndoToken(pluginId, client.getAccountId(), 'batch', { entryId: entry.id, run } satisfies BatchUndo);
+  const token = issueUndoToken(pluginId, undoAccount(client), 'batch', { entryId: entry.id, run } satisfies BatchUndo);
   return { done, failed: missing, undoToken: token };
 }
 
@@ -142,7 +142,7 @@ export async function doEmailBatch(pluginId: string, input: unknown): Promise<Ma
 export async function doEmailUndoBatch(pluginId: string, token: unknown): Promise<void> {
   const method = 'email.undoBatch';
   const client: IJMAPClient = sessionClient(method);
-  const { entryId, run } = redeemUndoToken<BatchUndo>(method, pluginId, client.getAccountId(), 'batch', token);
+  const { entryId, run } = redeemUndoToken<BatchUndo>(method, pluginId, undoAccount(client), 'batch', token);
   // Off the history first, so Ctrl+Z can't run it again; an entry already
   // taken by Ctrl+Z has run (or is running) the same undo.
   runUndo(entryId);
diff --git a/lib/plugin-sandbox/assistant/c.calendar.ts b/lib/plugin-sandbox/assistant/c.calendar.ts
index 0e87f5aff..4e51d7ffa 100644
--- a/lib/plugin-sandbox/assistant/c.calendar.ts
+++ b/lib/plugin-sandbox/assistant/c.calendar.ts
@@ -12,7 +12,7 @@ import { answerInvitation, attendeeOf, readOwnInvitation, type RsvpStatus } from
 import { readId, sessionClient } from '../host-api-input';
 import { readNamedEmail } from '../host-api-mail';
 import { doCalendarDeleteEvent } from '../host-api-calendar';
-import { issueUndoToken, redeemUndoToken } from './c.undo';
+import { issueUndoToken, redeemUndoToken, undoAccount } from './c.undo';
 import type { EventDeleteResult, InvitationResponseView } from './c.types';
 
 const STATUSES: readonly RsvpStatus[] = ['accepted', 'tentative', 'declined'];
@@ -159,14 +159,14 @@ export async function doCalendarDeleteWithUndo(pluginId: string, idArg: unknown)
   if (!deleted) return { undoToken: null };
   const copy: Record<string, unknown> = { ...event };
   for (const key of NOT_RECREATED) delete copy[key];
-  return { undoToken: issueUndoToken(pluginId, client.getAccountId(), 'event', copy) };
+  return { undoToken: issueUndoToken(pluginId, undoAccount(client), 'event', copy) };
 }
 
 /** Puts back an event calendar.deleteEvent deleted, from the host's copy. Sends no invitations. */
 export async function doCalendarUndoDelete(pluginId: string, tokenArg: unknown): Promise<{ id: string } | null> {
   const method = 'calendar.undoDelete';
   const client = sessionClient(method);
-  const copy = redeemUndoToken<Partial<CalendarEvent>>(method, pluginId, client.getAccountId(), 'event', tokenArg);
+  const copy = redeemUndoToken<Partial<CalendarEvent>>(method, pluginId, undoAccount(client), 'event', tokenArg);
   const created = await useCalendarStore.getState().createEvent(client, copy, false);
   return created ? { id: created.id } : null;
 }
diff --git a/lib/plugin-sandbox/assistant/c.filters.ts b/lib/plugin-sandbox/assistant/c.filters.ts
index a3f938c68..2e7d17aa3 100644
--- a/lib/plugin-sandbox/assistant/c.filters.ts
+++ b/lib/plugin-sandbox/assistant/c.filters.ts
@@ -20,7 +20,7 @@ import { isValidSieveHeaderName } from '../../sieve/generator';
 import { KEYWORD_PREFIX, KEYWORD_PREFIX_LEGACY } from '../../thread-utils';
 import { generateUUID } from '../../utils';
 import { isPlainRecord, readId, readObject, readString, sessionClient } from '../host-api-input';
-import { issueUndoToken, redeemUndoToken } from './c.undo';
+import { issueUndoToken, redeemUndoToken, undoAccount } from './c.undo';
 import type {
   FilterCreateResult, FilterRuleActionType, FilterRuleField, FilterRuleInfo, FilterRuleOp, FiltersListView,
 } from './c.types';
@@ -214,14 +214,14 @@ export async function doFiltersCreate(pluginId: string, input: unknown): Promise
   }
   if (!change) throw new Error(`${method}: nothing was written`);
   refreshFilterStore(client, accountId);
-  return { id: rule.id, undoToken: issueUndoToken(pluginId, client.getAccountId(), 'filters', change) };
+  return { id: rule.id, undoToken: issueUndoToken(pluginId, undoAccount(client), 'filters', change) };
 }
 
 /** Take back a rule filters.create added: the script gets its earlier bytes back. */
 export async function doFiltersUndo(pluginId: string, token: unknown): Promise<void> {
   const method = 'filters.undo';
   const client = sieveClient(method);
-  const change = redeemUndoToken<FiltersChange>(method, pluginId, client.getAccountId(), 'filters', token);
+  const change = redeemUndoToken<FiltersChange>(method, pluginId, undoAccount(client), 'filters', token);
   try {
     await restoreAccountFilters(client, change);
   } catch (err) {
diff --git a/lib/plugin-sandbox/assistant/c.settings.ts b/lib/plugin-sandbox/assistant/c.settings.ts
index 32b65c8a9..252cba2fd 100644
--- a/lib/plugin-sandbox/assistant/c.settings.ts
+++ b/lib/plugin-sandbox/assistant/c.settings.ts
@@ -26,7 +26,7 @@ import {
 } from '../../settings-schema';
 import { isPlainRecord, sessionClient } from '../host-api-input';
 import { messagesFor } from '../host-api-app';
-import { issueUndoToken, redeemUndoToken } from './c.undo';
+import { issueUndoToken, redeemUndoToken, undoAccount } from './c.undo';
 import type {
   SettingDescription, SettingRefusal, SettingValue, SettingsChangeResult, SettingsUndoResult,
 } from './c.types';
@@ -239,7 +239,7 @@ export async function doSetSettings(pluginId: string, arg: unknown): Promise<Set
     previous[key] = old;
   }
   const undoToken = Object.keys(previous).length > 0
-    ? issueUndoToken(pluginId, client.getAccountId(), 'settings', previous)
+    ? issueUndoToken(pluginId, undoAccount(client), 'settings', previous)
     : null;
   return { applied, refused, undoToken };
 }
@@ -252,7 +252,7 @@ export async function doSetSettings(pluginId: string, arg: unknown): Promise<Set
 export async function doUndoSettings(pluginId: string, token: unknown): Promise<SettingsUndoResult> {
   const method = 'app.undoSettings';
   const client = sessionClient(method);
-  const previous = redeemUndoToken<Record<string, SettingValue | null>>(method, pluginId, client.getAccountId(), 'settings', token);
+  const previous = redeemUndoToken<Record<string, SettingValue | null>>(method, pluginId, undoAccount(client), 'settings', token);
   const restored: string[] = [];
   const refused: SettingsUndoResult['refused'] = {};
   const policy = usePolicyStore.getState();
diff --git a/lib/plugin-sandbox/assistant/c.undo.ts b/lib/plugin-sandbox/assistant/c.undo.ts
index cf1d84702..6a59d0d6e 100644
--- a/lib/plugin-sandbox/assistant/c.undo.ts
+++ b/lib/plugin-sandbox/assistant/c.undo.ts
@@ -5,6 +5,8 @@
 // host a copy of something to re-create.
 
 import { generateUUID } from '../../utils';
+import type { IJMAPClient } from '../../jmap/client-interface';
+import { useAuthStore } from '@/stores/auth-store';
 
 /** How long an undo token can be used. */
 export const UNDO_TOKEN_TTL_MS = 30 * 60_000;
@@ -51,6 +53,11 @@ export function redeemUndoToken<T>(method: string, pluginId: string, accountId:
   return entry.data as T;
 }
 
+/** The account an undo token is bound to: the client's JMAP account, else the signed-in login. */
+export function undoAccount(client: IJMAPClient): string {
+  return client.getAccountId?.() || useAuthStore.getState().activeAccountId || '';
+}
+
 /** For tests. */
 export function clearUndoTokens(): void {
   tokens.clear();