diff --git a/src/app/hooks/useMessageTranslation.ts b/src/app/hooks/useMessageTranslation.ts
index b67c1752a..872ced76f 100644
--- a/src/app/hooks/useMessageTranslation.ts
+++ b/src/app/hooks/useMessageTranslation.ts
@@ -49,7 +49,9 @@ export const useMessageTranslation = (eventId: string, text: string): MsgTransla
   const [active, setActive] = useAtom(msgTranslationActiveAtomFamily(eventId));
   const [cache, setCache] = useAtom(translationCacheAtom);
 
-  const key = makeCacheKey(eventId, targetLang);
+  // The key includes a fingerprint of `text`, so an edit (same event id, new
+  // body) misses the old entry and re-translates instead of showing stale text.
+  const key = makeCacheKey(eventId, targetLang, text);
   const cached = findTranslation(cache, key);
 
   const [status, setStatus] = useState<MsgTranslationStatus>('idle');
@@ -72,11 +74,13 @@ export const useMessageTranslation = (eventId: string, text: string): MsgTransla
   // Auto-translate: when enabled, flip `active` on for foreign messages whose
   // model is already downloaded (no gesture/download needed). Messages needing
   // a first-time download keep the manual chip (which provides the gesture).
-  const autoTried = useRef(false);
+  // Store the text we last auto-tried so an edit (new text) re-triggers auto
+  // detection instead of being suppressed by a one-shot flag.
+  const autoTriedText = useRef<string | undefined>(undefined);
   useEffect(() => {
-    if (!supported || !autoTranslate || active || cached || autoTried.current || !eventId) return;
-    if (!text.trim()) return;
-    autoTried.current = true;
+    if (!supported || !autoTranslate || active || cached || !eventId) return;
+    if (!text.trim() || autoTriedText.current === text) return;
+    autoTriedText.current = text;
     let alive = true;
     (async () => {
       const from = await engine.detect(text);
diff --git a/src/app/pages/client/ClientRoot.tsx b/src/app/pages/client/ClientRoot.tsx
index 14c17e608..e4925bfcb 100644
--- a/src/app/pages/client/ClientRoot.tsx
+++ b/src/app/pages/client/ClientRoot.tsx
@@ -32,6 +32,7 @@ import {
   startClient,
 } from '../../../client/initMatrix';
 import { deleteSearchCacheDatabase } from '../../utils/searchCache';
+import { clearTranslationCache } from '../../state/translation';
 import { SplashScreen } from '../../components/splash-screen';
 import { ServerConfigsLoader } from '../../components/ServerConfigsLoader';
 import { CapabilitiesProvider } from '../../hooks/useCapabilities';
@@ -162,6 +163,9 @@ const useLogoutListener = (mx?: MatrixClient) => {
       // change) — the manual logout path already does, but this path didn't, so
       // the plaintext survived on disk (and persist() makes it non-evictable).
       await deleteSearchCacheDatabase();
+      // The message-translation cache also holds decrypted plaintext — wipe it
+      // on server-forced logout too.
+      clearTranslationCache();
       // Remove only the session credential keys — NOT settings, drafts, and
       // other preferences (N98). The SDK's IndexedDB stores are cleared above;
       // window.localStorage.clear() is reserved for the explicit reset path.
diff --git a/src/app/state/settings.ts b/src/app/state/settings.ts
index 6d8b94d83..1845e1956 100644
--- a/src/app/state/settings.ts
+++ b/src/app/state/settings.ts
@@ -1,4 +1,5 @@
 import { atom } from 'jotai';
+import { isSupportedTargetLang } from '../utils/translation/langUtils';
 
 const STORAGE_KEY = 'settings';
 export type DateFormat =
@@ -409,10 +410,12 @@ export const getSettings = (): Settings => {
         saved.ringtoneId === 'none'
           ? saved.ringtoneId
           : defaultSettings.ringtoneId,
-      // Coerce persisted target language to a non-empty string; anything else
-      // (missing/wrong type) falls back to the default.
+      // Coerce persisted target language to a curated, supported code; anything
+      // else (missing/wrong type/unknown) falls back to the default so the hook
+      // never targets a language the engine can't produce.
       translateTargetLang:
-        typeof saved.translateTargetLang === 'string' && saved.translateTargetLang.trim()
+        typeof saved.translateTargetLang === 'string' &&
+        isSupportedTargetLang(saved.translateTargetLang)
           ? saved.translateTargetLang
           : defaultSettings.translateTargetLang,
       autoTranslate:
diff --git a/src/app/state/translation.test.ts b/src/app/state/translation.test.ts
index ad0402547..85ca3d46f 100644
--- a/src/app/state/translation.test.ts
+++ b/src/app/state/translation.test.ts
@@ -18,9 +18,16 @@ const entry = (key: string, translated = `t-${key}`, fromLang = 'de') => ({
   fromLang,
 });
 
-test('makeCacheKey: eventId + normalized target', () => {
-  assert.equal(makeCacheKey('$abc', 'en-US'), '$abc:en');
-  assert.equal(makeCacheKey('$abc', 'EN'), '$abc:en');
+test('makeCacheKey: eventId + normalized target + content fingerprint', () => {
+  // Same event + target + text is stable and prefixed by event:normalizedTarget.
+  const k1 = makeCacheKey('$abc', 'en-US', 'hola');
+  const k2 = makeCacheKey('$abc', 'EN', 'hola');
+  assert.equal(k1, k2);
+  assert.ok(k1.startsWith('$abc:en:'));
+  // Different body (an edit) => different key, so a stale translation misses.
+  assert.notEqual(makeCacheKey('$abc', 'en', 'hola'), makeCacheKey('$abc', 'en', 'adios'));
+  // Missing text arg still yields a stable key.
+  assert.ok(makeCacheKey('$abc', 'en').startsWith('$abc:en:'));
 });
 
 test('addTranslation: prepends, newest first', () => {
diff --git a/src/app/state/translation.ts b/src/app/state/translation.ts
index 0a2bffc3a..b5858f80f 100644
--- a/src/app/state/translation.ts
+++ b/src/app/state/translation.ts
@@ -36,8 +36,21 @@ export const translationCacheAtom = atom(
   },
 );
 
-export const makeCacheKey = (eventId: string, targetLang: string): string =>
-  `${eventId}:${normalizeLang(targetLang)}`;
+// Small, fast, non-cryptographic string hash — just enough to detect that a
+// message's text changed (an edit reuses the same event id), so the key below
+// invalidates a stale translation of pre-edit text. Kept bitwise-free (and thus
+// within safe-integer range via the modulus) to satisfy the no-bitwise lint.
+const HASH_MOD = 2147483647; // 2^31 - 1
+const fingerprint = (text: string): string => {
+  let h = 0;
+  for (let i = 0; i < text.length; i += 1) {
+    h = (h * 31 + text.charCodeAt(i)) % HASH_MOD;
+  }
+  return h.toString(36);
+};
+
+export const makeCacheKey = (eventId: string, targetLang: string, text = ''): string =>
+  `${eventId}:${normalizeLang(targetLang)}:${fingerprint(text)}`;
 
 /** Look up a cached translation by key (returns undefined if absent). */
 export const findTranslation = (
@@ -64,3 +77,16 @@ export const addTranslation = (
 // (which flips it) and the inline body render (which reacts to it). Keyed by
 // event id so each message has its own independent state.
 export const msgTranslationActiveAtomFamily = atomFamily((_eventId: string) => atom(false));
+
+/**
+ * Wipe the persisted translation cache. Called on logout — cached entries are
+ * decrypted message plaintext, so they must not survive a session on a shared
+ * device (mirrors the search-index wipe).
+ */
+export const clearTranslationCache = (): void => {
+  try {
+    localStorage.removeItem(STORAGE_KEY);
+  } catch {
+    /* localStorage unavailable — nothing to clear */
+  }
+};
diff --git a/src/app/utils/translation/chromeEngine.ts b/src/app/utils/translation/chromeEngine.ts
index e903993ab..1e3627f27 100644
Binary files a/src/app/utils/translation/chromeEngine.ts and b/src/app/utils/translation/chromeEngine.ts differ
diff --git a/src/client/initMatrix.ts b/src/client/initMatrix.ts
index 6db8358bd..65c681c5f 100644
--- a/src/client/initMatrix.ts
+++ b/src/client/initMatrix.ts
@@ -7,6 +7,7 @@ import { LotusOidcTokenRefresher } from './oidcTokenRefresher';
 import { revokeOidcTokens } from './oidcLogout';
 import { pushSessionToSW } from '../sw-session';
 import { deleteSearchCacheDatabase } from '../app/utils/searchCache';
+import { clearTranslationCache } from '../app/state/translation';
 
 // Thrown when the local IndexedDB has a higher schema version than this SDK expects.
 // This happens after a downgrade (e.g. matrix-js-sdk was briefly upgraded and then reverted).
@@ -123,6 +124,8 @@ export const logoutClient = async (mx: MatrixClient) => {
   // The opt-in local search index stores decrypted plaintext — always wipe it
   // on logout. (clearLoginData below nukes all IDB databases, covering it too.)
   await deleteSearchCacheDatabase();
+  // The message-translation cache also holds decrypted plaintext — wipe it too.
+  clearTranslationCache();
   // Remove only the session credential keys, preserving user preferences and
   // unsent drafts (N98). The factory-reset path is clearLoginData() below.
   removeFallbackSession();