feat(desktop): optional wipe-on-close (Settings -> Sicherheit)

apps/desktop/electron/ipc-types.ts

@@ -106,6 +106,14 @@ export const CHANNELS = {
   // Used by the call cinema mode to flip the host BrowserWindow into real
   // OS fullscreen so the Windows taskbar / macOS menubar gets covered.
   WINDOW_SET_FULLSCREEN: 'window:set-fullscreen',
+
+  // Wipe-on-close — main process pushes this to the renderer right before
+  // exiting if the user has enabled the Settings → Sicherheit toggle. The
+  // renderer clears its sensitive caches (memoryWipe.ts) and acks via
+  // `app:wipe-before-quit:done`; main quits after the ack (or a 2s safety
+  // timeout, whichever comes first).
+  /** Main → renderer: about to quit. Renderer wipes, then resolves. */
+  APP_WIPE_BEFORE_QUIT: 'app:wipe-before-quit',
 } as const;
 
 // ---- Screen sources ------------------------------------------------------

apps/desktop/electron/main.ts

@@ -6,10 +6,11 @@
 // the old Tauri devUrl so nothing in the renderer code needs to change)
 // and from the built dist in packaged mode.
 
-import { app, BrowserWindow, desktopCapturer, Menu, session } from 'electron';
+import { app, BrowserWindow, desktopCapturer, ipcMain, Menu, session } from 'electron';
 import path from 'node:path';
 import { fileURLToPath } from 'node:url';
 
+import { CHANNELS } from './ipc-types';
 import { register as registerAudioLoopback } from './modules/audio-loopback';
 import { register as registerAutostart } from './modules/autostart';
 import { register as registerFsScoped } from './modules/fs-scoped';
@@ -263,6 +264,32 @@ if (!gotLock) {
     registerAudioLoopback(mainWindow);
   });
 
+  // Wipe-on-close: when the user enables it in Settings, the renderer is given
+  // a chance to clear all sensitive caches before the app process exits. If
+  // the renderer doesn't ack within 2 seconds we force-quit anyway — better
+  // to lose the wipe than to hang the app shutdown.
+  //
+  // Note: there's a separate `before-quit` listener in modules/tray.ts that
+  // tears down the Tray instance. Electron fires both; the tray listener is
+  // synchronous and doesn't touch event.preventDefault, so it doesn't fight
+  // our deferred-quit dance here. The `wipeRequested` flag guards re-entry
+  // when our own `app.quit()` below fires `before-quit` a second time.
+  let wipeRequested = false;
+  app.on('before-quit', (event) => {
+    if (wipeRequested) return;
+    if (!mainWindow || mainWindow.isDestroyed()) return;
+    wipeRequested = true;
+    event.preventDefault();
+
+    mainWindow.webContents.send(CHANNELS.APP_WIPE_BEFORE_QUIT);
+    const done = new Promise<void>((resolve) => {
+      ipcMain.once(CHANNELS.APP_WIPE_BEFORE_QUIT + ':done', () => resolve());
+    });
+    void Promise.race([done, new Promise<void>((r) => setTimeout(r, 2000))]).finally(() => {
+      app.quit();
+    });
+  });
+
   app.on('window-all-closed', () => {
     if (process.platform !== 'darwin') app.quit();
   });

apps/desktop/electron/preload-types.d.ts

@@ -95,6 +95,10 @@ export interface ElectronAPI {
   setAutoStart: (enabled: boolean) => Promise<void>;
 
   setFullscreen: (enabled: boolean) => Promise<void>;
+
+  /** Subscribe to the main-process pre-quit notification. Used by the
+   *  "Cache beim Schließen leeren" Settings toggle. */
+  onWipeBeforeQuit: (cb: () => Promise<void>) => () => void;
 }
 
 declare global {

apps/desktop/electron/preload.ts

@@ -159,6 +159,24 @@ const api = {
   // Window fullscreen ------------------------------------------------------
   setFullscreen: (enabled: boolean): Promise<void> =>
     ipcRenderer.invoke(CHANNELS.WINDOW_SET_FULLSCREEN, enabled),
+
+  // Wipe-on-close ----------------------------------------------------------
+  // Subscribe to the main-process pre-quit notification. The renderer's
+  // callback does the actual wipe (memoryWipe.ts) and resolves; we ack
+  // unconditionally so main can finish quitting — better to lose the wipe
+  // than to hang the app shutdown if the callback throws.
+  onWipeBeforeQuit: (cb: () => Promise<void>): Unsubscribe => {
+    const handler = async (_evt: Electron.IpcRendererEvent): Promise<void> => {
+      try {
+        await cb();
+      } catch (err) {
+        console.warn('[wipe] renderer cb failed', err);
+      }
+      ipcRenderer.send(CHANNELS.APP_WIPE_BEFORE_QUIT + ':done');
+    };
+    ipcRenderer.on(CHANNELS.APP_WIPE_BEFORE_QUIT, handler);
+    return () => ipcRenderer.removeListener(CHANNELS.APP_WIPE_BEFORE_QUIT, handler);
+  },
 } as const;
 
 export type ElectronAPI = typeof api;

apps/desktop/src/components/SecurityCenter.tsx

@@ -1,5 +1,6 @@
 import { useState } from 'react';
 
+import { isWipeOnCloseEnabled, setWipeOnClose } from '../lib/memoryWipeSettings';
 import {
   changePin,
   type LegacyMigrationReport,
@@ -19,6 +20,7 @@ export function SecurityCenter({ userId }: Props) {
   const [msg, setMsg] = useState<string | null>(null);
   const [recovery, setRecovery] = useState<string | null>(null);
   const [migration, setMigration] = useState<LegacyMigrationReport | null>(null);
+  const [wipeOnClose, setWipeOnCloseState] = useState<boolean>(() => isWipeOnCloseEnabled());
 
   async function handleRetryMigration() {
     setBusy(true); setMsg(null); setMigration(null);
@@ -126,6 +128,27 @@ export function SecurityCenter({ userId }: Props) {
         )}
       </section>
 
+      <section>
+        <h3 className="mb-2 text-xs font-medium uppercase tracking-wide text-fg-muted">
+          Cache beim Schließen leeren
+        </h3>
+        <p className="mb-2 text-xs text-fg-muted">
+          Beim Beenden der App werden alle entschlüsselten Caches gelöscht. Beim nächsten Start
+          musst du wieder deine PIN eingeben. Empfohlen für gemeinsam genutzte Rechner.
+        </p>
+        <label className="inline-flex cursor-pointer items-center gap-2 text-sm">
+          <input
+            type="checkbox"
+            checked={wipeOnClose}
+            onChange={(e) => {
+              setWipeOnClose(e.target.checked);
+              setWipeOnCloseState(e.target.checked);
+            }}
+          />
+          <span>Aktivieren</span>
+        </label>
+      </section>
+
       <section>
         <h3 className="mb-2 text-xs font-medium uppercase tracking-wide text-rose-400">Identität zurücksetzen</h3>
         <p className="mb-2 text-xs text-fg-muted">Erstellt einen neuen Schlüssel. Alle alten Chats werden unlesbar.</p>

apps/desktop/src/context/AuthContext.tsx

@@ -21,6 +21,7 @@ import { useTranslation } from 'react-i18next';
 
 import { ensureInstallId } from '../lib/installId';
 import { wipeLocalState } from '../lib/memoryWipe';
+import { isWipeOnCloseEnabled } from '../lib/memoryWipeSettings';
 import { setSecretStoreUser } from '../lib/secretStore';
 import { supabase } from '../lib/supabase';
 import { cachedUserKey, ensureLegacyMigrated } from '../lib/userIdentity';
@@ -195,6 +196,18 @@ export function AuthProvider({ children }: { children: ReactNode }) {
     void registerWebPush(installId);
   }, [session]);
 
+  // Wipe-on-close: register a handler the main process pings on `before-quit`
+  // when the user has enabled the Settings → Sicherheit toggle. No-op outside
+  // Electron (web build has no preload bridge) or when the toggle is off.
+  useEffect(() => {
+    if (typeof window.electronAPI?.onWipeBeforeQuit !== 'function') return;
+    const unsub = window.electronAPI.onWipeBeforeQuit(async () => {
+      if (!isWipeOnCloseEnabled()) return;
+      await wipeLocalState(session?.user.id ?? null);
+    });
+    return unsub;
+  }, [session?.user.id]);
+
   // Auto online/offline transition.
   //
   // - On mount with a session whose last persisted state is `offline`, flip

apps/desktop/src/lib/memoryWipe.ts

@@ -15,6 +15,7 @@ const PRESERVE_LOCAL_STORAGE = new Set([
   'chatapp.theme',
   'chatapp.locale',
   'chatapp.installId',
+  'chatapp.wipeOnClose.v1',
   'i18nextLng',
 ]);
 

apps/desktop/src/lib/memoryWipeSettings.ts

@@ -0,0 +1,24 @@
+// Persisted toggle for the "wipe local caches on app close" feature.
+// Read by SecurityCenter (UI) and AuthContext (renderer-side IPC handler).
+//
+// Stored in localStorage so the preference survives sessions without
+// touching the secret-store or SQLite. The key is on the preserve
+// whitelist in lib/memoryWipe.ts so a sign-out wipe (or a closing wipe)
+// doesn't blow away the user's own preference.
+const KEY = 'chatapp.wipeOnClose.v1';
+
+export function isWipeOnCloseEnabled(): boolean {
+  try {
+    return window.localStorage.getItem(KEY) === '1';
+  } catch {
+    return false;
+  }
+}
+
+export function setWipeOnClose(enabled: boolean): void {
+  try {
+    window.localStorage.setItem(KEY, enabled ? '1' : '0');
+  } catch {
+    /* ignored */
+  }
+}