fix(security): harden browser handoff boundaries

src/App.tsx

@@ -137,7 +137,7 @@ function App() {
   const maxConcurrentDownloads = useSettingsStore(state => state.maxConcurrentDownloads);
   const preventsSleepWhileDownloading = useSettingsStore(state => state.preventsSleepWhileDownloading);
   const activeTransferCount = downloads.filter(download => isTransferActiveStatus(download.status)).length;
-  const { addToast } = useToast();
+  const { addToast, removeToast } = useToast();
   const isMacUserAgent = navigator.userAgent.includes('Mac');
   const usesCustomWindowControls = !isMacUserAgent && platform.os !== 'macos';
   // Keep dialogs out of the titlebar area while platform detection is still
@@ -179,19 +179,20 @@ function App() {
 
     const actionLabel = action === 'shutdown' ? 'Shut down' : action === 'restart' ? 'Restart' : 'Sleep';
     let timerId: number | null = null;
+    let toastId: string | null = null;
     const cancel = () => {
-      if (timerId !== null) {
-        window.clearTimeout(timerId);
-        if (pendingPostActionTimer.current === timerId) {
-          pendingPostActionTimer.current = null;
-        }
-        timerId = null;
+      clearPendingPostActionTimer();
+      timerId = null;
+      if (toastId !== null) {
+        removeToast(toastId);
+        toastId = null;
       }
     };
 
-    addToast({
+    toastId = addToast({
       variant: 'warning',
       isActionable: true,
+      onDismiss: clearPendingPostActionTimer,
       message: (
         <div className="flex items-center gap-3">
           <span>{actionLabel} in 10 seconds.</span>
@@ -207,6 +208,10 @@ function App() {
     });
 
     timerId = window.setTimeout(() => {
+      if (toastId !== null) {
+        removeToast(toastId);
+        toastId = null;
+      }
       if (pendingPostActionTimer.current === timerId) {
         pendingPostActionTimer.current = null;
       }
@@ -233,7 +238,7 @@ function App() {
       });
     }, 10_000);
     pendingPostActionTimer.current = timerId;
-  }, [addToast, clearPendingPostActionTimer]);
+  }, [addToast, clearPendingPostActionTimer, removeToast]);
 
   const startSidebarResize = (event: React.PointerEvent<HTMLDivElement>) => {
     event.preventDefault();
@@ -326,6 +331,11 @@ function App() {
           }
         });
         unlistenExtension = await listen('extension-add-download', (event) => {
+          if (event.payload.request_id) {
+            void invoke('ack_extension_download', { requestId: event.payload.request_id }).catch(error => {
+              console.error('Failed to acknowledge browser extension download:', error);
+            });
+          }
           if (!startupInputReady.current || useSettingsStore.getState().showKeychainModal) {
             pendingStartupInputs.current.push({ type: 'extension', payload: event.payload });
             return;

src/bindings/ExtensionDownload.ts

@@ -1,4 +1,4 @@
 // This file was generated by [ts-rs](https://github.com/Aleph-Alpha/ts-rs). Do not edit this file manually.
 import type { ExtensionCookieScope } from "./ExtensionCookieScope";
 
-export type ExtensionDownload = { urls: Array<string>, referer: string | null, silent: boolean, filename: string | null, headers: string | null, cookies: string | null, cookie_scopes: Array<ExtensionCookieScope> | null, media: boolean, };
+export type ExtensionDownload = { request_id?: string, urls: Array<string>, referer: string | null, silent: boolean, filename: string | null, headers: string | null, cookies: string | null, cookie_scopes: Array<ExtensionCookieScope> | null, media: boolean, };

src/contexts/ToastContext.tsx

@@ -14,6 +14,7 @@ export interface ToastMessage {
   variant?: ToastVariant;
   duration?: number;
   isActionable?: boolean;
+  onDismiss?: () => void;
 }
 
 interface ToastState extends ToastMessage {
@@ -21,7 +22,7 @@ interface ToastState extends ToastMessage {
 }
 
 interface ToastContextType {
-  addToast: (toast: Omit<ToastMessage, 'id'>) => void;
+  addToast: (toast: Omit<ToastMessage, 'id'>) => string;
   removeToast: (id: string) => void;
 }
 
@@ -33,10 +34,12 @@ export const ToastProvider: React.FC<{ children: ReactNode }> = ({ children }) =
 
   const addToast = useCallback((toast: Omit<ToastMessage, 'id'>) => {
     nextToastId.current += 1;
+    const id = `toast-${nextToastId.current}`;
     setToasts(prev => {
-      const next = [...prev, { ...toast, id: `toast-${nextToastId.current}` }];
+      const next = [...prev, { ...toast, id }];
       return next.slice(-MAX_VISIBLE_TOASTS);
     });
+    return id;
   }, []);
 
   const removeToast = useCallback((id: string) => {
@@ -70,6 +73,7 @@ const ToastItem: React.FC<{ toast: ToastState; removeToast: (id: string) => void
   const [isHovered, setIsHovered] = useState(false);
   const timerStartedAt = useRef<number | null>(null);
   const remainingDuration = useRef<number | null>(null);
+  const onDismissCalled = useRef(false);
 
   useLayoutEffect(() => {
     const frame = requestAnimationFrame(() => setIsMounted(true));
@@ -99,6 +103,16 @@ const ToastItem: React.FC<{ toast: ToastState; removeToast: (id: string) => void
     };
   }, [toast, isHovered, removeToast]);
 
+  useEffect(() => {
+    const dismiss = () => {
+      if (onDismissCalled.current) return;
+      onDismissCalled.current = true;
+      toast.onDismiss?.();
+    };
+    if (toast.exiting) dismiss();
+    return dismiss;
+  }, [toast.exiting, toast.onDismiss]);
+
   useEffect(() => {
     if (toast.exiting) {
       const fallbackTimer = setTimeout(() => {

src/ipc.ts

@@ -65,6 +65,7 @@ type CommandMap = {
   grant_keychain_access: { args: undefined; result: PairingTokenHydration };
   acknowledge_pairing_token_change: { args: undefined; result: void };
   set_extension_frontend_ready: { args: { ready: boolean }; result: void };
+  ack_extension_download: { args: { requestId: string }; result: void };
   get_system_proxy: { args: undefined; result: string | null };
   get_file_category: { args: { filename: string }; result: DownloadCategory };
   check_for_updates: { args: undefined; result: ReleaseCheckOutcome };