fix(pwa): N105 — notification clicks work after the tab is closed

OS notifications were shown via page-level `new Notification()` whose onclick
only works while the originating tab is alive — clicking a notification after
closing the tab did nothing.

- New `showOsNotification()` (utils/dom) prefers `registration.showNotification()`
  so the notification is service-worker-owned and persists; falls back to
  `new Notification()` (with the previous onclick) when no SW is available, so
  worst case is unchanged behaviour.
- sw.ts gains a `notificationclick` handler: focuses an existing app window and
  forwards the target path, or opens the app if none is open.
- ClientNonUIFeatures forwards the SW `notificationClick` message to react-router
  `navigate()` (works for both hash and browser router configs), and uses a
  per-room `tag` to coalesce notifications (replacing the old notifRef.close()
  dedup a SW notification can't hold).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/pages/client/ClientNonUIFeatures.tsx

@@ -8,7 +8,7 @@ import LogoUnreadSVG from '../../../../public/res/lotus-unread.png';
 import LogoHighlightSVG from '../../../../public/res/lotus-highlight.png';
 import NotificationSound from '../../../../public/sound/notification.ogg';
 import InviteSound from '../../../../public/sound/invite.ogg';
-import { notificationPermission, setFavicon } from '../../utils/dom';
+import { notificationPermission, setFavicon, showOsNotification } from '../../utils/dom';
 import { NOTIFICATION_SOUND_MAP } from '../../utils/notificationSounds';
 import { useSetting } from '../../state/hooks/settings';
 import { settingsAtom } from '../../state/settings';
@@ -141,17 +141,21 @@ function InviteNotifications() {
         return;
       }
 
-      const noti = new window.Notification('Invitation', {
-        icon: LogoSVG,
-        badge: LogoSVG,
-        body: `You have ${count} new invitation request.`,
-        silent: true,
-      });
-
-      noti.onclick = () => {
-        if (!window.closed) navigate(getInboxInvitesPath());
-        noti.close();
-      };
+      const invitesPath = getInboxInvitesPath();
+      showOsNotification(
+        'Invitation',
+        {
+          icon: LogoSVG,
+          badge: LogoSVG,
+          body: `You have ${count} new invitation request.`,
+          silent: true,
+          tag: 'lotus-invites',
+          data: { path: invitesPath },
+        },
+        () => {
+          if (!window.closed) navigate(invitesPath);
+        },
+      );
     },
     [navigate, setToast],
   );
@@ -202,7 +206,6 @@ function PresenceUpdater() {
 
 function MessageNotifications() {
   const audioRef = useRef<HTMLAudioElement>(null);
-  const notifRef = useRef<Notification | undefined>(undefined);
   const unreadCacheRef = useRef<Map<string, UnreadInfo>>(new Map());
   const mx = useMatrixClient();
   const useAuthentication = useMediaAuthentication();
@@ -276,26 +279,42 @@ function MessageNotifications() {
       // persists in the notification center / lock screen / is readable by other
       // apps). For encrypted rooms show only the sender; the in-page toast above
       // still shows the preview while the user is actively looking at the screen.
-      const noti = new window.Notification(roomName, {
-        icon: LogoSVG,
-        badge: LogoSVG,
-        body: !encrypted && body ? `${username}: ${body}`.slice(0, 120) : username,
-        silent: true,
-      });
-
-      noti.onclick = () => {
-        window.focus();
-        navigate(roomPath);
-        noti.close();
-        notifRef.current = undefined;
-      };
-
-      notifRef.current?.close();
-      notifRef.current = noti;
+      showOsNotification(
+        roomName,
+        {
+          icon: LogoSVG,
+          badge: LogoSVG,
+          body: !encrypted && body ? `${username}: ${body}`.slice(0, 120) : username,
+          silent: true,
+          // Coalesce repeated notifications for the same room (replaces the old
+          // manual notifRef.close() dedup, which a SW notification can't hold).
+          tag: roomId,
+          data: { path: roomPath },
+        },
+        () => {
+          window.focus();
+          navigate(roomPath);
+        },
+      );
     },
     [navigate, setToast, mDirects],
   );
 
+  // N105: when a service-worker-owned notification is clicked, the SW focuses
+  // this tab and forwards the target path here so we can route to it (works even
+  // when the click happened while the tab was in the background / reopened).
+  useEffect(() => {
+    if (!('serviceWorker' in navigator)) return undefined;
+    const onMessage = (event: MessageEvent) => {
+      const data = event.data ?? {};
+      if (data.type === 'notificationClick' && typeof data.path === 'string') {
+        navigate(data.path);
+      }
+    };
+    navigator.serviceWorker.addEventListener('message', onMessage);
+    return () => navigator.serviceWorker.removeEventListener('message', onMessage);
+  }, [navigate]);
+
   const playSound = useCallback(() => {
     const audioElement = audioRef.current;
     audioElement?.play();

src/app/utils/dom.ts

@@ -254,6 +254,42 @@ export const notificationPermission = (permission: NotificationPermission) => {
   return true;
 };
 
+/**
+ * Show an OS notification.
+ *
+ * Prefers a service-worker-owned notification (`registration.showNotification`)
+ * so the notification persists and its click is handled by the SW
+ * `notificationclick` listener even after the originating tab is closed — the
+ * data.path is forwarded to the SW. Falls back to a page-level `Notification`
+ * (with the provided `onClick`) when no service worker is available, preserving
+ * the previous behaviour.
+ */
+export const showOsNotification = async (
+  title: string,
+  options: NotificationOptions & { data?: { path?: string } },
+  onClick?: () => void,
+): Promise<void> => {
+  try {
+    if ('serviceWorker' in navigator) {
+      const registration = await navigator.serviceWorker.ready;
+      if (registration && typeof registration.showNotification === 'function') {
+        await registration.showNotification(title, options);
+        return;
+      }
+    }
+  } catch {
+    // fall through to the page-level Notification below
+  }
+
+  const noti = new Notification(title, options);
+  if (onClick) {
+    noti.onclick = () => {
+      onClick();
+      noti.close();
+    };
+  }
+};
+
 export const getMouseEventCords = (event: MouseEvent) => ({
   x: event.clientX,
   y: event.clientY,

src/sw.ts

@@ -104,6 +104,39 @@ self.addEventListener('message', (event: ExtendableMessageEvent) => {
   }
 });
 
+/**
+ * N105: handle clicks on service-worker-owned notifications. This fires even
+ * when the originating tab was closed (a page-level `Notification.onclick`
+ * would not). Focus an existing app window and forward the target path so it
+ * can route there; if no window is open, open the app.
+ */
+self.addEventListener('notificationclick', (event: NotificationEvent) => {
+  event.notification.close();
+  const data = event.notification.data ?? {};
+  const path = typeof data.path === 'string' ? data.path : undefined;
+
+  event.waitUntil(
+    (async () => {
+      const windowClients = await self.clients.matchAll({
+        type: 'window',
+        includeUncontrolled: true,
+      });
+      const client = windowClients.find((c): c is WindowClient => 'focus' in c);
+      if (client) {
+        await client.focus();
+        if (path) client.postMessage({ type: 'notificationClick', path });
+        return;
+      }
+      // No app window open — open one at the app root (the client routes from
+      // there). Router config (hash vs browser) is page-owned, so we don't try
+      // to deep-link the URL here.
+      if (self.clients.openWindow) {
+        await self.clients.openWindow(self.registration.scope);
+      }
+    })(),
+  );
+});
+
 const MEDIA_PATHS = ['/_matrix/client/v1/media/download', '/_matrix/client/v1/media/thumbnail'];
 
 function mediaPath(url: string): boolean {