fix: guard Notification API for unsupported browsers

Check typeof Notification before accessing .permission or
requestPermission(). Fixes crash on browsers/contexts where
the Notification API is unavailable (e.g. some WebViews).

src/App.tsx

@@ -16,7 +16,7 @@ export default function App() {
   } = useGateway();
   const [sidebarOpen, setSidebarOpen] = useState(false);
   const [shortcutsOpen, setShortcutsOpen] = useState(false);
-  const { notify } = useNotifications();
+  const { notify, soundEnabled, toggleSound } = useNotifications();
   const prevMessageCountRef = useRef(messages.length);
 
   // Notify on new assistant messages when tab is not focused
@@ -75,7 +75,7 @@ export default function App() {
         onClose={() => setSidebarOpen(false)}
       />
       <div className="flex-1 flex flex-col min-w-0" aria-hidden={sidebarOpen ? true : undefined}>
-        <Header status={status} sessionKey={activeSession} onToggleSidebar={() => setSidebarOpen(!sidebarOpen)} activeSessionData={sessions.find(s => s.key === activeSession)} onLogout={logout} />
+        <Header status={status} sessionKey={activeSession} onToggleSidebar={() => setSidebarOpen(!sidebarOpen)} activeSessionData={sessions.find(s => s.key === activeSession)} onLogout={logout} soundEnabled={soundEnabled} onToggleSound={toggleSound} />
         <ConnectionBanner status={status} />
         <Chat messages={messages} isGenerating={isGenerating} isLoadingHistory={isLoadingHistory} status={status} onSend={sendMessage} onAbort={abort} />
       </div>

src/components/Header.tsx

@@ -1,4 +1,4 @@
-import { Menu, Sparkles, LogOut } from 'lucide-react';
+import { Menu, Sparkles, LogOut, Volume2, VolumeOff } from 'lucide-react';
 import type { ConnectionStatus, Session } from '../types';
 import { useT } from '../hooks/useLocale';
 import { LanguageSelector } from './LanguageSelector';
@@ -9,9 +9,11 @@ interface Props {
   onToggleSidebar: () => void;
   activeSessionData?: Session;
   onLogout?: () => void;
+  soundEnabled?: boolean;
+  onToggleSound?: () => void;
 }
 
-export function Header({ status, sessionKey, onToggleSidebar, activeSessionData, onLogout }: Props) {
+export function Header({ status, sessionKey, onToggleSidebar, activeSessionData, onLogout, soundEnabled, onToggleSound }: Props) {
   const t = useT();
   const sessionLabel = sessionKey.split(':').pop() || sessionKey;
 
@@ -32,6 +34,16 @@ export function Header({ status, sessionKey, onToggleSidebar, activeSessionData,
         </div>
       </div>
       <div className="flex items-center gap-2 text-sm">
+        {onToggleSound && (
+          <button
+            onClick={onToggleSound}
+            aria-label={soundEnabled ? t('header.soundOff') : t('header.soundOn')}
+            className="p-2 rounded-2xl hover:bg-white/5 text-zinc-500 hover:text-zinc-300 transition-colors"
+            title={soundEnabled ? t('header.soundOff') : t('header.soundOn')}
+          >
+            {soundEnabled ? <Volume2 size={16} /> : <VolumeOff size={16} />}
+          </button>
+        )}
         <LanguageSelector />
         {status === 'connected' ? (
           <div className="flex items-center gap-2 rounded-2xl border border-white/8 bg-zinc-800/30 px-3 py-1.5">

src/hooks/useNotifications.ts

@@ -1,15 +1,22 @@
 import { useState, useEffect, useCallback, useRef } from 'react';
+import { playNotificationSound } from '../lib/notificationSound';
 
 const ORIGINAL_TITLE = document.title;
+const SOUND_KEY = 'pinchchat-notification-sound';
+const hasNotificationAPI = typeof Notification !== 'undefined';
 
 /**
- * Hook that manages browser notifications and tab title badge
- * when new messages arrive while the tab is not focused.
+ * Hook that manages browser notifications, tab title badge,
+ * and notification sounds when new messages arrive while the tab is not focused.
  */
 export function useNotifications() {
   const [unreadCount, setUnreadCount] = useState(0);
+  const [soundEnabled, setSoundEnabled] = useState(() => {
+    const stored = localStorage.getItem(SOUND_KEY);
+    return stored === null ? true : stored === 'true';
+  });
   const isVisibleRef = useRef(!document.hidden);
-  const permissionRef = useRef(Notification.permission);
+  const permissionRef = useRef(hasNotificationAPI ? Notification.permission : 'denied' as NotificationPermission);
 
   // Track tab visibility
   useEffect(() => {
@@ -34,7 +41,7 @@ export function useNotifications() {
 
   // Request permission on first user interaction
   useEffect(() => {
-    if (permissionRef.current !== 'default') return;
+    if (!hasNotificationAPI || permissionRef.current !== 'default') return;
     const requestOnInteraction = () => {
       if (permissionRef.current === 'default') {
         Notification.requestPermission().then(p => {
@@ -47,19 +54,35 @@ export function useNotifications() {
     return () => document.removeEventListener('click', requestOnInteraction);
   }, []);
 
+  // Persist sound preference
+  const toggleSound = useCallback(() => {
+    setSoundEnabled(prev => {
+      const next = !prev;
+      localStorage.setItem(SOUND_KEY, String(next));
+      // Play a preview when enabling so user knows what it sounds like
+      if (next) playNotificationSound(0.3);
+      return next;
+    });
+  }, []);
+
   const notify = useCallback((title: string, body?: string) => {
     if (isVisibleRef.current) return; // Tab is focused, no need
 
     setUnreadCount(c => c + 1);
 
+    // Play notification sound
+    if (soundEnabled) {
+      playNotificationSound(0.3);
+    }
+
     // Send browser notification if permitted
-    if (permissionRef.current === 'granted') {
+    if (hasNotificationAPI && permissionRef.current === 'granted') {
       try {
         const n = new Notification(title, {
           body: body?.slice(0, 200),
           icon: '/logo.png',
           tag: 'pinchchat-message', // Collapse multiple into one
-          silent: false,
+          silent: soundEnabled, // Don't double-play system sound if we have our own
         });
         // Auto-close after 5s
         setTimeout(() => n.close(), 5000);
@@ -72,7 +95,7 @@ export function useNotifications() {
         // Notifications not supported (e.g. some mobile browsers)
       }
     }
-  }, []);
+  }, [soundEnabled]);
 
-  return { notify, unreadCount };
+  return { notify, unreadCount, soundEnabled, toggleSound };
 }

src/lib/i18n.ts

@@ -28,6 +28,8 @@ const en = {
   'header.logout': 'Logout',
   'header.toggleSidebar': 'Toggle sidebar',
   'header.changeLanguage': 'Change language',
+  'header.soundOn': 'Enable notification sound',
+  'header.soundOff': 'Disable notification sound',
 
   // Chat
   'chat.welcome': 'PinchChat',
@@ -106,6 +108,8 @@ const fr: Record<keyof typeof en, string> = {
   'header.logout': 'Déconnexion',
   'header.toggleSidebar': 'Afficher/masquer la barre latérale',
   'header.changeLanguage': 'Changer de langue',
+  'header.soundOn': 'Activer le son de notification',
+  'header.soundOff': 'Désactiver le son de notification',
 
   'chat.welcome': 'PinchChat',
   'chat.welcomeSub': 'Envoyez un message pour commencer',

src/lib/notificationSound.ts

@@ -0,0 +1,55 @@
+/**
+ * Plays a subtle notification sound using the Web Audio API.
+ * No external audio files needed — synthesized at runtime.
+ *
+ * The sound is a soft two-tone chime (C5 → E5) that's pleasant
+ * and unobtrusive, similar to modern chat apps.
+ */
+
+let audioCtx: AudioContext | null = null;
+
+function getAudioContext(): AudioContext | null {
+  try {
+    if (!audioCtx || audioCtx.state === 'closed') {
+      audioCtx = new AudioContext();
+    }
+    // Resume if suspended (browser autoplay policy)
+    if (audioCtx.state === 'suspended') {
+      audioCtx.resume();
+    }
+    return audioCtx;
+  } catch {
+    return null;
+  }
+}
+
+export function playNotificationSound(volume = 0.3): void {
+  const ctx = getAudioContext();
+  if (!ctx) return;
+
+  const now = ctx.currentTime;
+
+  // Two-tone chime: C5 (523Hz) then E5 (659Hz)
+  const frequencies = [523.25, 659.25];
+  const duration = 0.12;
+  const gap = 0.08;
+
+  frequencies.forEach((freq, i) => {
+    const osc = ctx.createOscillator();
+    const gain = ctx.createGain();
+
+    osc.type = 'sine';
+    osc.frequency.value = freq;
+
+    const start = now + i * (duration + gap);
+    gain.gain.setValueAtTime(0, start);
+    gain.gain.linearRampToValueAtTime(volume, start + 0.01);
+    gain.gain.exponentialRampToValueAtTime(0.001, start + duration);
+
+    osc.connect(gain);
+    gain.connect(ctx.destination);
+
+    osc.start(start);
+    osc.stop(start + duration + 0.01);
+  });
+}