fix(ui): preserve mobile home route and confirm Android exit

ui/flutter/lib/app/router/app_router.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'package:go_router/go_router.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
@@ -15,6 +16,7 @@ import '../../features/tasks/domain/task_record.dart';
 import '../../features/tasks/presentation/pages/task_details_page.dart';
 import '../../features/tasks/presentation/pages/task_files_page.dart';
 import 'shells/main_shell.dart';
+import 'mobile_exit_guard.dart';
 
 class AppRouter {
   static final GlobalKey<NavigatorState> rootNavigatorKey = GlobalKey<NavigatorState>();
@@ -27,6 +29,34 @@ class AppRouter {
   }
 
   static GoRouter build(WebAuthController webAuthController) {
+    // Keep desktop and web sections as peers; native mobile retains home below them.
+    final isMobile =
+        !kIsWeb && (defaultTargetPlatform == TargetPlatform.android || defaultTargetPlatform == TargetPlatform.iOS);
+    final sectionRoutes = [
+      GoRoute(
+        path: isMobile ? 'extensions' : '/extensions',
+        builder: (context, state) => const ExtensionsPage(),
+        routes: [
+          GoRoute(
+            path: ':id',
+            builder: (context, state) => ExtensionDetailsPage(
+              extensionId: state.pathParameters['id'] ?? '',
+              initialItem: state.extra is ExtensionListItem ? state.extra as ExtensionListItem : null,
+            ),
+          ),
+        ],
+      ),
+      GoRoute(
+        path: isMobile ? 'settings' : '/settings',
+        builder: (context, state) => const SettingsPage(),
+        routes: [
+          GoRoute(
+            path: ':section',
+            builder: (context, state) => SettingsPage(sectionKey: state.pathParameters['section']),
+          ),
+        ],
+      ),
+    ];
     return GoRouter(
       navigatorKey: rootNavigatorKey,
       refreshListenable: webAuthController,
@@ -48,7 +78,7 @@ class AppRouter {
           routes: [
             GoRoute(
               path: '/',
-              builder: (context, state) => const HomePage(),
+              builder: (context, state) => const MobileExitGuard(child: HomePage()),
               routes: [
                 GoRoute(path: 'create', builder: (context, state) => const CreateTaskWindowPage()),
                 GoRoute(
@@ -67,31 +97,10 @@ class AppRouter {
                     ),
                   ],
                 ),
+                if (isMobile) ...sectionRoutes,
               ],
             ),
-            GoRoute(
-              path: '/extensions',
-              builder: (context, state) => const ExtensionsPage(),
-              routes: [
-                GoRoute(
-                  path: ':id',
-                  builder: (context, state) => ExtensionDetailsPage(
-                    extensionId: state.pathParameters['id'] ?? '',
-                    initialItem: state.extra is ExtensionListItem ? state.extra as ExtensionListItem : null,
-                  ),
-                ),
-              ],
-            ),
-            GoRoute(
-              path: '/settings',
-              builder: (context, state) => const SettingsPage(),
-              routes: [
-                GoRoute(
-                  path: ':section',
-                  builder: (context, state) => SettingsPage(sectionKey: state.pathParameters['section']),
-                ),
-              ],
-            ),
+            if (!isMobile) ...sectionRoutes,
           ],
         ),
       ],

ui/flutter/lib/app/router/mobile_exit_guard.dart

@@ -0,0 +1,51 @@
+import 'dart:async';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter/widgets.dart';
+
+import '../../shared/navigation/app_exit_confirmation_controller.dart';
+
+/// Confirms app exit only on the home route; child routes pop normally.
+class MobileExitGuard extends StatefulWidget {
+  const MobileExitGuard({super.key, required this.child});
+
+  final Widget child;
+
+  @override
+  State<MobileExitGuard> createState() => _MobileExitGuardState();
+}
+
+class _MobileExitGuardState extends State<MobileExitGuard> with WidgetsBindingObserver {
+  final _controller = AppExitConfirmationController();
+
+  @override
+  void initState() {
+    super.initState();
+    WidgetsBinding.instance.addObserver(this);
+  }
+
+  @override
+  void didChangeAppLifecycleState(AppLifecycleState state) {
+    if (state != AppLifecycleState.resumed) _controller.dispose();
+  }
+
+  @override
+  void dispose() {
+    WidgetsBinding.instance.removeObserver(this);
+    _controller.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    if (kIsWeb || defaultTargetPlatform != TargetPlatform.android) return widget.child;
+
+    return PopScope(
+      canPop: false,
+      onPopInvokedWithResult: (didPop, _) {
+        if (!didPop) unawaited(_controller.handleBack(context));
+      },
+      child: widget.child,
+    );
+  }
+}

ui/flutter/lib/app/router/shells/main_shell.dart

@@ -18,8 +18,6 @@ import '../../../features/tasks/application/tasks_controller.dart';
 import '../../../features/tasks/presentation/widgets/pending_update_dialog.dart';
 import '../../../l10n/l10n.dart';
 import '../../../core/window/app_window_launcher.dart';
-import '../../../core/utils/breakpoints.dart';
-import '../../../shared/navigation/app_exit_confirmation_controller.dart';
 import '../../../shared/widgets/app_toast.dart';
 
 class MainShell extends ConsumerStatefulWidget {
@@ -34,7 +32,6 @@ class MainShell extends ConsumerStatefulWidget {
 class _MainShellState extends ConsumerState<MainShell> {
   String? _shownUpdateVersion;
   bool _handlingPendingUpdateRequest = false;
-  final _exitConfirmationController = AppExitConfirmationController();
 
   @override
   Widget build(BuildContext context) {
@@ -82,23 +79,7 @@ class _MainShellState extends ConsumerState<MainShell> {
         return widget.child;
       },
     );
-    return _buildMobileBackGuard(context, content);
-  }
-
-  Widget _buildMobileBackGuard(BuildContext context, Widget child) {
-    final isAndroidMobile =
-        !kIsWeb &&
-        defaultTargetPlatform == TargetPlatform.android &&
-        MediaQuery.sizeOf(context).width < Breakpoints.mobile;
-    if (!isAndroidMobile || context.canPop()) return child;
-
-    return PopScope(
-      canPop: false,
-      onPopInvokedWithResult: (didPop, _) {
-        if (!didPop) unawaited(_exitConfirmationController.handleBack(context));
-      },
-      child: child,
-    );
+    return content;
   }
 
   void _schedulePendingUpdateRequest(PendingUpdateRequest request) {

ui/flutter/lib/shared/navigation/app_exit_confirmation_controller.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
@@ -7,18 +9,37 @@ import '../widgets/app_toast.dart';
 class AppExitConfirmationController {
   static const confirmationWindow = Duration(seconds: 2);
 
-  DateTime? _lastBackAt;
+  OverlayEntry? _toast;
+  Timer? _timer;
 
   Future<void> handleBack(BuildContext context) async {
-    final now = DateTime.now();
-    final lastBackAt = _lastBackAt;
-    if (lastBackAt != null && now.difference(lastBackAt) <= confirmationWindow) {
-      _lastBackAt = null;
+    if (_toast != null) {
+      dispose();
       await SystemNavigator.pop();
       return;
     }
 
-    _lastBackAt = now;
-    showAppToast(context, context.l10n.pressBackAgainToExit);
+    final message = context.l10n.pressBackAgainToExit;
+    final themes = InheritedTheme.capture(from: context, to: Overlay.of(context, rootOverlay: true).context);
+    _toast = OverlayEntry(
+      builder: (_) => IgnorePointer(
+        child: Center(
+          child: Padding(
+            padding: const EdgeInsets.all(24),
+            child: themes.wrap(AppToastContent(message: message)),
+          ),
+        ),
+      ),
+    );
+    Overlay.of(context, rootOverlay: true).insert(_toast!);
+    _timer = Timer(confirmationWindow, dispose);
+  }
+
+  void dispose() {
+    _timer?.cancel();
+    _timer = null;
+    _toast?.remove();
+    _toast?.dispose();
+    _toast = null;
   }
 }

ui/flutter/lib/shared/widgets/app_toast.dart

@@ -11,11 +11,6 @@ enum AppToastType { info, success, error }
 /// short messages stay compact while long messages wrap before becoming wider
 /// than the configured maximum. Errors and normal notices use the same layout.
 void showAppToast(BuildContext context, String message, {AppToastType type = AppToastType.info}) {
-  final palette = AppPalette.of(context);
-  final borderColor = switch (type) {
-    AppToastType.error => palette.error.withValues(alpha: 0.55),
-    AppToastType.success || AppToastType.info => palette.border,
-  };
   shad.showToast(
     context: context,
     location: shad.ToastLocation.topCenter,
@@ -23,16 +18,34 @@ void showAppToast(BuildContext context, String message, {AppToastType type = App
       alignment: Alignment.topCenter,
       widthFactor: 1,
       heightFactor: 1,
-      child: Container(
-        key: const ValueKey('app-toast-content'),
-        padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 12),
-        decoration: BoxDecoration(
-          color: palette.cardBg,
-          borderRadius: BorderRadius.circular(8),
-          border: Border.all(color: borderColor),
-        ),
-        child: Text(message, style: TextStyle(color: palette.textPrimary, fontSize: 13, height: 1.2)),
-      ),
+      child: AppToastContent(message: message, type: type),
     ),
   );
 }
+
+/// Shared toast surface for edge notifications and centered exit prompts.
+class AppToastContent extends StatelessWidget {
+  const AppToastContent({super.key, required this.message, this.type = AppToastType.info});
+
+  final String message;
+  final AppToastType type;
+
+  @override
+  Widget build(BuildContext context) {
+    final palette = AppPalette.of(context);
+    final borderColor = switch (type) {
+      AppToastType.error => palette.error.withValues(alpha: 0.55),
+      AppToastType.success || AppToastType.info => palette.border,
+    };
+    return Container(
+      key: const ValueKey('app-toast-content'),
+      padding: const EdgeInsets.symmetric(horizontal: 14, vertical: 12),
+      decoration: BoxDecoration(
+        color: palette.cardBg,
+        borderRadius: BorderRadius.circular(8),
+        border: Border.all(color: borderColor),
+      ),
+      child: Text(message, style: TextStyle(color: palette.textPrimary, fontSize: 13, height: 1.2)),
+    );
+  }
+}

ui/flutter/test/app/router/app_router_test.dart

@@ -0,0 +1,36 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:go_router/go_router.dart';
+import 'package:gopeed/app/router/app_router.dart';
+import 'package:gopeed/features/auth/application/web_auth_controller.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  for (final platform in TargetPlatform.values) {
+    test('$platform preserves the expected section route stacks', () {
+      debugDefaultTargetPlatformOverride = platform;
+      addTearDown(() => debugDefaultTargetPlatformOverride = null);
+      final auth = WebAuthController();
+      final router = AppRouter.build(auth);
+      addTearDown(router.dispose);
+      addTearDown(auth.dispose);
+      final isMobile = platform == TargetPlatform.android || platform == TargetPlatform.iOS;
+
+      for (final entry in {
+        '/': ['/'],
+        '/extensions': isMobile ? ['/', 'extensions'] : ['/extensions'],
+        '/extensions/example': isMobile ? ['/', 'extensions', ':id'] : ['/extensions', ':id'],
+        '/settings': isMobile ? ['/', 'settings'] : ['/settings'],
+        '/settings/general': isMobile ? ['/', 'settings', ':section'] : ['/settings', ':section'],
+        '/tasks/example': ['/', 'tasks/:id'],
+        '/create': ['/', 'create'],
+      }.entries) {
+        final match = router.configuration.findMatch(Uri.parse(entry.key));
+        expect(match.isError, isFalse);
+        final shell = match.matches.single as ShellRouteMatch;
+        expect(shell.matches.map((match) => (match.route as GoRoute).path), entry.value);
+      }
+    });
+  }
+}

ui/flutter/test/app/router/mobile_exit_guard_test.dart

@@ -0,0 +1,130 @@
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:go_router/go_router.dart';
+import 'package:gopeed/app/router/mobile_exit_guard.dart';
+import 'package:gopeed/shared/navigation/app_exit_confirmation_controller.dart';
+import 'package:gopeed/shared/theme/app_theme.dart';
+import 'package:gopeed/shared/widgets/app_toast.dart';
+import 'package:shadcn_flutter/shadcn_flutter.dart' as shad;
+
+void main() {
+  late List<MethodCall> exits;
+  late GoRouter router;
+
+  setUp(() {
+    exits = [];
+    TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger.setMockMethodCallHandler(
+      SystemChannels.platform,
+      (call) async {
+        if (call.method == 'SystemNavigator.pop') exits.add(call);
+        return null;
+      },
+    );
+    router = GoRouter(
+      routes: [
+        ShellRoute(
+          builder: (_, _, child) => child,
+          routes: [
+            GoRoute(
+              path: '/',
+              builder: (_, _) => const MobileExitGuard(child: SizedBox.expand()),
+              routes: [
+                GoRoute(path: 'details', builder: (_, _) => const SizedBox.expand()),
+                for (final path in ['extensions', 'settings'])
+                  GoRoute(path: path, builder: (_, _) => const SizedBox.expand()),
+              ],
+            ),
+          ],
+        ),
+      ],
+    );
+  });
+
+  tearDown(() {
+    router.dispose();
+    TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger.setMockMethodCallHandler(
+      SystemChannels.platform,
+      null,
+    );
+  });
+
+  Future<void> mount(WidgetTester tester) async {
+    await tester.pumpWidget(
+      shad.ShadcnApp.router(theme: AppTheme.dark(), materialTheme: AppTheme.materialDark(), routerConfig: router),
+    );
+    await tester.pumpAndSettle();
+  }
+
+  testWidgets('root back shows centered prompt, second back exits', (tester) async {
+    await mount(tester);
+    await tester.binding.handlePopRoute();
+    await tester.pump();
+    expect(exits, isEmpty);
+    expect(find.byType(AppToastContent), findsOneWidget);
+    expect(tester.getCenter(find.byType(AppToastContent)), const Offset(400, 300));
+    await tester.pump(const Duration(milliseconds: 1900));
+    await tester.binding.handlePopRoute();
+    await tester.pump();
+    expect(exits, hasLength(1));
+    expect(find.byType(AppToastContent), findsNothing);
+  }, variant: TargetPlatformVariant.only(TargetPlatform.android));
+
+  testWidgets('expired prompt requires a fresh pair of back actions', (tester) async {
+    await mount(tester);
+    await tester.binding.handlePopRoute();
+    await tester.pump();
+    await tester.pump(AppExitConfirmationController.confirmationWindow);
+    expect(find.byType(AppToastContent), findsNothing);
+    await tester.binding.handlePopRoute();
+    await tester.pump();
+    expect(exits, isEmpty);
+    expect(find.byType(AppToastContent), findsOneWidget);
+    await tester.pumpWidget(const SizedBox());
+  }, variant: TargetPlatformVariant.only(TargetPlatform.android));
+
+  testWidgets('nested page pops without prompting or exiting', (tester) async {
+    await mount(tester);
+    router.push('/details');
+    await tester.pumpAndSettle();
+    await tester.binding.handlePopRoute();
+    await tester.pumpAndSettle();
+    expect(router.routeInformationProvider.value.uri.path, '/');
+    expect(find.byType(AppToastContent), findsNothing);
+    expect(exits, isEmpty);
+  }, variant: TargetPlatformVariant.only(TargetPlatform.android));
+  testWidgets('backgrounding clears the exit confirmation', (tester) async {
+    await mount(tester);
+    await tester.binding.handlePopRoute();
+    await tester.pump();
+    tester.binding.handleAppLifecycleStateChanged(AppLifecycleState.inactive);
+    tester.binding.handleAppLifecycleStateChanged(AppLifecycleState.resumed);
+    await tester.pump();
+    expect(find.byType(AppToastContent), findsNothing);
+    await tester.binding.handlePopRoute();
+    await tester.pump();
+    expect(exits, isEmpty);
+    expect(find.byType(AppToastContent), findsOneWidget);
+    await tester.pumpWidget(const SizedBox());
+  }, variant: TargetPlatformVariant.only(TargetPlatform.android));
+  for (final path in ['/extensions', '/settings']) {
+    testWidgets('$path returns to tasks before confirming exit', (tester) async {
+      await mount(tester);
+      router.go(path);
+      await tester.pumpAndSettle();
+      expect(router.canPop(), isTrue);
+      await tester.binding.handlePopRoute();
+      await tester.pumpAndSettle();
+      expect(router.routeInformationProvider.value.uri.path, '/');
+      expect(find.byType(AppToastContent), findsNothing);
+      expect(exits, isEmpty);
+      await tester.binding.handlePopRoute();
+      await tester.pump();
+      expect(find.byType(AppToastContent), findsOneWidget);
+      expect(exits, isEmpty);
+      await tester.binding.handlePopRoute();
+      await tester.pump();
+      expect(exits, hasLength(1));
+    }, variant: TargetPlatformVariant.only(TargetPlatform.android));
+  }
+}