fix(android): intercept back during cold startup and move exit toast down

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

@@ -17,6 +17,7 @@ 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';
+import 'runtime_page.dart';
 
 class AppRouter {
   static final GlobalKey<NavigatorState> rootNavigatorKey = GlobalKey<NavigatorState>();
@@ -35,24 +36,26 @@ class AppRouter {
     final sectionRoutes = [
       GoRoute(
         path: isMobile ? 'extensions' : '/extensions',
-        builder: (context, state) => const ExtensionsPage(),
+        builder: _runtimePage((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,
+            builder: _runtimePage(
+              (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(),
+        builder: _runtimePage((context, state) => const SettingsPage()),
         routes: [
           GoRoute(
             path: ':section',
-            builder: (context, state) => SettingsPage(sectionKey: state.pathParameters['section']),
+            builder: _runtimePage((context, state) => SettingsPage(sectionKey: state.pathParameters['section'])),
           ),
         ],
       ),
@@ -74,25 +77,29 @@ class AppRouter {
       routes: [
         GoRoute(path: '/login', parentNavigatorKey: rootNavigatorKey, builder: (context, state) => const LoginPage()),
         ShellRoute(
-          builder: (context, state, child) => MainShell(child: child),
+          builder: (context, state, child) => MobileExitGuard(child: MainShell(child: child)),
           routes: [
             GoRoute(
               path: '/',
-              builder: (context, state) => const MobileExitGuard(child: HomePage()),
+              builder: _runtimePage((context, state) => const HomePage()),
               routes: [
-                GoRoute(path: 'create', builder: (context, state) => const CreateTaskWindowPage()),
+                GoRoute(path: 'create', builder: _runtimePage((context, state) => const CreateTaskWindowPage())),
                 GoRoute(
                   path: 'tasks/:id',
-                  builder: (context, state) => TaskDetailsPage(
-                    taskId: state.pathParameters['id'] ?? '',
-                    initialTask: state.extra is TaskRecord ? state.extra as TaskRecord : null,
+                  builder: _runtimePage(
+                    (context, state) => TaskDetailsPage(
+                      taskId: state.pathParameters['id'] ?? '',
+                      initialTask: state.extra is TaskRecord ? state.extra as TaskRecord : null,
+                    ),
                   ),
                   routes: [
                     GoRoute(
                       path: 'files',
-                      builder: (context, state) => TaskFilesPage(
-                        taskId: state.pathParameters['id'] ?? '',
-                        initialTask: state.extra is TaskRecord ? state.extra as TaskRecord : null,
+                      builder: _runtimePage(
+                        (context, state) => TaskFilesPage(
+                          taskId: state.pathParameters['id'] ?? '',
+                          initialTask: state.extra is TaskRecord ? state.extra as TaskRecord : null,
+                        ),
                       ),
                     ),
                   ],
@@ -107,6 +114,10 @@ class AppRouter {
     );
   }
 
+  static GoRouterWidgetBuilder _runtimePage(GoRouterWidgetBuilder builder) {
+    return (context, state) => RuntimePage(builder: (context) => builder(context, state));
+  }
+
   static String _safeReturnLocation(String? location) {
     if (location == null || location.isEmpty) return '/';
     final uri = Uri.tryParse(location);

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

@@ -5,7 +5,8 @@ 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.
+/// Handles exit at the shell route after the nested Navigator declines a pop.
+/// Child routes and dialogs still pop through GoRouter before reaching this guard.
 class MobileExitGuard extends StatefulWidget {
   const MobileExitGuard({super.key, required this.child});
 
@@ -45,7 +46,16 @@ class _MobileExitGuardState extends State<MobileExitGuard> with WidgetsBindingOb
       onPopInvokedWithResult: (didPop, _) {
         if (!didPop) unawaited(_controller.handleBack(context));
       },
-      child: widget.child,
+      child: NotificationListener<NavigationNotification>(
+        onNotification: (notification) {
+          if (notification.canHandlePop) return false;
+          // An empty nested back stack still has this shell's exit guard.
+          // Otherwise its startup notification disables Android's back callback.
+          const NavigationNotification(canHandlePop: true).dispatch(context);
+          return true;
+        },
+        child: widget.child,
+      ),
     );
   }
 }

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

@@ -0,0 +1,30 @@
+import 'package:shadcn_flutter/shadcn_flutter.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../application/app_runtime_controller.dart';
+import '../../l10n/l10n.dart';
+
+/// Gates page content without unmounting the Navigator during startup.
+class RuntimePage extends ConsumerWidget {
+  const RuntimePage({super.key, required this.builder});
+
+  final WidgetBuilder builder;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    return ref
+        .watch(appRuntimeControllerProvider)
+        .when(
+          loading: () => const Scaffold(child: Center(child: CircularProgressIndicator())),
+          error: (error, _) => Scaffold(
+            child: Center(
+              child: ConstrainedBox(
+                constraints: const BoxConstraints(maxWidth: 420),
+                child: Text(context.l10n.runtimeInitializationFailed(error.toString()), textAlign: TextAlign.center),
+              ),
+            ),
+          ),
+          data: (_) => builder(context),
+        );
+  }
+}

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

@@ -4,7 +4,6 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
-import 'package:shadcn_flutter/shadcn_flutter.dart' as shad;
 
 import '../../../api/model/create_task.dart';
 import '../../application/app_deep_link_controller.dart';
@@ -16,7 +15,6 @@ import '../../../features/tasks/application/pending_create_task.dart';
 import '../../../features/tasks/application/pending_update_task.dart';
 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 '../../../shared/widgets/app_toast.dart';
 
@@ -62,24 +60,13 @@ class _MainShellState extends ConsumerState<MainShell> {
       }
     });
     final runtime = ref.watch(appRuntimeControllerProvider);
-    final content = runtime.when(
-      loading: () => const shad.Scaffold(child: Center(child: shad.CircularProgressIndicator())),
-      error: (error, _) => shad.Scaffold(
-        child: Center(
-          child: ConstrainedBox(
-            constraints: const BoxConstraints(maxWidth: 420),
-            child: Text(context.l10n.runtimeInitializationFailed(error.toString()), textAlign: TextAlign.center),
-          ),
-        ),
-      ),
-      data: (_) {
-        ref.watch(appPlatformControllerProvider);
-        ref.watch(appDeepLinkControllerProvider);
-        ref.watch(appNotificationControllerProvider);
-        return widget.child;
-      },
-    );
-    return content;
+    if (runtime.hasValue) {
+      ref.watch(appPlatformControllerProvider);
+      ref.watch(appDeepLinkControllerProvider);
+      ref.watch(appNotificationControllerProvider);
+    }
+    // Keep the nested Navigator mounted even while the runtime is starting.
+    return widget.child;
   }
 
   void _schedulePendingUpdateRequest(PendingUpdateRequest request) {

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

@@ -23,10 +23,13 @@ class AppExitConfirmationController {
     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)),
+        child: SafeArea(
+          child: Align(
+            alignment: Alignment.bottomCenter,
+            child: Padding(
+              padding: const EdgeInsets.all(24),
+              child: themes.wrap(AppToastContent(message: message)),
+            ),
           ),
         ),
       ),

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

@@ -0,0 +1,65 @@
+import 'dart:async';
+
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:gopeed/app/application/app_runtime_controller.dart';
+import 'package:gopeed/app/router/app_router.dart';
+import 'package:gopeed/features/auth/application/web_auth_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;
+
+class _StartingRuntime extends AppRuntimeController {
+  final pending = Completer<AppRuntimeState>();
+
+  @override
+  Future<AppRuntimeState> build() => pending.future;
+}
+
+void main() {
+  testWidgets(
+    'cold startup registers Android back and confirms exit before runtime is ready',
+    (tester) async {
+      final platformCalls = <MethodCall>[];
+      tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (call) async {
+        platformCalls.add(call);
+        return null;
+      });
+      addTearDown(() => tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, null));
+      final runtime = _StartingRuntime();
+      final auth = WebAuthController();
+      final router = AppRouter.build(auth);
+      addTearDown(router.dispose);
+      addTearDown(auth.dispose);
+      tester.binding.handleAppLifecycleStateChanged(AppLifecycleState.resumed);
+      await tester.pumpWidget(
+        ProviderScope(
+          overrides: [appRuntimeControllerProvider.overrideWith(() => runtime)],
+          child: shad.ShadcnApp.router(
+            theme: AppTheme.dark(),
+            materialTheme: AppTheme.materialDark(),
+            routerConfig: router,
+          ),
+        ),
+      );
+      await tester.pump();
+      await tester.pump();
+      expect(find.byType(shad.CircularProgressIndicator), findsOneWidget);
+      expect(
+        platformCalls.where((call) => call.method == 'SystemNavigator.setFrameworkHandlesBack').last.arguments,
+        isTrue,
+      );
+      await tester.binding.handlePopRoute();
+      await tester.pump();
+      expect(platformCalls.where((call) => call.method == 'SystemNavigator.pop'), isEmpty);
+      expect(find.byType(AppToastContent), findsOneWidget);
+      await tester.binding.handlePopRoute();
+      await tester.pump();
+      expect(platformCalls.where((call) => call.method == 'SystemNavigator.pop'), hasLength(1));
+      await tester.pumpWidget(const SizedBox());
+    },
+    variant: TargetPlatformVariant.only(TargetPlatform.android),
+  );
+}

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

@@ -24,11 +24,11 @@ void main() {
     router = GoRouter(
       routes: [
         ShellRoute(
-          builder: (_, _, child) => child,
+          builder: (_, _, child) => MobileExitGuard(child: child),
           routes: [
             GoRoute(
               path: '/',
-              builder: (_, _) => const MobileExitGuard(child: SizedBox.expand()),
+              builder: (_, _) => const SizedBox.expand(),
               routes: [
                 GoRoute(path: 'details', builder: (_, _) => const SizedBox.expand()),
                 for (final path in ['extensions', 'settings'])
@@ -56,13 +56,14 @@ void main() {
     await tester.pumpAndSettle();
   }
 
-  testWidgets('root back shows centered prompt, second back exits', (tester) async {
+  testWidgets('root back shows bottom 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));
+    expect(tester.getCenter(find.byType(AppToastContent)).dx, 400);
+    expect(tester.getBottomLeft(find.byType(AppToastContent)).dy, 576);
     await tester.pump(const Duration(milliseconds: 1900));
     await tester.binding.handlePopRoute();
     await tester.pump();
@@ -127,4 +128,34 @@ void main() {
       expect(exits, hasLength(1));
     }, variant: TargetPlatformVariant.only(TargetPlatform.android));
   }
+  testWidgets(
+    'dialog back dismisses the dialog before exit confirmation',
+    (tester) async {
+      await mount(tester);
+      final context = router.routerDelegate.navigatorKey.currentContext!;
+      showGeneralDialog<void>(
+        context: context,
+        pageBuilder: (_, _, _) => const Center(child: Text('Dialog content')),
+      );
+      await tester.pumpAndSettle();
+      await tester.binding.handlePopRoute();
+      await tester.pumpAndSettle();
+      expect(find.text('Dialog content'), findsNothing);
+      expect(find.byType(AppToastContent), findsNothing);
+      expect(exits, isEmpty);
+    },
+    variant: TargetPlatformVariant.only(TargetPlatform.android),
+  );
+
+  testWidgets('bottom prompt stays above the Android safe area', (tester) async {
+    tester.view.padding = const FakeViewPadding(bottom: 48);
+    tester.view.devicePixelRatio = 1;
+    addTearDown(tester.view.resetPadding);
+    addTearDown(tester.view.resetDevicePixelRatio);
+    await mount(tester);
+    await tester.binding.handlePopRoute();
+    await tester.pump();
+    expect(tester.getBottomLeft(find.byType(AppToastContent)).dy, tester.view.physicalSize.height - 48 - 24);
+    await tester.pumpWidget(const SizedBox());
+  }, variant: TargetPlatformVariant.only(TargetPlatform.android));
 }

ui/flutter/test/widget_test.dart

@@ -12,6 +12,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:go_router/go_router.dart';
 import 'package:shadcn_flutter/shadcn_flutter.dart' as shad;
 import 'package:window_manager/window_manager.dart';
+import 'package:gopeed/features/home/presentation/pages/home_page.dart';
 import 'package:gopeed/app/app.dart';
 import 'package:gopeed/app/router/app_router.dart';
 import 'package:gopeed/core/capabilities/app_capabilities.dart';
@@ -2254,15 +2255,16 @@ void main() {
     expect(tester.takeException(), isNull);
   });
 
-  testWidgets('settings mobile back returns one level before requiring a second back to exit', (
-    WidgetTester tester,
-  ) async {
+  testWidgets('settings mobile back returns through home before confirming exit', (WidgetTester tester) async {
     await _setTestSize(tester, const Size(390, 760));
     debugDefaultTargetPlatformOverride = TargetPlatform.android;
     addTearDown(() => debugDefaultTargetPlatformOverride = null);
     var systemPopCalls = 0;
+    bool? frameworkHandlesBack;
+    tester.binding.handleAppLifecycleStateChanged(AppLifecycleState.resumed);
     tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(SystemChannels.platform, (call) async {
       if (call.method == 'SystemNavigator.pop') systemPopCalls++;
+      if (call.method == 'SystemNavigator.setFrameworkHandlesBack') frameworkHandlesBack = call.arguments as bool;
       return null;
     });
     addTearDown(() {
@@ -2281,6 +2283,7 @@ void main() {
     );
     await tester.pumpAndSettle();
 
+    expect(frameworkHandlesBack, isTrue);
     await tester.tap(find.text('Settings'));
     await tester.pumpAndSettle();
     await tester.tap(find.text('Basic'));
@@ -2294,6 +2297,13 @@ void main() {
     expect(find.byKey(const ValueKey('theme-mode-system')), findsNothing);
     expect(systemPopCalls, 0);
 
+    await tester.binding.handlePopRoute();
+    await tester.pumpAndSettle();
+    expect(find.byType(HomePage), findsOneWidget);
+    expect(find.text('Press back again to exit'), findsNothing);
+    expect(systemPopCalls, 0);
+    expect(frameworkHandlesBack, isTrue);
+
     await tester.binding.handlePopRoute();
     await tester.pump();
     expect(find.text('Press back again to exit'), findsOneWidget);