improve back navigation and ask tabs to close when originated from intent

app/android/app/src/main/kotlin/eu/weblibre/gecko/MainActivity.kt

@@ -27,19 +27,30 @@ import io.flutter.embedding.engine.dart.DartExecutor
 import io.flutter.plugin.common.MethodChannel
 
 class MainActivity: FlutterFragmentActivity() {
-    private val CHANNEL = "eu.weblibre.flutter_mozilla_components/trim_memory"
+    private val TRIM_MEMORY_CHANNEL = "eu.weblibre.flutter_mozilla_components/trim_memory"
+    private val ACTIVITY_CHANNEL = "eu.weblibre.gecko/activity"
     private val ENGINE_ID = "engine_id"
-    private var channel: MethodChannel? = null
+    private var trimMemoryChannel: MethodChannel? = null
 
     override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
         super.configureFlutterEngine(flutterEngine)
 
-        channel = MethodChannel(flutterEngine.dartExecutor.binaryMessenger, CHANNEL)
+        trimMemoryChannel = MethodChannel(flutterEngine.dartExecutor.binaryMessenger, TRIM_MEMORY_CHANNEL)
+
+        MethodChannel(flutterEngine.dartExecutor.binaryMessenger, ACTIVITY_CHANNEL).setMethodCallHandler { call, result ->
+            when (call.method) {
+                "moveTaskToBack" -> {
+                    moveTaskToBack(true)
+                    result.success(null)
+                }
+                else -> result.notImplemented()
+            }
+        }
     }
 
     override fun onTrimMemory(level: Int) {
         super.onTrimMemory(level)
-        channel?.invokeMethod("onTrimMemory", level)
+        trimMemoryChannel?.invokeMethod("onTrimMemory", level)
     }
 
     override fun provideFlutterEngine(context: Context): FlutterEngine {

app/lib/features/geckoview/domain/repositories/tab.dart

@@ -54,6 +54,10 @@ class TabRepository extends _$TabRepository {
     return _tabFromIntent.contains(tabId);
   }
 
+  void clearLaunchedFromIntent(String tabId) {
+    _tabFromIntent.remove(tabId);
+  }
+
   Future<String?> _resolveParentIdForContext({
     required String? parentId,
     required String? targetContextId,

app/lib/features/geckoview/domain/repositories/tab.g.dart

@@ -41,7 +41,7 @@ final class TabRepositoryProvider
   }
 }
 
-String _$tabRepositoryHash() => r'f0ff983df4115bfed7ff3dbc8994592bc46a1daa';
+String _$tabRepositoryHash() => r'b300b88bc7817b533be46d8d0d933786b10212fb';
 
 abstract class _$TabRepository extends $Notifier<void> {
   void build();

app/lib/features/geckoview/features/browser/presentation/dialogs/keep_tab_dialog.dart

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2024-2026 Fabian Freund.
+ *
+ * This file is part of WebLibre
+ * (see https://weblibre.eu).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+import 'package:flutter/material.dart';
+
+/// Shows a dialog asking the user whether to keep a tab that was opened from another app.
+///
+/// Returns true if the user wants to keep the tab, false if they want to discard it.
+Future<bool?> showKeepTabDialog(BuildContext context) {
+  return showDialog<bool>(
+    context: context,
+    builder: (context) => AlertDialog(
+      title: const Text('Keep tab?'),
+      content: const Text(
+        'This tab was opened from another app. Do you want to keep it or discard it?',
+      ),
+      actions: [
+        TextButton(
+          onPressed: () => Navigator.of(context).pop(false),
+          child: const Text('Discard'),
+        ),
+        FilledButton(
+          onPressed: () => Navigator.of(context).pop(true),
+          child: const Text('Keep'),
+        ),
+      ],
+    ),
+  );
+}

app/lib/features/geckoview/features/browser/presentation/screens/browser.dart

@@ -21,7 +21,6 @@ import 'dart:async';
 import 'dart:math' as math;
 
 import 'package:flutter/material.dart';
-import 'package:flutter/services.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:go_router/go_router.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
@@ -42,6 +41,7 @@ import 'package:weblibre/features/geckoview/domain/repositories/tab.dart';
 import 'package:weblibre/features/geckoview/features/browser/domain/entities/sheet.dart';
 import 'package:weblibre/features/geckoview/features/browser/presentation/controllers/tab_bar_dismissable.dart';
 import 'package:weblibre/features/geckoview/features/browser/presentation/controllers/tab_view_controllers.dart';
+import 'package:weblibre/features/geckoview/features/browser/presentation/dialogs/keep_tab_dialog.dart';
 import 'package:weblibre/features/geckoview/features/browser/presentation/widgets/browser_modules/bottom_app_bar.dart';
 import 'package:weblibre/features/geckoview/features/browser/presentation/widgets/browser_modules/browser_fab.dart';
 import 'package:weblibre/features/geckoview/features/browser/presentation/widgets/browser_modules/browser_view.dart';
@@ -57,6 +57,7 @@ import 'package:weblibre/features/geckoview/features/find_in_page/presentation/w
 import 'package:weblibre/features/geckoview/features/readerview/presentation/controllers/readerable.dart';
 import 'package:weblibre/features/user/data/models/general_settings.dart';
 import 'package:weblibre/features/user/domain/repositories/general_settings.dart';
+import 'package:weblibre/utils/move_to_background.dart';
 import 'package:weblibre/utils/ui_helper.dart' as ui_helper;
 
 /// Callback for toolbar animation progress updates.
@@ -810,9 +811,26 @@ class _Browser extends HookConsumerWidget {
                 if (ref
                     .read(tabRepositoryProvider.notifier)
                     .hasLaunchedFromIntent(tabState?.id)) {
-                  //Mark back as unhandled and navigator will pop
-                  await SystemNavigator.pop();
-                  return false;
+                  if (!context.mounted) return false;
+
+                  final keep = await showKeepTabDialog(context);
+                  if (keep == true) {
+                    ref
+                        .read(tabRepositoryProvider.notifier)
+                        .clearLaunchedFromIntent(tabState!.id);
+
+                    await moveToBackground();
+                    return true;
+                  }
+
+                  if (tabState != null) {
+                    await ref
+                        .read(tabRepositoryProvider.notifier)
+                        .closeTab(tabState.id);
+                  }
+
+                  await moveToBackground();
+                  return true;
                 }
 
                 // Handle double back to close (if enabled)
@@ -836,9 +854,8 @@ class _Browser extends HookConsumerWidget {
 
                       return true;
                     } else {
-                      //Mark back as unhandled and navigator will pop
-                      await SystemNavigator.pop();
-                      return false;
+                      await moveToBackground();
+                      return true;
                     }
                   } else {
                     lastBackButtonPress.value = DateTime.now();

app/lib/utils/move_to_background.dart

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2024-2026 Fabian Freund.
+ *
+ * This file is part of WebLibre
+ * (see https://weblibre.eu).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+import 'package:flutter/services.dart';
+
+const _channel = MethodChannel('eu.weblibre.gecko/activity');
+
+/// Moves the app to the background without finishing the activity.
+/// Unlike [SystemNavigator.pop], this keeps the Flutter engine attached,
+/// avoiding crashes when the user returns to the app.
+Future<void> moveToBackground() async {
+  await _channel.invokeMethod('moveTaskToBack');
+}