[webview_flutter] Crash on startup after UISceneDelegate migration when registering Webview with Google Mobile Ads SDK

### What package does this bug report belong to?

webview_flutter

### What target platforms are you seeing this bug on?

iOS

### Have you already upgraded your packages?

Yes

### Dependency versions

<details><summary>pubspec.lock</summary>

```lock
# Generated by pub
# See https://dart.dev/tools/pub/glossary#lockfile
packages:
  async:
    dependency: transitive
    description:
      name: async
      sha256: "758e6d74e971c3e5aceb4110bfd6698efc7f501675bcfe0c775459a8140750eb"
      url: "https://pub.dev"
    source: hosted
    version: "2.13.0"
  boolean_selector:
    dependency: transitive
    description:
      name: boolean_selector
      sha256: "8aab1771e1243a5063b8b0ff68042d67334e3feab9e95b9490f9a6ebf73b42ea"
      url: "https://pub.dev"
    source: hosted
    version: "2.1.2"
  characters:
    dependency: transitive
    description:
      name: characters
      sha256: f71061c654a3380576a52b451dd5532377954cf9dbd272a78fc8479606670803
      url: "https://pub.dev"
    source: hosted
    version: "1.4.0"
  clock:
    dependency: transitive
    description:
      name: clock
      sha256: fddb70d9b5277016c77a80201021d40a2247104d9f4aa7bab7157b7e3f05b84b
      url: "https://pub.dev"
    source: hosted
    version: "1.1.2"
  collection:
    dependency: transitive
    description:
      name: collection
      sha256: "2f5709ae4d3d59dd8f7cd309b4e023046b57d8a6c82130785d2b0e5868084e76"
      url: "https://pub.dev"
    source: hosted
    version: "1.19.1"
  cupertino_icons:
    dependency: "direct main"
    description:
      name: cupertino_icons
      sha256: ba631d1c7f7bef6b729a622b7b752645a2d076dba9976925b8f25725a30e1ee6
      url: "https://pub.dev"
    source: hosted
    version: "1.0.8"
  fake_async:
    dependency: transitive
    description:
      name: fake_async
      sha256: "5368f224a74523e8d2e7399ea1638b37aecfca824a3cc4dfdf77bf1fa905ac44"
      url: "https://pub.dev"
    source: hosted
    version: "1.3.3"
  flutter:
    dependency: "direct main"
    description: flutter
    source: sdk
    version: "0.0.0"
  flutter_lints:
    dependency: "direct dev"
    description:
      name: flutter_lints
      sha256: "3105dc8492f6183fb076ccf1f351ac3d60564bff92e20bfc4af9cc1651f4e7e1"
      url: "https://pub.dev"
    source: hosted
    version: "6.0.0"
  flutter_test:
    dependency: "direct dev"
    description: flutter
    source: sdk
    version: "0.0.0"
  google_mobile_ads:
    dependency: "direct main"
    description:
      name: google_mobile_ads
      sha256: f35e040875bb54e8a3455bcffed3b4ac9e9263fbf7751b9fd1ae7f30793faee8
      url: "https://pub.dev"
    source: hosted
    version: "7.0.0"
  leak_tracker:
    dependency: transitive
    description:
      name: leak_tracker
      sha256: "33e2e26bdd85a0112ec15400c8cbffea70d0f9c3407491f672a2fad47915e2de"
      url: "https://pub.dev"
    source: hosted
    version: "11.0.2"
  leak_tracker_flutter_testing:
    dependency: transitive
    description:
      name: leak_tracker_flutter_testing
      sha256: "1dbc140bb5a23c75ea9c4811222756104fbcd1a27173f0c34ca01e16bea473c1"
      url: "https://pub.dev"
    source: hosted
    version: "3.0.10"
  leak_tracker_testing:
    dependency: transitive
    description:
      name: leak_tracker_testing
      sha256: "8d5a2d49f4a66b49744b23b018848400d23e54caf9463f4eb20df3eb8acb2eb1"
      url: "https://pub.dev"
    source: hosted
    version: "3.0.2"
  lints:
    dependency: transitive
    description:
      name: lints
      sha256: "12f842a479589fea194fe5c5a3095abc7be0c1f2ddfa9a0e76aed1dbd26a87df"
      url: "https://pub.dev"
    source: hosted
    version: "6.1.0"
  matcher:
    dependency: transitive
    description:
      name: matcher
      sha256: dc58c723c3c24bf8d3e2d3ad3f2f9d7bd9cf43ec6feaa64181775e60190153f2
      url: "https://pub.dev"
    source: hosted
    version: "0.12.17"
  material_color_utilities:
    dependency: transitive
    description:
      name: material_color_utilities
      sha256: f7142bb1154231d7ea5f96bc7bde4bda2a0945d2806bb11670e30b850d56bdec
      url: "https://pub.dev"
    source: hosted
    version: "0.11.1"
  meta:
    dependency: transitive
    description:
      name: meta
      sha256: "23f08335362185a5ea2ad3a4e597f1375e78bce8a040df5c600c8d3552ef2394"
      url: "https://pub.dev"
    source: hosted
    version: "1.17.0"
  path:
    dependency: transitive
    description:
      name: path
      sha256: "75cca69d1490965be98c73ceaea117e8a04dd21217b37b292c9ddbec0d955bc5"
      url: "https://pub.dev"
    source: hosted
    version: "1.9.1"
  plugin_platform_interface:
    dependency: transitive
    description:
      name: plugin_platform_interface
      sha256: "4820fbfdb9478b1ebae27888254d445073732dae3d6ea81f0b7e06d5dedc3f02"
      url: "https://pub.dev"
    source: hosted
    version: "2.1.8"
  sky_engine:
    dependency: transitive
    description: flutter
    source: sdk
    version: "0.0.0"
  source_span:
    dependency: transitive
    description:
      name: source_span
      sha256: "254ee5351d6cb365c859e20ee823c3bb479bf4a293c22d17a9f1bf144ce86f7c"
      url: "https://pub.dev"
    source: hosted
    version: "1.10.1"
  stack_trace:
    dependency: transitive
    description:
      name: stack_trace
      sha256: "8b27215b45d22309b5cddda1aa2b19bdfec9df0e765f2de506401c071d38d1b1"
      url: "https://pub.dev"
    source: hosted
    version: "1.12.1"
  stream_channel:
    dependency: transitive
    description:
      name: stream_channel
      sha256: "969e04c80b8bcdf826f8f16579c7b14d780458bd97f56d107d3950fdbeef059d"
      url: "https://pub.dev"
    source: hosted
    version: "2.1.4"
  string_scanner:
    dependency: transitive
    description:
      name: string_scanner
      sha256: "921cd31725b72fe181906c6a94d987c78e3b98c2e205b397ea399d4054872b43"
      url: "https://pub.dev"
    source: hosted
    version: "1.4.1"
  term_glyph:
    dependency: transitive
    description:
      name: term_glyph
      sha256: "7f554798625ea768a7518313e58f83891c7f5024f88e46e7182a4558850a4b8e"
      url: "https://pub.dev"
    source: hosted
    version: "1.2.2"
  test_api:
    dependency: transitive
    description:
      name: test_api
      sha256: ab2726c1a94d3176a45960b6234466ec367179b87dd74f1611adb1f3b5fb9d55
      url: "https://pub.dev"
    source: hosted
    version: "0.7.7"
  vector_math:
    dependency: transitive
    description:
      name: vector_math
      sha256: d530bd74fea330e6e364cda7a85019c434070188383e1cd8d9777ee586914c5b
      url: "https://pub.dev"
    source: hosted
    version: "2.2.0"
  vm_service:
    dependency: transitive
    description:
      name: vm_service
      sha256: "45caa6c5917fa127b5dbcfbd1fa60b14e583afdc08bfc96dda38886ca252eb60"
      url: "https://pub.dev"
    source: hosted
    version: "15.0.2"
  webview_flutter:
    dependency: "direct main"
    description:
      name: webview_flutter
      sha256: a3da219916aba44947d3a5478b1927876a09781174b5a2b67fa5be0555154bf9
      url: "https://pub.dev"
    source: hosted
    version: "4.13.1"
  webview_flutter_android:
    dependency: transitive
    description:
      name: webview_flutter_android
      sha256: eeeb3fcd5f0ff9f8446c9f4bbc18a99b809e40297528a3395597d03aafb9f510
      url: "https://pub.dev"
    source: hosted
    version: "4.10.11"
  webview_flutter_platform_interface:
    dependency: transitive
    description:
      name: webview_flutter_platform_interface
      sha256: "63d26ee3aca7256a83ccb576a50272edd7cfc80573a4305caa98985feb493ee0"
      url: "https://pub.dev"
    source: hosted
    version: "2.14.0"
  webview_flutter_wkwebview:
    dependency: transitive
    description:
      name: webview_flutter_wkwebview
      sha256: e49f378ed066efb13fc36186bbe0bd2425630d4ea0dbc71a18fdd0e4d8ed8ebc
      url: "https://pub.dev"
    source: hosted
    version: "3.23.5"
sdks:
  dart: ">=3.10.7 <4.0.0"
  flutter: "3.38.7"
```

</details>


### Steps to reproduce

1. I already asked the `google_mobile_ads` team (https://github.com/googleads/googleads-mobile-flutter/issues/1399) but was asked to file the issue here.
2. use minimal reproducible example from below
3. Run the application on an iOS Simulator with iOS-Version >= 26
4. The application crashes with the following console logs:
```
Resolving dependencies... 
Downloading packages... 
  characters 1.4.0 (1.4.1 available)
  matcher 0.12.17 (0.12.18 available)
  material_color_utilities 0.11.1 (0.13.0 available)
  meta 1.17.0 (1.18.1 available)
  test_api 0.7.7 (0.7.9 available)
Got dependencies!
5 packages have newer versions incompatible with dependency constraints.
Try `flutter pub outdated` for more information.
Launching lib/main.dart on iPhone 16e in debug mode...
Running Xcode build...                                                  
Xcode build done.                                            6,2s
Syncing files to device iPhone 16e...                              180ms

Flutter run key commands.
r Hot reload. 🔥🔥🔥
R Hot restart.
h List all available interactive commands.
d Detach (terminate "flutter run" but leave application running).
c Clear the screen
q Quit (terminate the application on the device).

A Dart VM Service on iPhone 16e is available at: http://127.0.0.1:51518/cvWlDcuXm1E=/
The Flutter DevTools debugger and profiler on iPhone 16e is available at: http://127.0.0.1:51518/cvWlDcuXm1E=/devtools/?uri=ws://127.0.0.1:51518/cvWlDcuXm1E=/ws
webview_flutter_wkwebview/WebViewFlutterWKWebViewExternalAPI.swift:31: Fatal error: Unexpectedly found nil while unwrapping an Optional value
``` 

### Expected results

The application runs without problems and displays the flutter.dev page inside the webview.

### Actual results

The application crashes on startup

### Code sample

<details open><summary>Code sample</summary>

Run `flutter create bug`, add dependencies `google_mobile_ads` and `webview_flutter` and update files as follows:

main.dart
```dart
import 'package:flutter/material.dart';
import 'package:google_mobile_ads/google_mobile_ads.dart';
import 'package:webview_flutter/webview_flutter.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(colorScheme: .fromSeed(seedColor: Colors.deepPurple)),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  late final WebViewController _controller;

  @override
  void initState() {
    super.initState();

    _createWebView();
  }

  Future<void> _createWebView() async {
    _controller = WebViewController()
      ..setJavaScriptMode(JavaScriptMode.unrestricted)
      ..setNavigationDelegate(
        NavigationDelegate(
          onProgress: (int progress) {
            // Update loading bar.
          },
          onPageStarted: (String url) {},
          onPageFinished: (String url) {},
          onHttpError: (HttpResponseError error) {},
          onWebResourceError: (WebResourceError error) {},
          onNavigationRequest: (NavigationRequest request) {
            if (request.url.startsWith('https://www.youtube.com/')) {
              return NavigationDecision.prevent;
            }
            return NavigationDecision.navigate;
          },
        ),
      );
    await MobileAds.instance.registerWebView(_controller);
    _controller.loadRequest(Uri.parse('https://flutter.dev'));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(widget.title),
      ),
      body: WebViewWidget(controller: _controller),
    );
  }
}
```
following official flutter docs to migrate to UISceneDelegate:
ios/Runner/Info.plist
```
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>CADisableMinimumFrameDurationOnPhone</key>
	<true/>
	<key>CFBundleDevelopmentRegion</key>
	<string>$(DEVELOPMENT_LANGUAGE)</string>
	<key>CFBundleDisplayName</key>
	<string>Bug</string>
	<key>CFBundleExecutable</key>
	<string>$(EXECUTABLE_NAME)</string>
	<key>CFBundleIdentifier</key>
	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
	<key>CFBundleInfoDictionaryVersion</key>
	<string>6.0</string>
	<key>CFBundleName</key>
	<string>bug</string>
	<key>CFBundlePackageType</key>
	<string>APPL</string>
	<key>CFBundleShortVersionString</key>
	<string>$(FLUTTER_BUILD_NAME)</string>
	<key>CFBundleSignature</key>
	<string>????</string>
	<key>CFBundleVersion</key>
	<string>$(FLUTTER_BUILD_NUMBER)</string>
	<key>LSRequiresIPhoneOS</key>
	<true/>
	<key>UIApplicationSceneManifest</key>
	<dict>
		<key>UIApplicationSupportsMultipleScenes</key>
		<false/>
		<key>UISceneConfigurations</key>
		<dict>
			<key>UIWindowSceneSessionRoleApplication</key>
			<array>
				<dict>
					<key>UISceneClassName</key>
					<string>UIWindowScene</string>
					<key>UISceneConfigurationName</key>
					<string>flutter</string>
					<key>UISceneDelegateClassName</key>
					<string>FlutterSceneDelegate</string>
					<key>UISceneStoryboardFile</key>
					<string>Main</string>
				</dict>
			</array>
		</dict>
	</dict>
	<key>UIApplicationSupportsIndirectInputEvents</key>
	<true/>
	<key>UILaunchStoryboardName</key>
	<string>LaunchScreen</string>
	<key>UIMainStoryboardFile</key>
	<string>Main</string>
	<key>UISupportedInterfaceOrientations</key>
	<array>
		<string>UIInterfaceOrientationPortrait</string>
		<string>UIInterfaceOrientationLandscapeLeft</string>
		<string>UIInterfaceOrientationLandscapeRight</string>
	</array>
	<key>UISupportedInterfaceOrientations~ipad</key>
	<array>
		<string>UIInterfaceOrientationPortrait</string>
		<string>UIInterfaceOrientationPortraitUpsideDown</string>
		<string>UIInterfaceOrientationLandscapeLeft</string>
		<string>UIInterfaceOrientationLandscapeRight</string>
	</array>
    <key>GADIntegrationManager</key>
    <string>webview</string>
</dict>
</plist>
```
ios/Runner/AppDelegate.swift
```
import Flutter
import UIKit

@main
@objc class AppDelegate: FlutterAppDelegate, FlutterImplicitEngineDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }

  func didInitializeImplicitFlutterEngine(_ engineBridge: FlutterImplicitEngineBridge) {
    GeneratedPluginRegistrant.register(with: engineBridge.pluginRegistry)
  }
}
```

</details>


### Screenshots or Videos

<details open>
<summary>Screenshots / Video demonstration</summary>

[Upload media here]

</details>


### Logs

<details open><summary>Logs</summary>

[verbose-log.txt](https://github.com/user-attachments/files/25052530/verbose-log.txt)

</details>


### Flutter Doctor output

<details open><summary>Doctor output</summary>

```console
[✓] Flutter (Channel stable, 3.38.7, on macOS 26.2 25C56 darwin-arm64, locale de-DE) [603ms]
    • Flutter version 3.38.7 on channel stable at /Users/luisgraml/development/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 3b62efc2a3 (3 weeks ago), 2026-01-13 13:47:42 -0800
    • Engine revision 78fc3012e4
    • Dart version 3.10.7
    • DevTools version 2.51.1
    • Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android, enable-ios, cli-animations, enable-native-assets,
      omit-legacy-version-file, enable-lldb-debugging, enable-uiscene-migration

[✓] Android toolchain - develop for Android devices (Android SDK version 36.0.0-rc5) [2,2s]
    • Android SDK at /Users/luisgraml/Library/Android/sdk
    • Emulator version 36.3.10.0 (build_id 14472402) (CL:N/A)
    • Platform android-36, build-tools 36.0.0-rc5
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
      This is the JDK bundled with the latest Android Studio installation on this machine.
      To manually set the JDK path, use: `flutter config --jdk-dir="path/to/jdk"`.
    • Java version OpenJDK Runtime Environment (build 21.0.8+-14196175-b1038.72)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 26.2) [1.965ms]
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 17C52
    • CocoaPods version 1.16.2

[✓] Chrome - develop for the web [8ms]
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Connected device (3 available) [6,4s]
    • iPhone 16e (mobile) • E1D6A4B8-3396-41E6-ABEE-29D9298EEFFC • ios            • com.apple.CoreSimulator.SimRuntime.iOS-26-1 (simulator)
    • macOS (desktop)     • macos                                • darwin-arm64   • macOS 26.2 25C56 darwin-arm64
    • Chrome (web)        • chrome                               • web-javascript • Google Chrome 144.0.7559.110
    ! Error: Browsing on the local area network for iPhone von Luis. Ensure the device is unlocked and attached with a cable or associated with the same local area network as this
      Mac.
      The device must be opted into Developer Mode to connect wirelessly. (code -27)

[✓] Network resources [291ms]
    • All expected network resources are available.

• No issues found!
```

</details>


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Uh oh!

[webview_flutter] Crash on startup after UISceneDelegate migration when registering Webview with Google Mobile Ads SDK #181865

What package does this bug report belong to?

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Uh oh!

[webview_flutter] Crash on startup after UISceneDelegate migration when registering Webview with Google Mobile Ads SDK #181865

Description

What package does this bug report belong to?

What target platforms are you seeing this bug on?

Have you already upgraded your packages?

Dependency versions

Steps to reproduce

Expected results

Actual results

Code sample

Screenshots or Videos

Logs

Flutter Doctor output

Metadata

Metadata

Assignees

Labels

Type

Fields

Projects

Milestone

Relationships

Development

Issue actions