iOS crash on launch with Flutter 3.41+ UIScene lifecycle — force-unwrap on nil window in plugin registration #46
Description
Describe the problem
Both cometchat_chat_uikit and cometchat_uikit_shared crash immediately on app launch when built with Flutter 3.41+, which auto-migrates iOS apps to the UIScene lifecycle.
The root cause is a force-unwrap (?!) on a nil window property during plugin registration:
SwiftCometchatChatUikitPlugin.swift:32:
let viewController = UIApplication.shared.delegate?.window?!.rootViewControllerCometchatUikitSharedPlugin.swift:46:
let viewController = UIApplication.shared.delegate?.window?!.rootViewControllerUnder the UIScene lifecycle, UIApplication.shared.delegate?.window is nil during plugin registration because the window is now owned by UIWindowScene, not the AppDelegate. The ?! operator force-unwraps nil and causes a brk 1 (EXC_BREAKPOINT / SIGTRAP) crash.
What was the expected behavior?
The app should launch without crashing. The viewController can safely be nil at registration time — replacing ?! with ?? fixes the issue and the app runs normally.
Reproduction
- Step 1: Create a Flutter app using
cometchat_chat_uikit: ^5.2.10 - Step 2: Build with Flutter 3.41+ (
flutter build ipa --release) — this auto-migrates to UIScene lifecycle - Step 3: Install on device via TestFlight or Ad Hoc
- Step 4: App crashes immediately on launch before any Dart code runs
Alternatively, to reproduce locally:
- Step 1: Add the UIScene manifest to
ios/Runner/Info.plist:
<key>UIApplicationSceneManifest</key>
<dict>
<key>UIApplicationSupportsMultipleScenes</key>
<false/>
<key>UISceneConfigurations</key>
<dict>
<key>UIWindowSceneSessionRoleApplication</key>
<array>
<dict>
<key>UISceneClassName</key>
<string>UIWindowScene</string>
<key>UISceneDelegateClassName</key>
<string>FlutterSceneDelegate</string>
<key>UISceneConfigurationName</key>
<string>flutter</string>
<key>UISceneStoryboardFile</key>
<string>Main</string>
</dict>
</array>
</dict>
</dict>- Step 2: Run
flutter run - Step 3: App crashes on launch
This issue is 100% reproducible.
Suggested fix — change ?! to ?? in both files:
let viewController = UIApplication.shared.delegate?.window??.rootViewControllerTested and confirmed working.
Crash log (truncated):
Exception Type: EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000001, 0x00000001008b8564
Thread 0 Crashed:
0 cometchat_chat_uikit 0x00000001008b8564
1 cometchat_chat_uikit 0x00000001008b80ac
2 Runner 0x00000001004780b8
3 Runner 0x0000000100478604
4 Flutter FlutterEngine performImplicitEngineCallback
Environment
- Version used: cometchat_chat_uikit 5.2.10, cometchat_uikit_shared 5.2.0, cometchat_sdk 4.1.0
- Flutter: 3.41.2 (stable)
- iOS: 18.5, iPhone 17 Pro Max
- Other modules/plugins/libraries that might be involved: Flutter's UIScene auto-migration (see Flutter docs). Apple will require UIScene lifecycle for all UIKit apps in the release following iOS 26.