A crash-free rate of 99.8% sounds excellent until you realise it only counts crashes your reporting tool was wired to see. In Flutter, an error can escape through four different doors, and most apps only guard one or two of them. The four doors Door Catches Missed if unwired FlutterError.onError Errors inside the framework: build, layout, paint, gesture callbacks Red screens, silent layout failures PlatformDispatcher.instance.onError Uncaught async errors in the root zone Most Future failures Isolate.current.addErrorListener Errors in isolates you spawned Every background-compute failure Native crash handler Platform-level crashes, plugin native code Anything that kills the process Here is all four, wired once at startup: Future < void > main () async { WidgetsFlutterBinding . ensureInitialized (); await Firebase . initializeApp (); final crashlytics = FirebaseCrashlytics .instance; // 1. Framework errors. FlutterError .onEr...