Web and desktop
The plugin's native half is registered on Android and iOS only — the pubspec.yaml says why: "web has no process to have died, and desktop is not a target". The Dart half works on both.
On the web
Since otel_zone 0.8.1 runGuarded runs on the web, so wrap main() the same way on every platform.
Before 0.8.1 it never ran its body there and the page stayed blank: it opened a ReceivePort, Dart's web runtime throws UnsupportedError for that, and the zone's own handler took the error. An app that wrote kIsWeb ? body() : observability.runGuarded(body) drops the kIsWeb branch once it pins 0.8.1 or later.
What is reported
Framework errors and uncaught async errors. Isolate.addErrorListener is not installed, and the web engine never calls PlatformDispatcher.onError: an error escaping one of its callbacks goes to the zone the callback was registered from, which inside runGuarded is this one.
Flushing a tab
Since 0.8.1 the queued records are also flushed when the tab is hidden — switching to another tab, minimising the window, or closing it. (They already were when the host page removes the app's last view.) The web engine never reports paused, so hidden is the state that does it. A flush still in flight when the page unloads can be cut short by the browser, so records sent as a tab closes are best effort.
What does nothing
Native crash capture and setCrashScreen do nothing on the web: the drain makes no platform call, and setCrashScreen keeps the value and sends nothing.
Tested in a browser
test/run-guarded-web_test.dart needs a browser. CI's web job runs it under both the JavaScript and the wasm compilers:
flutter test --platform chrome test/run-guarded-web_test.dart
flutter test --platform chrome --wasm test/run-guarded-web_test.dartPlain flutter test skips it.
On desktop
macOS, Linux and Windows get Dart-level capture only: all four runGuarded channels, the floor, the breadcrumbs and redact. The native crash drain makes no platform call and logs nothing there, and setCrashScreen keeps its value without sending it.