Tested via https://github.com/flutter/samples/tree/master/add_to_app/android_fullscreen and https://github.com/flutter/samples/tree/master/add_to_app/flutter_module.

Seems to occur both on master and on stable. flutter attach works on Android if started before the Flutter engine / service isolate starts. But after the engine is already running, flutter attach will way for a connection forever.

However, the observatory URL prompt was present in the 'past' logcat

13:43:57.678 30387 30553 I flutter : Observatory listening on http://127.0.0.1:37493/vtV6P-reD5I=/. The tool seems to not be picking it up.

Tested on API 29 and 30. Seems like a bug. We probably need e2e testing for this scenario.

Thanks for the heads up @redbrogdon. cc @blasten.