But when it's not in the AppContext in the current zone, it should find the parent AppContext, which should have it there.

Can you set up the code to force it to lose the race in order to verify this theory?

I thought this was the parent context, but let me test this theory. Also, I'll check if I can reliably reproduce this. I only get this in 20% cases on one of the devicelab machines.

I thought this was the parent context

If this is being run via flutter daemon, then it goes through the bootstrap runner, which sets up the parent context here:

This happens when running flutter run.

flutter run --machine, if that makes any difference?

@tvolkert and I just had a offline conversation. The issue seems to be in the AppContext's zone management code, where it incorrectly flips pointers from one zone to another. The long-term fix is to stop doing that and make AppContext immutable. It is a small change in AppContext but will have a huge effect on the rest of flutter_tools package using it. To unblock this specific issue we agreed to accept this fix and implement a long-term fix as a follow-up. @tvolkert is writing up an issue for that as we speak.

Full issue described here: #15352