Seeing this on some but not all of my CI machines. All on macOS 15.4 and Xcode 16.3. Started the same day we upgraded from macOS 15.3 and Xcode 16.2. This feels like an Apple tooling problem and not a "holding it wrong" problem. I'm following the instructions in the linked Flutter issue above to work around.

I was getting this with some frequency prior to Xcode 15.3 in projects that had SPM build-time plugins. Now on Xcode 15.3 it's nearly every other build.

Slightly earlier post: https://developer.apple.com/forums/thread/710930