Somehow my fastlane upload pipeline stopped working, due to shadowing the system rsync binary.
I would have never guessed this root cause.
Historically it would take me hours of debugging and head banging, but Opus 4.5 just did it under one minute by itself.
Found it! You have a Homebrew rsync (3.4.1) that's being used instead of Apple's built-in openrsync:
- which rsync → /Users/mango/tools/brew/bin/rsync (Homebrew 3.4.1)
- /usr/bin/rsync → Apple's openrsync (protocol 29)
Xcode's export process is mixing these two incompatible versions, causing the "syntax or usage error" when they try to communicate.