On macOS, unityctl editor run prints this error:
.unityctl is not a valid directory name. Please make sure there are no unallowed characters in the name.
Unity on macOS validates the -logFile argument and rejects paths containing directories that start with a dot. The error is printed to stderr but Unity continues anyway (log file is still written).
Tested on: Unity 6000.0.63f1, macOS
Workarounds that work:
Logs/UnityCtl/editor.log
_unityctl/editor.log
Proposed fix: Store editor logs in Logs/UnityCtl/ instead of .unityctl/. Keep .unityctl/ for config files (bridge.json, config.json) since those aren't passed to Unity.