The discovery `daemon` fixture probed UDS readiness by connecting and
immediately closing. That entered Tractor's actor handshake without an
`Aid` payload and destabilized the remote registrar on macOS before
test roots attempted discovery.
Run the child through a small `open_root_actor()` wrapper and publish a
filesystem sentinel only after runtime startup completes. Poll that
sentinel with process-liveness checks and guaranteed setup-failure
cleanup, without touching the transport socket.
Cover transport-free readiness and deterministic polling backoff.
Caught-during: review remediation
Found-via: `/run-tests` discovery daemon fixture consumers
Cause: initial sentinel drafts mishandled `pytest.Testdir`, emitted
invalid `python -c` syntax, and misplaced return-code logging.
Review: PR #480 (goodboy)
https://github.com/goodboy/tractor/pull/480
(this patch was generated in some part by `opencode` using
`gpt-5.6-sol` (`openai`))
Gud Boi