Post-#21561 the liveness probe in acquire_scoped_lock() routes through
gateway.status._pid_exists (psutil-first, safe on Windows), not
os.kill(pid, 0). The two new macOS regression tests were patching
status.os.kill, which had no effect — the unmocked psutil call returned
False for PID 99999, marking the lock stale before the new code branch
ran. The 'replaces' test passed only because acquired=True was already
the expected outcome; the 'keeps' test failed in CI.
Switch both tests to monkeypatch status._pid_exists directly, matching
the existing test_acquire_scoped_lock_rejects_live_other_process pattern,
so they actually exercise the new start_time=None + cmdline-based
staleness branch.
Teknium
629c33c633