cleanupXcodeIdeCallToolTransientArtifacts deletes any owner directory whose PID is not alive via isPidAlive(ownerPid). Since the directory name encodes only the PID and instanceId, and the check is purely PID-based, a long-dead owner whose PID has been recycled by an unrelated process will be considered alive (false negative — safe), but more importantly, the matching only validates ownerPid > 0 without confirming the instanceId belongs to a stale runtime. If two runtimes share a PID across reboots, stale dirs may remain. Conversely, this is a TOCTOU pattern: between isPidAlive and fs.rm, a new runtime could claim that PID/instanceId combo and have its artifacts deleted. Given startup-only invocation with includeCurrentOwner:false, the practical risk is limited but a concurrent startup of another instance with reused PID could lose data.

cleanupXcodeIdeCallToolTransientArtifactsSync returns {attemptedCount:0, errors:[]} silently when getRuntimeInstanceIfConfigured() returns null. If this is called from a process-exit handler expecting cleanup, callers cannot distinguish 'no runtime to clean' from 'cleanup skipped'. This is informational rather than a security issue.