Thanks, Quinn. I appreciate the clarification and the pointer to your POSIX semaphore guidance. I understand that the semaphore approach is a reasonable best-effort restart detector. My remaining question is specifically about supported guarantees rather than practical reliability. Does Apple document any public mechanism that guarantees all three properties? A value or signal unique to every device boot. A value the app cannot reset and a backup restore cannot roll back. An observable change across every same-device backup restore, including restores that preserve existing device state. I understand that the semaphore technique relies on a reasonable cleanup assumption rather than an explicitly documented guarantee. If no public API provides these properties, confirmation of that limitation would also be helpful. Thanks again!