the canary's failure had to be inferred from what stopped answering; the prometheus scrape was the only forensics that survived the pod. put the runtime's own state there: switches (flat = wedged loop), fibers by state, futex waiters (climbing = lost wakes), timer/inject depth, poller registrations (collapse = erosion), spill pool depth. computed only when scraped, on the loop thread, zero cost otherwise. compiled out entirely on the Threaded backend. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>