A start and a finish sent seconds apart can reach Sentry in either order, and a start that lands second is never closed, so a fast rollup was reported as a timeout on nights it succeeded. Hnefatafl's monitor did so nine nights in fifteen. One check-in at the end cannot race; a run that hangs sends nothing and is marked missed. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01GwFKMuQnPAEHJ5yA1q4orh