Main, 7 October 2026, 15:07 UK: one global exclusive measure flock across unrelated measurements stalled build-1 at load 120 with
free slots (a stopped probe held it 5.5 h; an exclusive waiter queued every new shared taker) and build-2 behind a one-core VDF
bench. lease.sh (installed at /srv/builds/_bin/lease by provision.sh and by hand on both boxes) takes one flock per core for a
pinned measurement and the quiet file for a whole-box one; remote-run.sh takes quiet shared only for unbounded runs, excludes
leased cores from its set, and its keeper refreshes the holder file and calls lease reap (a STOPPED holder of a lease, quiet or a
slot for 5 minutes is killed with a line in _log/reaped.log). Keepers close the lock descriptors they inherit (an orphaned sleep
held a slot and the worktree lock 20 s past the release; the slot self-test had rotted on that since the worktree lock landed).
tools/ci/box-locks-check.sh runs lease.sh --self-test and remote-run.sh --self-test-slots on build-1. provision.sh also carries
the 16 libraries headless Chromium needs (installed by hand on both boxes at 14:5x UK) and a headless self-test step.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>