Swarming failing tests

A loop that turns a test suite's failures into merged fixes, unattended, for hours:

known.json --cluster by signature--> work items --one headless worker each, own worktree-->
  result JSON --serial gate: apply on main, compat check, run smoke + targets + sample,
  zero regressions, >=1 target flips--> fast-forward main --> re-check the whole cluster --> repeat

Every mechanism in it fixed a failure that cost hours on 2026-10-12, when Haiku 5.5 workers built hcc (a C compiler in Python) against ~42K tests: 1,051 hub workers, 464 merges, $24.88 of worker spend by 18:30Z. The catalogue of those failures, each with its signal and where it is handled, is references/run-2026-10-12.md.