The plan's metric order is diff-quality FIRST, but cells never ran the
fixtures' own run-tests.js, so a refusal, a broken implementation, and
working code were indistinguishable in aggregates (Codex adversarial catch).
Tasks with an oracle declare checkCmd; every cell records checks=pass|fail|none
in the report line and eval store. Selftest pins the oracle declarations and
that the planted bug fails its own check pre-fix.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>