gating
Build and audit verification gates — deterministic checks that block a pipeline and can be shown to go red.
The characteristic failure of a gate is not a wrong check. A wrong check gets noticed. It is a check that cannot fail, which reports PASS forever and is indistinguishable from a working one from the outside.
So the object under suspicion here is the check itself.
The three obligations
| Anchor | something your own code did not produce | published constant, closed form, invariant, theoretical bound |
| Known-bad | a case the gate demonstrably rejects | break the subject plausibly, run the gate, confirm red |
| Coverage limit | what it cannot catch, in writing | holes are invisible from inside a green run |
scripts/gate.py enforces the last two: a gate that registers no known-bad or
no coverage limit reports INCONCLUSIVE and exits 2, not PASS.
Scripts
# mutation pass — which single-token changes does the gate NOT notice?
python3 scripts/mutate.py --target src/codec.py -- python3 calibrate.pymutate.py is stdlib-only, uses tokenize (so it never corrupts strings or
comments), restores the file even on interrupt, and refuses to run when the
gate is already red. It works against any gate command; mutmut and
cosmic-ray go deeper once it stops finding survivors.
gate.py is a ~150-line harness: anchor(), bracket(), known_bad(),
coverage(), note(), and a report() that returns a process exit code.
Relationship to challenging
challenging asks would a careful reader object? — LLM judgement against a
persona, verdicts of SHIP/REVISE/RETHINK. gating asks can this check go
red? — deterministic, anchored, exit-coded.
Complements with different blind spots: an adversarial reviewer will not recompute your constants, and a gate will not notice that your framing is wrong. Note also that a same-model reviewer is an independent context, not an independent reviewer; where shared priors are the risk, an anchor beats a reviewer because an anchor is not negotiable.
See SKILL.md for the build and audit procedures and the
anti-pattern table, references/anchors.md for
choosing an oracle, and references/auditing.md for
the six-pass "can this fail?" sweep over an existing suite.