Build and audit verification gates — deterministic checks that block a\npipeline and can be shown to go red.
\nThe characteristic failure of a gate is not a wrong check. A wrong check gets\nnoticed. It is a check that cannot fail, which reports PASS forever and is\nindistinguishable from a working one from the outside.
\nSo the object under suspicion here is the check itself.
\n| \n | \n | \n |
|---|---|---|
| Anchor | \nsomething your own code did not produce | \npublished constant, closed form, invariant, theoretical bound | \n
| Known-bad | \na case the gate demonstrably rejects | \nbreak the subject plausibly, run the gate, confirm red | \n
| Coverage limit | \nwhat it cannot catch, in writing | \nholes are invisible from inside a green run | \n
scripts/gate.py enforces the last two: a gate that registers no known-bad or\nno coverage limit reports INCONCLUSIVE and exits 2, not PASS.
# mutation pass — which single-token changes does the gate NOT notice?\npython3 scripts/mutate.py --target src/codec.py -- python3 calibrate.py\nmutate.py is stdlib-only, uses tokenize (so it never corrupts strings or\ncomments), restores the file even on interrupt, and refuses to run when the\ngate is already red. It works against any gate command; mutmut and\ncosmic-ray go deeper once it stops finding survivors.
gate.py is a ~150-line harness: anchor(), bracket(), known_bad(),\ncoverage(), note(), and a report() that returns a process exit code.
challengingchallenging asks would a careful reader object? — LLM judgement against a\npersona, verdicts of SHIP/REVISE/RETHINK. gating asks can this check go\nred? — deterministic, anchored, exit-coded.
Complements with different blind spots: an adversarial reviewer will not\nrecompute your constants, and a gate will not notice that your framing is\nwrong. Note also that a same-model reviewer is an independent context, not\nan independent reviewer; where shared priors are the risk, an anchor beats a\nreviewer because an anchor is not negotiable.
\nSee SKILL.md for the build and audit procedures and the\nanti-pattern table, references/anchors.md for\nchoosing an oracle, and references/auditing.md for\nthe six-pass \"can this fail?\" sweep over an existing suite.