AGENTS.md@src/bernstein/core/quality git:20260825.62c88b2A

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# Quality gates and verification

The verification layer between a worker's diff and merge or human review: a
configurable gate pipeline plus the janitor's claim verification.

## Key files

| File | Purpose |
|---|---|
| `gate_pipeline.py` | `VALID_GATE_NAMES` registry, `GateStatus`, pipeline dataclasses |
| `gate_runner.py` | Gate dispatch and execution (subprocess discipline, timeouts) |
| `quality_gates.py` | `QualityGatesConfig` plus the core gate implementations |
| `janitor.py` | Claim verification: did the agent do what its result claims |
| `absence_coverage.py` | Absence-claim coverage verification: classifies a completion built on an absence claim (`glob_exists`/`file_contains` "not found", or a journal read) as `unverified` unless a coverage record backs it (#3650/#3769/#3770/#3771) |
| `verifier_ladder.py` | Multi-tier verifier ladder with signed, re-derivable per-tier receipts (#2927) |
| `review_pipeline/` | Fresh-context cross-model review gate, the ruleset a verdict is produced under (`review_pipeline/ruleset.py`), and the bounded review -> fix -> re-check contour with one chained receipt per pass (`review_pipeline/contour.py`, #4481) |
| `formal_verification.py` | Z3/Lean4 checks over scalar task metadata |

## Invariants

- Gate names are a closed set: a step name must be in `VALID_GATE_NAMES` or come
  from a registered gate plugin; anything else is rejected (`gate_runner.py`).
- Defaults are deliberate: `lint`, `pii_scan`, `dlp_scan`, `run_config` on;
  `tests`, `type_check`, heavier gates off (`quality_gates.py`); never flip one as
  a side effect. `run_config` is a safety invariant (`../config/run_overlay.py`).
- Blocking vs advisory semantics are per-gate; a new gate declares which. No
  package-level `__getattr__` re-export magic here (`__init__.py` explains why).
- Absence-claim coverage fails closed: a coverage record that cannot be read back
  classifies as no-coverage, never as a fabricated pass (`absence_coverage.py`).
- The review contour fails closed too: a spent budget, a missing fix runner, or a
  fix pass that landed no commit ends in `needs-operator` and a non-zero exit
  code, never in an approval (`review_pipeline/contour.py`); an empty ruleset
  leaves the reviewer prompt byte-identical (`review_pipeline/ruleset.py`).

## Testing

Single files only, e.g. `uv run pytest tests/unit/test_quality_gates.py -x -q`;
runner and pipeline behaviour lives in the `test_gate_*.py` files.

<!-- Reviewed 2026-08-24 against this subtree; the notes above still hold. -->