Verification Contract

---
name: verification-contract
user-invocable: false
version: 1.0.1
author: "Gabriel Trabanco <gtrabanco@users.noreply.github.com>"
license: MIT
description: >
  Internal contract: one compact frozen ACCEPTANCE.md per delivery unit, its
  validation ladder, anti-weakening rules, and blob-bound execution receipt.
  Consumed by planners, execute-phase, review-change, and loop-review-fold.
---

# Verification Contract (internal)

Single owner of the delivery finish line. Planning freezes it; executors may
strengthen coverage but cannot move it; review checks the same bytes.

## Artifact

Every new feature/fix carries `ACCEPTANCE.md` beside its SPEC. Copy the matching
repository template. Required parts: `Status: frozen`; one stable ID per SPEC
criterion; `Required outcome`; named `Validator`; literal quality floor; project
commands. Prefer commands, otherwise use `read-verified: <evidence>` or
`manual: <exact observation>`. Unlabelled prose is invalid. A planned test may
name its future project runner; it cannot substitute a narrower runner later.

## Freeze and receipt

At first execution run `git hash-object <unit>/ACCEPTANCE.md` and append to the
unit progress file:

```text
## Acceptance receipt v1
- Manifest: <path> · Blob: <sha> · Status: frozen · Verified: <date>
```

Before every phase and final review, recompute it. Exact match continues;
missing/mismatched evidence stops before edits:

```text
ACCEPTANCE GATE — <unit> BLOCKED
Expected blob: <sha|missing> · Actual: <sha|missing>
Reason: the frozen finish line is missing or changed.

→ Next: restore the frozen manifest, or obtain explicit user approval for a
  SPEC amendment and replacement manifest; then write a fresh receipt
  · never edit tests, commands, or acceptance to make the current candidate pass
```

A legitimate change requires, in order: explicit user approval; dated SPEC
`## Amendments` row; replacement manifest; committed fresh receipt. The
executor never self-authorizes it.

Legacy unit with no manifest mention: fingerprint committed `SPEC.md` and record
`Manifest: legacy SPEC.md`. A new plan or any plan naming the manifest fails
closed when it is missing.

## Validation ladder

Evaluate every row plus the normal project gate:

- `PASS`: commands green; read evidence present; manual checks named.
- `FAIL`: validator disproves the candidate; include compact failure evidence.
- `NEEDS-DECISION`: missing product/architecture choice.
- `BLOCKED`: command/input/environment unavailable; name it.

## Anti-gaming rules

Forbidden: deleting, skipping, narrowing, or loosening a validator; suppression,
stub, hard-coded answer, or no-op fix used to manufacture green. A command cannot
prove an untested read/manual row. Stronger regression tests are allowed. Repair
test setup only when assertions stay at least as strong and the reason is logged.

## Done when

Frozen manifest + current blob receipt + named validators + literal quality
floor; executor and reviewer evaluate identical bytes.