---
name: mechanical-refactor-verify
description: Make mechanical refactoring (file splits, function moves, module extractions, renames) machine-checkable instead of eyeballed. Reproduce a relocation commit byte-for-byte from faithful primitives, and split an extraction into a verifiable prepare + move + postpare. Use when doing or reviewing such changes.
user_invocable: true
argument: "split <base>..<tip> | construct <base>..<tip> [--match REGEX] [--out DIR] | verify --base <base> --branch <branch> --proof <folder> [--jobs N] [--skip-passed]"
---

# Mechanical Refactor — Machine-Checkable Verification

## 1. Overview

- The correctness of a mechanical change (file split, function move, module extraction,
  rename) must be **machine-checkable, not eyeballed** — the proof is something anyone can
  re-run, whoever made the change and whenever.
- **One property**: *a commit is a pure relocation*. **One proof**: **reproduce** —
  regenerate the move from the base commit with faithful primitives, run the formatter,
  byte-diff against the target.
- Empty diff = the proof. Any residual = a bundled non-move change, surfaced for review.
- A reshape must not ride along: split into optional **prepare** + certified **move** +
  optional **postpare** (`guide-split.md`).

## 2. Commands — what do you want to do?

The skill takes an argument naming one of three commands; invoked without one, pick the
row matching your task.

- **`split <base>..<tip>`** — author a compliant refactor branch: split it into commits,
  satisfy the contract (extract, move, file split) → `guide-split.md`: §1 splits the PR
  into classified pieces (the chain contract: classification format, correct labeling,
  proofs PASS, non-mechanical commits correctness-reviewed); §2 splits one piece into
  prepare + move + postpare (the case recipes and the anti-patterns). The argument is the
  chain to author (or a single commit / a description of the change to split).
- **`construct <base>..<tip> [--match REGEX] [--out DIR]`** — construct the proof, for
  the chain or one commit → `guide-construct-proof.md`: §1 generates + publishes the
  whole chain's proof folder (the flags are the generator's:
  `scripts/mechanical_refactor_proof_generator.py <base>..<tip> --match REGEX --out DIR`);
  §2 proves a single commit — pass just `<commit>` (the generator, or a hand-written
  `Repro` when it reports `UNSUPPORTED`).
- **`verify --base <base> --branch <branch> --proof <folder> [--jobs N] [--skip-passed]`**
  — verify someone's proof: a whole chain / PR branch → `guide-verify-proof.md`: run the
  chain verifier with exactly these flags
  (`scripts/mechanical_refactor_reproduction_cli.py`) — it checks every commit declares
  `mechanical_provable` or `non_mechanical_provable`, runs **every** provable commit's
  proof (never a sample), and writes one full report; then audit the authored surfaces
  and the `HUMAN_REVIEW` rows. Re-running one commit's script is for diagnosis only.
- **Decide whether a change counts as a clean move** → `spec-reproduction-utils.md`: the
  property, the whole whitelist / not-allowed list, and each primitive's contract. The
  source of truth for the reproduction module; if any other file disagrees, it wins.
- **Change this skill itself** (edit the engine, the generator, or the spec) →
  `guide-modify-skill.md`: the spec-leads rule, the faithfulness invariant, and the testing
  bar a change must clear before it is trusted.

## 3. Files

- [`guide-split.md`](guide-split.md) — split the PR into classified pieces (§1, the
  chain contract) and each piece into prepare + move + postpare (§2: case recipes, what
  stays mechanical, anti-patterns).
- [`guide-construct-proof.md`](guide-construct-proof.md) — produce the proof: the whole
  chain's proof folder + publishing (§1), and a single commit's proof — generator or
  hand-written `Repro` (§2).
- [`guide-verify-proof.md`](guide-verify-proof.md) — consume the proof: the whole-chain
  verifier, single-commit re-runs, verdicts, and the audit checklist for authored
  surfaces.
- [`spec-reproduction-utils.md`](spec-reproduction-utils.md) — the normative spec of the
  clean-move property and the reproduction primitives.
- [`spec-reproduction-cli.md`](spec-reproduction-cli.md) — the normative spec of the
  verified-chain property: the classification word rule, the proof obligation, the report,
  and the exit codes.
- [`guide-modify-skill.md`](guide-modify-skill.md) — change the engine, the generator, or
  the spec: the spec-leads rule, the byte-faithfulness invariant, and the testing bar.
- [`scripts/mechanical_refactor_proof_generator.py`](scripts/mechanical_refactor_proof_generator.py) —
  the **generator**: infers a reproduce recipe from a commit's diff and emits/runs a
  standalone, auditable script per commit, with a `PASS` / `RESIDUAL` / `UNSUPPORTED` verdict.
- [`scripts/mechanical_refactor_reproduction_utils.py`](scripts/mechanical_refactor_reproduction_utils.py) — the
  **proof engine**: the `Repro` builder's faithful relocation primitives plus the worktree +
  pre-commit + byte-diff scaffold. Self-contained — only git and the standard library.
- [`scripts/mechanical_refactor_reproduction_cli.py`](scripts/mechanical_refactor_reproduction_cli.py) — the
  **chain verifier**: classifies every commit in `base..branch`, runs every provable
  commit's proof from the proof folder, and emits the full chain report.
- [`scripts/tests/`](scripts/tests/) — pytest suites, one folder per module:
  `reproduction_utils/` for the proof engine, `proof_generator/` for the generator,
  `reproduction_cli/` for the chain verifier.