refactor

name	refactor
description	Restructure existing code without changing its behavior, through a test-gated refactoring loop: a named target, a green suite over that target before any edit, a planned sequence of small named refactorings, and the full suite re-run after every step. Use when the user wants to refactor, restructure, clean up, simplify, or improve the design of existing code, or to apply refactoring recommendations from a code-review or architectural-analysis report. This skill changes code; it does not review code (use code-review), assess architecture (use architectural-analysis), or build new behavior test-first (use tdd). Do not use it on code inside an active tdd loop; the refactor step of tdd owns that cleanup.
argument-hint	[file, module, named smell, or a path to review findings]
allowed-tools	Read, Write, Edit, Glob, Grep, Bash(git *), Bash(find *), Bash(npm *), Bash(npx *), Bash(pnpm *), Bash(yarn *), Bash(pytest *), Bash(python3 *), Bash(go *), Bash(cargo *), Bash(make *), Bash(bundle *), Bash(rake *)

Project Context

• git installed: !which git 2>/dev/null || echo "not installed"
• current branch: !git branch --show-current 2>/dev/null || echo unknown
• working tree: !git status --porcelain 2>/dev/null | head -5
• CLAUDE.md: !find . -maxdepth 1 -name "CLAUDE.md" -type f
• project-discovery.md: !find . -maxdepth 3 -name "project-discovery.md" -type f

Constraints (read before anything else)

This skill restructures existing production and test code in your working tree. It is an execution skill, not a document generator. These constraints shape every step and override any instinct to move faster. The canon they derive from, with provenance, is in references/refactoring-discipline.md; pull that reference when a step needs the full rule or a step feels off.

• Behavior preservation is the definition. A refactoring changes internal structure without changing observable behavior. A change that alters behavior is not a refactoring done badly; it is not a refactoring at all. When a planned step turns out to require a behavior change, it leaves this skill's scope: defer it with a note naming the behavior change it needs.
• Tests are the license to refactor. No edit until the full suite has been run, observed green, and the target's behavior is covered. If coverage of the target cannot be established, stop and offer the characterization path in the reference; never refactor blind.
• Small named steps, green to green. Each step is one named refactoring with a bounded mechanic (extract function, rename, move, inline, and so on), and the suite runs after every step. A red suite after a step means revert the step, not patch forward.
• The declared scope is a contract. The target named in Step 1 bounds every edit. When a step starts pulling in files outside that scope, stop, report the spread, and let the user re-scope. Spreading edits are how a refactoring silently becomes a rewrite.
• Never alongside an active tdd loop. If the working tree shows a red-green cycle in flight (failing tests, a half-implemented behavior), do not run: the refactor step of /tdd owns cleanup inside the loop, and restructuring while a test is red violates the two-hats rule both skills share.
• Refactor-only changes. No behavior fixes, no features, no drive-by bug fixes, even when you spot one. Record what you found and leave it. If the user asks for commits, each commit contains refactoring only.
• YAGNI governs the plan. Apply ../../references/yagni-rule.md: every refactoring in the plan needs evidence the code has a reason to change (a review finding, named duplication, a confusing read documented by the user, upcoming work in that area). Removing duplication is the job; adding speculative abstraction, configuration, or indirection is not. Defer evidence-free items with a reopen trigger.

Refactor

Step 1: Bind the Target and Resolve Project Config

Bind the target. Resolve the request to a named target: specific files or directories, a named code smell in a named place, or the refactoring findings in a provided document (a /code-review report, an /architectural-analysis report, or equivalent). When a findings document is given, extract only the refactoring-shaped findings (structural suggestions, duplication, naming, coupling) and record each finding's ID so the summary can trace back to it. If the request is open-ended ("clean up the codebase", "improve quality") with no named target, ask the user for one before doing anything: open-ended refactoring runs are the documented failure mode this skill exists to avoid, and a wrong guess here burns the whole run.

Resolve commands. Read CLAUDE.md's ## Project Discovery section for the test command (under ### Commands and Tests), the lint command, the build command, language, and framework. If absent, fall back to project-discovery.md. If still absent, run ${CLAUDE_SKILL_DIR}/scripts/detect-refactor-context.sh and parse its output for git state and manifest-inferred commands. A missing test command is a hard blocker: exhaust inference, then ask the user, because this skill cannot run without a way to verify behavior. Also note any type-check command the project has; where one exists it runs alongside the tests as a second behavior-preservation check.

Resolve standards and decisions. Resolve the coding-standards directory and ADR directory the same way: CLAUDE.md's ## Project Discovery section, then project-discovery.md, then Glob defaults (docs/, docs/adr/, docs/coding-standards/, docs/decisions/). Also check CLAUDE.md and AGENTS.md for inline standards. Read the standards and ADRs whose titles, paths, or one-line summaries indicate they govern the target area; cap at five documents. The target's restructured form must conform to these. If none exist, state that plainly and infer conventions from the surrounding code.

Step 2: Establish the Safety Net

Check the tree. If working tree in Project Context shows failing mid-cycle work or the user describes an in-flight tdd loop on this code, stop and say why (the never-alongside-tdd constraint). Uncommitted but complete work is fine; recommend committing it first so refactoring diffs stay clean, then proceed.

Run the full suite. Run the resolved test command with Bash. Paste the runner's summary line. If anything is red, stop: a red suite is not a license to refactor. Report the failures and recommend fixing them first (via /investigate or /tdd), or re-scoping the target away from the broken area.

Establish coverage of the target. Confirm the target's observable behavior is exercised by the suite: find the tests that drive the target (Glob and Grep for the target's public symbols in test files), and run them scoped if the runner supports it. State plainly which behaviors are covered and which are not. If the target has no meaningful coverage, stop and offer two ways forward, and wait for the user's choice: narrow the target to the covered part, or write characterization tests first using the protocol in references/refactoring-discipline.md. Characterization tests pin current observed behavior (including current bugs) and are a lower-confidence net than intent-written tests; say so in the report.

Step 3: Plan the Sequence Before Editing

Plan the whole run before the first edit. Produce a numbered refactoring plan where each item is:

• One named refactoring (the vocabulary is in the reference; use the project's language idioms, not Java mechanics), applied to a named place.
• The evidence for it. The finding ID, the duplicated code, the standard or ADR it brings the code into conformance with, or the user's stated pain. Items without evidence are deferred per the YAGNI constraint, with a reopen trigger, never silently dropped.
• Its expected blast radius. The files the step should touch. This is what the scope stop-rule in Step 4 checks against.

Order the plan so each step leaves the code releasable: small, independent steps first, dependent steps after the steps they need. Report the plan to the user, then continue immediately; this is a report, not a gate. The one exception: if the request explicitly asks to review or approve the plan first, wait for approval.

Step 4: Execute, One Named Refactoring at a Time

Take the plan items in order. For each:

1. Make the one change. Apply the single named refactoring, touching only the files in its declared blast radius. Stay in the refactoring hat: no behavior fixes, no extras spotted along the way (record them for the summary instead).
2. Run the full suite (and the type-check command where one was resolved). Paste the runner's summary line. Paste full output only when something fails or looks unexpected.
3. Green: cross the item off and move to the next.
4. Red: revert this step. When git is available and the tree was clean at start, git checkout/git restore the touched files. When git is absent, or the tree was already dirty at start, undo the edits directly instead, so reverting this step does not discard the user's other work. Do not patch forward over a red suite; a failed step means the mechanic was unsafe or the coverage was thinner than it looked. Diagnose, then either retry with a smaller step or defer the item with what you learned.
5. Stop rules. If the step needed files outside its declared blast radius, or the only way to make it work changes observable behavior, or two consecutive plan items have been reverted: stop, report where things stand (everything already applied is green and stands), and let the user re-scope.

If the user asked for commits, commit after each green step or each logical group of green steps, message naming the refactoring applied, refactoring only.

Step 5: Final Verification and Summary

Run the full test suite, the lint command, and the build command from Step 1. Paste the summary line from each. If lint or build fails on code this skill touched, fix it and re-run; that is in scope.

Summarize for the user:

• Each refactoring applied, named, with the evidence it rested on (finding IDs from the source report where one was used) and the files it touched.
• Deferred items: the YAGNI deferrals with reopen triggers, any items deferred because they required behavior changes, and any stop-rule exits.
• Anything spotted but deliberately left alone (bugs, smells outside scope), so it can feed /issue-triage or the next /code-review.
• Which coding standards and ADRs the restructured code now conforms to.
• Final test, lint, and build status, with output shown, not asserted.
• If characterization tests were written, say so and recommend replacing them with intent-written tests over time.