refactor

name	refactor
description	Improve code structure without changing behavior. Use when refactoring, restructuring, simplifying, or extracting code. Also for reducing duplication, renaming for clarity, or addressing code smells. Enforces one change → test → commit when the commit can stay scoped. NOT for style/formatting (use /lint), features, or bug fixes.
allowed-tools	*

Refactoring

Improve code structure without changing behavior. One small step at a time.

Work one refactoring at a time: change, test, commit. Don't batch changes.

When to Use

Use when the user says "refactor", "clean up", "restructure", "extract", "rename", or "simplify", or when you've identified a code smell. Skip for adding a feature or fixing a bug (use tdd-enforcer) and for formatting/style fixes (use /lint).

Code smells (common triggers):

• Duplicated code (same logic in multiple places)
• Long function (>30 lines, doing too much)
• Magic numbers/strings (unexplained literals)
• Deep nesting (>3 levels of indentation)
• Dead code (unused functions, unreachable branches)
• Poor naming (unclear what something does)
• Wrong level of abstraction (special cases piled on shared infrastructure instead of a generalized mechanism; detect via shotgun surgery — one logical change forces edits in many places)

Scout first. Default for any multi-smell or unnamed request ("clean this up", "tidy this module"). Skip it only when the user named one specific smell — then go straight to Phase 3 with a one-entry ledger.

Discovery is the one phase that may fan out. Sweep in independent read-only passes — /lint + /audit for the mechanical smells (long function, deep nesting, magic literals, duplication, dead code — already detected there), plus separate judgment passes for the semantic ones (reuse / duplicated intent, wrong level of abstraction). Per smell category or per module these passes are independent, so run them concurrently (sub-agents where your harness supports it) and merge the findings — the same fan-out-then-merge shape as quality-review's independent reviewer passes. The model policy differs, though: these are discovery passes, not reviews of your own work, so quality-review's no-weaker reviewer rule does not apply — you (the orchestrator) verify the merged ledger. Spread the passes across smells/modules; cheaper or varied models are fine. Coverage diversity is the lever here, not model tier.

Merge into a ledger, not a loose list: each entry is a smell + location, ordered prioritized and dependency-aware — leaf-first, so no fix lands before the change it depends on (the Mikado ordering). Persist it as the Phase 5 checklist and never silently truncate — if you cap it, say what you dropped. A scout that reads as "nothing else" when it truncated is a bug.

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Phase 1: ASSESS

Is this actually refactoring?

User Intent	Action
"Make this cleaner"	✓ Refactoring
"Add validation"	✗ New behavior → tdd-enforcer
"Fix this bug"	✗ Bug fix → tdd-enforcer or systematic-debugger
"Format this code"	✗ Style → /lint

If not refactoring: Explain and suggest correct approach.

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Phase 2: PROTECT

Does the code have tests?

Coverage	Action
Well-tested	Skip to Phase 3
Partial coverage	Add characterization tests for untested parts
No tests	Add characterization tests first

When writing characterization tests: Characterization tests are still tests — apply behavioral testing principles (assert on what the system does, not how).

If the code can't be exercised under test (hard-wired dependencies, no instantiation point): introduce a seam first — the smallest dependency-break that lets a test run — then characterize. That seam is itself a Tier-3 refactoring; make it under whatever coverage exists, in its own step. (Feathers, Working Effectively with Legacy Code.)

Characterization Tests

Capture current behavior before refactoring:

// Characterization test - captures ACTUAL behavior
it('processOrder returns current behavior', () => {
  const result = processOrder({ items: [], user: null });
  // Whatever it returns NOW is the expected value
  expect(result).toEqual({ status: 'empty', total: 0 });
});

Purpose: Safety net, not specification. Test what the code DOES, not what it SHOULD do.

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Phase 3: REFACTOR

One refactoring at a time; run tests after every change.

Discovery fans out; mutation never does. The scout step (in "When to Use", above) may run parallel read-only passes. Execution is the opposite — one change, in isolation, then test, then commit — because the safety net lives here. Parallel or batched edits forfeit the revert protocol (Phase 4), break git bisect, and destroy single-change test attribution: you can no longer tell which edit turned the suite red. The one-change rule is per-edit, not per-session — you still work through every ledger entry (Phase 5), just one at a time.

Refactoring Catalog

Tier 1 - Lowest Risk (behavior-preserving when references are complete):

Smell	Refactoring	Example
Unclear name	Rename	d → discountAmount
Long function	Extract Function	Pull 10 lines into calculateTax()
Unnecessary variable	Inline Variable	Remove temp = x; return temp;
Misplaced code	Move Function	Move validate() to Validator class

Not "behavior change impossible" — each has a failure mode when references or context are incomplete: Rename breaks exported/public-API names, string or reflection/serialized references, and tests that assert on the name; Inline Variable changes behavior if the variable captured a once-computed value but the expression is side-effecting or re-evaluated (e.g. inlining const now = Date.now() used twice); Move Function can shift this/closure binding or introduce import-cycle / load-order effects (the validate() → class example above changes this). Verify all references before calling any of these done. Only Extract Function is near-unconditionally safe.

// ❌ Before: unclear name
const d = price * 0.2;

// ✅ After: Rename
const discountAmount = price * 0.2;

Tier 2 - Safe with Tests (low risk if tests exist):

Smell	Refactoring	Example
Repeated expression	Extract Variable	order.items.length > 0 → const hasItems = ...
Complex conditional	Decompose Conditional	Extract if branches to named functions
Nested conditionals	Guard Clauses	Early returns instead of deep nesting
Magic literal	Replace Magic Literal	0.2 → VIP_DISCOUNT_RATE
Unused code	Remove Dead Code	Delete unreachable branches

// ❌ Before: nested conditionals
function getDiscount(user) {
  if (user) {
    if (user.isVIP) {
      return 0.2;
    } else {
      return 0.1;
    }
  }
  return 0;
}

// ✅ After: Guard Clauses
function getDiscount(user) {
  if (!user) return 0;
  if (user.isVIP) return 0.2;
  return 0.1;
}

Tier 3 - Requires Care (higher risk, break into smaller steps):

Smell	Refactoring	Caution
God class	Extract Class	Do incrementally, move one method at a time
Type-checking conditionals	Replace with Polymorphism	Requires class hierarchy
Too many parameters	Introduce Parameter Object	Changes function signature
Complex loop	Replace Loop with Pipeline	Ensure equivalent behavior
Wrong level of abstraction	Generalize the Mechanism (a design move, not one catalog refactoring — sequence it as Extract / Move / Inline steps, each its own edit)	Replace the special-case pile with one general path; pull the abstraction to the right altitude — don't add another branch

Tie-breaker: If multiple refactorings apply, choose smallest scope first (Rename < Extract Variable < Extract Function < Extract Class).

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Phase 4: VERIFY

After each refactoring:

1. Run tests - Must pass
2. Regression checklist (tests can miss these) - did the change silently drop a guard or anchor that an extract or move was carrying, introduce setup/teardown asymmetry in a test, give a predicate method a side effect, or flip a config default? If any, fix or revert before continuing.
3. If tests pass (and the checklist is clean): Run the commit safety check below, then commit with refactor: [what changed] only when the commit can stay scoped.
4. If tests fail: Revert immediately

Commit Safety Check

Before committing a green refactor, inspect git status --short --branch and the files changed by this refactor.

Choose exactly one outcome:

• clean branch — if the branch is named and the only changes are this refactor plus its required tests/generated mirrors, commit with refactor: [what changed].
• mixed dirty tree — if pre-existing feature or user changes are present, commit only the isolated refactor files when they can be staged without unrelated work. If isolation is not obvious, do not create a mixed feature+refactor commit; defer the commit, report why, and leave unrelated work untouched.
• detached HEAD — create or switch to a branch before committing. If branch creation would disturb the user's state or unrelated work is already present, defer the commit and report the exact branch/worktree reason.

Deferring a commit is not skipping the one-change rule; it is preserving the same single-change attribution that rule exists to protect.

Revert Protocol

git checkout -- <changed-files>

After revert:

• Was the refactoring too large? → Try smaller step
• Did it accidentally change behavior? → Reconsider approach
• DO NOT attempt to "fix" a failed refactoring

After 2 Failed Attempts

STOP. Ask user:

"I've attempted this refactoring twice and tests keep failing. This suggests either:

1. The refactoring is too large (need smaller steps)
2. The code has hidden dependencies
3. Tests are brittle

How would you like to proceed?"

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Phase 5: ITERATE

Walk the scout ledger leaf-first. Each entry gets its own Phase 3 → Phase 4 cycle; mark it done (or struck, with a reason) before starting the next. The ledger is the completeness contract — you stop when every entry is resolved or explicitly deferred, not when you're tired of the diff. Don't let an unfinished ledger read as "nothing left."

Ledger entries remaining?
├─ Yes → take next leaf-first entry → Phase 3 (one refactoring) → Phase 4 → mark done
└─ No → Done
    ├─ Run `/audit` to verify no dead code or new issues
    └─ Report what was resolved and what was deferred (with reasons)

A single-named-smell request has a one-entry ledger — resolve it, audit, done.

Audit catches: Dead code left behind, new duplication (should decrease!), architecture violations.

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Edge Cases

Partial test coverage:

• Identify which functions are tested vs untested
• Add characterization tests only for code you're about to refactor
• Don't boil the ocean - test what you touch

Refactoring reveals a bug:

• STOP refactoring
• Note the bug location
• Ask the user whether to fix it now (switching to tdd-enforcer) or continue refactoring

User requests large refactoring:

• Break it into steps and name the first one before starting
• Complete each step fully before next
• Never batch multiple refactorings in one edit

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Anti-Patterns

Don't	Do
Batch multiple refactorings	One refactoring → test → commit
"Fix" a failed refactoring	Revert, then try smaller step
Refactor without tests	Add characterization tests first
Change behavior during refactor	That's a feature/fix, not refactoring
Create a mixed feature+refactor commit	Commit only an isolated refactor, or defer with the reason
Skip a safe commit	Commit after every green test when the commit can stay scoped