refactor

name	refactor
description	Safe refactoring methodology. Behavior-preserving transformations only. Tests green before AND after. Triggers: refactor, clean, simplify, restructure, extract, inline.
allowed-tools	Read, Edit, Bash, Grep, Glob

AgentDB read-start has run. Check for prior refactor attempts on same code. Skill-specific: skills/refactor/reference/refactor-research.md General: reference/architecture-research.md

1. Baseline — run full test suite. (gate: all tests green before touching anything)
2. Scope audit — grep/glob every instance of the target symbol/pattern across the codebase. List them ALL before changing ANY.
3. Count files → determine tier. 1-2 files: execute directly. 3-5 files: write one-paragraph plan. 6+ files: CONFIRM handshake.
4. Define success — write down EXACTLY what changes. Anything outside that list is scope creep → separate contract.
5. Check coverage — if target code has no tests: generate JiT behavioral tests FIRST (see step 6), run them green, then proceed.
6. JiT tests (when needed) — ask Claude to generate behavioral tests for current code (what it does, not how). Run green. These are disposable; delete after if not worth keeping. (gate: JiT tests pass before refactor starts)
7. Execute — one transformation per commit:
   • Extract function: only at 3+ repetitions (Rule of Three)
   • Inline: wrapper with exactly one call site → inline it
   • Rename: state full scope explicitly — ALL files, imports, tests, docs (Opus follows literally; ambiguous scope = partial refactor)
   • Move: code in wrong module → move to correct location
   • Simplify conditional: nested if/else → guard clauses / early return
   • Remove dead code: unused code → delete (no "just in case")
8. Agentic safety checks (after each transformation):
   • Phantom abstraction: abstraction with one call site → inline, wait for second use
   • Comment drift: audit every comment for accuracy — stale comments worse than none
   • Parallel agent artifacts: if multiple agents touched the file, check git log for overlapping changes
   • Scope creep: diff changes against the defined list from step 4; extras → revert + new task
   • AI behavior drift: AI rewrites change edge-case behavior even when asked to preserve it. After any AI-assisted refactor, run the original input set (or quick property tests) against both versions. Functional equivalence on happy paths does not imply equivalence on edges.
9. Verify — run full test suite. (gate: all tests green after each commit; red = stop, revert last change)
10. Metrics — measure before/after: cyclomatic complexity, function length, duplication. Successful refactor reduces complexity 15-25%. No improvement = shuffled, not simplified.
11. Commit — one logical change per commit. Format: refactor(scope): description. File must end shorter or justify growth in commit body.

<anti_patterns> Large refactors in one commit. Impossible to review or revert. Refactoring without test coverage. You can't verify behavior preservation. Adding features during refactor. Separate concerns, separate commits. Abstracting before you have 3 concrete examples. Wait for patterns to emerge. "While I'm here, I'll also..." No. Separate contract. </anti_patterns>

<on_complete> agentdb write-end '{"skill":"refactor","type":"<extract|inline|rename|simplify>","files_touched":,"tests_status":"green","behavior_changed":false}'

Record what was refactored and verify tests remained green throughout. </on_complete>