behavior-preserving-cleanup

name	behavior-preserving-cleanup
description	Use for a clarity-only pass that must not change behavior — simplifying, renaming, de-duplicating, or restructuring code, configs, research scripts, or prose. Gates on understanding the target before touching it and re-verifies after each change so behavior stays fixed.
metadata	{"short-description":"Simplify without changing behavior, behind a comprehension gate"}

Behavior-Preserving Cleanup

For passes whose only goal is clarity — not new behavior or bug fixes. The risk is "simplifying" something you do not fully understand and silently changing what it does. Two guards prevent that.

When to use

• simplifying or restructuring code, a config, a research script, or prose
• removing duplication or dead-looking content
• any edit that should leave behavior unchanged

When not to use

• feature work or bug fixes (use engineering-lifecycle and delivery-verification-gate)
• changes that are meant to alter behavior

Method

1. Comprehension gate (Chesterton's Fence). Before changing the target, state: its responsibility, who calls or depends on it, its edge and error paths, why it may be written the way it is (check history or git blame when available), and whether a test or runnable check defines its expected behavior. If any answer is unknown, STOP and read more — do not edit yet.
2. Change in small steps. Make one behavior-preserving edit at a time.
3. Verify after each change. Re-run the defining check (or re-read the behavior) after each edit; the behavior must be identical. If you cannot confirm it, revert that step.

Guardrails

• never remove content you do not understand on the assumption it is unused
• if no check pins the behavior, establish one before simplifying
• keep behavior identical — a cleanup that changes output is a defect, not a cleanup

Recommended templates

When this skill is involved, consider these workflow templates (install via the workflow-templates artifact profile, or --with-deps to pull backing skills):

• engineering-delivery-loop-runbook -- Bounded build-and-deliver loop runbook: single-path implementation with seen-to-fail proof, cross-agent diff verification, behavior-preserving cleanup, and credit-gated heavy-compute offload.