Verify Refactor — act101 Agent Skill

Verify Refactor

Verify a refactor preserved behavior — composes contract, side-effect, and CFG-equivalence checks across two versions of a function. Use after editing a function to confirm the change is safe.

verify-refactor

Confirm a function's refactor is behavior-preserving by composing three Engineer-tier verification ops over a two-version comparison (git working-tree vs HEAD by default, or an explicit before/after pair).

Scope note: this skill verifies ONE function pair. For a changed SET of functions with git context, use act gate (see the safe-to-merge skill) — its verdict vocabulary (MERGE/REVIEW/BLOCK/UNKNOWN) is intentionally distinct from this skill's per-function SAFE/REVIEW/UNSAFE/UNKNOWN.

Tools

Step	Tool	What it answers
1	`verify_contract_preserved`	Did the public + behavioral contract (signature, effects, control, returns, guards, raises) change?
2	`verify_side_effects`	Which side effects were added/removed? Was a cleanup dropped?
3	`verify_behavioral_equivalence`	Is the control-flow shape equivalent (no new/removed branches, loops, exception paths)?

All three are Engineer. verify_behavioral_equivalence at scope:"port" is Enterprise.

How to run

Call verify_contract_preserved with target + file. If the verdict is broken, report the broken dimensions and stop — the refactor changed the contract.
Call verify_side_effects. Surface any dropped_cleanup: true prominently — a removed write/close while an allocation is kept is a likely leak.
Call verify_behavioral_equivalence. equivalent confirms the shape held; changed lists which dimensions; unknown means a grammar dimension (e.g. Go exceptions) could not be judged — say so, do not claim safety.

Verdict

SAFE — contract preserved, no dropped cleanup, behaviorally equivalent.
REVIEW — contract preserved but effects changed, or CFG changed in an expected way; summarize what moved.
UNSAFE — contract broken, dropped_cleanup: true, or behavior changed unexpectedly.
UNKNOWN — any op returned unknown on a not-modeled dimension; never upgrade UNKNOWN to SAFE.

Summary format

Report: the verdict, the three op results in one line each, and the specific dimensions/effects that changed. Quote modeled_kinds when a verdict is UNKNOWN.