Transform — Behavior-Preserving Applier — refactor-chain · do-the-work executor

Bundle: refactor-chain (self-diagnosing, self-healing fix-it pipeline). Phase: do-the-work · Prerequisite: refactor-safety-net (a GREEN baseline exists) + an approved step (from the lane plan, or opted-in from refactor-reimagine) · Next: the verify gate, then the next step, then the review gate. Adaptivity / conditional: repo-agnostic. It is the only skill in the lane that edits code, and it does so strictly through the checkpoint→apply→verify loop so every change is small, verified, and reversible.

Purpose

This is the hands-on-keyboard step. Given one approved, behavior-preserving transformation (a rename, an extract, a move, an inline, a signature change), it applies that change safely: it first takes a rollback checkpoint, then makes the smallest version of the change, then re-runs the recorded baseline to prove behavior is identical (same pass-set), then advances. If behavior drifted, it does not push forward — it self-heals (retry a cleaner way) or rolls the step back, and never leaves the repo half-changed and red. It is the executor the whole chain's safety story depends on, wired directly into the harness loop.