Use when fixing a bug, making a targeted edit to existing code, or planning a multi-step change. Edit-scope discipline — every changed line must trace to the request; no drive-by reformatting, no improving adjacent code, no deleting pre-existing dead code. Goal-driven workflow — write the failing test that reproduces a bug before fixing it; refactors require the suite green before and after; multi-step work gets a brief plan with a per-step verify check.
