Skill: safe-change

When to use

Modifying any function, class, or module called from more than one place.

Steps

1. Run impact-check skill — get list of all callers and dependents.
2. Note current observable behaviour (return values, side effects).
3. Make the minimal change. Do not touch adjacent code.
4. For each caller from step 1: verify backward-compatible or explicitly update the caller.
5. CHECK: ls <test-dir>/*<module>* 2>/dev/null | head -3 — if tests exist, RUN: <test-cmd>. If none, note explicitly in commit message.
6. Confirm: "Changed X. Verified Y still works." Then invoke verify-before-commit.

Rules

• If backward compatibility is impossible, surface to user before proceeding.
• Touch only what the task requires — no opportunistic refactoring.
• If no tests exist, that is acceptable to note — do not add tests outside task scope.