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 minimal change. Don't touch adjacent code.
4. For each caller from step 1: verify backward-compatible or explicitly update 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

• Backward compatibility impossible → surface to user before proceeding.
• Touch only what task requires — no opportunistic refactoring.
• No tests exist → acceptable to note — don't add tests outside task scope.