regression-checklisted

# Regression Check Check for regressions in: **$ARGUMENTS** (depth defaults to deep) ## Steps 1. **Map the change surface** — Identify what was modified: - Which files changed? - Which functions/exports were modified? - Did any public interfaces change (function signatures, types, API responses)? 2. **Trace downstream consumers** — For each changed export/interface: - Who imports this module? (`grep` for import statements) - Who calls these functions? (find all call sites) - Are there any dynamic consumers (string-based imports, reflection)? 3. **Classify risk per consumer**: - **Breaking**: signature changed, return type changed, thrown error changed - **Behavioral**: same interface but different output for some inputs - **Safe**: internal-only change, consumers unaffected 4. **Check test coverage**: - Are the changed code paths covered by existing tests? - Do existing tests assert on the specific behaviors that changed? - Are downstream consumers tested with integration tests? - Run existing tests — do they still pass? 5. **Identify coverage gaps**: - Consumers with no tests at all - Tests that pass but don't assert on the changed behavior - Missing edge case tests for new code paths 6. **Check non-obvious regressions**: - Performance: did the change add a loop, remove a cache, increase query count? - Security: did the change modify auth, validation, or data access? - Ordering: does the change affect sort orde