When we decide a new API is the right design, migrate callers and remove the old API in the same refactor wave instead of preserving compatibility layers.
Rule:
- Do not keep legacy API paths only because internal callers still exist
- Inventory callers, migrate them, and delete the old API immediately
- Treat temporary adapters as exceptional and time-boxed, not default architecture
- Update tests to assert the new contract, and delete tests that only protect pre-refactor implementation details
When this applies:
- No external users depend on backward compatibility
- The project can absorb coordinated breaking changes
- The new API is part of a simplification or refactor initiative
Keeping both old and new APIs creates dual-path complexity, slows cleanup, and makes the codebase feel append-only.