The Python Type-Checking Paradox: Why Your Test Suite Is the Real Priority

As the Python ecosystem fragments into multiple type-checkers like Mypy and Pyrefly, library maintainers face a growing burden of cross-tool compatibility. Prioritizing type-checking on test suites rather than just internal code ensures that a package's public API remains robust for users, regardless of which tool they prefer. This strategy is becoming crucial for maintaining a high-quality developer experience in modern libraries.