Worked on enhancing type checking accuracy in the facebook/pyrefly repository by implementing support for the py.typed marker, aligning the tool with PEP 561 standards. Developed logic in Rust to detect package roots and correctly handle both top-level and submodule imports, ensuring that untyped-import warnings are only triggered for genuinely untyped modules. This approach reduced false positives and improved the reliability of type-checking feedback. Added comprehensive regression tests to cover various typed and untyped package scenarios, strengthening the software testing process. The work focused on improving onboarding for typed packages and refining the overall type checking workflow within the project.