Worked on the bufbuild/protovalidate repository to deliver enhanced Protobuf validation by introducing new field_mask rules, including const, in, and not_in, which enable more granular field-level constraints within protobuf messages. This feature was implemented using Go and ProtoBuf, focusing on strengthening data integrity and enforcing validation policies at the message boundary. The approach involved aligning the implementation with open issues and collaborating on test planning to ensure robust coverage. By expanding the validation capabilities, the work improved the safety of downstream data flows and supported more reliable API design, demonstrating proficiency in validation logic and collaborative development practices.