Worked on enhancing API data contract reliability in the litestar-org/litestar repository by addressing a nuanced bug in Pydantic DTO handling. Focused on backend development using Python and Pydantic, the work involved fixing the treatment of Optional computed fields so that when such a field returns None, it is correctly represented as optional in the data transfer structure. This adjustment reduces unexpected null handling for API clients and ensures more predictable responses. Regression tests were added to verify API stability when computed fields are None, strengthening the robustness of API contracts and improving the reliability of client-side integrations with minimal code changes.