Worked on the microsoft/OpenAPI.NET repository to address a critical serialization issue in OpenAPI schema handling. Focused on backend development and API design using C#, the developer delivered a targeted bug fix ensuring that additionalProperties: false is consistently emitted for both OpenAPI 3.0 and 3.1 when AdditionalPropertiesAllowed is false. To validate this behavior, they refactored unit tests to a theory-based approach, increasing coverage across versions and reducing integration risk for downstream clients. This work improved specification compliance and output consistency, enhancing the reliability of the library while demonstrating careful attention to cross-version compatibility and robust test-driven development practices.