Worked on stabilizing OpenAPI discriminator mapping within the microsoft/typespec repository, focusing on resolving a critical issue where the first variant of a union could be omitted from the OpenAPI discriminator mapping due to circular reference handling. Addressed this by implementing an onValue listener that updates the mapping after circular references are resolved, ensuring all union variants are accurately represented in the final API specification. Enhanced the getDiscriminatorMapping logic to handle placeholders and added targeted tests to prevent future regressions. Utilized TypeScript and applied expertise in API development and OpenAPI Specification to improve the reliability of client generation and API output.