Worked on the modelcontextprotocol/typescript-sdk repository to address a critical issue affecting request integrity during onprogress operations. Focused on API integration and SDK development using TypeScript, the developer delivered a targeted bug fix that ensures existing _meta properties are preserved by merging them with the new progressToken. This approach prevents metadata loss and maintains the stability of request parameters when progress-enabled requests are used. The solution was thoroughly code reviewed and regression tested to safeguard against parameter drift, resulting in improved reliability for client integrations. The work demonstrates careful attention to detail in maintaining robust API behavior and data consistency.