Worked on the nodejs/undici repository to enhance the core fetch logic and stabilize tests, focusing on improving reliability and maintainability of the HTTP client. Refactored the mainFetch function by removing an unnecessary Promise used for cleanup, which simplified the fetch execution flow and reduced potential edge cases. Updated related tests to align with the new fetch behavior, resulting in more reliable and less flaky CI runs. Emphasized clear error handling and reduced code overhead, enabling faster iteration for future development. Utilized JavaScript and Node.js, applying skills in Fetch API, test engineering, and code quality to deliver these improvements.