Worked on the langchain-ai/langsmith-sdk repository, focusing on backend stability by addressing a critical bug in attachment download flows. Improved the reliability of attachment downloads by correcting how URLs are constructed, ensuring that both relative API paths and full URLs are properly resolved using the api_url. This fix, implemented in Python, enhanced the SDK’s handling of presigned URLs and reduced runtime errors and support tickets. Demonstrated skills in API integration, backend development, and robust URL handling, while maintaining backward compatibility and avoiding breaking changes. The work contributed to a smoother developer experience and more dependable attachment management within the SDK.