Jiaming Li contributed to backend development on localstack/moto and langchain-ai/langchain, focusing on stability and feature enhancements using Python and the AWS SDK. On localstack/moto, Jiaming addressed a Route53 tag deletion crash by adding resource existence checks and regression tests, and improved EC2 block device status reporting with a new status conversion method and expanded test coverage. For langchain-ai/langchain, Jiaming implemented accurate multimodal token estimation by extending token counting logic to handle images with a fixed penalty, improving pricing accuracy for image-containing messages. The work demonstrated careful attention to correctness, maintainability, and comprehensive unit testing throughout both repositories.