The SDK shipped a major version bump (v4.0.0) in mid-March while maintaining a v3 stable branch in parallel, with both tracks now converging on improved LangChain integration and observability features. The v4 branch focused on foundational changes like migrating build tooling from Poetry to uv and fixing media upload efficiency by reusing HTTP clients, while recent patches addressed OpenAI integration details like Response API token parsing and instruction capture. The v3 stable line received backports of the LangChain root observation metadata flag and continued refinements to experiment runs and batch evaluation, including better trace field selection for performance and proper session ID parsing in scores.