Langchain Middleware

For production LangChain agents that need human oversight on risky operations like sending emails or deleting data. Sets up human-in-the-loop middleware that pauses execution before dangerous tool calls, letting humans approve, edit arguments, or reject with feedback. Also covers custom middleware hooks for logging, retries, and error handling. The resume pattern with Command objects handles the back-and-forth flow cleanly. Requires a checkpointer and thread_id configuration, which trips up developers initially but makes sense once you need to pause and resume agent execution across different processes.