langchain-middleware

You can require human approval for dangerous tool calls in LangChain agents by applying HumanInTheLoopMiddleware to pause execution before sensitive actions. It uses checkpointer persistence and thread_id tracking to maintain context while waiting for a human decision.

The human-in-the-loop pattern for LangChain middleware intercepts agent execution at specific hooks like before_model or wrap_tool_call to pause workflows. This ensures safe, controllable behavior by requiring human oversight before proceeding with sensitive operations.

You resume a LangChain agent after human review using command-resume patterns. This involves sending structured outputs like approve, edit, or reject decisions back to the paused agent, which then resumes execution from its checkpointer-persisted state.

Yes, you can configure per-tool interrupt policies for LangChain agents. The middleware approach allows you to define specific rules that determine which tools require human approval and which can execute automatically, satisfying detailed human-in-the-loop configuration requirements.

Yes, human-in-the-loop middleware works with both Python and TypeScript LangChain workflows. The interrupt and checkpoint patterns apply across both language implementations, allowing you to pause execution and require approval regardless of your development environment.

A limitation of using middleware to pause LangChain agents is the requirement for checkpointer persistence to maintain state. You must manage thread_id tracking and ensure your environment supports persistent storage to successfully pause and resume workflows during human review.