langchain-middleware

You can implement human-in-the-loop approval for LangGraph tool calls using HumanInTheLoopMiddleware to pause execution, review arguments, and resume workflows after human decisions. It supports approve, edit, or reject actions.

Human-in-the-loop middleware in LangGraph agents is a governance layer that intercepts dangerous tool calls before execution. It allows operators to review, edit, or reject tool arguments, ensuring safety and compliance in production workflows.

Yes, you can customize hooks when pausing LangGraph agents for human review. The middleware supports before_model, after_model, wrap_tool_call, before_agent, and after_agent hooks to intercept and modify agent behavior.

You resume a LangGraph agent after rejecting a tool call using command resume patterns. This mechanism continues the workflow by injecting human decisions, such as approve, edit, or reject, back into the agent graph.

Yes, LangGraph middleware works with checkpointer for state persistence. The human-in-the-loop middleware integrates with checkpointer and command resume patterns to maintain workflow state across human approval pauses.