langchain-middleware

Add human-in-the-loop approval to LangChain agents by implementing middleware that pauses execution before tool calls. This pattern requires a checkpointer and thread_id to intercept actions like sending emails, allowing human review, editing, or rejection.

Middleware in LangChain is used to intercept agent execution flow for custom processing, error handling, logging, and retry mechanisms. It provides production-ready control over tool calls and ensures data integrity through structured output validation.

Yes, you need a checkpointer and a thread_id to enable human-in-the-loop functionality in LangChain. These components are required to pause and resume agent execution state during middleware interception for human approval.

You can validate structured output from LangChain agents using middleware that enforces predefined schemas. This ensures agent outputs conform to required data structures, maintaining data integrity in production-ready workflows.

The best way to intercept dangerous tool calls in LangChain is custom middleware. It halts execution before critical actions like deleting data, enabling custom interception logic for logging, error handling, or human approval.