Overview

The agent loop
Additional resources

Middleware provides a way to more tightly control what happens inside the agent. Middleware is useful for the following:

Tracking agent behavior with logging, analytics, and debugging.
Transforming prompts, tool selection, and output formatting.
Adding retries, fallbacks, and early termination logic.
Applying rate limits, guardrails, and PII detection.

Add middleware by passing them to create_agent:

from langchain.agents import create_agent
from langchain.agents.middleware import SummarizationMiddleware, HumanInTheLoopMiddleware

agent = create_agent(
    model="gpt-4o",
    tools=[...],
    middleware=[
        SummarizationMiddleware(...),
        HumanInTheLoopMiddleware(...)
    ],
)