How Middleware Lets You Customize Your Agent Harness

Agent harnesses connect a large language model to its environment and tools, but customizing their core operational loop for specific use cases can be challenging. LangChain introduces "Agent Middleware" as a solution, offering a structured way to inject custom logic into an agent's lifecycle. This is achieved through a series of hooks like `before_model` and `wrap_tool_call` that allow developers to implement features such as PII redaction, dynamic tool selection, and context summarization. By using middleware, developers can build robust, production-ready agents with business-specific logic and compliance guardrails on a standard foundation.