Agent Harness

The execution scaffold around an LLM that manages the agent loop, tool invocation, memory, and safety controls.

An agent harness is everything around the model that makes an agent work: the loop controller, the tool dispatcher, the memory store, the safety filters, the logging layer, and the cost meter. Choosing a harness is choosing operational shape: LangChain and CrewAI are opinionated harnesses with batteries included; Anthropic’s effective harnesses guide argues for minimalist harnesses that expose the loop clearly.

In production deployments, the harness is where most bugs hide. Model behavior gets the credit when things work; harness misconfiguration gets the blame when they don’t.