AI 101

Harness

Sketch: an engine alone on a stand with a shrugging person; then the same engine inside a car labelled steering, wheels, dashboard, trunk and router.

A harness is the software built around an AI model that gives it instructions, tools, memory and a screen, so it can do real work.

Think of it like this: The harness is the car built around the engine: the steering is the instructions, the wheels are the tools, the dashboard is the screen and the trunk is memory. Without a car, raw engine power goes nowhere.

Source:

https://code.claude.com/docs/en/overview (checked Oct 15, 2026)
https://www.anthropic.com/engineering/building-effective-agents (checked Oct 15, 2026)

RelatedAI model Agent Tool use Memory System prompt

Used inAgent Agent framework Agent loop AI model Chatbot Coding agent Context window IDE MCP host Memory Model router System prompt

and 1 more

Tool use