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'What Is a Harness?' Gave the Agent-Harness Category a Four-Part Definition and 477 HN Points
Published 2026-08-20, the piece defines an agent harness as software providing an environment for a model to operate in, made of four parts: a system prompt governing behavior, tools the model can invoke, an agentic loop for iteration, and a translation layer that lets one harness drive models from different providers. The argument for builders is ownership: unlike an embedded assistant, you can run and modify your own harness, so the translation layer is what prevents vendor capture. Named examples are Pi (pi.dev, open source and local), Lefos (email-based), OpenClaw, and Claude Code as the first popular one.
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