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Harness, Scaffold, and the AI Agent Terms Worth Getting Right

SpeculationResearchMay 25, 2026

Hugging Face published a glossary by Sergio Paniego and Aritra Roy Gosthipaty clarifying AI agent terminology that has blurred amid rapid field evolution. The article distinguishes between scaffolding, the behavior-defining layer around a model, and harness, the execution layer that runs the agent. It also defines related terms including agent, context engineering, policy, tool use, skills, sub-agents, and training concepts like RL environment, trainer, rollout, and reward.

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Hugging FaceCompanyAritra Roy GosthipatyPersonSergio PaniegoPerson
Canonical: https://huggingface.co/blog/agent-glossary