AI Agent Terminology Decoded: What Harness and Scaffold Really Mean

Understanding AI Agent Terminology: Harness, Scaffold, and What They Really Mean Core question this article answers: In the fast-moving field of AI agents, what do “harness” and “scaffold” actually mean? How do they relate to the model and the agent itself? And why does getting these terms right matter for building real systems? If you’re new to AI agents—or even if you’re already using tools like Claude Code or Codex—you’ve probably run into a wall of confusing terms. At ICLR 2026, researchers were still asking: “What do you mean by ‘harness’ and ‘scaffold’? I’ve heard a dozen different explanations.” This …