Defining the Harness: Distinguishing model logic from agent scaffolding
JeremyCMorgan · x · 2026-08-31
This post highlights the concept of a "Harness" in AI agent architecture, clearing up common confusion between the model and its surrounding control layer.
Using a climbing harness as a metaphor, the article defines a Harness as the equipment that supports and controls the agent. Just as a climbing harness secures a climber and holds their tools, an Agent Harness manages the AI model by handling context assembly, tool routing, retry loops, and verification. It does not generate intelligence but governs how that intelligence is applied.
This distinction is practically useful for debugging: when an agent fails, it helps engineers determine whether the fault lies with the model's reasoning or the scaffolding's logic.
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