What Is Harness Engineering — Designing the Reins for AI Agents
In Part 1 of this series, I talked about the decline of prompt engineering. With CLI-based tools on the scene, the value of manually crafting elaborate prompts was fading. But as 2026 unfolded, I realized that what replaced prompt engineering wasn't simply "better tools." Prompt engineering gave way to context engineering, and now context engineering is giving way to an entirely new paradigm: harness engineering . In this post, I'll break down what harness engineering is, why it matters right now, and what its key components look like. A Harness for a Horse, a Harness for an Agent A harness originally refers to the tack fitted onto a horse. Bridle, saddle, stirrups — equipment designed not to suppress the horse's power, but to channel it in the right direction. In AI, the term means exactly the same thing. A harness is the entire external system that controls and directs an AI agent's powerful capabilities toward the right outcomes. Written as an equation:...