Harness Engineering: The Core Engineering Discipline of the AI Agent Era

March 27, 2026 · 2253 words · 11 min

2025 was the year AI agents exploded. 2026’s defining theme is the Agent Harness — the runtime control framework that wraps around agents. OpenAI and Anthropic have both published dedicated articles on harness engineering, and systematic academic papers have emerged. This post breaks down this emerging discipline from an engineering perspective: what it is, why it matters, and how to do it.