Agent Harnesses Are Dead. Long Live Agent Harnesses. João (Joe) Moura Apr 14, 2026

Agent Harnesses Are Dead. Long Live Agent Harnesses. I said it at a Dev Day 2025 (DeepLearning.AI conference) last year: Frameworks are cheap. A few people in the audience looked uncomfortable. But I think the statement aged well. Now it's not just frameworks. Harnesses are getting the same treatment, and the cycle is only getting faster. Building anything is getting cheaper by the month. Vibe-code an app over the weekend. Spin up an agent with a few API calls. The distance between idea and working prototype has collapsed to almost nothing, and will collapse to nothing faster than most expect. And yet the industry is spending most of its energy debating what to call the building tools. We built our harness back in 2023 when we launched, what people now all agree to be the right abstraction, of multi agentic…