In this letter from The Batch (issue 359), Andrew Ng acknowledges the virality of the term "loop engineering" — popularized by Boris Cherny (creator of Claude Code) and Peter Steinberger (creator of OpenClaw) — and shares the three key loops that structure his approach to building 0-to-1 products, and also to deciding what to build. The diagram presents them nested, by increasing time scale, connecting four nodes: coding agent → product spec/evals → developer vision → external feedback.
The agentic coding loop (~minutes) starts from a product specification and, optionally, a set of evals: the agent writes code, tests it, and iterates until it is bug-free and compliant. Ng notes that "closing the loop" took off in late 2025 and changes the game — his agent was able to work for about an hour on a keyboard learning app for his daughter, checking its own work in a browser, without intervention. This is a very active area of invention.
The developer feedback loop (~tens of minutes to hours) has the developer review the product and steer the agent. As agents now test their own code much better, time spent on manual QA has dropped sharply, freeing the developer for higher-level product decisions (features, UI, user flows). Translating a vision into a spec — then clarifying it after a first implementation, and building evals when a recurring problem appears — remains real work.
Ng emphasizes the human context advantage: even though AI-native teams automate the collection of usage data, synthesis of customer feedback, and competitive analysis, humans know more about the users and the operating context. Many call this "taste"; Ng prefers "context advantage," as it points to a clearer path for improving AI. As long as the human knows something the AI doesn't, human-in-the-loop remains necessary to inject that knowledge.
The external feedback loop (~days) gathers friends, alpha testers, and production A/B testing — slow tactics whose data feeds the vision, which drives the spec, which drives the agent.
Ng concludes that, as agents accelerate development, more and more engineers take on a partial product management role. The hardest part is shaping the vision and balancing building with user feedback — "it is important to do both." He sees this as an encouraging sign: engineers are expanding into product, just as PMs and designers now do more engineering.