What Is Harness Engineering, and Why Did OpenAI Just Build a Million Lines of Code Without Writing a Single One?

Stephen Diaz

Published on: 10/04/2026

OpenAI built one million lines of production code with zero human-written code using a method they call Harness Engineering. Three engineers, five months, 1,500 merged pull requests. Here is the Steering Model framework and what it means for business owners.