HARNESS ENGINEERING: HOW OPENAI SHIPS WITHOUT WRITING CODE

Summary from the TLDR Dev newsletter

Harness engineering is where engineers focus more on building the environment and “harnesses” (like OpenAI's Codex) around AI agents, so that they can build software without manually written code. OpenAI's approach involved making applications legible for agents to query runtime states and structuring documentation with progressive disclosure using an AGENTS.md table of contents. To manage high agent throughput, OpenAI adopted a merge philosophy prioritizing fast corrections over perfect prevention, and continuously addressed technical debt through "golden principles" enforced by background cleanup agents.