Think of a Large Language Model (LLM) like a brilliant scholar. To do their job well, they don’t just need their own brain; they need a good workspace—a desk with the right books, a filing cabinet that’s easy to navigate, and a clear set of instructions on how to process information. In the tech world, this “workspace” is called a harness.

Up until now, these harnesses have been built by human engineers through trial and error. While we have tools to automatically improve the AI’s “brain” (the model weights), the code that actually manages the AI’s information has remained stubbornly manual.

Meta-Harness automatically optimizes model harnesses — the code determining what to store, retrieve, and present to an LLM — surpassing hand-designed systems on text classification, math reasoning, and agentic coding.