Codebases have always had two readers: the machine that compiles them and the person who maintains them. README.md belonged to the second. Now over 60,000 GitHub repositories include AGENTS.md, a file addressed to neither.
What goes into these files is remarkably familiar. Build conventions, security guardrails, workflow quirks. The kind of thing you'd explain to a new hire over coffee. Developers didn't invent new knowledge for their agent audience. They just redirected existing institutional memory toward a different reader.
That quiet redirection suggests the web is acquiring a second native audience, and infrastructure is already reshaping around it.