AGENTS.md crossed 60,000 open-source projects yesterday, and more importantly, every major coding agent now supports it. What started as a lightweight alternative to vendor-locked CLAUDE.md files has become the de facto standard for agent-instruction files — and the ecosystem just tipped.
The agents.md site, which launched quietly a few months ago, now lists Codex, Cursor, Claude Code, Amp, Gemini CLI, GitHub Copilot, Zed, Windsurf, Devin, Aider, Cline/RooCode, Junie, Factory, Goose, and a dozen more. The GitHub issue in the Claude Code repo asking for native AGENTS.md support (instead of only CLAUDE.md) has 360 reactions and 117 upvotes on HN today.
The thesis is simple: README.md is for humans — quickstarts, contribution guides, project philosophy. AGENTS.md is for agents — build steps, test commands, code conventions, environment setup. A clean separation that keeps human docs concise and agent docs precise.
Why this matters:
- Vendor lock-in is dying. Anthropic shipped
CLAUDE.md. OpenAI shipsCODEX.md. Cursor had its own. But developers don't want to maintain three files. The market settled on a neutral name before anyone could entrench a monopoly. - 60k repos is an inflection point. That's enough training signal that new coding agents will adopt it by default. The network effect is real.
- Hosting platforms are already adapting. Compartment Up, which we covered yesterday, serves
/AGENTS.mdas a machine-readable deployment manifest.
This is the quiet kind of standardization that defines a maturing category. No committee. No RFC. Just "everyone supports it, so we support it too." If you maintain an open-source project and your agent instructions still live in a CLAUDE.md nobody else reads, rename the file. The ecosystem just made that decision for you.