Quoting Thariq Shihipar

Anthropic added AGENTS.md support to Claude Code starting in version 2.1.277, according to Thariq Shihipar. In folders with no CLAUDE.md file, Claude Code will now check for and use AGENTS.md, a feature built on the company's upcoming Claude Code mods system for customizing the harness. The AGENTS.md mod is built in, and Shihipar said users will be able to build custom versions of project instructions themselves.

We're adding support for AGENTS.md to Claude Code. Starting today in version 2.1.277, if there is no CLAUDE.md in a folder, Claude will check for and use AGENTS.md. AGENTS.md support is built off of Claude Code mods, our upcoming way to customize the Claude Code harness. This is a built-in mod, but you’ll be able to build custom versions of project instructions yourself as you’d like too. You can see the source for the mod here https://github.com/anthropics/claude-code/tree/main/mods/agents-md — Thariq Shihipar https://twitter.com/trq212/status/2101009392611278961 , there are more mods here https://github.com/anthropics/claude-code/tree/main/mods Tags: thariq-shihipar https://simonwillison.net/tags/thariq-shihipar , coding-agents https://simonwillison.net/tags/coding-agents , anthropic https://simonwillison.net/tags/anthropic , claude-code https://simonwillison.net/tags/claude-code , generative-ai https://simonwillison.net/tags/generative-ai , ai https://simonwillison.net/tags/ai , llms https://simonwillison.net/tags/llms