Anthropic added AGENTS.md support to Claude Code on Friday, so the tool now reads that file in any folder without a CLAUDE.md, starting with version 2.1.277. Users who don’t want the behavior can switch it off with the /config command. Developers running Claude Code next to OpenAI’s Codex or other agents have until now kept a pair of Markdown instruction files covering the same coding conventions and tool preferences, syncing them by hand or with symlinks. OpenAI built AGENTS.md and handed it to the Agentic AI Foundation under the Linux Foundation last year, and Anthropic had stuck with its own file until now, despite developers asking it to read both.
