Claude Code finally adds native AGENTS.md support, ending the dual-file era

量子位 · wechat · 2026-09-20

As of Sep 19, Claude Code natively supports AGENTS.md — OpenAI's project instruction file format — becoming the last major AI coding tool to do so.

Background: AGENTS.md is a standardized root-level Markdown file for AI coding assistants, donated to the Linux Foundation's Agentic AI Foundation in Dec 2025. A survey found 6.2% of active GitHub repos contain AGENTS.md vs 5.4% for CLAUDE.md, forcing many teams to maintain two 90%-overlapping files. Workarounds like symlinks (fragile on Windows) and @imports were common but flawed.

Implementation: Version 2.1.277 uses fallback — the default "claude-md-or-agents-md" mode reads AGENTS.md only when no CLAUDE.md exists (even an empty one wins). Three other modes are available via /config: CLAUDE.md only, both, or org-level instructions. The feature ships as a built-in Mod (plugin), part of Claude Code's September plugin system that hooks into lifecycle events.

Known gaps: nested AGENTS.md files only trigger on text Reads; /memory and don't recognize them; --add-dir directories skip them; @import authorization rides on CLAUDE.md's dialog — all because the plugin event system doesn't cover those cases yet.

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Claude Code finally adds native AGENTS.md support, ending the dual-file era

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