Claude Code 2.1.277 adds native AGENTS.md support as first built-in 'mod'
trq212 · x · 2026-09-19
Anthropic shipped AGENTS.md support in Claude Code v2.1.277: when a project has no CLAUDE.md, Claude now discovers and reads AGENTS.md instead, toggleable via /config.
- The feature is built on Claude Code mods, an upcoming mechanism for customizing the harness. AGENTS.md support is a built-in mod, and users will be able to build their own custom project-instruction mods.
- Source is open-sourced in anthropics/claude-code. The plugin works via an instructionFiles option, defaulting to claude-md-or-agents-md: with no project-owned instruction files, every AGENTS.md and .claude/AGENTS.md along the path from root to working directory is loaded exactly as CLAUDE.md would be; any CLAUDE.md-family file claims the project and the plugin stays out.
- Managed org files, the user's /.claude/CLAUDE.md, and .claude/rules do not count toward that check.
Related event: Claude Code v2.1.277 adds support for the AGENTS.md standard(12 posts)→
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