Claude Code Adds AGENTS.md Support Starting with v2.1.277
On September 19, Anthropic announced that Claude Code CLI supports the AGENTS.md standard starting from v2.1.277: when no CLAUDE.md exists in the project directory, Claude automatically finds and uses AGENTS.md as the project instructions file, with the behavior toggleable in /config under Project instructions. The community widely read this as Anthropic's official adoption of the cross-coding-agent community standard, answering prior community calls.
Confirmed
- Early signal: @jevans102 cited a Reddit user's discovery that a mods/agents-md directory had appeared in Anthropic's claude-code repository before the official announcement
- Trigger logic: with no CLAUDE.md present, Claude reads AGENTS.md as a fallback for project instructions
- The behavior can be modified or toggled in /config under Project instructions
- AGENTS.md is a cross-agent project documentation standard describing conventions and context to coding agents
- Beyond AGENTS.md support, v2.1.277 shipped a total of 87 CLI changes (@ClaudeCodeLog)
- Multiple developers, including @pvncher, @trq212, @petergyang, @zeeg, @jarrodwatts, @SabooShubham and @iannuttall, relayed and confirmed the news the same day
Why it matters
Coding agents previously relied on their own private config files (e.g., CLAUDE.md). With official AGENTS.md support, developers can maintain a single project instructions file readable by multiple agents supporting the standard, sharply reducing multi-tool configuration overhead. @iannuttall also voiced the hope that Claude Code would more proactively discover and use such standard config files in the future.
2026-09-19 ~ 2026-09-20 · 33 related posts
Primary sources
- Claude Code 2.1.277 adds native AGENTS.md support as first built-in 'mod' — trq212 · 2026-09-19
- Claude Code v2.1.277 adds AGENTS.md support when CLAUDE.md is missing — altryne · 2026-09-19
- [source] Claude Code is getting native AGENTS.md support, spotted on GitHub — jevans102 · 2026-09-19
- Anthropic finally adds AGENTS.md support to Claude Code — iannuttall · 2026-09-19
- [source] Claude Code 2.1.277 ships 87 CLI changes, adds AGENTS.md support — ClaudeCodeLog · 2026-09-19
- After Shopify CEO's threat, ClaudeCode finally ships AGENTS.md support in v2.1.277 — AGI Hunt · 2026-09-19
- Claude Code adopts AGENTS.md, unifying the cross-vendor project instructions standard — 机器之心 · 2026-09-19
- Claude Code finally adds native AGENTS.md support, ending the dual-file era — 量子位 · 2026-09-20
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