Claude Code now reads AGENTS.md if CLAUDE.md is not present in the...

Claude Code now reads AGENTS.md if CLAUDE.md is not present in the project

Anthropic released Claude Code 2.1.277 on September 18, 2026, where the agent reads AGENTS.md if CLAUDE.md is absent, and the mode is switched via “Project instructions” in /config.

Compiled by Sergey KostenchukPublished 2026-09-19Updated 2026-09-19

2026-09-19 Coding Anthropic

🛠 Claude Code now reads AGENTS.md if CLAUDE.md is not present

In the Claude Code 2.1.277 release on September 18, Anthropic added a fallback: if the project does not have CLAUDE.md, the agent reads AGENTS.md. The mode is switched via “Project instructions” in /config, and the feature became the first public mod for Claude Code with open source code.

🌍 AGENTS.md is already supported by Codex, Cursor, Gemini CLI, and GitHub Copilot. Now a single instructions file also works in Claude Code — symlinks and @-imports that broke in CI/CD are no longer needed.

👤 Update to 2.1.277 and remove workarounds: AGENTS.md will be picked up automatically if CLAUDE.md is not present. The “both files at once” mode leaves CLAUDE.md for Claude-specific rules. In Bedrock, Vertex AI, and Foundry, the fallback is not yet available.

Source 1: https://github.com/anthropics/claude-code/releases/tag/v2.1.277 Source 2: https://github.com/anthropics/claude-code/blob/main/mods/agents-md/README.md

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