Claude Code Adds AGENTS.md Fallback, Cutting Instruction File Sprawl
Claude Code now supports AGENTS.md, giving development teams a shared instruction format across multiple AI coding agents and reducing configuration drift.
Anthropic has added AGENTS.md support to its Claude Code tool. Previously, developers may have encountered multiple instruction files for coding agents such as CLAUDE.md for Claude Code, AGENTS.md for Codex, Cursor, and others. On September 18, Anthropic released Claude Code version 2.1.277, which now checks for AGENTS.md if CLAUDE.md is not present in a folder.
Anthropic and OpenAI are both founding platinum members of the Agentic AI Foundation, which maintains the AGENTS.md format. Over 60,000 open-source projects utilize this format, and it is now seen as a shared standard for coding agents rather than a vendor-specific solution. Claude Code reads AGENTS.md only when no CLAUDE.md is found in the working directory or any above it.
If both files exist, Claude reads CLAUDE.md and ignores AGENTS.md. AGENTS.md is treated as configuration, and Anthropic suggests designating it as the source of truth for coding agent behavior. Teams should check for AGENTS.md and CLAUDE.local.md files to ensure proper configuration. The AGENTS.md feature is not available on Bedrock, Vertex, or Foundry platforms yet, and sessions without feature flags from Anthropic cannot read AGENTS.md.
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