Claude Code finally adds AGENTS.md support for cross-tool compatibility

Anthropic took a step toward cross-platform compatibility on Friday by announcing support for the AGENTS.md file format in Claude Code, the company's AI-powered coding tool. The move aligns Anthropic with a growing ecosystem of AI developer tools that share a common set of markdown-based project instructions, reducing friction for developers who work across multiple platforms.

Claude Code Gets AGENTS.md Support

Starting with version 2.1.277, released on September 18, Claude Code will read an AGENTS.md file in any project directory that does not already contain a CLAUDE.md file. Previously, Claude Code only recognized its proprietary CLAUDE.md format, forcing developers who used multiple AI coding assistants to maintain separate instruction files for each tool. The new fallback behavior can be toggled under "Project instructions" in the tool's configuration menu, though it is not yet available on Bedrock, Vertex, or Foundry deployments.news.ycombinator+2

AGENTS.md is an open format, now stewarded by the Agentic AI Foundation under the Linux Foundation, that provides AI coding agents with project-specific guidance such as build commands, testing rules, and code style conventions. Originally released by OpenAI in August 2025 alongside its Codex tool, the format is already in use across more than 60,000 open-source repositories and is supported by tools including OpenAI Codex, Google Alphabet Inc.'s ↗ 0.21% Jules, Cursor, and Amp. Anthropic's adoption means Claude Code joins what has become a de facto industry standard.agents+1

A Compatibility Win for Developers

The change addresses a long-standing developer complaint. Until now, teams using both Claude Code and other AI assistants had to create redundant instruction files or resort to workarounds like symbolic links and import directives. With the new fallback, a single AGENTS.md file can now serve as the shared instruction set for most major coding agents.agyn+1

The update is part of a broader pattern of convergence in AI tooling. Anthropic had earlier introduced the SKILL.md agent skills format in late 2025, which OpenAI and Microsoft ↘ 0.80% subsequently adopted. That earlier episode of cross-company standardization set a precedent for the kind of interoperability developers had been requesting.gopubby+1

Limits of the Update

The AGENTS.md support in Claude Code does come with constraints. Notably, Claude Code does not yet support the `.agents/skills` directory structure that accompanies the AGENTS.md specification. And the fallback only activates when no CLAUDE.md file exists — projects that already use Anthropic's proprietary format will continue to rely on it exclusively. For developers who need both, the recommended approach remains importing AGENTS.md from within a CLAUDE.md file.news.ycombinator+1