❯ Claude Code adds AGENTS.md support, accepting the instruction spec OpenAI drove

the concessionAnthropic added AGENTS.md support to Claude Code: from version 2.1.277, the tool reads AGENTS.md in any folder without a CLAUDE.md, and users can turn it off with /config. Anthropic had previously declined a request to support the spec, per The Register.

who owns the specAGENTS.md is a universal format OpenAI launched in August 2025, now supported by Codex, Cursor, GitHub Copilot, Gemini CLI and Devin among others; more than 60,000 open source projects have adopted it, per The Register. OpenAI donated it last December to the Agentic AI Foundation under the Linux Foundation — where Anthropic is a platinum member and to which it donated its own MCP protocol. Both companies’ specs already sit in the same basket.

the cost of interopClaude Code’s popularity gave Anthropic the latitude to insist on its own standard, and this concession says it did the math: spec separatism was not paying for itself. For teams whose single repository gets worked over by several coding agents in turn, one fewer instruction file to maintain is a real saving. What to watch is whether CLAUDE.md gradually recedes into a compatibility layer.

▪ SIGNALBoth companies donated their specs to the same foundation — the standards war at the agent layer is effectively over.