Anthropic on Friday surprised the developer community by supporting rival OpenAI's mechanism for passing marching orders to AI agents. This makes life easier for folks who use both platforms.
"We're adding support for AGENTS.md to Claude Code," said Claude Code engineer Thariq Shihipar in a social media post. "Starting today in version 2.1.277, if there is no CLAUDE.md in a folder, Claude will check for and use AGENTS.md."
Claude Code users can toggle this behavior, he said, with the command.
Until now, developers who use Claude Code alongside OpenAI Codex or other non-Anthropic tools have had to maintain two sets of Markdown instructions for their AI agents: CLAUDE.md and AGENTS.md, not to mention project-specific versions of these files.
These documents get read by coding agents with every request. They outline expected behavior, preferred tool usage, coding conventions, and so on. They lay the foundation of the agent's context.
The two formats are similar but not identical – CLAUDE.md may contain Claude-specific instructions while AGENTS.md is intended to be tool agnostic.
Because these documents can change, those working with AI agents have implemented various workarounds, like creating symlinks to keep CLAUDE.md and AGENTS.md in sync.
Last year, OpenAI contributed AGENTS.md to the Agentic AI Foundation, under the Linux Foundation, in a bid to build support for its standard. As of December 2025, more than 60,000 open source projects implemented AGENTS.md.
The popularity of Claude Code has given Anthropic the latitude to insist on its own standards, but it appears the company has decided there's nothing to be gained from continued specification separatism.
For those who use AI coding tools, this detente is an event of modest significance. Many widely followed software developers applauded the decision in social media posts.
Thibault Sottiaux, OpenAI's head of core product, remarked, "Yay! This is the way. Come to the light," to which Shihipar responded with the handshake emoji (🤝). It's enough to bring a tear to the eye. ®