# Anthropic decides to support OpenAI's markdown instructions spec > Source: > Published: 2026-09-18 21:33:16+00:00 # Anthropic decides to support OpenAI's markdown instructions spec Source: [The Register](https://www.theregister.com) Devs cheer relief from compatibility headache [Anthropic](https://www.machinebrief.com/glossary/anthropic)on Friday surprised the developer community by supporting rival [OpenAI](https://www.machinebrief.com/glossary/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](https://www.machinebrief.com/glossary/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 /config 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](https://www.machinebrief.com/glossary/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. ® Get AI news in your inbox Daily digest of what matters in AI. ## Key Terms Explained Agentic AI Agentic AI refers to AI systems that can autonomously plan, execute multi-step tasks, use tools, and make decisions with minimal human oversight. Anthropic An AI safety company founded in 2021 by former OpenAI researchers, including Dario and Daniela Amodei. Claude Anthropic's family of AI assistants, including Claude Haiku, Sonnet, and Opus. OpenAI The AI company behind ChatGPT, GPT-4, DALL-E, and Whisper.