theregister.com web signal

Anthropic Adopts OpenAI's AGENTS.md Spec in Claude Code 2.1.277, Falls Back to It When CLAUDE.md Absent

By Alexis Dufresne Published September 19, 2026 at 08:03 UTC

Anthropic OpenAI Coding Tools ai-business

Summary

Anthropic's Claude Code 2.1.277 now falls back to AGENTS.md when no CLAUDE.md is present in a folder, adopting the spec OpenAI contributed to the Agentic AI Foundation last year. The spec is already used by 60,000+ open-source projects, so shared instruction files can now drive both Codex-style tools and Claude Code without duplication.

Originally reported by theregister.com

Read the original article →

Original headline: Anthropic Adopts OpenAI's AGENTS.md Spec in Claude Code 2.1.277, Falls Back to It When CLAUDE.md Absent