Anthropic introduces support for AGENTS.md in claude code 2.1.277

On September 19, 2026, Anthropic's Claude Code team announced via X that the 2.1.277 version of the tool now supports AGENTS.md. This update allows Claude to check for and use AGENTS.md if a CLAUDE.md file is absent. AGENTS.md is designed to provide a standardized set of rules for AI tools, acting as a universal guideline. The addition aims to reduce configuration and switching costs for users, enabling a unified set of instructions for AI across different tools. This feature benefits both developers and end-users by simplifying project transitions and collaboration. The update was shared by engineer Thariq Shihipar, who emphasized the importance of shared rules in AI development.