Anthropic updates Claude Code to support AGENTS.md standard

Anthropic has released an update to Claude Code (version 2.1.277) that introduces native support for AGENTS.md, an industry-standard instruction file for AI coding agents. Previously, Claude Code relied on a proprietary CLAUDE.md format, forcing developers to maintain duplicate instruction sets for different AI tools.

The move follows significant industry pressure, including public comments from Shopify CEO Tobi Lutke, who suggested considering a ban on Claude Code within his company if it did not support the standard. The AGENTS.md format is promoted by the Agentic AI Foundation (AAIF) to provide a single source of truth for build commands, testing procedures, and coding conventions across various AI agents.

To maximize the effectiveness of these instruction files, developers are encouraged to move away from vague prose and instead use concrete code blocks. Effective templates for AGENTS.md or CLAUDE.md should include metadata, project context, specific coding conventions (using Preferred/Avoid patterns), testing requirements, a list of restricted files, and precise command references to prevent model hallucinations.