6 AGENTS.md Examples From Real Production Repos

AGENTS.md is a widely adopted open-format Markdown file placed at a repository's root, designed to provide AI coding agents with project-specific commands and rules, including build and test commands, code style guidelines, and guardrails. As of 2026, it has been integrated into over 60,000 open-source projects and is read by multiple AI coding agents such as OpenAI Codex, Google's Jules, and GitHub Copilot, making it a versatile tool for maintaining consistent coding conventions across various platforms. Notable implementations include OpenAI Codex's extensive linting rules, Sentry's consolidation of agent instructions into a single source of truth, Apache Airflow's enforcement of naming conventions, and Cloudflare's emphasis on package manager guardrails. The best AGENTS.md files are concise, command-first, and specific, with a focus on rules that prevent build failures, ensuring they remain useful and effective. While files like openai/codex span over 300 lines and are tailored for specific environments, most teams benefit from a more concise 40 to 80 line document. Security is a key consideration, as AGENTS.md forms part of the software supply chain, necessitating careful review and management to prevent misuse.

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