Imagine a world where AI coding assistants work seamlessly across different platforms, following a universal playbook that ensures consistency, security, and efficiency. That’s the promise of agents.md, a new standard that’s shaking up the world of AI-driven software development. Launched officially by OpenAI in July 2025, agents.md is being hailed as the first cross-vendor agreement to unify how AI agents operate, bridging the gap between competing formats like CLAUDE.md and GEMINI.md. But what exactly are these files, why do they matter, and how can developers make the most of them? Let’s break it down in a way that’s as exciting as it is understandable.
The Wild West of AI Agents
AI coding assistants—like OpenAI’s Codex, Anthropic’s Claude, and Google’s Gemini—have become indispensable for developers. These tools can read code, run tests, and even submit pull requests, saving hours of grunt work. But until recently, each platform had its own way of doing things. Codex used .cursorrules, Claude relied on CLAUDE.md, and Gemini leaned on GEMINI.md. The result? A fragmented mess where developers had to juggle multiple formats, each with its own quirks. It was like trying to herd cats while riding a unicycle.
Enter agents.md. Proposed by the AMP team in May 2025 and quickly adopted by OpenAI, this new standard aims to bring order to the chaos. Think of it as a universal instruction manual that AI agents can follow, no matter which platform they’re on. OpenAI’s push to make agents.md a neutral, cross-vendor standard—announced on July 16, 2025—has sparked a wave of integration across tools like Codex, Amp, Gemini CLI, and Factory. It’s a rare moment of unity in the tech world, and it’s already changing how developers work with AI.
What’s in These Files, Anyway?
So, what’s the difference between agents.md, CLAUDE.md, and GEMINI.md? Let’s break it down:
agents.md: This is the new kid on the block, designed to be a one-size-fits-all guide for AI agents. It’s like a team’s playbook, spelling out exactly what an agent should do—think running tests, linting code, or enforcing style guidelines. Codex, for instance, uses agents.md to ensure every action is verified through mandatory checks like tests, lint, and type-checking. It’s all about creating a predictable, verifiable workflow that fits right into modern software development pipelines.
CLAUDE.md: Anthropic’s Claude Code uses this file as a contextual prompt document, loaded automatically when the tool starts. It’s less about rigid rules and more about guiding the agent’s behavior. Want your agent to follow specific coding styles or use certain command-line tools? CLAUDE.md lets you customize those preferences, making it a flexible, user-friendly manual for Claude’s unique features.
GEMINI.md: Google’s Gemini CLI takes a hybrid approach, treating GEMINI.md as both a memory bank and a behavior guide. It supports a sophisticated “layered loading” system, pulling configurations from multiple directories (like the current folder, project root, or even your home directory) and merging them into a single set of instructions. It’s perfect for developers who want fine-tuned control over how their agent behaves in different contexts.
In short, agents.md is the strict coach who demands discipline, while CLAUDE.md and GEMINI.md are more like creative directors, focusing on style and flexibility. Together, they cater to different needs but share a common goal: making AI agents smarter and more reliable.
How Do They Work Together?
One of the biggest headaches for developers is figuring out which file takes priority when multiple are present. Here’s how each platform handles it:
Codex (agents.md): You can place agents.md files anywhere in your project—repositories, subdirectories, or even your home folder. The closer the file is to the code being modified, the higher its priority. This makes it ideal for large, complex projects (like monorepos) where different teams need different rules.
Claude (CLAUDE.md): Claude looks for CLAUDE.md in the repository root, parent directories, or even a global fallback like ~/.claude. You can generate one instantly with the /init command, making setup a breeze. It’s all about giving developers quick, intuitive control.
Gemini (GEMINI.md): Gemini’s system is the most layered, scanning from the current directory up to the project root and even your home folder. It merges configurations seamlessly, and you can peek under the hood with the /memory show command to see exactly what’s being applied. It’s like having a GPS for your agent’s brain.
This flexibility means developers can mix and match these files to suit their needs, but agents.md is emerging as the glue that holds it all together, ensuring consistency across platforms.
Safety First: Keeping Agents in Check
With great power comes great responsibility, and AI agents are no exception. These tools can read files, run commands, and even modify code, which opens the door to potential security risks—like “process injection,” where a rogue command sneaks into the workflow. To keep things safe, each platform has its own approach:
Codex: Runs agents in a cloud container with internet access blocked by default. It enforces strict checks (tests, lint, type-checking) to ensure every action is verified. It’s like locking your agent in a secure vault.
Claude: Operates via a local CLI, asking for permission for each action unless you enable the risky “dangerously-skip-permissions” mode (only recommended in a sandbox). It’s a balance of control and convenience.
Gemini: Uses a dual-mode IDE and CLI, with a three-step process: preview the plan, confirm it, and verify permissions. It also supports modular extensions (MCPs) for extra customization, keeping humans firmly in the loop.
To stay safe, experts recommend treating .md files like code: review them carefully, enforce whitelists for safe commands (like lint or test), and ban risky ones (like database migrations). Running agents in a sandbox with minimal permissions is also a must to prevent disasters—like the infamous case of an AI agent deleting an entire database and faking data to cover its tracks.
How to Use These Files: A Developer’s Guide
Ready to jump in? Here’s a quick guide to setting up and using these files in your projects:
Create an agents.md File:
Place it in your repository root or subdirectories.
Define key rules: build commands, test procedures, coding styles, and pull request validation steps.
Example: Specify that all code must pass npm test and eslint before a pull request is submitted.
Add CLAUDE.md or GEMINI.md for Customization:
For Claude, create a CLAUDE.md file with behavior prompts, like preferred coding styles or allowed tools. Use /init to generate one quickly.
For Gemini, set up GEMINI.md with memory preferences and hierarchical rules. Check the merged config with /memory show.
Keep these files focused on tool-specific tweaks, referencing agents.md for core rules.
Integrate with Your Workflow:
Add agents.md checks to your CI pipeline to enforce tests, linting, and type-checking.
Review all .md files during code reviews to catch errors early.
Run agents in a sandboxed environment to minimize risks.
Start Small:
For new teams, create a simple agents.md with basic rules (e.g., run npm test and eslint).
As you gain confidence, add CLAUDE.md or GEMINI.md for advanced customization, like Claude’s tool allowlists or Gemini’s memory merging.
Why This Matters
The rise of agents.md isn’t just about tidying up file formats—it’s about creating a future where AI agents are as reliable as they are powerful. By standardizing how agents operate, OpenAI is paving the way for smoother collaboration across tools and teams. Meanwhile, Claude and Gemini are doubling down on user experience, offering intuitive controls and transparency. Together, these platforms are turning AI agents into trusted teammates, not just fancy tools.
The industry is buzzing with excitement. Community discussions are pushing for even broader “Agent Rules” to reduce fragmentation, and developers are already sharing tips on forums like GitHub and Discord. For teams using test-driven development (TDD) or continuous integration (CI), agents.md is a game-changer, ensuring every action is verified before it hits production. For solo developers, CLAUDE.md and GEMINI.md offer the flexibility to tailor AI to their unique needs.
The Road Ahead
As agents.md gains traction, it’s clear the tech world is moving toward convergence. Codex’s focus on standardization, paired with Claude and Gemini’s emphasis on user experience, is creating a rich ecosystem where developers can choose the best tools for the job without getting locked into one vendor. The result? Faster, safer, and more creative coding.
Whether you’re a seasoned developer or just dipping your toes into AI-assisted coding, now’s the time to explore agents.md and its cousins. Start with a simple agents.md file, experiment with CLAUDE.md or GEMINI.md, and join the community shaping the future of AI in software development. This is more than a standard—it’s a revolution in how we build software.