For two years every coding tool shipped its own little config dialect: .cursorrules, .github/copilot-instructions.md, CLAUDE.md, .windsurfrules. Same idea, five file names, zero portability. Switching tools meant rewriting your conventions from scratch. That era is over.

What happened

The major agents now read one shared convention: a single AGENTS.md at the repo root, written in plain markdown. One file, every tool - Cursor, Copilot’s coding agent, Windsurf, Zed, Aider, Gemini CLI and the rest all parse the same document, which is now stewarded by the Agentic AI Foundation under the Linux Foundation. Your conventions stopped being locked to a vendor and became part of your repository: versioned, reviewable, portable.

This matters more than it sounds. The context file is the highest-leverage artifact in vibe coding: it is the cache of every correction you ever made. Making it portable means your accumulated judgment finally moves with you.

The 15-minute migration

  1. Find your existing rule files (.cursorrules, .github/copilot-instructions.md, CLAUDE.md, etc.).
  2. Create AGENTS.md at the repo root and merge their contents - deduplicate as you go.
  3. Keep the old files for one release if teammates are mid-transition, then delete them. Two sources of truth rot fast.
  4. Commit it. It now ships with the repo and onboards every agent and human alike.

If a tool you use still insists on its own file, make that file a one-liner that points at AGENTS.md rather than duplicating content.

The copy-paste skeleton

Short, imperative lines beat paragraphs. Start here and let it grow from your corrections:

# AGENTS.md

## What this is

[Two sentences: what the project does, who it's for.]

## Commands

- dev: [command]
- test: [command]
- lint: [command]
- build: [command]

## Conventions

- [naming rule, e.g. "named exports only"]
- [where tests live and how to name them]
- [error-handling style]
- [styling/tokens rule, e.g. "use design tokens, never raw hex colors"]

## Forbidden moves

- [the mistake the agent keeps making, e.g. "do not add new dependencies without asking"]
- [another recurring mistake]

## Definition of done

- Tests pass, lint clean, no TODO left unexplained.

Keep it alive

When the agent breaks a convention, don’t just fix the output - add a line under the right heading. The file is a growing record of your corrections. After a month the agent stops repeating your history, and any new tool you try inherits the same discipline on day one.

Keep it under roughly a hundred lines. If a rule needs more than one sentence, split it or link out. The file that gets read is the file that stays short.