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AGENTS.md

AGENTS.md for Bevy

AGENTS.md is a plain markdown file at the root of a repo. Coding agents from Cursor, Codex, Copilot, and others read it before they edit. This copy is written for a Bevy project. This repository is a Bevy game. Data lives in components, behavior lives in systems, and schedules stay explicit. Do not reach for a God object.

The example uses a balanced, readable style, pragmatic tests, and comments only where the intent is not obvious. Open the generator to make the agent stricter, switch to test-first, quiet the comments, or pick a different file.

The example assumes Bevy. It does not assume a particular physics crate or UI crate unless Cargo.toml already depends on it.

Customize in the generatorBrowse the library

Example file

Balanced strictness, readable style, pragmatic tests. Download name: AGENTS.md

# AGENTS.md

Instructions for coding agents working in this Bevy repository. Cursor, Claude Code, Codex, Copilot, and other agents should follow this file before they guess.

## Stack

This repository is a Bevy game. Data lives in components, behavior lives in systems, and schedules stay explicit. Do not reach for a God object.

## Layout

- Plugins group related systems. The app binary adds plugins. It does not contain the rules.
- Components are plain data. Systems are functions.
- Assets use the project's asset path and handles, not filesystem reads scattered through systems.

## Commands

- Run: `cargo run`
- Test: `cargo test`
- Check: `cargo clippy --all-targets -- -D warnings`

Use the script the repo already defines when it differs from the command above.

## Conventions

- Query the smallest component set that proves the rule.
- Use commands to spawn and despawn. Do not mutate the world unsafely.
- Exclusive systems are rare. Prefer a normal system with the right system param.
- Put one-shot work in `OnEnter` or an event. Do not gate it with a boolean checked every frame.
- Do not `unwrap` on a missing asset handle.
- Run `cargo fmt` and clippy on gameplay changes.

## Testing

Add or update tests when behavior changes.

Test a pure system with a minimal App or a plain function. Do not boot the full game.

## Style

- Optimize for the next reader over the shortest diff.
- Comment only when the why is non-obvious.
- Name things the way neighboring files already do.
- Do not reformat code you did not change.

## Errors

- Fail at the boundary. Do not swallow errors.
- Log a missing asset and skip the spawn. A missing optional component is absence, not a panic.

## Scope

- Do the requested task. Do not refactor unrelated code.
- Match the rigor already in the repo. Fix what you touch.
- Ask one clarifying question only when the task cannot be finished without it. Otherwise state the assumption and continue.

## Avoid

- Do not store an Entity and assume it still exists next frame without a check.
- Do not allocate a new collection inside a hot system every frame.
- Do not use thread-local hacks to smuggle state. Use a resource.
- Do not add a second ECS mindset. Bevy's world is the world.

## Done when

- The requested behavior works.
- `cargo test` passes and `cargo clippy --all-targets -- -D warnings` is clean for non-trivial changes.
- The diff stays inside the task.
- You list anything you could not run.

Add it to the project

  1. 01

    Copy a starting file

    Copy the example AGENTS.md on this page, or open the generator if you want different testing, strictness, or comment rules.

  2. 02

    Save it at AGENTS.md

    Save it as `AGENTS.md` at the root of the Bevy repo. A nested AGENTS.md can override these rules inside one directory later.

  3. 03

    Start a fresh agent session

    Rules files are read when a session starts. A chat that is already open may still be using the old instructions.

  4. 04

    Give it one small task

    Ask for one change a Bevy agent often gets wrong, such as a system that queries the components it needs and does not spawn entities every frame by accident. If it ignores the file, confirm the path and start a new session.

Questions about this file

Where do I put AGENTS.md in a Bevy repo?

Save it as `AGENTS.md` at the root of the Bevy repo. A nested AGENTS.md can override these rules inside one directory later.

Which tools read this AGENTS.md?

AGENTS.md is the shared file. Cursor, OpenAI Codex, and a growing set of coding agents read it from the repository root. Nested copies can narrow the rules for one folder.

What does the Bevy example assume?

The example assumes Bevy. It does not assume a particular physics crate or UI crate unless Cargo.toml already depends on it.

Does VibeSpell upload my repository?

No. Recipe pages are static, and the generator builds the file in your browser from the options you pick. Your source code never leaves the machine.

Other files for Bevy

AGENTS.md for other stacks