Report · marked 10 Oct 2026

bevyengine/bevy

An agent will struggle here, mostly for fixable reasons.

Rust · 48,829 stars · 3,077 files · branch main

49 /100 C+

Instructions 3/27Whether the repo tells an agent how to behave before it starts guessing. Losing marks on agent instruction file and instruction quality.Setup 0/14Whether an agent can install the project and get it running without a human. Losing marks on deterministic install and discoverable commands.Verification loop 20/22Whether an agent can check its own work. This is the category that most decides whether agent output is trustworthy. Losing marks on tests exist.Context economy 13/20Whether the repo fits in a context window, or fights it. Losing marks on file sizes fit in context and repository weight.Navigability 10/10How quickly anything new can orient itself. Full marks.

Higher is better. Accent marks what is costing you most.

Fix these first

Agent instruction file

Add an AGENTS.md at the root: what the project is, how to install, how to run, how to test, and the two or three conventions a newcomer always gets wrong.

Instruction quality

Instructions earn their keep by naming exact commands. 'Run the tests with `pnpm test`' beats three paragraphs of philosophy.

Deterministic install

Commit the lockfile your package manager generates. Without it, an agent's install and your install are different builds, and 'works on my machine' becomes unfalsifiable.

The full marking

Every deduction below names the file or setting it came from.

Instructions 3/27 F

Whether the repo tells an agent how to behave before it starts guessing.

✗Agent instruction file 0/12

None found. Every agent that opens this repo starts from zero.

Add an AGENTS.md at the root: what the project is, how to install, how to run, how to test, and the two or three conventions a newcomer always gets wrong.

Looked for AGENTS.md, CLAUDE.md, .github/copilot-instructions.md, .cursorrules

✗Instruction quality 0/12

Nothing to judge, since there are no instructions.

Instructions earn their keep by naming exact commands. 'Run the tests with `pnpm test`' beats three paragraphs of philosophy.

✓README as an entry point 3/3

README has a clear getting-started section.

Setup 0/14 F

Whether an agent can install the project and get it running without a human.

✗Deterministic install 0/6

No lockfile. An agent installing dependencies may not get what CI got.

Commit the lockfile your package manager generates. Without it, an agent's install and your install are different builds, and 'works on my machine' becomes unfalsifiable.

✗Discoverable commands 0/6

No declared commands. An agent has to infer how to build and run this from the file tree.

Declare the handful of commands that matter in package.json scripts, a Makefile, or a justfile. Naming them turns guesswork into a lookup.

–Environment config n/a

Not applicable — this reads as a library, with no environment to configure.

✗Pinned runtime version 0/2

No pinned runtime version.

Add a .nvmrc, .python-version, or equivalent so the agent's toolchain matches yours.

–Reproducible environment n/a

Not applicable — a library doesn't need a container to be worked on.

Verification loop 20/22 A

Whether an agent can check its own work. This is the category that most decides whether agent output is trustworthy.

✗Tests exist 6/8

141 test files against 1950 source files.

e.g. .github/start-mobile-example/specs/screenshot.js, .github/start-wasm-example/tests/wasm_example.spec.ts, assets/shaders/fallback_image_test.wesl

✓Test command is discoverable 7/7

An agent can find and run `cargo test`.

✓Continuous integration 4/4

14 GitHub Actions workflows define what "passing" means.

✓Lint and format rules 3/3

clippy.toml encodes the house style.

–Static type checking n/a

Not applicable — the Rust compiler type checks every build.

Context economy 13/20 B

Whether the repo fits in a context window, or fights it.

✓No committed build output 6/6

No generated directories committed.

✓.gitignore hygiene 3/3

.gitignore covers 26 patterns.

✗File sizes fit in context 2/6

24 source files are over 100KB.

A single file that fills the context window forces an agent to work from fragments, and it will confidently edit code it never saw. Splitting the worst offenders pays for itself immediately.

crates/bevy_pbr/src/render/mesh.rs — 197KB

crates/bevy_ecs/src/world/mod.rs — 186KB

crates/bevy_ecs/src/query/fetch.rs — 170KB

✗Repository weight 2/5

About 179MB checked out. Large enough that cloning and searching are both slow.

Large binaries and vendored trees slow every operation an agent performs. Git LFS or a separate assets repo keeps the working tree navigable.

Here is your AGENTS.md

Drafted from what is actually in this repository: the install command from your lockfile, the commands you already declare, your real directory layout. Anything marked TODO needs a person. Save it at the root as AGENTS.md.

AGENTS.md — drafted for bevyengine/bevy

# AGENTS.md

A refreshingly simple data-driven game engine built in Rust

## Setup

```
# TODO: the install command. No lockfile was found, so this could not be inferred.
```

## Commands

```
cargo test   # run the test suite
```

## Layout

- `crates/`   1327 source files
- `examples/` 464 source files
- `benches/`  106 source files
- `tools/`    34 source files
- `tests/`    11 source files
- `errors/`   1 source file

## Conventions

- Tests live alongside the code they cover, following `.github/start-mobile-example/specs/screenshot.js`.
- CI defines what passing means. See `.github/workflows/action-on-PR-labeled.yml`, and keep it green.
- TODO: add the two or three conventions a newcomer always gets wrong here.

## Gotchas

- `crates/bevy_pbr/src/render/mesh.rs` is 197KB. It will not fit comfortably in context, so read it in parts.
- No lockfile is committed, so an install here may not match what CI produced.

---

Drafted by agentreadme.com from what is in this repository. Everything marked TODO
needs a human. Check it in as AGENTS.md at the root.

Open the raw markdown or curl -o AGENTS.md agentreadme.com/draft/bevyengine/bevy.md

A draft gets the commands right and stops at the things only a maintainer knows. What a good Rust AGENTS.md looks like covers what to add by hand, and what AGENTS.md is explains the format itself.

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Think this mark is wrong?

Every deduction above names the file it came from, so this can be settled by looking. If a check missed something, that is a rule worth fixing.

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