Report · marked 11 Oct 2026

astral-sh/ruff

Solid foundations, held back in a few specific places.

Rust · 49,989 stars · 11,238 files · branch main

82 /100 A-

Instructions 25/27Whether the repo tells an agent how to behave before it starts guessing. Losing marks on instruction quality.Setup 16/20Whether an agent can install the project and get it running without a human. Losing marks on environment config.Verification loop 22/22Whether an agent can check its own work. This is the category that most decides whether agent output is trustworthy. Full marks.Context economy 8/20Whether the repo fits in a context window, or fights it. Losing marks on no committed build output and file sizes fit in context.Navigability 10/10How quickly anything new can orient itself. Full marks.

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

Fix these first

File sizes fit in context

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.

Environment config

Add a .env.example listing every variable with a safe placeholder value. It's the cheapest possible fix and it unblocks the whole first run.

No committed build output

Add these to .gitignore and `git rm -r --cached` them. Generated files pollute search results, so an agent grepping for a function finds the compiled copy and edits the wrong file.

The full marking

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

Instructions 25/27 A+

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

✓Agent instruction file 12/12

AGENTS.md is present, which is the format the most tools read.

Also found: CLAUDE.md

✗Instruction quality 10/12

Specific enough that an agent can act on it.

Worth fixing: it's 20k characters, which burns context on every single turn.

names the actual commands to run

uses headings, so an agent can skim it

includes copyable code blocks

✓README as an entry point 3/3

README has a clear getting-started section.

Setup 16/20 A-

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

✓Deterministic install 6/6

uv.lock pins the dependency tree.

Found uv.lock

✓Discoverable commands 6/6

Commands are declared where an agent will look for them.

scripts/ directory

✗Environment config 0/4

Nothing documents the environment this needs. An agent will get a runtime error it can't diagnose.

Add a .env.example listing every variable with a safe placeholder value. It's the cheapest possible fix and it unblocks the whole first run.

✓Pinned runtime version 2/2

The language runtime version is pinned.

Found rust-toolchain.toml

✓Reproducible environment 2/2

.devcontainer/devcontainer.json gives a known-good environment.

Verification loop 22/22 A+

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

✓Tests exist 8/8

3754 test files against 5086 source files.

e.g. crates/ruff/resources/test/fixtures/cache_mutable/.gitignore, crates/ruff/resources/test/fixtures/cache_remove_old_files/source.py, crates/ruff/resources/test/fixtures/formatted.py

✓Test command is discoverable 7/7

An agent can find and run `cargo test`.

✓Continuous integration 4/4

23 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 8/20 C

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

✗No committed build output 3/6

Generated output is committed: venv/.

Add these to .gitignore and `git rm -r --cached` them. Generated files pollute search results, so an agent grepping for a function finds the compiled copy and edits the wrong file.

✓.gitignore hygiene 3/3

.gitignore covers 106 patterns.

✗File sizes fit in context 0/6

45 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/ty_python_semantic/src/types/infer/builder.rs — 539KB

crates/ty_python_semantic/src/types.rs — 519KB

crates/ty_python_semantic/src/types/call/bind.rs — 456KB

✗Repository weight 2/5

About 218MB 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 astral-sh/ruff

# AGENTS.md

An extremely fast Python linter and code formatter, written in Rust.

## Setup

```
uv sync
```

## Commands

```
ruff check .   # lint
cargo test     # run the test suite
```

## Layout

- `crates/`     4968 source files
- `playground/` 49 source files
- `scripts/`    43 source files
- `python/`     14 source files
- `fuzz/`       7 source files
- `docs/`       2 source files

## Conventions

- Tests live alongside the code they cover, following `crates/ruff/resources/test/fixtures/cache_mutable/.gitignore`.
- CI defines what passing means. See `.github/workflows/build-binaries.yml`, and keep it green.
- TODO: add the two or three conventions a newcomer always gets wrong here.

## Gotchas

- `crates/ty_python_semantic/src/types/infer/builder.rs` is 539KB. It will not fit comfortably in context, so read it in parts.

---

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/astral-sh/ruff.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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[![agent ready](https://agentreadme.com/badge/astral-sh/ruff.svg)](https://agentreadme.com/astral-sh/ruff)

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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.

Open an issue, already filled in