Report · marked 10 Oct 2026

openai/codex

An agent can work here, but it will waste turns finding its footing.

Rust · 128,500 stars · 9,098 files · branch main

61 /100 B-

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 14/14Whether an agent can install the project and get it running without a human. Full marks.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 9/20Whether the repo fits in a context window, or fights it. Losing marks on file sizes fit in context and repository weight.Navigability 9/10How quickly anything new can orient itself. Losing marks on repository description.

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.

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.

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 14/14 A+

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

✓Deterministic install 6/6

pnpm-lock.yaml pins the dependency tree.

Found pnpm-lock.yaml

✓Discoverable commands 6/6

Commands are declared where an agent will look for them.

package.json scripts (format, format:fix, write-hooks-schema)

justfile

scripts/ directory

–Environment config n/a

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

✓Pinned runtime version 2/2

The language runtime version is pinned.

package.json engines.node >=22

–Reproducible environment n/a

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

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

1310 test files against 6243 source files.

e.g. .github/scripts/macos-signing/test_notarize_with_akv.py, .github/scripts/macos-signing/test_provisioned_macos_cli_package.py, .github/scripts/macos-signing/test_sign_macos_cli_package.py

✓Test command is discoverable 7/7

An agent can find and run `pytest`.

✓Continuous integration 4/4

28 GitHub Actions workflows define what "passing" means.

✓Lint and format rules 3/3

ruff.toml encodes the house style.

–Static type checking n/a

Not applicable — the Rust compiler type checks every build.

Context economy 9/20 C

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 56 patterns.

✗File sizes fit in context 0/6

92 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.

codex-rs/tui/src/bottom_pane/chat_composer.rs — 487KB

codex-rs/core/src/session/tests.rs — 481KB

codex-rs/core/src/config/config_tests.rs — 421KB

✗Repository weight 0/5

About 677MB 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 openai/codex

# AGENTS.md

Lightweight coding agent that runs in your terminal

## Setup

```
pnpm install
```

## Commands

```
pnpm format               # format
pnpm format:fix
pnpm write-hooks-schema
```

## Layout

- `codex-rs/`    5996 source files
- `sdk/`         105 source files
- `scripts/`     47 source files
- `third_party/` 27 source files
- `tools/`       18 source files
- `bazel/`       4 source files

## Conventions

- Tests live alongside the code they cover, following `.github/scripts/macos-signing/test_notarize_with_akv.py`.
- CI defines what passing means. See `.github/workflows/bazel.yml`, and keep it green.
- TODO: add the two or three conventions a newcomer always gets wrong here.

## Gotchas

- `codex-rs/tui/src/bottom_pane/chat_composer.rs` is 487KB. 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/openai/codex.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/openai/codex.svg)](https://agentreadme.com/openai/codex)

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