Source: https://seerepo.com/compare/openai/codex/vs/rust-lang/mdBook
Markdown source: https://seerepo.com/compare/openai/codex/vs/rust-lang/mdBook.md
Description: codex and mdBook share 5 technologies: axum, Tokio, pulldown-cmark, tracing, and tracing-subscriber. Both are written in Rust.

# codex vs mdBook

codex and mdBook share 5 technologies: axum, Tokio, pulldown-cmark, tracing, and tracing-subscriber. Both are written in Rust.

- [openai/codex](https://seerepo.com/r/openai/codex): Lightweight coding agent that runs in your terminal
- [rust-lang/mdBook](https://seerepo.com/r/rust-lang/mdBook): Create book from markdown files. Like Gitbook but implemented in Rust

## What they share and what sets them apart

- In common: axum, Tokio, pulldown-cmark, tracing, tracing-subscriber
- Only in codex: lru, SQLite, Sentry, tower, objc2-app-kit, objc2-foundation, Ratatui, crossterm, keyring, hmac, rmcp, png, image, zip, schemars, Pydantic, log, tracing-appender
- Only in mdBook: handlebars, html5ever, listenfd

## Side by side

| | codex | mdBook |
|---|---|---|
| Size | 2,320,674 lines written, 4,216 code files | 20,533 lines written, 66 code files |
| Who writes it | 2.8% of its commits signed by AI. With Codex, Claude Code, and GitHub Copilot | 0.1% of its commits signed by AI. With Codex |
| Activity | Last push November 4, 2026, 13,099 commits, 133,103 stars | Last push November 2, 2026, 2,281 commits, 22,266 stars |
| Tests | 2,448 test files. 51.6% of its code files have a test that imports them | 73 test files. 10.6% of its code files have a test that imports them |

- Size: Lines written by people and agents, without generated ones; code files, without tests.
- Who writes it: A commit counts as AI's when it carries its signature: a Co-Authored-By line, its author name or the merge of its branch.
- Activity: From GitHub and its history, on the day SeeRepo read it.
- Tests: The files that test the code, and the share of code files a test imports.

## Frequently asked questions

### Which is bigger, codex or mdBook?

codex, with 2,320,674 lines written; mdBook has 20,533.

The proof: [openai/codex's code at commit 021fccb](https://github.com/openai/codex/tree/021fccb046508938c4754982efccfb51d6e8356e)

### Which has more GitHub stars, codex or mdBook?

codex, with 133,103 stars; mdBook has 22,266.

The proof: [openai/codex on GitHub](https://github.com/openai/codex)

### Which has more tests, codex or mdBook?

codex, with 2,448 test files; mdBook has 73.

The proof: [openai/codex's code at commit 021fccb](https://github.com/openai/codex/tree/021fccb046508938c4754982efccfb51d6e8356e)

### Which was updated more recently, codex or mdBook?

codex: its last push was on November 4, 2026, and mdBook's on November 2, 2026.

The proof: [openai/codex's commits on GitHub](https://github.com/openai/codex/commits)

### Which has more commits signed by AI, codex or mdBook?

codex: an AI signed 2.8% of its commits, with Codex, Claude Code, and GitHub Copilot; in mdBook, 0.1%.

The proof: [the commits each tool signed in openai/codex](https://seerepo.com/r/openai/codex/ai)

## Sources

- openai/codex: Read on November 4, 2026, at commit 021fccb (https://github.com/openai/codex/tree/021fccb046508938c4754982efccfb51d6e8356e)
- rust-lang/mdBook: Read on November 5, 2026, at commit 7fb5bc8 (https://github.com/rust-lang/mdBook/tree/7fb5bc8ee83366ba5170d1f303e74b1151f32731)

## What is your repo built with?

Any public repo, with no account: https://seerepo.com/r/owner/repo/built, with the owner and name it has on GitHub.