# How Codex is built - by Gergely Orosz

<https://newsletter.pragmaticengineer.com/p/how-codex-is-built>

- Host: [newsletter.pragmaticengineer.com](https://links.thingelstad.xyz/hosts/newsletter.pragmaticengineer.com/)
- Saved: February 18, 2026 (2026-02-19T02:47:37Z)
- Record: https://links.thingelstad.xyz/links/11f113cf67db/
- JSON: https://links.thingelstad.xyz/links/11f113cf67db.json

## What Jamie wrote

Pragmatic Engineer deep dive on OpenAI's Codex — 1M+ weekly users, Rust-based, writes 90%+ of its own code, changing engineering practices at OpenAI itself. Companion piece to the Claude Code deep dive. Highly relevant for CTOs thinking about AI-native dev workflows. Pull quote: "Codex itself writes more than 90% of the app's code, the team estimates."

## Facts

- Kind: [Page](https://links.thingelstad.xyz/kinds/page/)

## Same host

- [How Claude Code is built - Gergely Orosz](https://links.thingelstad.xyz/links/142b7d54413b/) (newsletter.pragmaticengineer.com, September 25, 2025)
- [Steve Yegge on AI Agents and the Future of Software Engineering](https://links.thingelstad.xyz/links/e9ff4efb5941/) (newsletter.pragmaticengineer.com, February 18, 2026)
- [Why is Meta destroying its engineering organization?](https://links.thingelstad.xyz/links/799eb45228cf/) (newsletter.pragmaticengineer.com, June 17, 2026)
- [What is happening with code reviews? - Gergely Orosz](https://links.thingelstad.xyz/links/e58a87cbfcd5/) (newsletter.pragmaticengineer.com, September 17, 2026)

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- [I guess I kinda get why people hate AI](https://links.thingelstad.xyz/links/b38e3d3a0ae9/) (anthony.noided.media, February 18, 2026)

## Elsewhere

- Wayback Machine: https://web.archive.org/web/*/https://newsletter.pragmaticengineer.com/p/how-codex-is-built