Vendor-published New product (internal)
OpenAI team ships an internal product with zero hand-written code: ~1M lines and ~1,500 merged PRs in five months with Codex
Starting from an empty repo in late August 2025, an OpenAI team built and shipped an internal beta with daily internal users and external alpha testers, with a rule that humans never write code directly. Codex CLI generated the scaffold, CI config and even the AGENTS.md file, and Codex opened, reviewed and responded to feedback on PRs while engineers steered.
The numbers (as reported)
| Duration | ~5 months |
|---|---|
| Codebase size | On the order of 1 million lines (incl. infra, tooling, docs) |
| PRs merged | ~1,500 |
| Team | 3 engineers, growing to 7 |
| Throughput | ~3.5 PRs per engineer per day |
| Hand-written code | 0 lines |
| Time vs hand-coding | ~1/10th (team's estimate) |
Facts
- Company / subject
- OpenAI
- Tools
- OpenAI Codex
- Codebase
- greenfield
- Work type
- New product (internal)
- Stack
- —
- Published
- 2026-02-11
- Last checked
- 2026-10-19
Caveats
Written by the vendor about its own tool. Line count includes docs and tooling. No cost, time-vs-estimate or quality figures.