Three Engineers Ship Million-Line Codebase Using AI Agents Without Writing a Single Line of Code
Summary
Three engineers ship a million-line codebase without writing a single line of code, using OpenAI's Codex agents to autonomously handle the entire development lifecycle — from bug fixes to pull requests — at a pace of 3.5 PRs per engineer per day.
Key Points
- A small team of three engineers builds and ships a real software product with over one million lines of code entirely written by Codex agents, achieving roughly 3.5 pull requests per engineer per day with zero manually written code.
- Engineers are redefining their roles by focusing on designing environments, specifying intent, and building feedback loops — including structured repository documentation, custom linters, and agent-legible observability tools — rather than writing code directly.
- Codex agents now autonomously handle the full development lifecycle, from reproducing bugs and implementing fixes to opening pull requests and merging changes, while a continuous 'garbage collection' process enforces coding standards and prevents architectural drift.