How a Small Team Launched the Sora Android App in 28 Days Using Codex

A small engineering team used Codex (an early version of GPT-5.1-Codex) to take the Sora Android app from prototype to global launch in just 28 days. In the process, they consumed about 5 billion tokens, and after launch the app hit #1 on the Play Store while achieving a 99.9% crash-free rate.

Rather than adding more people to speed things up, the team chose a strategy of maximizing individual engineer productivity through Codex. This decision took into account Brooks' Law, which holds that adding more people can actually reduce efficiency.

They treated Codex like a newly hired senior engineer, using it as follows:

• Strengths: Quickly understanding a massive codebase, writing high-quality unit tests, incorporating feedback, and running tasks in parallel.
• Limitations: Lack of context on product strategy or internal conventions, inability to verify actual app runtime results (UI/UX experience), and limits in deep architectural design capability.

For efficient collaboration, they placed AGENT.md files throughout the codebase to share guidelines and best practices. This helped Codex consistently follow the team's style guide and coding conventions.