How we used Codex to build Sora for Android in 28 days

December 13, 2025

TL;DR

The Sora Android app was developed from prototype to global launch in 28 days by a small engineering team using Codex and an early GPT-5.1-Codex model.
The team applied Brooks' Law by using a small, empowered team with AI assistance rather than adding more engineers to a time-pressured project.
Codex excels at understanding codebases, writing tests, and applying feedback, but requires clear direction on architecture, product strategy, and user experience.
Effective use of Codex involved establishing a strong foundational architecture, providing concrete examples (like iOS code), and planning changes collaboratively before coding.
AI-assisted development increases the need for human rigor, with engineers focusing on systems understanding, architectural decisions, and collaborative work with AI.

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