Build an Android app in 28 days with parallel Codex runs
OpenAI engineers had several Codex sessions write most of the Sora Android app in 28 days; OpenAI reports it reached #1 in the Play Store on launch day.
Done with OpenAI Codex
What they did
OpenAI engineers built the Sora Android app with a small team. They ran several Codex sessions at the same time. The engineers planned the app's overall structure and hand-wrote rough sample features for Codex to copy. They also wrote rules for the agent. Codex then wrote most of the feature code, and the engineers reviewed it.
How it went
OpenAI reports the app was built from Oct 8 to Nov 5, 2025. It used roughly 5 billion tokens, the units of text the AI reads and writes. OpenAI says it reached #1 in the Play Store on launch day.
Worth knowing
The human work moved to the start. Sample features and written rules gave Codex patterns to follow before it wrote most of the code.
Try it yourself with OpenAI Codex
I'm building [app description] for [platform]. First, read the architecture notes in [docs path] and the example feature in [example feature path], which shows how features should be structured. Then implement [feature name] following the same patterns, conventions and file layout. Before writing code, show me your plan: which files you'll create or change and how they map to the example. Wait for my approval. After implementing, run the build and tests, summarize what changed, and flag anywhere you departed from the example pattern so I can review it.
Swap the highlighted [parts] for your own details.
Source: Company blog (OpenAI) · Patrick Hum, RJ Marsan · Dec 12, 2025
Written with AI assistance from the original post and checked against our editorial guidelines. Results are as reported by the source, not independently verified.
