OpenAI has revealed that it built and shipped the Sora Android app in just 28 days, showcasing the transformative impact of AI-assisted software development. Developed between October 8 and November 5, 2025, the app was created by a four-engineer team that relied heavily on OpenAI’s AI coding agent, Codex, to meet aggressive timelines without expanding headcount.

According to OpenAI, Codex generated nearly 85 percent of the app’s codebase, helping the team deliver a highly stable product with a 99.9 percent crash-free rate. Upon launch, the Sora Android app debuted at number one on the Google Play Store, with Android users creating over one million videos within the first 24 hours.

OpenAI engineers Patrick Hum and Rj Marsan noted that the team deliberately avoided adding more engineers, referencing Fred Brooks’ principle that increasing team size late in a project often slows progress. Instead, Codex was treated like a senior engineer, handling implementation while human developers focused on architecture, system design, and user experience.

Codex excelled at navigating large codebases, writing unit tests, and translating logic across platforms, including converting Swift code to Kotlin. OpenAI CEO Sam Altman highlighted that Codex now powers most new code internally, enabling engineers to complete 70 percent more pull requests weekly. As productivity surged, decision-making and coordination emerged as the primary bottlenecks, underscoring a new era of AI-driven software engineering.