The most important OpenAI announcement you probably missed at DevDay 2025
OpenAI’s annual developer conference on Monday was a spectacle of ambitious AI product launches, from one app store for ChatGPT to a stunning Video generation API who brought creative concepts to life. But for the companies and tech leaders watching closely, the most consequential announcement was the silence general availability of Codexthe company’s AI software engineer. This release signals a profound change in the way software – and by extension, modern business – is built.
While other announcements captured the public’s imagination, the production-ready release of Codexboosted by one new specialized model and a suite of enterprise-level toolsis the driving force behind the entire vision of OpenAI. It is the tool that builds the tools, the proven agent in a world teeming with agentic potential, and the clearest articulation of the company’s strategy to win the business.
The general availability of Codex moves it from a “research preview” to a fully supported product, complete with a new product software development kit (SDK)A Weak integrationand administrative controls for security and monitoring. This transition declares Codex ready for mission-critical work within the world’s largest companies.
“We think this is the best time in history to be a builder; it’s never been faster to go from idea to product,” said Sam Altman, CEO of OpenAI, during the opening speech presentation. “It used to take months or years to build software. You saw that now it can take minutes to build with AI.”
That acceleration is not theoretical. It’s a reality born out of OpenAI’s own internal use – a massive “dogfooding” effort that serves as the ultimate case study for enterprise customers.
Inside GPT-5-Codex: the AI model that codes autonomously for hours and delivers 70% productivity gains
The gist of the Codex upgrade is GPT-5 Codexa version of OpenAI’s latest flagship model that is “intentionally trained for Codex and agentic coding.” The new model is designed to function as an autonomous teammate and goes far beyond simple code completion.
“Personally, I like to think of it as a human teammate,” explains Tibo Sottiaux, an OpenAI engineer, during a technical session on Codex. “You can attach a program to it on your computer, you can delegate to it, or, as you’ll see, you can give it a task without explicit directions.”
This new model makes it possible “adaptive thinking“, allowing it to dynamically adjust the time and computational effort spent on a task based on its complexity. For simple requests it is fast and efficient, but for complex refactoring projects it can take hours.
One engineer noted during the technical session, “I have seen the GPT-5-Codex model run productively for over seven hours… during a marathon session.” This ability to perform long-running, complex tasks is a significant step beyond the simple, one-off interactions that characterize most AI coding assistants.
The results within OpenAI are dramatic. The company reported that 92% of its engineering staff now use Codex on a daily basis, and that these engineers are completing 70% more pull requests (a measure of code contribution) each week. Usage has increased tenfold since August.
“When we as a team see the statistics, it feels great,” says Sottiaux. “But it’s even better to be with someone at lunch who then says, ‘Hey, I use Codex all the time. Here’s something fun I do with it. Want to hear about it?'”
How OpenAI uses Codex to build its own AI products and catch hundreds of bugs every day
Perhaps the most compelling argument for Codex’s importance is that it is the foundational layer upon which OpenAI’s other notable announcements are built. During the DevDay eventthe company presented custom arcade games and a dynamic, AI-powered website for the conference itself, all developed with the help of Codex.
In one session, engineers demonstrated how they built “Storyboard,” a custom creative tool for the film industry, in just 48 hours during an internal hackathon. “We decided to test Codex, our coding agent… we sent jobs to Codex between meetings. We were able to very easily review and merge PRs into production, which Codex even allowed us to do from our phones,” said Allison August, solutions engineering leader at OpenAI.
This reveals a crucial insight: the rapid innovation demonstrated at DevDay is a direct result of the productivity flywheel created by Codex. The AI is a core part of the manufacturing process for all other AI products.
An important enterprise-focused feature is the new, more robust code review capability. OpenAI said it has “purposefully trained GPT-5-Codex to be great at extremely thorough code review,” allowing it to examine dependencies and validate a programmer’s intent against the actual implementation to find high-quality bugs. Internally, almost every pull request at OpenAI is now reviewed by Codex, catching hundreds of issues every day before they reach a human reviewer.
“It saves you time and you ship with more confidence,” Sottiaux said. “There’s nothing worse than finding a bug after we’ve actually released the feature.”
Why enterprise software teams choose Codex over GitHub Copilot for mission-critical development
The maturation of Codex is central to OpenAI’s broader strategy to conquer the enterprise market, a move essential to justify its massive valuation and unprecedented computing spend. During a press conference, CEO Sam Altman confirmed the strategic shift.
“The models are there now, and you can expect a huge focus from us on really winning companies with great products, starting here,” Altman said during a private news conference.
OpenAI president and co-founder Greg Brockman immediately added, “And you can already see it in Codex, which I think has just been an incredible success and has really grown super fast.”
For technical decision makers, the message is clear. While consumer-facing agents booking dinner reservations are still finding their feet, Codex is a proven enterprise agent delivering substantial ROI today. Companies like Cisco have already rolled out Codex to their engineering organizations, reducing code review times by 50% and reducing project timelines from weeks to days.
With the new one Codex SDKcompanies can now embed this agentic power directly into their own custom workflows, such as automating fixes in a CI/CD pipeline or even creating self-development applications. During a live demo, an engineer demonstrated a mobile app that updated its own user interface in real time based on a natural language prompt, all powered by the built-in Codex SDK.
While the launch of a app ecosystem in ChatGPT and the breathtaking images of the Sora 2 API rightly generated headlines, the general availability of Codex marks a more fundamental and immediate transformation. It is the silent yet powerful engine that powers the next era of software development, turning the abstract promise of AI-powered productivity into a tangible, deployable reality for today’s businesses.
