OpenAI Introduces GPT-5-Codex, an AI Model Built Just for Coding

OpenAI has announced its newest model, GPT-5-Codex. The new model has been optimized for agentic coding in OpenAI’s suite of AI-powered software engineering tools, which is called Codex. This year, AI programs that can write and edit software have emerged as the most lucrative use case for AI, propelling multiple companies to huge revenue increases. These tools are being used both by professional developers to make their work more efficient, and by casual vibe coders, who lack the technical skill to create websites and apps. The Sam Altman-led company claims that by training this new AI model on real-world engineering tasks, it can outperform the default model. In a benchmark that compared that model and GPT-5-Codex’s ability to refactor code (essentially reorganizing and cleaning up code), GPT-5-Codex scored nearly 20 percent higher than the default model, which is simply called GPT-5. GPT-5-Codex is also said to be a strong independent worker. It can work autonomously on software for long stretches of time. According to a press release, OpenAI has seen the model “work independently for more than seven hours at a time on large, complex tasks, iterating on its implementation, fixing test failures, and ultimately delivering a successful implementation.” The new model could also help alleviate one of the most notable pain points of vibe coding: bad code. Many software developers have remarked that much of their time working with AI-assisted code editors is spent cleaning up the AI’s code, which isn’t always as thoughtfully written as a human expert’s would be. But OpenAI says that GPT-5-Codex has been “trained specifically for conducting code reviews and finding critical flaws.” In practice, the company says, this means GPT-5-Codex will review an entire codebase to identify flaws and autonomously test apps to find errors. OpenAI says that Codex currently handles “the vast majority” of proposed changes to code being written by OpenAI staffers, “catching hundreds of issues every day—often before a human review begins.” But even with its improved code review abilities, OpenAI still recommends using Codex as an additional reviewer; it says in a press release that it is “not a replacement for human reviews.” Unlike the normal version of GPT-5, GPT-5-Codex won’t be immediately available via API, and OpenAI recommends only using the model for coding tasks in Codex-supported environments. In addition, Codex is coming to mobile devices for the first time. Previously, to access Codex, you’d either need to use ChatGPT on a desktop computer or invoke Codex in an IDE (integrated development environment) like VSCode or Cursor. Now, Codex will be accessible in the ChatGPT iOS app, enabling easier coding on the go. Codex, and GPT-5-Codex, is available across all of ChatGPT’s paid tiers, with $20-per-month ChatGPT Plus members getting enough access to “cover a few focused coding sessions each week.” Meanwhile, $200-per-month ChatGPT Pro members will get enough to “support a full workweek across multiple projects.” Companies that pay for ChatGPT’s SMB-focused Business plan can purchase credits to give their developers more access to Codex, while larger companies with ChatGPT’s Enterprise plan get a shared credit pool. In OpenAI’s press release, engineers and tech leads at companies including Cisco, Duolingo, Ramp, Vanta, and Virgin Atlantic praised Codex’s utility, but it remains to be seen if GPT-5-Codex can help OpenAI take market share away from Anthropic, whose similar Claude Code product has proved very popular with professional and casual software developers. BY BEN SHERRY @BENLUCASSHERRY