OpenAI Upgrades Codex with New GPT-5 Model for Advanced Coding Tasks

OpenAI has unveiled GPT-5-Codex, a specialized version of its GPT-5 model designed specifically for autonomous software development, marking a significant leap forward in AI-powered coding tools. The new model is now rolling out to all ChatGPT Plus, Pro, Business, Edu, and Enterprise users, as well as being integrated into Codex products accessible via terminal, IDE, GitHub, and ChatGPT. OpenAI plans to extend access to API customers in the future. GPT-5-Codex is built to tackle complex programming tasks end to end, mimicking the workflow of a human software engineer. Unlike earlier versions, it can autonomously manage long-term coding projects, iterating through debugging, testing, and refinement over extended periods—up to seven hours in some cases. This dynamic thinking capability allows the model to adjust its processing time in real time based on task complexity, rather than relying on a fixed allocation or a pre-determined router system. This feature, described by Codex product lead Alexander Embiricos as “dynamic thinking,” gives GPT-5-Codex a critical edge over previous models. While GPT-5’s router in ChatGPT routes queries to different models based on initial assessment, GPT-5-Codex can reevaluate its approach mid-task—deciding after five minutes that a problem requires an additional hour of deep analysis. This adaptability leads to more thorough and accurate outcomes. In benchmark tests, GPT-5-Codex outperforms GPT-5 on SWE-bench Verified, a leading standard for measuring agentic coding ability, as well as on code refactoring tasks drawn from large, real-world repositories. The model also shows marked improvement in code review quality. OpenAI had experienced software engineers evaluate its feedback, and they found that GPT-5-Codex made fewer incorrect comments while delivering more high-impact, actionable suggestions. The launch comes at a pivotal moment in the AI coding space, which has become increasingly competitive. Tools like Claude Code, Cursor, and GitHub Copilot are gaining traction, with Cursor recently surpassing $500 million in annual recurring revenue (ARR) and Windsurf drawing intense interest from Google and Cognition in a high-profile acquisition battle. OpenAI’s move with GPT-5-Codex is clearly aimed at reinforcing its leadership in intelligent programming assistance. The model is part of a broader evolution of Codex, which has transitioned from a simple coding assistant to a full-stack development partner. Since its initial CLI launch in April, followed by a web app in May, Codex has matured into a consistent, cross-platform experience. It’s now seamlessly integrated with users’ ChatGPT accounts, enabling smooth switching between local and cloud-based workflows. OpenAI’s strategy reflects a growing industry shift toward agentic AI—systems that can plan, execute, and iterate on complex tasks without constant human intervention. By focusing on real-world engineering challenges, GPT-5-Codex aims to deliver not just code snippets, but fully functional, tested, and maintainable solutions. While the model’s ability to run for hours on a single task raises questions about computational cost and efficiency, OpenAI’s emphasis on dynamic thinking suggests a deeper understanding of how AI can best support developers. The update underscores the company’s commitment to building AI that doesn’t just assist but actively collaborates in the software development lifecycle. As AI coding tools continue to evolve, GPT-5-Codex sets a new benchmark for autonomy, adaptability, and real-world performance—positioning OpenAI at the forefront of the next generation of intelligent programming assistants.