OpenAI has launched GPT-5-Codex, an upgraded version of GPT-5 designed for software engineering tasks, alongside major updates to its Codex platform. The new model is now the default for cloud tasks and code reviews and can also be used locally via Codex CLI and IDE extensions.
“Codex moves closer to what we’ve been building toward all along—a teammate that understands your context, works alongside you and reliably takes on work for your team,” OpenAI said in its announcement.
GPT-5-Codex was trained on complex engineering tasks such as debugging, feature development, large-scale refactoring and code reviews. In tests, it demonstrated a 51.3% accuracy rate on code refactoring tasks compared to GPT-5’s 33.9%.
The model can dynamically adjust how much time it spends on tasks, ranging from short sessions to working independently for more than seven hours.
OpenAI reported that GPT-5-Codex generates fewer incorrect review comments than GPT-5 (4.4% vs. 13.7%) and produces more high-impact comments (52.4% vs. 39.4%). It has also been deployed internally at OpenAI, where the company said it reviews “the vast majority of its PRs, catching hundreds of issues every day—often before a human review begins”.
Developers can now use Codex across multiple environments, including the terminal, IDEs like VS Code, GitHub, the web and even mobile. Updates include a rebuilt Codex CLI with support for screenshots and diagrams, a task to-do list, improved terminal UI and three new approval modes for managing access. The new IDE extension integrates cloud tasks directly into editors, allowing seamless context switching.
Codex also now offers code review capabilities directly on GitHub. Developers can trigger reviews by mentioning “@codex review” in a pull request and can specify focus areas such as security vulnerabilities.
Early adopters include Cisco Meraki, Duolingo, Ramp, Vanta, Virgin Atlantic and Gap.
“With Codex, I offloaded the refactoring and test generation while focusing on other priorities,” said Tres Wong-Godfrey, tech lead at Cisco Meraki. “It produced high-quality, fully tested code that I could quickly hand back—keeping the feature on schedule without adding risk.”
To improve security, Codex runs in sandboxed environments by default, with network access disabled unless explicitly approved. Developers can configure access levels depending on risk tolerance. OpenAI emphasised that Codex should serve as an additional reviewer, not a replacement for human review.
Codex is available under ChatGPT Plus, Pro, Business, Edu and Enterprise plans. Pro supports full workweeks of usage, while Enterprise plans provide pooled credits for teams. API availability for GPT-5-Codex is planned.
