OpenAI's Codex is now writing almost all of its code
OpenAI made its AI coding assistant, Codex, generally available to paying users worldwide on October 6, 2025.
CEO Sam Altman shared that almost all new code at OpenAI is now written with Codex.
New features like Slack integration and an SDK for custom tools were also announced.
Codex is now reviewing nearly every pull request
With Codex, OpenAI's engineers have boosted their weekly pull requests by 70%. The AI now reviews nearly every pull request.
Since August, daily usage has jumped tenfold—GPT-5-Codex processed over 40 trillion tokens in three weeks.
Codex is now integrated into Slack
Companies worldwide—including Cisco and Duolingo—are using Codex to speed up coding.
Cisco cut review time for complex code by half since adopting it.
Developers can now trigger Codex right from Slack or embed it into their own apps with the new SDK.
AI coding assistants are becoming essential for developers
The fast growth of Codex points to a bigger shift: AI-powered coding tools are quickly becoming must-haves for startups and big companies alike, helping teams move faster, though concerns about code quality remain.