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Title: Inside OpenAI’s fast-growing Codex: The people building the AI that codes alongside you URL Source: http://www.fastcompany.com/91498841/openai-codex-growing-fast-agentic-engineering Published Time: 2026-02-27T13:00:00+00:00 Markdown Content: Inside OpenAI’s fast-growing Codex: The people building the AI that codes alongside you - Fast Company =============== [Try our mini crossword with a business twist: **Play Fast Company Mini Crossword**](https://www.fastcompany.com/games/mini-crossword)  LOGIN [](https://www.fastcompany.com/) [SUBSCRIBE](https://www.fastcompany.com/subscribe?itm_source=topnav&itm_medium=button&itm_campaign=sticky) * [Premium](https://www.fastcompany.com/premium?itm_source=dek&itm_medium=lander&itm_campaign=main) * [Tech](https://www.fastcompany.com/technology) * [Design](https://www.fastcompany.com/co-design) * [News](https://www.fastcompany.com/news) * [Leadership](https://www.fastcompany.com/leadership-2) * [Work Life](https://www.fastcompany.com/work-life) * [Games](https://www.fastcompany.com/games) * [Podcasts](http://www.fastcompany.com/podcasts) * [Video](https://www.fastcompany.com/videos) * [INNOVATION FESTIVAL](http://www.fastcompany.com/section/fast-company-innovation-festival) | [Custom Studio](http://www.fastcompany.com/fcw) * [IBM](https://www.fastcompany.com/fcw/ibm) * [Texas A&M University](https://www.fastcompany.com/fcw/texas-am-university) advertisement 02-27-2026[TECH](https://www.fastcompany.com/technology) [Inside OpenAI’s fast-growing Codex: The people building the AI that codes alongside you =======================================================================================](http://www.fastcompany.com/91498841/openai-codex-growing-fast-agentic-engineering) OpenAI leaders reveal how the company’s rapidly growing coding agent works, why developers are delegating tasks to it, and what that means for the future of software work. SHARE Facebook LinkedIn Bluesky X Link ADD ON GOOGLE  [Screenshots: OpenAI]  BY[Mark Sullivan](http://www.fastcompany.com/user/mark-sullivan) Listen to this Article[More info](http://www.fastcompany.com/about-us#voice) 0:00 / 0:00 OpenAI’s Codex [AI](https://www.fastcompany.com/section/artificial-intelligence "AI") coding assistant is having a growth spurt. OpenAI tells _Fast Company_ that its weekly active users have tripled since the start of the year, while overall usage (measured in tokens) has increased fivefold. The surge is likely driven by the release of new models—GPT-5.2 last December and [GPT-5.3-Codex](https://www.fastcompany.com/91488584/openai-gpt-5-3-codex-release) in early February—as well as the launch of Codex’s app version a few weeks ago. OpenAI says the app has been downloaded more than a million times. Across all access points—including the cloud, app, and command line—more than a million developers and other users now rely on Codex at least once a week, according to the company. Generating computer code has emerged as one of the first AI applications making a measurable impact in business. But tools like Codex and Anthropic’s Claude Code have evolved far beyond simple code generators. Powered by more capable models, they function more like assistant engineers—able to converse with developers in plain language about a new software project and iteratively develop a plan. The agent can then execute that plan, which may include analyzing a broader codebase, writing and revising code, conducting research, running tests, and producing documentation. When finished, it can explain its reasoning and the decisions it made to the human engineer. More importantly, Codex has evolved into an agentic platform, where multiple agents can carry out many of these tasks simultaneously across different pieces of a software project. They can hunt for bugs, for example, while an engineer reviews progress, focuses on another assignment, or steps away for lunch. Peter Steinberger, the OpenClaw creator and an elite-level coder, [calls this new mode of working](https://steipete.me/posts/just-talk-to-it) “agentic engineering.”  **Thibault Sottiaux** [Photo: OpenAI] The tools have evolved quickly. Codex and [Claude Code](https://www.fastcompany.com/91488000/anthropics-new-claude-opus-4-6-aims-to-think-through-bigger-codebases) both launched in the first half of 2025. OpenAI had previously introduced a Codex model in 2021—the system that powered the early AI coding assistant GitHub Copilot—but the Codex coding assistant that exists today debuted in May 2025. Thibault Sottiaux, who leads the Codex group at OpenAI, says the product got a major boost with the December 2025 release of the [GPT-5.2 model](https://www.fastcompany.com/91459501/openai-just-released-new-gpt-5-2-model-heres-what-you-need-know), which he says can hold more project data in memory and reason over it more effectively than earlier versions. “The model was more reliable—working by itself autonomously and reaching really good results,” he tells _Fast Company_. Codex’s user base broadened again with the February 2 release of the Codex desktop app for Mac, which OpenAI describes as a “command center” where users can deploy and manage multiple agents. The company says more than half a million people are now accessing Codex through ChatGPT’s Free and Go subscription tiers, and it believes many of them are non-coders, since power users typically rely on higher-priced plans that offer greater usage limits and faster speeds. The biggest bang came with the February 5th launch of GPT‑5.3‑Codex, which substantially improved Codex’s coding chops, as well as its capacity for reasoning its way through complex, long-running tasks that involve research and tool use. In X posts and Reddit discussions many [developers](https://x.com/theo/status/2020279916760355142?s=20)[raved](https://x.com/kieranklaassen/status/2020894445554880963?s=20) about the tool’s capacity for quickly writing usable code for real-world projects, often on the first try. Expand to continue reading ↓ * * * #### Explore Topics * [Artificial Intelligence](http://www.fastcompany.com/section/artificial-intelligence) * [OpenAI](http://www.fastcompany.com/section/openai) advertisement Featured Video When I was nine years old Claire's went from tween mall icon to bankrupt — twice? Behind its glittery facade, Claire's is a financial mess. The tween retail icon behind millions of ear piercings and Y2K accessories filed for bankruptcy in August 2025, closing hundreds of stores and selling its North American business for just $104 million. So how does a brand with $1.4 billion in global sales end up with more than $500 million in debt? Fast Company staff writer Elizabeth Segran has been covering the company's ups and downs for years. In this episode of FC Explains, she breaks down the full Claire's story, from its mall-era dominance and surprising pandemic comeback to its failed IPO, crushing debt load, tariff difficulties, and the rise of sleeker competitors like Lovisa, Studs, and Rowan. More Videos 0 seconds of 4 minutes, 52 seconds Volume 0% Press shift question mark to access a list of keyboard shortcuts Keyboard Shortcuts Enabled Disabled Shortcuts Open/Close/ or ? Play/Pause SPACE Increase Volume↑ Decrease Volume↓ Seek Forward→ Seek Backward← Captions On/Off c Fullscreen/Exit Fullscreen f Mute/Unmute m Decrease Caption Size- Increase Caption Size+ or = Seek %0-9 Next Up 2026 FIFA World Cup: Here’s how the biggest brands are spending millions 05:09 Subtitle Settings Off Explains S3 Ep6 Claires Final Site Kc Font Color White Font Opacity 100% Font Size 100% Font Family sans-serif Character Edge None Edge Color Black Background Color Black Background Opacity 75% Window Color Black Window Opacity 0% Reset White Black Red Green Blue Yellow Magenta Cyan 100%75%50%25% 200%175%150%125%100%75%50% Arial Courier Georgia Impact Lucida Console Tahoma Times New Roman Trebuchet MS Verdana None Raised Depressed Uniform Drop Shadow White Black Red Green Blue Yellow Magenta Cyan White Black Red Green Blue Yellow Magenta Cyan 100%75%50%25%0% White Black Red Green Blue Yellow Magenta Cyan 100%75%50%25%0% Auto 270p 1080p 720p 406p 270p 180p Live 00:00 04:52 04:52 More Videos Close ### Claire's went from tween mall icon to bankrupt — twice? 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