OpenAI’s Codex began as a cloud agent that did not gain traction. The team pivoted to a local terminal and editor version. Usage of the editor extension grew over tenfold by October 2025. Codex later added a desktop app for managing multiple agents. It merged into the ChatGPT desktop app by July 2026. Codex and ChatGPT for Work now have 40 million weekly active users. Thibault Sottiaux was promoted to lead OpenAI’s core products. The shift relied on reasoning models that plan before responding. These models excel at programming due to fast feedback loops. OpenAI’s first reasoning model, o1, launched in September 2024.
What changed
Codex was initially a cloud-based agent that failed to find product-market fit.
What it unlocks
Running multiple coding agents locally on a developer’s computer in their terminal and code editor.
- 5M weekly active users by June 2026
- 40M weekly active users for Codex and ChatGPT for Work
- 10x usage growth by October 2025
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