When we asked questions related to why Codex runs in a certain way, Codex decided to debug its own systems. It connected to logs, SSH'd into research dev boxes, and analyzed ML instabilities.
Thibault SottiauxHead of Codex · Leader, 
OpenAI
Press report: How Codex is built, The Pragmatic Engineer, February 17, 2026, at 3. How Codex builds itself, Using Codex to debug Codex. Reported by Gergely Orosz.
Thibault Sottiaux, Head of Codex. Leads the team that builds the product he describes, so he speaks from inside it; OpenAI sells Codex.
OpenAI sells AI or agent tools or services, so it has a reason to publish flattering numbers about AI. The passage stays in the archive; read it with that in mind.
Checked against the source by a first reader, then confirmed independently by a second reader who fetched the source without seeing the first reader's notes (Independent review agent (Claude Sonnet), blind second pass from passage text and citation only, no repository access, 2026-11-04).
Exact match inside a direct quote the article attributes to Thibault Sottiaux ('Tibo told me: “When we asked…”'), in Using Codex to debug Codex. His own words.
Thibault Sottiaux (OpenAI), “How Codex is built”, The Pragmatic Engineer, 2026-02-17, at 3. How Codex builds itself, Using Codex to debug Codex. https://newsletter.pragmaticengineer.com/p/how-codex-is-built Archived at https://the-ai-record.com/passages/openai-asked-questions-why-codex-runs-certain-2026
Codex is really built for multitasking. There's this understanding that most tasks will just get done to completion. People on our team have figured out what Codex is and isn't capable of. There is a tricky thing in all of this, though: we have to relearn these capabilities with every model
Thibault SottiauxHead of Codex · Leader, OpenAI
Press report: How Codex is built, The Pragmatic Engineer, February 17, 2026, at 3. How Codex builds itself. Reported by Gergely Orosz.
We take a stance with the sandboxing that hurts us in terms of general adoption. However, we do not want to promote something that could be unsafe by default. As a dev, you can always go into your configuration and disable these settings if you want.
Thibault SottiauxHead of Codex · Leader, OpenAI
Press report: How Codex is built, The Pragmatic Engineer, February 17, 2026, at 2. Technology and architecture choices. Reported by Gergely Orosz.
Something wrong? Report a correction. JSON: /api/v1/passages/openai-asked-questions-why-codex-runs-certain-2026.json