OpenAI Codex Made Crystal Clear · chapter 1: From Autocomplete to Delegation
The Codex timeline, April 2025 to August 2026, as reported by the cited history and...
2026-08-30
Model milestones alternate with product milestones; the green endpoint marks the current GPT-5.6 model family as of this book's stamp date, 2026-08-28.
Below: the paragraph from the book that builds this idea, then the diagram itself (Figure 1.2), and a recap. About a minute of reading.
The product moves tracked the models. February 2026 brought a desktop app built to manage multiple agents over long periods. March 2026 added Codex Security, a vulnerability detection tool grown from OpenAI's internal Aardvark project, still in research preview as this book goes to print. And on July 9, 2026, the desktop app merged into the ChatGPT app itself, which is why the docs now live under a merged hub and why this book keeps saying "one agent, many windows." Adoption grew with it: reports cite over 1 million monthly developers before February 2026, over 2 million weekly by March 2026 with usage up fivefold since the start of the year, and OpenAI's June 2026 announcement cited more than 5 million weekly users. Treat every such count as stamped by its announcement date, not as a current fact. Figure 1.2 lays the whole ribbon out.
Recap
- The idea: Model milestones alternate with product milestones; the green endpoint marks the current GPT-5.6 model family as of this book's stamp date, 2026-08-28.
- The picture: Figure 1.2, from chapter 1 ("From Autocomplete to Delegation") of OpenAI Codex Made Crystal Clear.
- Go deeper: the chapter builds this step by step, with recipes and sources at the end.
This diagram is one of many in OpenAI Codex Made Crystal Clear.
Every chapter opens with the gist, draws the hard ideas, and ends with recipes and sources.
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