OpenAI's DevDay is Tuesday, September 29, at Fort Mason in San Francisco, with Sam Altman keynoting at 10am PT and a free livestream for everyone else. That's the confirmed part. The rumor mill around what actually gets announced is running unusually hot this year — here's the roundup, all of it unconfirmed.

The biggest rumor is an always-on agent reportedly called “o.” TestingCatalog found references across ChatGPT's configuration — “o” as a display name, “-o” as an email suffix, and a mention on the $100 Pro plan upgrade page — pointing to a persistent agent that keeps working outside a normal chat session, possibly with its own email identity from the start. One X account claims it will run on an Astra variant called “aeon” built for long-running tasks, and Tibo Sottiaux has been dropping hints of his own. None of it is confirmed by OpenAI.

On pricing and speed: TestingCatalog reports a $500-per-month ChatGPT Pro Max tier powered by Cerebras, promising the fastest speeds for work and Codex. Separately, OpenAI appears ready to widen access to its Ultrafast API mode — up to 750 output tokens per second, described as 14x faster than Standard — with a Standard/Fast/Ultrafast speed selector spotted in the Responses API playground. Both would fit a DevDay focused on production API infrastructure.

Then there's GPT-6 Cyber. Fortune reports OpenAI will preview the cybersecurity-focused model at DevDay — its fourth security model this year — alongside an enterprise security orchestration platform, with select customers already alpha-testing through the invite-only Daybreak Red program. As always with pre-keynote rumors: expect some of these to land, some to slip, and at least one surprise nobody saw coming.