Where is Gemini 3.5 Pro? The case of the missing AI model.

At the Google I/O event in May, CEO Sundar Pichai announced that the company's newest frontier model, Gemini 3.5 Pro, would launch in June.

"We are also excited for 3.5 Pro," Pichai said at a pre-Google I/O media briefing. "We are using it internally. It's showing great improvements. We are still testing and refining it, and it will roll out to everyone next month."

That never happened.

June eventually turned into July, and then August, and as of Sept. 10, there's still no sign of the model. The Google DeepMind website states, "3.5 Pro coming soon," as it has for months. Meanwhile, the long-time leader of Google DeepMind, Demis Hassabis, has been shuffled into a new position.

As Google stalls on Gemini 3.5 Pro, its chief AI rivals are releasing boundary-breaking new models. OpenAI recently released GPT-6 Astra, kicking off a new generation of GPT models, and Anthropic recently released Fable 5.1. Both models have made critical advances in cyber coding capabilities. They've also been used to resolve famous open questions in research-level mathematics, such as the Jacobian Conjecture and the Navier-Stokes problem (the latter was resolved with quite a bit of controversy, however). Chinese AI lab Moonshot also released Kimi K3, a massive open-source model with 2.8 trillion parameters.