I asked Google CEO Pichai what happened to the missing Gemini 3.5 Pro model that never shipped.

He gave me an interesting window into the hard decisions big labs have to make in model development:

"While training the 3.5 series, we had Flash and Pro, which we were working on. An area we internalized through the middle of this year was that there were gaps in agentic capabilities, particularly around coding...

We wanted to definitely hill climb there, and the team felt the fastest way to do so was using Flash. It's a smaller model and more efficient, so you can really get a lot more iterative loops there. That's what led to 3.5, 3.6, 3.7, and 3.8 Flash.

By the time we got that done, we had a chance to apply it to Pro, but Argon pre-training was done."