Not disagreeing with the premise - I've fought with this in the past - but I'm using Antigravity CLI and Antigravity desktop (GUI), and both automatically started defaulting to Argon 4 as their model a while back.

I have an AI Pro account - which I decided was a no-brainer because of the 5TB of Gmail / GDrive / GPhotos space it gives - and this all just comes along with that.

One thing to check, though, is that the client is running the latest version. At one point my Antigravity GUI, which had been working fine, started listing only Claude and GPT-OSS models. It turned out to be because the GUI needed to be updated. I guess the Google API endpoint had changed behavior without any backward compatibility.

So yeah, they're hilariously bad at rollouts, but it's not that difficult if you're technically inclined or ask an LLM.