I wonder if it's done locally or through the cloud. Some of the language around the release of Gemini Nano implies that it may be done locally?
https://store.google.com/intl/en/ideas/articles/pixel-featur...
https://store.google.com/intl/en/ideas/articles/pixel-featur...
It is only on the Pixel 8, not the previous models and their mid-range $ variants so they aren't giving it away for free just yet