I built a very similar extension [1] a couple of months ago that supports a wide range of models, including Claude, and enables them to take control of a user's browser using tools for mouse and keyboard actions, observation, etc. It's a fun little project to look at to understand how this type of thing works. It's clear to me that the tech just isn't there yet. The information density of a web page with standard rep…
The DOM is merely inexpensive, but obviously the answer can't be solely in the DOM but in the visual representation layer because that's the final presentation to the user's face.
Also the DOM is already the subject of cat and mouse games, this will just add a new scale and urgency to the problem. Now people will be putting fake content into the DOM and hiding content in the visual layer.