Every long article I read has the same problem: a word or concept I half-know that would make the whole paragraph click if I just looked it up. The tab-switch kills it. I open a new tab, read a bit, come back, and I've lost the thread. So I skip it, and the read stays shallow.
I built rabbitholes to fix that for myself. Highlight any text on any page, and a shadow-DOM tooltip renders an explanation from Claude Haiku 4.5 next to your cursor. It doesn't inject anything into the host page — shadow DOM keeps the overlay isolated, so it can't break layouts or leak styles into the site you're reading.
The part I use most: every word in the explanation is itself clickable. Drag across a phrase to select it. The tooltip rebuilds around that term, with the original context still in the background. You can go four hops deep into a Wikipedia article about Byzantine tax policy without opening a single new tab. A counter tracks how many hops you've taken; the trail is shareable.
If I want more than Claude's training data, a globe icon re-answers the same query enriched with Brave Search results, with source chips I can click through. A pencil icon opens a free-form follow-up that inherits the current context so I don't have to re-explain where I am in a topic.
