I was reading about the Dreyfus affair and hit "syndicalism" — a word I'd skimmed past a dozen times. I knew the shape of it, not the substance. Opening a new tab meant losing the paragraph I was in, reorienting, reading something adjacent, and coming back with my thread broken. rabbitholes is a Chrome extension that solves the specific version of this problem: you want the context, but you don't want to leave. Highlight any text and a shadow-DOM tooltip renders an explanation next to your cursor — Claude Haiku 4.5, direct from your browser to api.anthropic.com, no intermediary server. Shadow DOM means the tooltip doesn't touch the host page's styles or DOM; you can close it and the page is exactly as you left it. The part I use most: every word in the response is itself clickable. You can drag across a phrase to select it. So when the explanation of "syndicalism" mentions "anarcho-syndicalism" and you want that too, you don't open a tab — you click the word. The extension tracks depth with a hop counter.…