Marginalia: Margin notes for AI chats от Midhun

Google-Docs-style follow-up comment threads on Gemini, ChatGPT and Claude — highlight text, ask in the margin, keep your place.

Ask follow-up questions in the margins - without burying the answer you're reading.

When an AI gives you a long answer and one phrase needs unpacking, you normally ask in the main chat and scroll away from your place. Marginalia gives you Google-doc-style comment threads instead: highlight the phrase, ask your question in a comment box that opens right next to it, and the reply streams into the box while the original answer stays put.

How it works:
* Highlight text in an AI answer on chatgpt.com or claude.ai or gemini.google.com
* Click the Comment pill ( or right-click -> "Ask About..." or press Ctrl + Shift + H)
* A comment thread opens in the right margin, anchored to your highlight
* Ask follow-ups in the thread - replies come from the AI you're already using.

Features:
* Multi-turn threads that persist per conversation and re-anchor when you return
* Docs-style layout: focusing a thread aligns it with its highlight
* Minimize threads to chips, expand to full screen, or resolve them for later
* An all-threads panel (Alt + Shit + A) with open/resolved filter and click-to-jump
* Follows each site's light/dark theme
* Keyboard-first: cycle threads with Alt+↑/↓, re-bindable shortcut

Your data stays yours:
Threads and settings are stored locally on your browser. Your questions go only to the AI service you are already using - either through your existing signed-in session or through the providers official API if you add your own API key in Settings ( ChatGPT requires an OpenAI key). Keys are stored locally and sent only to that provider. Marginalia has no server and collects nothing.

The source code is open-source and is available for community review.