A computer you share with Claude. One per conversation.

CC3 is a spatial desktop that people and their Claudes use together, live. Instead of replying with a wall of text, Claude answers by building things on the desktop: documents, spreadsheets, slides, whiteboards, polls, quizzes, forms, boards and small apps. You tick, drag and vote in them, and one click hands the turn back to Claude.

Desktop, agent and textbook live in one HTML file.

• Answers are things you use. Ask for a plan and get a board you can drag. Ask for a quiz and get a quiz you can take.
• Watch it happen. Files appear where they will land and fill in as Claude writes. The cube in the corner is Claude; it flies to whatever Claude is working on.
• Two hands, one desktop. You work with the mouse, Claude works with words. Everything lands in the same store and the same log, and any change can be undone.
• Better together. Share it and everyone sees each other's pointers, selections and typing. Each person can bring their own Claude on a private channel. Polls, quizzes and forms keep each person's answers apart.
• Built-in tools. A word processor, spreadsheet, presentations, whiteboard, polls, quizzes, forms, boards, timelines, cards, records and small websites. Nobody sees code.
• Hackable. When nothing built in fits, apps are written in Tanke, a small JavaScript language for desktops. Programs are plain JavaScript with a shared console.

Claude writing on the desktop	A turn, drawn on a CC3 canvas

Give Claude a published CC3 link, or upload dist/cc3.html, and say something like "start the computer". The file carries its own instructions for Claude: it publishes a fresh artifact for the conversation (with its own storage) and starts building on it. Share the artifact from its Share menu to work on it together.

Open dist/cc3.html directly, or serve this folder and open index.html. Outside Claude, files are kept in your browser. To use the built-in agent (the bar at the bottom), open Settings and add an Anthropic API key or an OpenAI-compatible endpoint. Keys stay in memory for the visit and are sent only to the endpoint you name.

Claude in the chat works in turns, and each turn is two calls: it reads one document (the view: what changed, by name, and what you are looking at) and writes one document (the turn). The turn is plain text in a block format. A line starting with @@ opens a file:

@@poll Lunch
Where should we eat?
- Thai
- Pizza
- Salad bar

Your page plays the turn in, makes each block a file and logs every change. Claude never writes files directly, so nothing it writes can break the desktop.

A custom app in Tanke:

app("Standup").add(
  toolbar(heading("Standup"), spacer(), facepile()),
  input("What are you on today?", act((text, c) => c.setMy("today", text))),
  stack(live(c => c.everyone("today").map(x => `${x.isMe ? "You" : x.name}: ${x.value}`).join("\n") || "Nobody yet")),
)

The full manual is book.md, which is also what Claude reads before it works. It opens from the drawer inside the app.

• On claude.ai, files of type page (@@page, a small sandboxed HTML page) currently render blank inside the hosted computer, both on the desktop and in focus mode. They work when the file runs on its own. Use the built-in apps, or publish a page as its own artifact and link to it with @@link.

CC3 is free to use, change and share, including commercially, under the Apache License 2.0.

In return, if you redistribute CC3 or something built from it, keep the LICENSE and NOTICE files, mark the files you changed, and show the credit from NOTICE where your project lists its credits. A line like this is enough:

Built on CC3 by Ramon Marc, Mold & Yeast.

If CC3 helped you, a link back or a mention is very welcome.

"Claude" is a trademark of Anthropic, PBC.

Ramon Marc · Mold & Yeast