tandem

Have you ever been working on a piece of writing with an LLM and caught yourself copy-pasting the same paragraph into the chat for the fifth time just so the model knows what you're talking about? That's the friction Tandem eliminates. Open a file directly, or just tell Claude "let's work on my draft in tandem" — the document appears in the editor, and from that point on you highlight text and Claude sees it directly. No pasting, no "here's the paragraph I mean," no losing your place.

And because Tandem hooks into Claude as an MCP server, you're not stuck in some stripped-down document-editing silo. It's the full Claude — with all its knowledge, your conversation context, and every tool it has access to — just now it can also see and edit your document.

Why Tandem?

• No more copy-paste ping-pong. Select text in the editor, and Claude reads your selection directly. Ask "what do you think of this?" or "make this more concise" — Claude knows exactly which text you mean.
• Your full LLM, not a toy editor. Tandem connects via MCP, so Claude keeps all its knowledge, all its tools, and your full conversation context. Need it to cross-reference your document against a codebase, a URL, or another file? It can — it's still Claude.
• Iterate in place. Claude can suggest rewrites, leave comments, flag issues, and edit text — all appearing as annotations you accept, dismiss, or tweak right in the document.

Quick Start

Option A: Desktop App

Download the installer for your platform from the latest release.

The desktop app bundles everything — no Node.js required. It auto-configures Claude Code on launch, manages the server as a background process, and updates itself automatically. Just install and open.

Option B: npm Global Install

Requires Node.js 22+ (download) and Claude Code (npm install -g @anthropic-ai/claude-code).

npm install -g tandem-editor
tandem setup     # registers MCP tools + installs Claude Code skill
tandem           # starts server + opens editor

tandem setup auto-detects Claude Code and Claude Desktop, writes MCP configuration, and installs a skill (~/.claude/skills/tandem/SKILL.md) that teaches Claude how to use Tandem's tools effectively. Re-run after upgrading (npm update -g tandem-editor && tandem setup).

Quickstart: Claude Code plugin (recommended)

Install the plugin to expose Tandem's tools and real-time event stream into Claude Desktop chats and Cowork VM sessions:

claude plugin marketplace add bloknayrb/tandem
claude plugin install tandem@tandem-editor

Tandem must be running on the host before the plugin can do anything. The plugin spawns two stdio MCP processes (tandem mcp-stdio and tandem channel) that proxy to http://localhost:3479. If the server isn't up they fail fast and log "Tandem server not reachable at …". Start the Tauri desktop app or run tandem start on the host first, then open Claude.

Legacy stdio channel shim

If you can't install the plugin, use the older channel shim:

tandem setup --with-channel-shim

This writes a tandem-channel entry to your Claude Code MCP config. Start Claude Code with:

claude --dangerously-load-development-channels server:tandem-channel

Don't combine this with the plugin — both subscribe to /api/events and you'll get duplicate notifications for every event.

Connect Claude Code

For the full Tandem experience, start Claude Code with the channel push flag:

Desktop app users: Claude Code is configured automatically on every launch — skip tandem setup and just start Claude Code. The tandem_* tools will be available immediately.

claude --dangerously-load-development-channels server:tandem-channel

This is the magic-sauce mode — and it's the one I'd recommend you run with. The channel shim pushes events (selections, annotations, chat) to Claude over SSE the moment they happen, so Tandem genuinely feels like there's another person on the other end of the document: someone watching what you highlight, reacting to edits you accept, and chiming in on a paragraph the instant you select it, the way a collaborator on a Google Doc would. The --dangerously-load-development-channels flag is an experimental Claude Code feature, which is why it isn't on by default — but turning it on is what makes the whole experience click.

Recommended layout: snap the Claude Code terminal to one side of your screen and the Tandem editor window to the other. You'll be flipping attention between them constantly, and having both visible is what makes the side-by-side-collaborator feeling land.

Then try:

"Open sample/welcome.md and review it with me"