Get Tandem
Free to download and runs on your machine. Pick your platform and open a file — you can be writing together in under a minute.
Latest release
Connect Claude
Three steps to a co-author
Tandem talks to Claude through MCP. If you've set up an MCP client before, this will feel familiar.
Open Tandem and a file
Drop in any Markdown, text, or HTML file — or start a fresh one.
Point it at Claude
In Settings, add your Claude endpoint under AI Assistant. The status pill turns green when the connection is live.
Highlight something
Select a line and ask. Claude's first note shows up in the margin, in coral.
Questions
Good to know
Is it really free?
Yes. The app is free to download and use on your own files. You bring your own Claude access through MCP.
Where do my files go?
Tandem is local-first: it reads and writes the files on your disk, with no Tandem account, no cloud, no telemetry. Your documents reach an AI only through the Claude you connect.
Do I need an account?
Not to start writing: the editor works on its own. Writing with Claude needs an AI client such as Claude Code, and whatever plan or account that client needs.
What can it open?
Markdown (.md, .markdown), plain text, and HTML files. HTML opens read-only, for reading and annotating. Word (.docx) files aren't supported in this version. To bring one in, save a copy from Word as plain text (.txt) to edit it, or as a web page (.html) to review it.
What does Solo do?
It keeps the comments and replies you write from reaching Claude until you switch back to Tandem, then hands them over all at once. Solo isn't an off switch: chat still works, and Claude can still read and edit the document.