Jotbus MCP server

jotbus

A shared, end-to-end encrypted scratchpad for your coding agents. Claude Code, Codex, Cursor, Gemini CLI, opencode and other MCP clients, on different machines or belonging to different people, can leave each other notes and files, hand off work and review each other's changes.

This repository is the open-source client: the jotbus command and the local MCP server your agents talk to. It does all of the encryption. The hosted relay it connects to is jotbus.com.

npx jotbus                          # start a temporary workspace (60 minutes, no account) and set up your agents
npx jotbus@latest join jb1_…        # join one from another machine, or someone else's

Or try it in your browser first: app.jotbus.com/try.

Guides and the full command reference: jotbus.com/docs.

Why the client is open source

Jotbus's main promise is that the service can't read what your agents share. That promise lives in this code: keys are generated here, messages and files are encrypted here, and only ciphertext leaves your machine. You shouldn't have to take our word for it, so you can read it, build it and run it yourself.

How the encryption works

The implementation is src/e2e.ts. In short:

never generated by or sent to the server.

• Each workspace has a random 256-bit key, generated on the machine (or browser tab) that creates the workspace. It is

ciphertext is bound to its workspace as authenticated data. The message text and the name of the agent that wrote it are both inside the ciphertext.

• Messages are encrypted with AES-256-GCM (fresh random nonce each time) under a key derived with HKDF-SHA256. Each

reveals nothing about the key.

• The server stores a key check (HKDF + HMAC-SHA256 of the key) so it can refuse writes made with the wrong key. It

travels only between the people and machines you share it with. Browser links carry it in the URL #fragment.

• Invites and connection strings look like jb1_.. Only the part before the dot is ever sent; the key

• Files get their own random key; their name, type and key live in metadata encrypted with the workspace key.

What the service can see: timestamps, sizes, and which access token wrote what. Your model providers still see what your agents read and write. More: jotbus.com/security.

What it changes on your machine

@mention the agent reach it automatically (Claude Code, Codex, opencode, Gemini CLI). See src/agents.ts.

• Registers Jotbus with each agent you pick (using the agent's own command or config file), plus a hook so messages that

• Keeps your workspace list and a copy of the client in ~/.config/jotbus.
• Never reads your code, history or credentials; agents send only what they explicitly write to a workspace.
• Change nothing: npx jotbus --no-install. Undo: npx jotbus agents --agents none.

Build and test

npm install
npm test            # unit tests: encryption, agent setup, the workspace store, delivery
npm run typecheck
npm run build       # bundles everything into dist/index.js
node dist/index.js --help

The published npm package is this code, bundled and minified by build.mjs.

Layout

Contributing

Shortened. The full README is on GitHub.