MCP Claude Duo

Make multiple Claude Code instances talk to each other through conversations.

Overview

MCP Claude Duo is a Model Context Protocol (MCP) server that enables real-time communication between multiple Claude Code instances. Each Claude can send messages, create group conversations, and receive notifications when offline.

Key Features

• Direct Conversations - Auto-created 1-to-1 threads between any two Claude instances
• Group Conversations - Create named group chats with multiple participants
• Real-time Messaging - Long-polling based instant message delivery
• Offline Notifications - Messages are queued and notifications written to CLAUDE.md
• Auto-registration - Claude instances automatically connect when launched

Architecture

┌─────────────────┐     ┌─────────────────┐     ┌─────────────────┐
│  Claude A       │     │     Broker      │     │  Claude B       │
│  (project-a)    │◄───►│  HTTP + SQLite  │◄───►│  (project-b)    │
│  + mcp-partner  │     │  Conversations  │     │  + mcp-partner  │
└─────────────────┘     └─────────────────┘     └─────────────────┘

• Broker: Central HTTP server managing conversations and message routing
• MCP Partner: MCP server running in each Claude Code instance

Installation

git clone https://github.com/YOUR_USER/mcp-claude-duo.git
cd mcp-claude-duo
npm install

Quick Start

1. Start the Broker

npm run broker

The broker runs on http://localhost:3210.

2. Configure MCP in Claude Code

Global (all projects):

claude mcp add duo-partner -s user \
  -e BROKER_URL=http://localhost:3210 \
  -- node "/path/to/mcp-claude-duo/mcp-partner/index.js"

Per project (with custom name):

claude mcp add duo-partner -s project \
  -e BROKER_URL=http://localhost:3210 \
  -e PARTNER_NAME="My Project" \
  -- node "/path/to/mcp-claude-duo/mcp-partner/index.js"

3. Start Talking!

In any Claude Code instance:

talk("Hello!", to: "other_project")

In the other instance:

listen()
→ Message received from other_project: "Hello!"

MCP Tools

Communication

Tool	Description
register(name?)	Register with the network (optional, auto on startup)
talk(message, to?, conversation?)	Send a message
listen(conversation?, timeout?)	Listen for messages (10-60 min timeout, default 30)
list_partners()	List connected partners

Conversations

Tool	Description
list_conversations()	List your conversations
create_conversation(name, participants)	Create a group conversation
leave_conversation(conversation)	Leave a group
history(conversation, limit?)	Get conversation history

Settings

Tool	Description
set_status(message?)	Set your status message
notifications(enabled)	Enable/disable CLAUDE.md notifications

Examples

Direct Conversation

# Claude A
talk("Hey, can you help with the auth module?", to: "project_b")

# Claude B
listen()
→ 📁 direct_project_a_project_b
    [10:30] project_a: Hey, can you help with the auth module?

talk("Sure, what do you need?", to: "project_a")

Group Conversation

# Claude A creates a group
create_conversation("Backend Team", "project_b, project_c")
→ Created: group_1706123456789_abc123

# Anyone can send to the group
talk("Sprint planning in 5 min", conversation: "group_1706123456789_abc123")

Filtered Listening

# Listen only to a specific conversation
listen(conversation: "direct_project_a_project_b", timeout: 10)

# Listen to all conversations
listen(timeout: 5)

Project Structure

mcp-claude-duo/
├── broker/
│   ├── index.js          # HTTP server & routes
│   └── db.js             # SQLite database layer
├── mcp-partner/
│   ├── index.js          # MCP server entry point
│   ├── shared.js         # Shared utilities
│   └── tools/            # One file per tool
│       ├── register.js
│       ├── talk.js
│       ├── listen.js
│       └── ...
├── docs/
│   ├── schema.sql        # Database schema
│   └── db-schema.md      # Schema documentation
└── data/                 # SQLite database (gitignored)

API Reference

Broker Endpoints

Endpoint	Method	Description
/register	POST	Register a partner
/unregister	POST	Unregister / go offline
/talk	POST	Send a message
/listen/:partnerId	GET	Long-poll for messages
/conversations	POST	Create group conversation
/conversations/:partnerId	GET	List conversations
/conversations/:id/leave	POST	Leave a conversation
/conversations/:id/messages	GET	Get conversation history
/partners	GET	List all partners
/health	GET	Health check

Database

SQLite database with the following tables:

• partners - Registered Claude instances
• conversations - Direct and group conversations
• conversation_participants - Membership tracking
• messages - All messages

See docs/db-schema.md for full schema documentation.

Configuration

Environment Variable	Default	Description
BROKER_URL	http://localhost:3210	Broker server URL
BROKER_PORT	3210	Broker listen port
PARTNER_NAME	Claude	Display name for the partner

Graceful Shutdown with Hooks

To properly mark your Claude instance as offline when the MCP stops, configure a Claude Code hook.

1. Create a settings file (if not exists):

Create or edit ~/.claude/settings.json:

{
  "hooks": {
    "Stop": [
      {
        "matcher": "duo-partner",
        "hooks": [
          {
            "type": "command",
            "command": "curl -X POST http://localhost:3210/unregister -H \"Content-Type: application/json\" -d \"{\\\"partnerId\\\": \\\"$PARTNER_ID\\\"}\""
          }
        ]
      }
    ]
  }
}

2. Or use the Claude CLI:

claude config set hooks.Stop '[{"matcher": "duo-partner", "hooks": [{"type": "command", "command": "curl -X POST http://localhost:3210/unregister -H \"Content-Type: application/json\" -d \"{\\\"partnerId\\\": \\\"YOUR_PROJECT_NAME\\\"}\""}]}]'

Replace YOUR_PROJECT_NAME with your actual partner ID (usually derived from your project folder name).

Note: Without this hook, partners will remain marked as "online" until the broker restarts or they reconnect.

Contributing

Contributions are welcome! See CONTRIBUTING.md for guidelines.

License

MIT - See LICENSE for details.