Letterbox MCP Server

by dovahkiin-vio.github.dovahkiin-v/letterboxv1.2.2

File-based comms protocol for AI-to-AI dialogue between terminal agents.

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Maintained45d ago

Install Letterbox MCP server

claude mcp add letterbox -e LETTERBOX_CHANNEL='<letterbox-channel>' -e LETTERBOX_SENDER='<letterbox-sender>' -e LETTERBOX_INSTANCE_ID='<letterbox-instance-id>' -- uvx letterbox

{
  "mcpServers": {
    "letterbox": {
      "command": "uvx",
      "args": [
        "letterbox"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "<letterbox-channel>",
        "LETTERBOX_SENDER": "<letterbox-sender>",
        "LETTERBOX_INSTANCE_ID": "<letterbox-instance-id>"
      }
    }
  }
}

Add to ~/.cursor/mcp.json (global) or .cursor/mcp.json (project).

{
  "mcpServers": {
    "letterbox": {
      "command": "uvx",
      "args": [
        "letterbox"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "<letterbox-channel>",
        "LETTERBOX_SENDER": "<letterbox-sender>",
        "LETTERBOX_INSTANCE_ID": "<letterbox-instance-id>"
      }
    }
  }
}

Settings → Developer → Edit Config (claude_desktop_config.json), then restart.

{
  "servers": {
    "letterbox": {
      "type": "stdio",
      "command": "uvx",
      "args": [
        "letterbox"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "<letterbox-channel>",
        "LETTERBOX_SENDER": "<letterbox-sender>",
        "LETTERBOX_INSTANCE_ID": "<letterbox-instance-id>"
      }
    }
  }
}

Add to .vscode/mcp.json in your workspace.

{
  "mcpServers": {
    "letterbox": {
      "command": "uvx",
      "args": [
        "letterbox"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "<letterbox-channel>",
        "LETTERBOX_SENDER": "<letterbox-sender>",
        "LETTERBOX_INSTANCE_ID": "<letterbox-instance-id>"
      }
    }
  }
}

Add to ~/.codeium/windsurf/mcp_config.json.

Configuration

Variable	Required	Secret	Description
LETTERBOX_CHANNEL	yes	—	Channel name to open. Normally set by the letterbox PTY-parent when it spawns this server; set it manually only when running the MCP server standalone.
LETTERBOX_SENDER	yes	—	This endpoint's identity on the channel — the name the peer agent sees on every message.
LETTERBOX_INSTANCE_ID	yes	—	Per-launch instance id, the watcher/own-write join key that stops an agent seeing its own messages as incoming. Must be unique per launch.

Freshness

Maintained — last maintenance signal 45d ago. The newest of the signals below sets the band.

Last commit (default branch)
2026-08-25 · 45d ago · GitHub
Latest release
2026-07-02 · 3mo ago · GitHub · v1.2.0
Package published
no data · npm/PyPI
Registry entry updated
2026-08-24 · 46d ago · official registry · v1.2.2

FAQ

›How do I install the Letterbox MCP server in Claude Code?

Run: claude mcp add letterbox -e LETTERBOX_CHANNEL='<letterbox-channel>' -e LETTERBOX_SENDER='<letterbox-sender>' -e LETTERBOX_INSTANCE_ID='<letterbox-instance-id>' -- uvx letterbox. For Cursor, VS Code, Claude Desktop and Windsurf, use the install tabs above.

›Does Letterbox require an API key?

Yes. It expects LETTERBOX_CHANNEL, LETTERBOX_SENDER, LETTERBOX_INSTANCE_ID.

›Can I use Letterbox as a remote (hosted) MCP server?

No hosted endpoint is published; it runs locally over stdio.

›Is Letterbox in the official MCP registry?

Yes, as io.github.dovahkiin-v/letterbox.