Letterbox

io.github.dovahkiin-v/letterbox · v1.2.2

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

Source code Set it up

Connect Runs on your machine

Terminal

claude mcp add letterbox -e LETTERBOX_CHANNEL=<LETTERBOX_CHANNEL> -e LETTERBOX_SENDER=<LETTERBOX_SENDER> -e LETTERBOX_INSTANCE_ID=<LETTERBOX_INSTANCE_ID> -- uvx letterbox==1.2.2

claude_desktop_config.json

{
  "mcpServers": {
    "letterbox": {
      "command": "uvx",
      "args": [
        "letterbox==1.2.2"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "<LETTERBOX_CHANNEL>",
        "LETTERBOX_SENDER": "<LETTERBOX_SENDER>",
        "LETTERBOX_INSTANCE_ID": "<LETTERBOX_INSTANCE_ID>"
      }
    }
  }
}

~/.cursor/mcp.json

{
  "mcpServers": {
    "letterbox": {
      "command": "uvx",
      "args": [
        "letterbox==1.2.2"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "<LETTERBOX_CHANNEL>",
        "LETTERBOX_SENDER": "<LETTERBOX_SENDER>",
        "LETTERBOX_INSTANCE_ID": "<LETTERBOX_INSTANCE_ID>"
      }
    }
  }
}

.vscode/mcp.json

{
  "servers": {
    "letterbox": {
      "type": "stdio",
      "command": "uvx",
      "args": [
        "letterbox==1.2.2"
      ],
      "env": {
        "LETTERBOX_CHANNEL": "<LETTERBOX_CHANNEL>",
        "LETTERBOX_SENDER": "<LETTERBOX_SENDER>",
        "LETTERBOX_INSTANCE_ID": "<LETTERBOX_INSTANCE_ID>"
      }
    }
  }
}

Replace the values in angle brackets with your own. Keys stay on your machine; we never see them.

Tools

This server runs locally, so its tools are listed by your MCP client once it starts.

Environment variables

Name	Description
`LETTERBOX_CHANNEL` Required	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` Required	This endpoint's identity on the channel — the name the peer agent sees on every message.
`LETTERBOX_INSTANCE_ID` Required	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.

Details

Package	`[email protected]` (PYPI, stdio)
First published	24 Aug 2026
Last updated	24 Aug 2026
Registry name	`io.github.dovahkiin-v/letterbox`

More developer tools servers See all

Live status

Local install

Installed and run on your own machine, so there is no public endpoint to check.

Pair it with live search

Agents that use Letterbox often also need current facts. NestDaddy MCP gives your AI today's internet: web search, real-time breaking news and full page reading in one connector.

See NestDaddy MCP

For maintainers

[![NestDaddy MCP](https://nestdaddy.com/mcp/servers/io-github-dovahkiin-v-letterbox/badge.svg)](https://nestdaddy.com/mcp/servers/io-github-dovahkiin-v-letterbox)

Add the badge to your README. It turns green while your server passes our daily check. Listing details come from the official MCP registry; update them there.

Listing data from the official MCP registry. Status and tools from NestDaddy's daily check. Browse all MCP servers.