PTY Debug Server

MCP server for debugging PTY/TTY/TUI programs. Enables Claude Code to spawn, interact with, and capture screen output from any terminal-based program.

Use Case: TUI Debugging

This MCP server allows Claude Code to control Claude Code itself, vim, top, and other TUI programs. This enables:

• Automated TUI testing
• Debugging terminal applications
• Screen scraping from interactive programs
• CI/CD integration for TUI apps

Demo: Claude Code controlling Claude Code

1. spawn_session({ command: "claude" })
2. send_input({ specialKey: "shift+tab" })  // cycle modes
3. send_input({ input: "what is 1+1?" })
4. send_input({ specialKey: "enter" })
5. get_snapshot()  // see Claude's response

Demo: Claude Code controlling vim

1. spawn_session({ command: "vim", args: ["test.txt"] })
2. send_input({ input: "i" })              // enter INSERT mode
3. send_input({ input: "Hello World!" })   // type text
4. send_input({ specialKey: "escape" })    // exit INSERT mode
5. send_input({ input: ":wq" })            // save command
6. send_input({ specialKey: "enter" })     // execute

Installation

Claude Code

claude mcp add pty-debug -- npx -y @so2liu/pty-mcp-server@latest

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "pty-debug": {
      "command": "npx",
      "args": ["-y", "@so2liu/pty-mcp-server@latest"]
    }
  }
}

VS Code / Copilot

Add to VS Code settings or .vscode/mcp.json:

{
  "mcpServers": {
    "pty-debug": {
      "command": "npx",
      "args": ["-y", "@so2liu/pty-mcp-server@latest"]
    }
  }
}

Cursor

Add to ~/.cursor/mcp.json:

{
  "mcpServers": {
    "pty-debug": {
      "command": "npx",
      "args": ["-y", "@so2liu/pty-mcp-server@latest"]
    }
  }
}

Cline

Add to Cline MCP settings:

{
  "mcpServers": {
    "pty-debug": {
      "command": "npx",
      "args": ["-y", "@so2liu/pty-mcp-server@latest"]
    }
  }
}

Gemini CLI

gemini mcp add pty-debug -- npx -y @so2liu/pty-mcp-server@latest

Codex CLI

codex mcp add pty-debug -- npx -y @so2liu/pty-mcp-server@latest

MCP Tools

Tool	Description
spawn_session	Start a TUI program in a PTY
send_input	Send text or special keys
get_snapshot	Capture current screen state
resize_terminal	Change terminal dimensions
list_sessions	List active sessions
close_session	Terminate a session

Special Keys

Supports all common shortcuts:

• Basic: enter, tab, shift+tab, escape, backspace, delete
• Arrows: up, down, left, right
• With modifiers: shift+up, ctrl+right, alt+left, etc.
• Control: ctrl+a to ctrl+z
• Alt: alt+a to alt+z
• Function: f1 to f12
• Navigation: home, end, pageup, pagedown

Screen Snapshot Format

-------------------------------------------------------------------------------------
 1 |Processes: 643 total, 3 running, 640 sleeping                          17:57:23 |
 2 |Load Avg: 2.38, 2.75, 2.88  CPU usage: 13.13% user, 4.49% sys                    |
 3 |...                                                                              |
-------------------------------------------------------------------------------------

Development

# Install dependencies
bun install

# Development mode
bun run dev

# Build
bun run build

# Lint
bun run lint

Tech Stack

• Node.js (runtime)
• TypeScript
• node-pty (PTY spawning)
• @xterm/headless (terminal emulation)
• @modelcontextprotocol/sdk (MCP server)

Publishing

Releases are automatically published to npm via GitHub Actions.

Setup (one-time)

1. Create npm granular token at https://www.npmjs.com/settings/tokens/granular-access-tokens/new

   • Expiration: 90 days
   • Packages: @so2liu/pty-mcp-server
   • Permissions: Read and write

2. Add NPM_TOKEN secret at https://github.com/so2liu/pty-mcp/settings/secrets/actions

3. Set calendar reminder to rotate token every 90 days

Release new version

1. Update version in package.json
2. Create a GitHub release with tag (e.g., v1.0.1)
3. GitHub Actions will automatically publish to npm

License

MIT