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CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Overview

MCP server providing direct USB control of Elgato Stream Deck devices. Bypasses Elgato software entirely using python-elgato-streamdeck.

Development Commands

# Setup
uv venv && uv pip install -e ".[dev]"

# Run server (for Claude Desktop)
uv run server.py

# Lint
uv run ruff check .
uv run ruff check --fix .

# Format
uv run ruff format .

# Run tests (no hardware required)
uv run pytest tests/ -v

# Test without deck (fails gracefully if no hardware)
python -c "from server import state; print(state.get_deck_info())"

Claude Desktop Config

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "streamdeck": {
      "command": "uv",
      "args": ["--directory", "/path/to/streamdeck-mcp", "run", "server.py"]
    }
  }
}

Architecture

Single-file server (server.py) using MCP's Server class with stdio transport.

server.py
├── StreamDeckState      # Connection, pages, buttons, callbacks
│   ├── connect()        # Find and open first USB deck
│   ├── set_button_*()   # Image/action configuration
│   ├── *_page()         # Page CRUD and switching
│   └── _key_callback()  # Physical button press handler
├── @server.list_tools() # Tool definitions
└── @server.call_tool()  # Tool handlers

State persistence: ~/.streamdeck-mcp/pages.json (appearance) and buttons.json (actions).

Key Concepts

  • Button indexing: 0-based, left-to-right, top-to-bottom. 5x3 deck = keys 0-14.
Stream Deck Original (15 keys):
┌────┬────┬────┬────┬────┐
│  0 │  1 │  2 │  3 │  4 │
├────┼────┼────┼────┼────┤
│  5 │  6 │  7 │  8 │  9 │
├────┼────┼────┼────┼────┤
│ 10 │ 11 │ 12 │ 13 │ 14 │
└────┴────┴────┴────┴────┘
  • Pages: Named profiles. "main" is default and undeletable.
  • Actions: page:name for page switching, or shell commands (requires running server).
  • Image generation: Pillow renders button images. Accepts an MDI icon name (e.g. mdi:cpu-64-bit — ~7400 glyphs bundled in streamdeck_assets/) or freeform text, plus icon_color / bg_color. icon and text are mutually exclusive; use the button's title field on streamdeck_write_page for labels so they don't collide with Elgato's title overlay.

USB Permissions

  • macOS: brew install hidapi (usually works)
  • Linux: Needs udev rule — see README
  • Windows: May need Zadig driver

Troubleshooting

  1. "No Stream Deck found" — Check USB, permissions, hidapi installed
  2. Button images blank — Pillow not installed or font not found
  3. State not persisting — Check write permissions on ~/.streamdeck-mcp/