Cray Browser

Browser automation MCP server for Claude Code. Control a real Chrome browser through 8 tools — navigate, click, type, scroll, and more.

Architecture

Claude Code <--stdio--> MCP Server (server.py)
                            |
                     Unix socket (bridge.py)
                            |
                     Native Host (native_host.py)
                            |
                   Chrome Native Messaging
                            |
                  Chrome Extension (service-worker.js)
                            |
                     Chrome DevTools Protocol
                            |
                        Web Page

Setup

1. Install the Chrome extension

1. Open chrome://extensions/
2. Enable Developer mode
3. Click Load unpacked and select the cray-extension/ folder
4. Copy the extension ID

2. Register the native messaging host

python3 install.py <extension-id>

3. Add to Claude Code

{
  "mcpServers": {
    "cray-browser": {
      "command": "python3",
      "args": ["/path/to/cray-browser/server.py"]
    }
  }
}

4. Connect

Click the Cray Browser extension icon in Chrome to establish the connection.

Tools

Tool	Description
browser_navigate(url)	Go to URL
browser_view()	Refresh page state
browser_click(index)	Click element by index
browser_input(index, text)	Type into input field
browser_scroll(direction, amount)	Scroll up/down
browser_press_key(key)	Press key or combo (e.g. Enter, Control+a)
browser_move_mouse(x, y)	Hover at coordinates
browser_find_keyword(keyword)	Find text on page

Every tool returns:

• Numbered interactive element list (click by index)
• Clean screenshot (for reading visual content)
• Annotated screenshot (numbered boxes on clickable elements)
• Page markdown (omitted when brief=true)

Tips

• Use brief=true when you don't need page text (faster)
• Element indices reset after every action — always use the latest list
• For charts/visuals, use the clean screenshot + browser_move_mouse for tooltip data
• HTML is truncated at 400KB to stay under Chrome's 1MB native messaging limit