MCP Proxy Sidecar

What is MCP Proxy Sidecar?

MCP Proxy Sidecar is a fork of the JetBrains MCP Server that adds WebSocket monitoring capabilities. It acts as a proxy between MCP clients (like Claude Desktop) and JetBrains IDEs, broadcasting all tool calls via WebSocket for real-time observability.

How to use MCP Proxy Sidecar?

Install the JetBrains MCP Server plugin, then configure your MCP client (e.g., Claude Desktop) to run npx -y mcp-proxy-sidecar with optional environment variables such as WS_PORT. The sidecar automatically scans ports 63342–63352 to find the IDE.

Key features of MCP Proxy Sidecar

• Real-time WebSocket notifications for all MCP tool calls
• Configurable WebSocket port via WS_PORT environment variable
• Automatic port scanning for IDE connection (63342–63352)
• Debug logging toggle via LOG_ENABLED environment variable
• Fork maintains full compatibility with the original JetBrains implementation

Use cases of MCP Proxy Sidecar

• Monitor all MCP tool calls from a JetBrains IDE in real time
• Debug and inspect arguments and timestamps of IDE operations
• Integrate with external monitoring dashboards via WebSocket

FAQ from MCP Proxy Sidecar

What is the difference between MCP Proxy Sidecar and the original JetBrains MCP Server?

MCP Proxy Sidecar is a fork that adds WebSocket notifications for monitoring tool calls. It retains all original features while broadcasting call details in real time.

How do I configure the WebSocket port?

Set the WS_PORT environment variable to your desired port (default: 27042) in your MCP client configuration (e.g., claude_desktop_config.json).

What are the runtime dependencies?

Node.js 20.x and pnpm (latest) are required for development. For usage, only Node.js is needed (via npx).

Where does the tool call data live?

Data is broadcast locally via WebSocket on 127.0.0.1; no external service is involved.

What transport does MCP Proxy Sidecar use?

MCP communication uses stdio, and monitoring is provided over WebSocket (default port 27042).