devserver

DevServer MCP provides real-time error notifications from your development server directly into Claude Code via Server-Sent Events (SSE). It monitors the logs produced by your dev server, parses and categorizes errors by type and severity (e.g., TypeScript compilation errors, Svelte warnings, Vite build failures, network/API errors, runtime JavaScript errors, and accessibility issues), and streams structured error data to connected Claude Code instances. Multiple Claude Code clients can connect simultaneously, each receiving timely alerts and a history of recent errors to facilitate quick triage and fixes. Connect to the MCP using Claude Code’s integration command, typically by pointing to the SSE endpoint (for example http://127.0.0.1:9338/sse) and ensuring the dev server port remains stable across restarts. The tooling also exposes commands to retrieve current server health, error summaries, histories, and file-specific error lists, enabling a comprehensive debugging workflow without scanning raw logs.

Prerequisites:

• Node.js installed (recommended recent LTS)
• pnpm installed (for installation and build steps)
• Access to your project repository with standard dev scripts

Step-by-step install and run:

1. Install dependencies and build the MCP server package:

pnpm install
pnpm build

2. Start the MCP server in monitor mode (default port 9338):

node dist/server.js --monitor pnpm run dev

3. Connect Claude Code to the MCP server via SSE:

claude mcp add --transport sse devserver-mcp http://127.0.0.1:9338/sse

4. If you need a different port per project, start the server on that port and connect with the corresponding URL, e.g.:

node dist/server.js --port 9339 --monitor pnpm run dev
claude mcp add --transport sse devserver-mcp http://127.0.0.1:9339/sse

Tips and notes:

• The MCP defaults to port 9338; you can customize per project using the --port flag.
• Ensure the Claude Code client connects to the same port as the server’s SSE endpoint to avoid disconnections.
• If you encounter port conflicts, choose an unused port and re-connect Claude Code to the new SSE URL.
• The configuration file (devserver-mcp.config.json) supports patterns, history limits, correlation windows, and path filters to tailor error collection to your project.
• For multiple projects, run each project on a distinct port and add separate Claude Code connections with unique client names.
• If real-time notifications stop, verify MCP connection status and the server process with ps/traffic checks, then restart the monitor command and re-establish the SSE connection.