Fix: Cursor MCP server not connecting

Cursor shows "MCP server not connected" even though the same server works in Claude Code. Frustrating. Fixable.

Symptoms

• Red indicator next to the MCP in Cursor settings
• "Failed to start server" in the developer console
• Works fine in Claude Code or terminal, but not Cursor

The fix (do these in order)

1. Check the config file location

Cursor reads MCP config from a different path than Claude Code:

• Claude Code: ~/.config/claude-code/mcp.json
• Cursor: ~/.cursor/mcp.json

Copying between them is the #1 cause.

2. Verify the command path is absolute

Cursor doesn't always inherit your shell's PATH. If your config says:

{
  "command": "npx"
}

Change it to the absolute path:

{
  "command": "/Users/YOU/.bun/bin/bunx"
}

Find the absolute path with which npx (or which bunx).

3. Restart Cursor completely

⌘Q, not close-window. Cursor caches MCP handles aggressively.

4. Check the developer console

Help → Toggle Developer Tools → Console. Filter for "mcp". Real errors show up here with a stack trace.

5. Node version mismatch

Some MCPs require Node 20+. Cursor may be running an older Node if you have multiple installed. Pin it in your config:

{
  "command": "/opt/homebrew/opt/node@20/bin/node",
  "args": ["/path/to/server/index.js"]
}

Still broken?

• Check the MCP's own GitHub issues — your version may have a known bug
• Try the server outside Cursor: npx @modelcontextprotocol/server-filesystem /tmp should print a startup message
• Join the Cursor Discord #mcp channel — the maintainers respond fast

TL;DR: Wrong config path, missing PATH, or stale Cursor state. Nine times out of ten it's one of those three.