Cursor IDE's MCP server name caching Issue - always Red status

[Sergej]

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Cursor IDE MCP Server Name Caching Issue - always show red status

Quick Summary

Cursor IDE caches MCP server names after failed connections, causing servers to permanently show red status even after fixing issues.

Workaround: Use completely fresh server names.

The Problem

When developing MCP servers, if your server shows red status during debugging (due to bugs, missing deps, etc.), Cursor caches that server name as “tainted.” Even after completely fixing your server code, it will stay red forever with that name.

I tested it in my repository: GitHub - speakASAP/task-management: A multi-node distributed todo application built with the Model Context Protocol (MCP) that provides intelligent task management and prioritization using free AI analysis.

What I Discovered

• Server code works perfectly (tested via command line)
• Cursor shows red status with the original name
• Cursor shows green status with a fresh name
• This happens consistently across multiple test cases

Workaround

Simply rename your server to something Cursor has never seen:

Before (tainted):

{
  "mcpServers": {
    "my-mcp-server": { ... }
  }
}

After (fresh):

{
  "mcpServers": {
    "my-mcp-server-fresh": { ... }
  }
}

My Testing Process

I created 15+ test servers with different names and complexity levels:

• Simple servers (1-2 tools, zero deps)
• Complex servers (6 tools, Redis, AI)
• All work perfectly via command line
• Only fresh names show green in Cursor

Root Cause

Cursor appears to cache server names internally and mark them as “bad” after any red status period. This cache:

• Survives Cursor restarts
• Survives system reboots
• Survives config changes
• Only resolved by using new names

For Developers

If your MCP server is working via command line but showing red in Cursor:

1. Check your server name - is it one you’ve used before?
2. Try a completely fresh name - this usually fixes it
3. Test manually first - make sure your server actually works

Bug Report

I’ve created a detailed bug report for the Cursor team. This significantly impacts the MCP development experience and should be fixed.

Has anyone else experienced this issue? Would love to hear your experiences and any other workarounds you’ve found.

---

This was discovered while building a task management MCP server with 6 tools. The server works perfectly but required a fresh name to show green status in Cursor.

Steps to Reproduce

1. Create an MCP server with a specific name (e.g., my-mcp-server)
2. Introduce a bug in the server code (missing dependency, syntax error, etc.)
3. Configure in Cursor - server shows red status (expected)
4. Fix the bug completely - server code is now perfect
5. Restart Cursor - server still shows red status (unexpected)
6. Test server manually - server works perfectly via command line
7. Change server name to something completely new (e.g., my-mcp-server-v2)
8. Restart Cursor - server now shows green status

Expected Behavior

• Server status should reflect the current state of the server code
• Fixing server issues should result in green status
• Server names should not be permanently cached as “bad”

Operating System

MacOS

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.7.33
VSCode Version: 1.99.3
Commit: a84f941711ad680a635c8a3456002833186c4840
Date: 2025-10-03T03:28:06.574Z
Electron: 34.5.8
Chromium: 132.0.6834.210
Node.js: 20.19.1
V8: 13.2.152.41-electron.0
OS: Darwin x64 22.6.0

Does this stop you from using Cursor

No - Cursor works, but with this issue