Jonathan Gastón Löwenstern

Posted on May 7 • Edited on May 13

MCP filesystem: Server disconnected

#mcp #ai #howtofix #howto

If you’re excited about using your Claude Desktop app with the new Model Context Protocol (MCP) but keep running into frustrating configuration errors, you’re not alone. This is especially common if you’re a Node Version Manager (nvm) user.

The Problem

You followed the “Quickstart guide: For Claude Desktop User,” carefully copied the JSON configuration into your own claude_desktop_config.json file, but it keeps failing repeatedly.

You’ll likely see this specific error alert: “MCP filesystem: Server disconnected”

After some investigation, I discovered the root cause from a comment in the project’s GitHub repository (see Sources section below):

The MCP Server Commands environment cannot directly access Node.js executables installed via nvm unless they are properly configured.

The Solution: Create a Wrapper Script

This elegant solution creates a wrapper script that ensures the correct Node.js environment is used:

Step 1: Find your Node.js path

First, determine your nvm-installed Node.js path:

which node

This will return something like: /Users/username/.nvm/versions/node/v16.x.x/bin/node

Step 2: Create a wrapper script

Create a new file at /usr/local/bin/npx-for-claude with the following content:

##!/usr/bin/env bash  

export PATH="/Users/YOUR-USERNAME/.nvm/versions/node/YOUR-NODE-VERSION/bin:$PATH"  
exec npx "$@"

Make sure to replace:

YOUR-USERNAME with your actual username
YOUR-NODE-VERSION with your actual Node.js version (e.g., v16.20.0)

Step 3: Make the wrapper script executable

chmod +x /usr/local/bin/npx-for-claude

Step 4: Configure Claude Desktop

Edit your claude_desktop_config.json file to use the wrapper script:

{  
    "mcpServers": {  
        "filesystem": {  
            "command": "npx-for-claude",  
            "args": [  
                "-y",  
                "@modelcontextprotocol/server-filesystem",  
                "/Users/username/path/to/allowed/directory"  
            ]  
        }  
    }  
}

Final Step

Restart your Claude Desktop app, and it should start working with the new configuration!

Why This Works

This solution works because:

The wrapper script sets up the correct PATH environment that includes your nvm-installed Node.js binaries
It then executes the npx command with all the arguments passed to it

The wrapper script essentially bridges the gap between Claude Desktop’s execution environment and your nvm setup, allowing you to use the standard configuration pattern recommended in the documentation.

Source

This solution was inspired by some comments in the ModelContextProtocol GitHub repository: Issue #64

I have also added this solution as a comment on this GitHub issue: comment

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