[BUG] Filesystem MCP extension crashes on Windows — built-in Node.js incompatibility

Bug Description

The built-in Filesystem MCP extension consistently crashes on Windows when launched via Claude Desktop's built-in Node.js. The server starts, receives the initialize message, then silently exits ~1-4 seconds later with no error output on stderr.

Environment

• Claude Desktop version: 1.1.3963
• OS: Windows 11 Pro 10.0.26200
• System Node.js: v22.19.0

Steps to Reproduce

1. Install the Filesystem extension via Claude Desktop UI (Developer / Chat Connector)
2. Add any valid directory
3. Restart Claude Desktop
4. Observe "MCP server could not be attached" error

Log Output (from %APPDATA%\Claude\logs\mcp-server-Filesystem.log)

[Filesystem] [info] Using built-in Node.js for MCP server: Filesystem
[Filesystem] [info] Server started and connected successfully
[Filesystem] [info] Message from client: {"method":"initialize",...}
[Filesystem] [info] Server transport closed unexpectedly, this is likely due to the process exiting early.
[Filesystem] [error] Server disconnected.

No stderr output — the process exits silently.

Workaround

Installing @modelcontextprotocol/server-filesystem globally and configuring it in claude_desktop_config.json with "command": "node" (using the system Node.js instead of the built-in one) works correctly. The server name must NOT be "filesystem" as Claude Desktop ignores config entries with that name.

"local-fs": {
  "command": "node",
  "args": [
    "C:\Users\<user>\AppData\Roaming\npm\node_modules\@modelcontextprotocol\server-filesystem\dist\index.js",
    "C:\path\to\allowed\directory"
  ]
}

Key Observations

• The same server works perfectly when run with system Node.js (v22.19.0)
• Claude Desktop's built-in Node.js causes the crash — no other changes needed to reproduce
• Naming a config entry "filesystem" causes Claude Desktop to silently ignore it and use the built-in version anyway
• Tested multiple times with clean installs/uninstalls of the extension