Bug: GOOGLE_REFRESH_TOKEN not passed to MCP server process

Bug: GOOGLE_REFRESH_TOKEN not passed to MCP server process

Summary

When configuring google-drive MCP server in claude_desktop_config.json, the GOOGLE_REFRESH_TOKEN environment variable is not being passed to the spawned MCP server process, while other environment variables (GOOGLE_CLIENT_ID, GOOGLE_CLIENT_SECRET, GOOGLE_REDIRECT_URI) are passed correctly.

Environment

• OS: macOS 26.2 (Build 25C56)
• Claude Desktop: Latest version
• MCP Server: mcp-google-drive@1.6.2
• Install location: /opt/homebrew/bin/mcp-google-drive

Configuration

claude_desktop_config.json:

{
  "mcpServers": {
    "google-drive": {
      "command": "/opt/homebrew/bin/mcp-google-drive",
      "env": {
        "GOOGLE_CLIENT_ID": "xxxxxxxxxxxx-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.apps.googleusercontent.com",
        "GOOGLE_CLIENT_SECRET": "GOCSPX-xxxxxxxxxxxxxxxxxxxxxxxx",
        "GOOGLE_REFRESH_TOKEN": "1//xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
        "GOOGLE_REDIRECT_URI": "http://localhost"
      }
    }
  }
}

Observed Behavior

When checking the environment variables of the running mcp-google-drive process:

$ ps eww <PID> | tr ' ' '\n' | grep "GOOGLE"
GOOGLE_CLIENT_ID=xxxxxxxxxxxx-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.apps.googleusercontent.com
GOOGLE_CLIENT_SECRET=GOCSPX-xxxxxxxxxxxxxxxxxxxxxxxx
GOOGLE_REDIRECT_URI=http://localhost

Note: GOOGLE_REFRESH_TOKEN is missing from the process environment variables!

Expected Behavior

All environment variables defined in the env section of the config should be passed to the spawned MCP server process, including GOOGLE_REFRESH_TOKEN.

Impact

Without the refresh token, the MCP server cannot authenticate with Google Drive API and fails with:

MCP error -32603: Authentication not ready after 3 seconds

MCP server logs show:

[ERROR] MCP-Google-Drive: Failed to initialize Google Drive API: Error: No authentication credentials provided
[ERROR] MCP-Google-Drive: Authentication failed after 3 attempts

Steps to Reproduce

1. Configure google-drive MCP server in claude_desktop_config.json with all required environment variables including GOOGLE_REFRESH_TOKEN
2. Restart Claude Desktop
3. Start a new conversation session
4. Attempt to use any Google Drive MCP tool
5. Check the environment variables of the spawned mcp-google-drive process using: ps eww <PID> | tr ' ' '\n' | grep "GOOGLE"

Additional Notes

• JSON configuration is valid (verified with python3 -m json.tool)
• The refresh token is present in the config file
• Restarting Claude Desktop does not resolve the issue
• Killing and restarting the MCP process does not help
• Other MCP servers (MS365, Notion) work correctly in the same configuration

Workaround Attempted

• Fully restarted Claude Desktop (Cmd+Q and relaunch)
• Killed all mcp-google-drive processes to force respawn
• Validated JSON configuration format
• No workaround found

Possible Cause

This appears to be a bug in how Claude Desktop passes environment variables to MCP server processes. Specifically, GOOGLE_REFRESH_TOKEN is being filtered out or not transmitted, while other variables are passed correctly.