todiagram-mcp-windows-fix

Windows-compatible fork of @todiagram/todiagram-mcp that fixes ERR_UNSUPPORTED_ESM_URL_SCHEME on Node.js v22+ and v25+ on Windows.

Connect ToDiagram to Cursor, Claude, Windsurf, and other AI assistants — now works on Windows!

⚠️ The Problem

The original @todiagram/todiagram-mcp crashes on Windows with:

Fatal error in main(): Error [ERR_UNSUPPORTED_ESM_URL_SCHEME]:
Only URLs with a scheme in: file, data, and node are supported by the default ESM loader.
On Windows, absolute paths must be valid file:// URLs. Received protocol 'c:'

Root cause: In dist/mcp-server.js, the lazyLoadUtil() function dynamically imports tool modules using path.join(), which on Windows produces paths like C:\Users\...\tools\file.js. The Node.js ESM loader requires file:// URLs, not bare Windows paths.

Related MCP server: fcp-drawio

✅ The Fix

A one-line change in dist/mcp-server.js:

- import { fileURLToPath } from "url";
+ import { fileURLToPath, pathToFileURL } from "url";

  // ... in lazyLoadUtil():
- await import(toolPath);
+ await import(pathToFileURL(toolPath).href);

pathToFileURL() converts C:\Users\...\file.js → file:///C:/Users/.../file.js, which the ESM loader accepts on all platforms.

📦 Install

npm install -g todiagram-mcp-windows-fix

🔧 MCP Configuration

Claude Code (.mcp.json)

{
  "mcpServers": {
    "todiagram": {
      "type": "stdio",
      "command": "todiagram",
      "env": {
        "TODIAGRAM_API_KEY": "your-api-key-here"
      }
    }
  }
}

Or via npx

{
  "mcpServers": {
    "todiagram": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "todiagram-mcp-windows-fix"],
      "env": {
        "TODIAGRAM_API_KEY": "your-api-key-here"
      }
    }
  }
}

API Key Setup

1. Go to ToDiagram Editor

2. Click the account icon at top right

3. Go to API Key section

4. Create a key with a descriptive name and expiry time

🐛 Upstream Issue

This fix should be applied to the original @todiagram/todiagram-mcp package. The upstream issue is in src/mcp-server.ts:

// Current (broken on Windows):
for (const toolPath of toolsPaths) {
    await import(toolPath);
}

// Fix:
import { pathToFileURL } from "url";
for (const toolPath of toolsPaths) {
    await import(pathToFileURL(toolPath).href);
}

Affected platforms: Windows with Node.js v22+ (any version using ESM loader with strict URL scheme validation)

Affected versions: @todiagram/todiagram-mcp v1.1.0 and likely earlier versions

✅ Platform Compatibility

📄 License

FSL-1.1-ALv2 (same as upstream)