The Problem

When setting up Playwright MCP server in Claude Desktop on macOS with Bun, you might encounter these errors:

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ReferenceError: performance is not defined
ERROR: npm v10.9.0 is known not to run on Node.js v14.19.2
SyntaxError: Unexpected token '&&='

This happens because Playwright requires Node.js APIs that aren’t available in Bun’s runtime environment.

Root Cause

The issue occurs when:

1. Using bunx to run Node.js-based MCP servers like Playwright
2. npx finds the wrong Node.js version in PATH (e.g., v14 instead of v22)
3. Modern npm/Node.js features conflict with older Node.js versions

Solution

Instead of using bunx, configure Claude to use Node.js directly with explicit PATH control:

Step 1: Update Claude MCP Configuration

Edit your claude_desktop_config.json:

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{
  "mcpServers": {
    "playwright": {
      "command": "/Users/username/.nvm/versions/node/v22.11.0/bin/npx",
      "args": ["@playwright/mcp@latest"],
      "env": {
        "PATH": "/Users/username/.nvm/versions/node/v22.11.0/bin:/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin"
      }
    },
    "brave-search": {
      "command": "/Users/username/.nvm/versions/node/v22.11.0/bin/npx", 
      "args": ["-y", "@modelcontextprotocol/server-brave-search"],
      "env": {
        "BRAVE_API_KEY": "your-api-key",
        "PATH": "/Users/username/.nvm/versions/node/v22.11.0/bin:/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin"
      }
    }
  }
}

Step 2: Key Changes Explained

• Direct Node.js path: Use full path to Node.js v22 npx
• Explicit PATH: Ensure Node.js v22 comes first in PATH environment
• Remove bunx: Don’t use Bun for Node.js-specific packages

Step 3: Verify Node.js Version

Check your Node.js installation:

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/Users/username/.nvm/versions/node/v22.11.0/bin/node --version
# Should output: v22.11.0

Why This Works

1. Compatibility: Node.js packages run in their native environment
2. PATH priority: Node.js v22 takes precedence over older versions
3. Environment isolation: Each MCP server gets its own environment

Alternative: Use Extensions

For simpler setup, consider using Claude Desktop extensions instead of manual MCP configuration. Extensions handle Node.js version management automatically.

Conclusion

When mixing Bun and Node.js in Claude MCP servers, use the right tool for each job. Keep Bun for Bun-compatible packages and use Node.js directly for Node.js-specific packages like Playwright.

This approach ensures reliable MCP server functionality without runtime conflicts.