Plugin MCP servers show errors when claude.ai has unconnected connectors with same URL

Description

When installing Slack and Linear as Claude Code plugins (via /plugin), the plugin errors tab shows 2 errors even though the plugins are fully functional (authenticated and working):

slack
  MCP server 'slack' skipped — same command/URL as already-configured 'claude.ai Slack'
  Remove 'claude.ai Slack' from your MCP config if you want the plugin's version instead

linear
  MCP server 'linear' skipped — same command/URL as already-configured 'claude.ai Linear'
  Remove 'claude.ai Linear' from your MCP config if you want the plugin's version instead

Steps to reproduce

1. Install slack and linear plugins via /plugin in Claude Code
2. Authenticate both plugins successfully
3. Go to /plugin → Errors tab — shows 2 errors

Expected behavior

No errors should appear, since:

• The claude.ai connectors for Slack and Linear are not connected (shown under "Not connected" in claude.ai Settings → Connectors)
• The plugins are installed, authenticated, and working correctly in Claude Code
• Disabling the connectors in /mcp does not resolve the issue — they reappear

Actual behavior

The plugin system detects a URL collision (mcp.slack.com/mcp, mcp.linear.app/mcp) with claude.ai's built-in connector definitions, even though those connectors are not connected/enabled. The errors are cosmetic — the plugins function correctly despite the warnings.

Environment

• Claude Code CLI (macOS)
• Plugins: slack@1.0.0, linear from claude-plugins-official marketplace