MCP Server OAuth flow fails for all scope requests on GitLab.com

Summary

The GitLab MCP server at https://gitlab.com/api/v4/mcp cannot complete OAuth authentication on GitLab.com. Any scope requested results in: "The requested scope is invalid, unknown, or malformed."

Steps to reproduce

1. Add GitLab as a custom MCP connector in Claude (claude.ai)
2. Enter MCP server URL: https://gitlab.com/api/v4/mcp
3. Initiate the OAuth flow
4. Observe the error on the GitLab authorization page

Testing performed

Scopes requested	Result
All scopes from original URL (see below)	❌ "scope is invalid, unknown, or malformed"
Only documented scopes (removed mcp, self_rotate, ai_workflows, user:*)	❌ Same error
Only api	❌ Same error
No scope parameter	✅ Authorization prompt appears

This suggests the MCP OAuth application may not have any scopes configured/enabled on GitLab.com.

Original scope parameter from authorization URL

scope=api+read_api+read_user+create_runner+manage_runner+k8s_proxy+self_rotate+mcp+read_repository+write_repository+read_registry+write_registry+read_virtual_registry+write_virtual_registry+read_observability+write_observability+ai_features+sudo+admin_mode+read_service_ping+openid+profile+email+ai_workflows+user%3A%2A

Note: Some of these scopes (mcp, self_rotate, ai_workflows, user:*) do not appear in GitLab's OAuth documentation, but even standard scopes like api fail.

Expected behavior

The MCP OAuth application should be able to request standard GitLab OAuth scopes (at minimum api) without errors.

Environment

• GitLab.com (SaaS)
• MCP endpoint: https://gitlab.com/api/v4/mcp

/label typebug MCP