[BUG] BigQuery MCP connector on claude.ai/code fails with redirect_uri_mismatch for Google Workspace accounts

Bug Description

When attempting to connect the BigQuery MCP connector via the Claude Code Web UI (claude.ai/code), Google OAuth returns a redirect_uri_mismatch error (HTTP 400). The OAuth flow never completes.

Environment

• Platform: Claude Code on the Web (claude.ai/code)
• Connection method: UI Connector (Settings → Connectors → BigQuery)
• Google account type: Google Workspace (organizational account)

Steps to Reproduce

1. Open claude.ai/code
2. Navigate to Connectors settings
3. Select BigQuery MCP connector
4. Click "Connect" to initiate OAuth flow
5. Google login page appears → select Google Workspace account
6. Error page shown: "Access blocked: This app's request is invalid"
7. Error: 400: redirect_uri_mismatch

Expected Behavior

OAuth flow should complete successfully and the BigQuery MCP connector should be authenticated.

Actual Behavior

Google OAuth rejects the request with redirect_uri_mismatch, indicating the redirect URI in the OAuth request does not match any URI registered in the OAuth client configuration.

Notes

• This occurs on the Web UI (claude.ai/code), not CLI or Desktop
• The redirect_uri_mismatch issues reported in #29934, #37747, #10439 are about CLI/Desktop and involve localhost port/protocol problems. This is a different issue since the Web UI would use a server-side callback URL (e.g., https://claude.ai/api/mcp/auth_callback)
• Google Workspace admin has reviewed third-party app settings but could not identify which app to approve (the OAuth client ID does not clearly map to an app in the admin console)
• Not yet tested with a personal Gmail account to isolate whether this is Workspace-specific

Related Issues

• #29934 - MCP OAuth fails with providers requiring HTTPS redirect URIs (CLI)
• #37747 - MCP OAuth regression: redirect_uris missing port (CLI)
• #30588 - Google Workspace MCP OAuth fails with invalid_scope
• #46140 - Bearer token never sent after OAuth completes (Web UI)