[BUG]

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Authenticating the "claude.ai Google Cloud BigQuery" MCP connector fails with an OAuth error.

What Should Happen?

The OAuth flow should complete and authorize the connector to access BigQuery.

Actual behavior:
Google rejects the request because the OAuth client ID referenced by the connector doesn't exist/isn't registered — this appears to be a server-side misconfiguration of the connector itself (not a permissions or account-policy issue), since the error occurs before any consent can be granted.

Error Messages/Logs

Error 401: invalid_client
Request details: flowName=GeneralOAuthFlow

Steps to Reproduce

In Claude Code, run /mcp and select "claude.ai Google Cloud BigQuery"
Click through the authorization prompt to open the external OAuth URL
Get redirected to Google's "Sign in with Google" / consent screen
Page shows: "Access blocked: Authorization Error — The OAuth client was not found" with "Error 401: invalid_client" and "Request details: flowName=GeneralOAuthFlow"

Claude Model

Sonnet (default)

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

4.6

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

Environment:

Claude Code running as VS Code extension on Windows 11
Account: [deb@seekfindinvest.com](mailto:deb@seekfindinvest.com) (Google Workspace)
gcloud CLI auth works fine for the same account/project — issue is isolated to the claude.ai-managed BigQuery connector's OAuth registration