Widget embed fails with 403 PERMISSION_DENIED: “Configuration is not authorized on …googleusercontent.com” (Google Sites + Apps Script)

Google Cloud Build with AI Agents
1

Hello,

I’m seeing a consistent failure when embedding an AI Applications widget into Google Sites and into an Apps Script web app.

What fails

When a user clicks the widget search bar, the widget calls:

https://content-eu-discoveryengine.googleapis.com/v1alpha/locations/eu/lookupWidgetConfig

and gets:

{
  "error": {
    "code": 403,
    "message": "Access Denied.",
    "status": "PERMISSION_DENIED"
  }
}

The UI shows: “Configuration is not authorized on ‘’.”

The <host> is dynamic, e.g.:

  • Google Sites: NNNNNNNN-atari-embeds.googleusercontent.com (numeric prefix changes)
  • Apps Script: n-...-script.googleusercontent.com

Comparison with a working app

I have another AI Application widget in the same organization that embeds into Google Sites successfully. * Its Integration allowed domains are minimal: only googleusercontent.com and sites.google.com .

  • It works without any “Configuration is not authorized…” errors.
  • The non-working app is configured similarly (same “Search with follow-ups” style and similar settings). The main difference is that the failing app uses Google Drive connected data stores (Drive connector).

I also attempted adding more domains to the failing app (including googleusercontent.com , atari-embeds.googleusercontent.com , sites.google.com , script.google.com , drive.google.com , etc.). Changes were saved and I waited (per the UI note), but the error persists.

Questions

  1. Are these dynamic googleusercontent embed hosts (e.g., NNNNNNNN-atari-embeds.googleusercontent.com , n-…-script.googleusercontent.com ) expected/supported for widget embedding? If yes, what exact domain(s) should be allowlisted so it works reliably?
  2. Is there any known limitation/bug where widgets backed by Google Drive connected data stores fail lookupWidgetConfig authorization (403) when embedded, while non-Drive apps work?

Happy to share additional details or screenshots if needed. I must be missing something.

Thanks for your time!