Antigravity login and Handshake Failure and Incorrect GCH Project ID Prompt

​I am reporting a persistent authentication failure with the Google Antigravity desktop application.
​The Problem:
I successfully authenticate via the browser and reach the confirmation page. However, the desktop application does not receive the handshake signal. After multiple attempts, the app incorrectly prompts me to enter a Google Cloud Project ID, which is not applicable to my account.
​Troubleshooting Performed:
I have successfully authenticated in both Chrome and Microsoft Edge. I have completely disabled Windows Firewall across Domain, Private, and Public profiles. I have also cleared the local application cache and session data in AppData and restarted the system.
​The browser confirms OAuth Success, but the app remains stuck or defaults to the GCH login screen. This appears to be a backend provisioning issue or a failure in the local protocol handler.

OS: Windows