The issue stems from how Google OAuth 2.0 handles refresh tokens based on the prompt parameter. Here's an explanation and solution based on the provided details:

Problem Analysis Refresh Token Behavior:

Localhost: By default, Google might issue a refresh token when running on localhost without requiring explicit user consent (due to testing or relaxed restrictions). Cloud (GCE): In a production environment with verified domains and SSL, Google adheres more strictly to consent policies, requiring explicit user consent to grant a refresh token. access_type and prompt Parameters:

The access_type="offline" ensures that a refresh token can be returned. The prompt="consent" forces the consent screen to appear, ensuring Google re-prompts the user for permission to grant a refresh token. Without prompt="consent", Google might skip re-prompting if the user has already authorized the app, potentially not issuing a refresh token. Why Changing to prompt="consent" Fixed the Issue:

The consent prompt ensures the user explicitly agrees to grant offline access again, which triggers the issuance of a refresh token even on your public server. Updated Code Here’s how you should structure your authorization URL generation:

python code

authorization_url, state = gcp.authorization_url( authorization_base_url, access_type="offline", # Request offline access for refresh tokens prompt="consent", # Force the consent screen to ensure refresh token is issued include_granted_scopes='true' # Allow incremental scope requests )

Key Considerations Prompt Behavior:

Use prompt="consent" sparingly in production to avoid annoying users with repeated consent screens. Once a refresh token is issued, you don’t need to request it again unless explicitly required. Secure Storage of Tokens:

Always securely store the refresh_token and access_token in a backend database or encrypted storage to prevent unauthorized access. Documentation Gaps:

The confusion arises because Google doesn’t explicitly state the interaction between access_type and prompt in their main documentation. Your discovery highlights this subtle dependency. Token Scopes:

Ensure that the scope you request matches the required permissions for your app. Incorrect or overly restrictive scopes might also prevent refresh token issuance. Why It’s Different Between Localhost and Cloud Google may treat localhost as a "development" or "test" environment, issuing refresh tokens without the need for prompt="consent". In a "production" environment (GCE with a verified domain and HTTPS), stricter adherence to OAuth 2.0 policies is enforced.