To provide "instant access" and a seamless experience for Community (Experience Cloud) users, the architect must choose an authentication and provisioning strategy that handles user creation on-the-fly. While both SAML and OpenID Connect (OIDC) are viable for SSO, OpenID Connect is the modern standard for consumer-facing "Social" or external identity integrations because it is built on OAuth 2.0.
The critical component for "self-service" is the Registration Handler. When an OpenID Connect Authentication Provider is configured in Salesforce, you must associate it with an Apex class that implements the Auth.RegistrationHandler interface. This handler is executed during the SSO flow if the user does not already exist. It provides the architect with full programmatic control to:
* Match the incoming identity to an existing Contact or Account.
* Create a new Contact record if one doesn't exist.
* Provision a new User record with the correct Profile, Permission Sets, and Locale settings.
* Link the User to the correct Account hierarchy, which is vital for Community security models.
Option A suggests Just-in-Time (JIT) provisioning, which is a declarative way to create users. However, JIT is often too rigid for Experience Cloud requirements, as it has limited ability to perform complex data lookups or handle the specific linking of Contacts to Accounts required for external users. Option C is technically mismatched in common Salesforce terminology; while SAML uses JIT, the Registration Handler is the native, specific mechanism designed to work with Authentication Providers (like OIDC). By using B, the company ensures that a subscriber logging in for the first time via the IAM system is instantly and accurately provisioned in Salesforce, eliminating the need for multiple accounts.