Which scenario exemplifies a Service Provider (SP) initiated flow?

In a Service Provider (SP) initiated flow, the user directly interacts with the service provider's application first. When the end user logs in by navigating directly to the app, it indicates that they start their authentication journey from the service provider's site. This means the service provider prompts the user to authenticate themselves as part of accessing the application.

Specifically, in this scenario, the user typically reaches the application first and is then either prompted for credentials or redirected to an identity provider if single sign-on (SSO) is implemented. This is distinct from the identity provider being the initial point of access, which would characterize an identity provider (IdP) initiated flow.

The other scenarios involve either direct credential input, which does not inherently indicate a flow direction, or processes that assume an ongoing session without highlighting the initial point of interaction. Thus, navigating directly to the app effectively showcases a clear instance of an SP-initiated authentication flow.