In many multi-tenant applications, an invitation is a time-limited, one-time handshake between two parties inside an app context (e.g. organization, workspace, team, or document).

After the invitation email is accepted, the link should bring the recipient into the app at a specific contextual entry point (for example, a workspace, organization, or document reference). From that point:

Existing users continue through the regular sign-in flow (if not already signed in)

New users continue through the standard sign-up flow

At that point, the application takes full control of the user experience and logic.

From Firebase’s perspective, the responsibility would primarily be to confirm identity and intent, rather than enforce app-specific behavior. Conceptually, this is closer to the email verification flow than to a persistent authentication method.

This capability is foundational for B2B and multi-tenant applications and currently requires workarounds using Cloud Functions and external email services.