BaseKt client auth SPI: AuthClient, OAuthCapable, SessionManager, RFC 7636 PKCE (S256), and multiplatform OAuth redirect flows.

BaseKt Firebase Auth client: multiplatform Identity Toolkit sign-in, sign-up, Secure Token refresh, and password reset over Ktor HttpClient.

BaseKt Supabase Auth client: multiplatform GoTrue sign-in, sign-up, token refresh, password recovery, and OAuth 2.0 PKCE over Ktor HttpClient.