How to get user session of KeyCloak or clients using API?

Hi, I have a problem and need some help.

I have three applications. Application A is not bind to KeyCloak and application B, C is applied KeyCloak SSO. Application B use OIDC, application C use SAML for SSO.

Below is what I want.

  1. If an user login to application A.
  2. Application A get the user’s session for KeyCloak or application B and C using API. (Application A has username, password or API key.)
  3. So if the user go to application B or C, he don’t need to login.

I want to know there are APIs for get user’s session for KeyCloak or clients(OIDC/SAML).
Or please let me know how to make above process possible…

Thank you.