Need help with SAML based SSO POC

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Hi, I am working on a POC to showcase SSO using SAML.

I have two apps, one frontend and one backend for each app. Let’s say,

  1. App 1 (frontend running on 4200, backend running on 3000)
  2. App 2 (frontend running on 4201, backend running on 3001)

I am using auth0 as IDP for the demonstration, in actual scenario the IDP will be a separate server.

I have setup the auth0 to work with app 1 so basically SAML token is posted to a callback URL of app 1. The session is working as expected. Now I want to login from app 2 without having to enter my auth0 credential. But I am confused as auth0 is configured to work with app 1. How it will communicate the SAML token to app 2.

Am I thinking in a wrong way? or missing anything. Please help me, it is urgent.