I am trying to do this based on actions → flows
/**
 * @param {Event} event - Details about the user and the context in which they are logging in.
 * @param {PostLoginAPI} api - Interface whose methods can be used to change the behavior of the login.
 */
exports.onExecutePostLogin = async (event, api) => {
  const namespace = 'https://api';
  if (event.authorization) {
    api.idToken.setCustomClaim(`${namespace}/roles`, event.authorization.roles);
    api.accessToken.setCustomClaim(`${namespace}/roles`, event.authorization.roles);
    const token = api.redirect.encodeToken({
    secret: event.secrets.MY_REDIRECT_SECRET,
    expiresInSeconds: 60, 
    payload: {
      // Custom claims to be added to the token
      email: event.user.email,
    },
    });
    if (event.authorization.roles.includes("Admin")) {
      api.redirect.sendUserTo("http://localhost:8910/admin", {
      query: { session_token: token }
    });
    }
  }
}
For some odd reason the page now goes straight back to the main page without login in.