Getting the SessionID (sid) for logout in BFF pattern


I’m trying to connect the Duende BFF solution to Auth0. In Auth0, I’ve created a Single Page Application. The dotnet part looks like, coming from the Duende BFF WASM dotnet 6 sample:

builder.Services.AddAuthentication(options =>
        options.DefaultScheme = "cookie";
        options.DefaultChallengeScheme = "oidc";
        options.DefaultSignOutScheme = "oidc";
    .AddCookie("cookie", options =>
        options.Cookie.Name = "__Host-blazor";
        options.Cookie.SameSite = SameSiteMode.Strict;
    .AddOpenIdConnect("oidc", options =>
        options.Authority = "";
        options.ClientId = "MY-CLIENTID";
        options.ClientSecret = "MY-CLIENTSECRET";
        options.ResponseType = "code";
        options.ResponseMode = "query";

        options.MapInboundClaims = false;
        options.GetClaimsFromUserInfoEndpoint = true;
        options.SaveTokens = true;

In Auth0 dashboard I’ve added a rule to add the sid to a response’s user claim. I’ve got this solution from a forum/community post, but I’m not sure if this is correct as I cannot observe any effect:

function (user, context, callback) {
  var namespace = 'https://localhost:7189/';
  context.idToken[namespace + 'sid'] = user.sid;
  callback(null, user, context);

When debugging, then I don’t see the expected session id (sid) which is needed for properly logout:

Is there any hint what is going wrong here or how this can be better debugged to understand how and where the session id can be taken from?