diff --git a/Source/ProofOfConcept/Program.cs b/Source/ProofOfConcept/Program.cs
index cbc3d90..0279aeb 100644
--- a/Source/ProofOfConcept/Program.cs
+++ b/Source/ProofOfConcept/Program.cs
@@ -31,66 +31,59 @@ builder.Services.AddHealthChecks()
     .AddAsyncCheck("", cancellationToken => Task.FromResult(HealthCheckResult.Healthy()), ["ready"]); //TODO: Check tag
 builder.Services.AddHttpContextAccessor();
 
-builder.Services.AddAuthentication(o =>
-{
-    o.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
-    o.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;
-})
-.AddCookie()
-.AddOpenIdConnect(o =>
-{
-    const string TeslaAuthority = "https://auth.tesla.com/oauth2/v3";
-    const string TeslaMetadataEndpoint  = $"{TeslaAuthority}/.well-known/openid-configuration";
-    const string FleetAuthTokenEndpoint = "https://fleet-auth.prd.vn.cloud.tesla.com/oauth2/v3/token";
-    const string FleetApiAudience = "https://fleet-api.prd.eu.vn.cloud.tesla.com";
-
-    // Let the middleware do discovery/JWKS (on demand), but override token endpoint
-    o.ConfigurationManager = new TeslaOIDCConfigurationManager(TeslaMetadataEndpoint, FleetAuthTokenEndpoint);
-
-    // Standard OIDC settings
-    o.Authority = TeslaAuthority;                 // discovery + /authorize
-    o.ClientId = "b2240ee4-332a-4252-91aa-bbcc24f78fdb";
-    o.ClientSecret = "ta-secret.YG+XSdlvr6Lv8U-x";
-    o.ResponseType = OpenIdConnectResponseType.Code;
-    o.UsePkce = true;
-    o.SaveTokens = true;
-
-    // This must match exactly what you register at Tesla
-    o.CallbackPath = new PathString("/token-exchange");
-    
-    // Scopes you actually need
-    o.Scope.Clear();
-    o.Scope.Add("openid");
-    o.Scope.Add("offline_access");
-    o.Scope.Add("vehicle_device_data");
-    o.Scope.Add("vehicle_location");
-
-    // Optional Tesla parameters
-    o.AdditionalAuthorizationParameters.Add("prompt_missing_scopes", "true");
-    o.AdditionalAuthorizationParameters.Add("require_requested_scopes", "true");
-    o.AdditionalAuthorizationParameters.Add("show_keypair_step", "true");
-
-    // If keys rotate during runtime, auto-refresh JWKS
-    o.RefreshOnIssuerKeyNotFound = true;
-
-    // Set token validation parameters
-    o.TokenValidationParameters.ValidIssuers = ["https://fleet-auth.tesla.com/oauth2/v3/nts", "https://auth.tesla.com/oauth2/v3", "https://fleet-auth.prd.vn.cloud.tesla.com/oauth2/v3/nts"];
-
-    var signingKeyResolver = new TeslaOIDCConfigurationManager.SigningKeyResolver(o.Backchannel, TimeSpan.FromHours(12));
-    o.TokenValidationParameters.IssuerSigningKeyResolver = signingKeyResolver.Resolve;
-
-    // Add Tesla's required audience to the token request
-    o.Events = new OpenIdConnectEvents
+builder.Services
+    .AddAuthentication(o =>
     {
-        OnAuthorizationCodeReceived = ctx =>
+        o.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
+        o.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;
+    })
+    .AddCookie()
+    .AddOpenIdConnect(o =>
+    {
+        // === Use Fleet-Auth third-party OIDC config ===
+        // Issuer in that doc: https://fleet-auth.tesla.com/oauth2/v3/nts
+        o.Authority = "https://fleet-auth.tesla.com/oauth2/v3/nts";
+
+        // Point directly at the third-party metadata you found:
+        o.MetadataAddress = "https://fleet-auth.prd.vn.cloud.tesla.com/oauth2/v3/thirdparty/.well-known/openid-configuration";
+
+        // Standard OIDC web app settings
+        o.ResponseType = OpenIdConnectResponseType.Code;
+        o.UsePkce = true;
+        o.SaveTokens = true;
+
+        o.ClientId     = "b2240ee4-332a-4252-91aa-bbcc24f78fdb";
+        o.ClientSecret = "ta-secret.YG+XSdlvr6Lv8U-x";
+
+        // Must exactly match what you registered in Tesla portal
+        o.CallbackPath = new PathString("/token-exchange");
+
+        // Set scopes
+        o.Scope.Clear();
+        o.Scope.Add("openid");
+        o.Scope.Add("offline_access");
+        o.Scope.Add("vehicle_device_data");
+        o.Scope.Add("vehicle_location");
+
+        // Optional Tesla flags
+        o.AdditionalAuthorizationParameters.Add("require_requested_scopes", "true");
+        o.AdditionalAuthorizationParameters.Add("show_keypair_step", "true");
+        o.AdditionalAuthorizationParameters.Add("prompt_missing_scopes", "true");
+
+        // ✅ Add the Fleet API audience to the token POST
+        const string FleetApiAudience = "https://fleet-api.prd.eu.vn.cloud.tesla.com"; // set your region base
+        o.Events = new OpenIdConnectEvents
         {
-            if (ctx.TokenEndpointRequest is not null) 
+            OnAuthorizationCodeReceived = ctx =>
+            {
                 ctx.TokenEndpointRequest.Parameters["audience"] = FleetApiAudience;
-            
-            return Task.CompletedTask;
-        }
-    };
-});
+                return Task.CompletedTask;
+            }
+        };
+
+        // Auto-refresh keys if Tesla rotates JWKS
+        o.RefreshOnIssuerKeyNotFound = true;
+    });
 
 // Add own services
 builder.Services.AddSingleton<IMessageProcessor, MessageProcessor>();