Try server feature to get internal details.

src/ProfanityFilter.WebApi/Components/Pages/Home.razor.cs

@@ -1,4 +1,7 @@
-namespace ProfanityFilter.WebApi.Components.Pages;
+using Microsoft.AspNetCore.Hosting.Server.Features;
+using Microsoft.Extensions.Logging;
+
+namespace ProfanityFilter.WebApi.Components.Pages;
 
 [StreamRendering]
 public sealed partial class Home : IAsyncDisposable
@@ -25,6 +28,9 @@ public sealed partial class Home : IAsyncDisposable
     [Inject]
     public required NavigationManager Nav { get; set; }
 
+    [Inject]
+    public required IServerAddressesFeature ServerAddresses { get; set; }
+
     [Inject]
     public required ILocalStorageService LocalStorage { get; set; }
 
@@ -62,7 +68,11 @@ protected override async Task OnAfterRenderAsync(bool firstRender)
 
         if (_hub is null)
         {
-            var uri = new UriBuilder(Nav.BaseUri)
+            var baseAddress = ServerAddresses.Addresses.FirstOrDefault();
+
+            Logger.LogInformation("Attempting hub base address: {Address}", baseAddress);
+
+            var uri = new UriBuilder(baseAddress ?? Nav.BaseUri)
             {
                 Path = "/profanity/hub"
             };

src/ProfanityFilter.WebApi/Program.cs

@@ -1,8 +1,19 @@
 // Copyright (c) David Pine. All rights reserved.
 // Licensed under the MIT License.
 
+using Microsoft.AspNetCore.Hosting.Server;
+using Microsoft.AspNetCore.Hosting.Server.Features;
+
 var builder = WebApplication.CreateBuilder(args);
 
+builder.Services.AddSingleton<IServerAddressesFeature>(sp =>
+{
+    var server = sp.GetRequiredService<IServer>();
+
+    return server.Features.Get<IServerAddressesFeature>()
+        ?? throw new InvalidOperationException("There's no IServerAddressesFeature in the IServer.");
+});
+
 builder.Services.AddRedaction(static redaction =>
     redaction.SetRedactor<CharacterRedactor>(
         classifications: [DataClassifications.SensitiveData]));