diff --git a/src/ReactiveUI.AndroidX/Builder/AndroidXReactiveUIBuilderExtensions.cs b/src/ReactiveUI.AndroidX/Builder/AndroidXReactiveUIBuilderExtensions.cs
index 888d25e65c..db2aec63a6 100644
--- a/src/ReactiveUI.AndroidX/Builder/AndroidXReactiveUIBuilderExtensions.cs
+++ b/src/ReactiveUI.AndroidX/Builder/AndroidXReactiveUIBuilderExtensions.cs
@@ -34,6 +34,7 @@ public static IReactiveUIBuilder WithAndroidX(this IReactiveUIBuilder builder)
 
         return builder
             .WithMainThreadScheduler(HandlerScheduler.MainThreadScheduler)
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
             .WithPlatformModule<AndroidX.Registrations>();
     }
 
diff --git a/src/ReactiveUI.Blazor/Builder/BlazorReactiveUIBuilderExtensions.cs b/src/ReactiveUI.Blazor/Builder/BlazorReactiveUIBuilderExtensions.cs
index 976d08c7a6..1ea780e358 100644
--- a/src/ReactiveUI.Blazor/Builder/BlazorReactiveUIBuilderExtensions.cs
+++ b/src/ReactiveUI.Blazor/Builder/BlazorReactiveUIBuilderExtensions.cs
@@ -40,6 +40,25 @@ public static IReactiveUIBuilder WithBlazor(this IReactiveUIBuilder builder)
 
         return builder
             .WithBlazorScheduler()
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
+            .WithPlatformModule<Blazor.Registrations>();
+    }
+
+    /// <summary>
+    /// Configures ReactiveUI for Blazor platform with appropriate schedulers.
+    /// </summary>
+    /// <param name="builder">The builder instance.</param>
+    /// <returns>The builder instance for chaining.</returns>
+    public static IReactiveUIBuilder WithBlazorWasm(this IReactiveUIBuilder builder)
+    {
+        if (builder is null)
+        {
+            throw new ArgumentNullException(nameof(builder));
+        }
+
+        return builder
+            .WithBlazorWasmScheduler()
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
             .WithPlatformModule<Blazor.Registrations>();
     }
 
diff --git a/src/ReactiveUI.Blazor/Registrations.cs b/src/ReactiveUI.Blazor/Registrations.cs
index 7161dbdb8b..7dc94ceb87 100644
--- a/src/ReactiveUI.Blazor/Registrations.cs
+++ b/src/ReactiveUI.Blazor/Registrations.cs
@@ -46,8 +46,5 @@ public void Register(IRegistrar registrar)
         {
             PlatformEnlightenmentProvider.Current.EnableWasm();
         }
-
-        RxSchedulers.TaskpoolScheduler = TaskPoolScheduler.Default;
-        RxSchedulers.MainThreadScheduler = CurrentThreadScheduler.Instance;
     }
 }
diff --git a/src/ReactiveUI.Maui/Builder/MauiReactiveUIBuilderExtensions.cs b/src/ReactiveUI.Maui/Builder/MauiReactiveUIBuilderExtensions.cs
index 7945f71db1..56f94a0ad8 100644
--- a/src/ReactiveUI.Maui/Builder/MauiReactiveUIBuilderExtensions.cs
+++ b/src/ReactiveUI.Maui/Builder/MauiReactiveUIBuilderExtensions.cs
@@ -70,6 +70,7 @@ public static IReactiveUIBuilder WithMaui(this IReactiveUIBuilder builder, IDisp
 
         return builder
             .WithMauiScheduler(dispatcher)
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
             .WithPlatformModule<Maui.Registrations>()
             .WithPlatformServices();
     }
diff --git a/src/ReactiveUI.Maui/Registrations.cs b/src/ReactiveUI.Maui/Registrations.cs
index f35817b8b1..3267b0a66f 100644
--- a/src/ReactiveUI.Maui/Registrations.cs
+++ b/src/ReactiveUI.Maui/Registrations.cs
@@ -36,12 +36,6 @@ public void Register(IRegistrar registrar)
         registrar.RegisterConstant<IPropertyBindingHook>(static () => new AutoDataTemplateBindingHook());
         registrar.RegisterConstant<IBindingFallbackConverter>(static () => new ComponentModelFallbackConverter());
 
-        if (!ModeDetector.InUnitTestRunner())
-        {
-            RxSchedulers.MainThreadScheduler = new WaitForDispatcherScheduler(static () => DispatcherQueueScheduler.Current);
-            RxSchedulers.TaskpoolScheduler = TaskPoolScheduler.Default;
-        }
-
         RxSchedulers.SuppressViewCommandBindingMessage = true;
 #endif
     }
diff --git a/src/ReactiveUI.WinUI/Builder/WinUIReactiveUIBuilderExtensions.cs b/src/ReactiveUI.WinUI/Builder/WinUIReactiveUIBuilderExtensions.cs
index 8b4a34c89e..96b035730a 100644
--- a/src/ReactiveUI.WinUI/Builder/WinUIReactiveUIBuilderExtensions.cs
+++ b/src/ReactiveUI.WinUI/Builder/WinUIReactiveUIBuilderExtensions.cs
@@ -29,6 +29,7 @@ public static IReactiveUIBuilder WithWinUI(this IReactiveUIBuilder builder)
 
         return builder
             .WithWinUIScheduler()
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
             .WithPlatformModule<WinUI.Registrations>();
     }
 
diff --git a/src/ReactiveUI.Winforms/Builder/WinFormsReactiveUIBuilderExtensions.cs b/src/ReactiveUI.Winforms/Builder/WinFormsReactiveUIBuilderExtensions.cs
index 6c45a0b3bc..285c8380e6 100644
--- a/src/ReactiveUI.Winforms/Builder/WinFormsReactiveUIBuilderExtensions.cs
+++ b/src/ReactiveUI.Winforms/Builder/WinFormsReactiveUIBuilderExtensions.cs
@@ -33,6 +33,7 @@ public static IReactiveUIBuilder WithWinForms(this IReactiveUIBuilder builder)
 
         return builder
             .WithMainThreadScheduler(WinFormsMainThreadScheduler)
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default)
             .WithPlatformModule<Winforms.Registrations>();
     }
 
diff --git a/src/ReactiveUI.Winforms/Registrations.cs b/src/ReactiveUI.Winforms/Registrations.cs
index cdb3e49068..47d813b439 100644
--- a/src/ReactiveUI.Winforms/Registrations.cs
+++ b/src/ReactiveUI.Winforms/Registrations.cs
@@ -31,7 +31,6 @@ public void Register(IRegistrar registrar)
         if (!ModeDetector.InUnitTestRunner())
         {
             WindowsFormsSynchronizationContext.AutoInstall = true;
-            RxSchedulers.MainThreadScheduler = new WaitForDispatcherScheduler(static () => new SynchronizationContextScheduler(new WindowsFormsSynchronizationContext()));
         }
     }
 }
diff --git a/src/ReactiveUI.Wpf/Builder/WpfReactiveUIBuilderExtensions.cs b/src/ReactiveUI.Wpf/Builder/WpfReactiveUIBuilderExtensions.cs
index 8f9c6b7583..57924c3de5 100644
--- a/src/ReactiveUI.Wpf/Builder/WpfReactiveUIBuilderExtensions.cs
+++ b/src/ReactiveUI.Wpf/Builder/WpfReactiveUIBuilderExtensions.cs
@@ -32,7 +32,8 @@ public static IReactiveUIBuilder WithWpf(this IReactiveUIBuilder builder)
         return builder
             .WithPlatformModule<Wpf.Registrations>()
             .WithPlatformServices()
-            .WithWpfScheduler();
+            .WithWpfScheduler()
+            .WithTaskPoolScheduler(TaskPoolScheduler.Default);
     }
 
     /// <summary>
diff --git a/src/ReactiveUI.Wpf/Registrations.cs b/src/ReactiveUI.Wpf/Registrations.cs
index 81bed3f43e..ed4234ccce 100644
--- a/src/ReactiveUI.Wpf/Registrations.cs
+++ b/src/ReactiveUI.Wpf/Registrations.cs
@@ -29,13 +29,6 @@ public void Register(IRegistrar registrar)
         registrar.RegisterConstant<IPropertyBindingHook>(static () => new AutoDataTemplateBindingHook());
         registrar.RegisterConstant<IBindingFallbackConverter>(static () => new ComponentModelFallbackConverter());
 
-        if (!ModeDetector.InUnitTestRunner())
-        {
-            // NB: On .NET Core, trying to touch DispatcherScheduler blows up :cry:
-            RxSchedulers.MainThreadScheduler = new WaitForDispatcherScheduler(static () => DispatcherScheduler.Current);
-            RxSchedulers.TaskpoolScheduler = TaskPoolScheduler.Default;
-        }
-
         RxSchedulers.SuppressViewCommandBindingMessage = true;
     }
 }
diff --git a/src/ReactiveUI/Builder/IReactiveUIBuilder.cs b/src/ReactiveUI/Builder/IReactiveUIBuilder.cs
index de16ecf61f..bf469adb9a 100644
--- a/src/ReactiveUI/Builder/IReactiveUIBuilder.cs
+++ b/src/ReactiveUI/Builder/IReactiveUIBuilder.cs
@@ -38,12 +38,18 @@ namespace ReactiveUI.Builder;
 /// <seealso cref="IAppBuilder" />
 public interface IReactiveUIBuilder : IAppBuilder
 {
+    /// <summary>
+    /// Configures the message bus.
+    /// </summary>
+    /// <returns>The builder instance for chaining.</returns>
+    IReactiveUIBuilder WithMessageBus();
+
     /// <summary>
     /// Configures the message bus.
     /// </summary>
     /// <param name="configure">A delegate to configure the message bus.</param>
     /// <returns>The builder instance for chaining.</returns>
-    IReactiveUIBuilder ConfigureMessageBus(Action<MessageBus> configure);
+    IReactiveUIBuilder WithMessageBus(Action<IMessageBus> configure);
 
     /// <summary>
     /// Registers a custom message bus instance.
@@ -121,6 +127,18 @@ IReactiveUIBuilder RegisterView<TView, TViewModel>()
     IReactiveUIBuilder RegisterViewModel<TViewModel>()
         where TViewModel : class, IReactiveObject, new();
 
+    /// <summary>
+    /// Registers a constant instance of the specified view model type for use in the reactive UI builder.
+    /// </summary>
+    /// <remarks>The registered view model instance is created once using its parameterless constructor and
+    /// reused for all requests. Use this method when the view model does not require per-request state or
+    /// dependencies.</remarks>
+    /// <typeparam name="TViewModel">The type of the view model to register. Must be a reference type that implements IReactiveObject and has a
+    /// parameterless constructor.</typeparam>
+    /// <returns>The current instance of the reactive UI builder, enabling method chaining.</returns>
+    IReactiveUIBuilder RegisterConstantViewModel<TViewModel>()
+        where TViewModel : class, IReactiveObject, new();
+
     /// <summary>
     /// Withes the main thread scheduler.
     /// </summary>
diff --git a/src/ReactiveUI/Builder/ReactiveUIBuilder.cs b/src/ReactiveUI/Builder/ReactiveUIBuilder.cs
index d0d94fe2d1..405474ed7a 100644
--- a/src/ReactiveUI/Builder/ReactiveUIBuilder.cs
+++ b/src/ReactiveUI/Builder/ReactiveUIBuilder.cs
@@ -272,19 +272,29 @@ public IReactiveUIBuilder ForPlatforms(params Action<IReactiveUIBuilder>[] platf
         return this;
     }
 
+    /// <summary>
+    /// Configures the ReactiveUI message bus.
+    /// </summary>
+    /// <returns>The builder instance for chaining.</returns>
+    public IReactiveUIBuilder WithMessageBus() =>
+        WithRegistrationOnBuild(resolver =>
+        {
+            _messageBus = new MessageBus();
+            resolver.RegisterConstant<IMessageBus>(_messageBus);
+        });
+
     /// <summary>
     /// Configures the ReactiveUI message bus.
     /// </summary>
     /// <param name="configure">The configuration action.</param>
     /// <returns>The builder instance for chaining.</returns>
-    public IReactiveUIBuilder ConfigureMessageBus(Action<MessageBus> configure) =>
+    public IReactiveUIBuilder WithMessageBus(Action<IMessageBus> configure) =>
         WithRegistrationOnBuild(resolver =>
-            resolver.Register<IMessageBus>(() =>
-            {
-                var messageBus = new MessageBus();
-                configure(messageBus);
-                return messageBus;
-            }));
+        {
+            _messageBus = new MessageBus();
+            configure(_messageBus);
+            resolver.RegisterConstant<IMessageBus>(_messageBus);
+        });
 
     /// <summary>
     /// Registers a custom message bus instance.
@@ -632,6 +642,18 @@ public IReactiveUIBuilder RegisterViewModel<TViewModel>()
         where TViewModel : class, IReactiveObject, new() =>
             WithRegistration(static resolver => resolver.Register<TViewModel>(static () => new()));
 
+    /// <summary>
+    /// Registers a constant instance of the specified view model type in the dependency resolver.
+    /// </summary>
+    /// <remarks>This method creates a single instance of the specified view model type and registers it as a
+    /// constant in the resolver. All requests for this view model type will return the same instance.</remarks>
+    /// <typeparam name="TViewModel">The type of the view model to register. Must be a class that implements IReactiveObject and has a parameterless
+    /// constructor.</typeparam>
+    /// <returns>The current builder instance, enabling further configuration of the dependency resolver.</returns>
+    public IReactiveUIBuilder RegisterConstantViewModel<TViewModel>()
+        where TViewModel : class, IReactiveObject, new() =>
+            WithRegistration(static resolver => resolver.RegisterConstant(new TViewModel()));
+
     /// <summary>
     /// Registers a custom view model with the dependency resolver.
     /// </summary>
diff --git a/src/ReactiveUI/Mixins/BuilderMixins.cs b/src/ReactiveUI/Mixins/BuilderMixins.cs
index 3a38bd3135..c1113034a4 100644
--- a/src/ReactiveUI/Mixins/BuilderMixins.cs
+++ b/src/ReactiveUI/Mixins/BuilderMixins.cs
@@ -306,6 +306,22 @@ public static IReactiveUIBuilder ForPlatforms(this IReactiveUIBuilder reactiveUI
         return reactiveUIBuilder;
     }
 
+    /// <summary>
+    /// Configures the ReactiveUI message bus.
+    /// </summary>
+    /// <param name="reactiveUIBuilder">The reactive UI builder.</param>
+    /// <returns>
+    /// The builder instance for chaining.
+    /// </returns>
+    /// <exception cref="ArgumentNullException">reactiveUIBuilder.</exception>
+    public static IReactiveUIBuilder WithMessageBus(this IReactiveUIBuilder reactiveUIBuilder)
+    {
+        ArgumentExceptionHelper.ThrowIfNull(reactiveUIBuilder);
+
+        reactiveUIBuilder.WithMessageBus();
+        return reactiveUIBuilder;
+    }
+
     /// <summary>
     /// Configures the ReactiveUI message bus.
     /// </summary>
@@ -315,11 +331,11 @@ public static IReactiveUIBuilder ForPlatforms(this IReactiveUIBuilder reactiveUI
     /// The builder instance for chaining.
     /// </returns>
     /// <exception cref="ArgumentNullException">reactiveUIBuilder.</exception>
-    public static IReactiveUIBuilder ConfigureMessageBus(this IReactiveUIBuilder reactiveUIBuilder, Action<MessageBus> configure)
+    public static IReactiveUIBuilder WithMessageBus(this IReactiveUIBuilder reactiveUIBuilder, Action<IMessageBus> configure)
     {
         ArgumentExceptionHelper.ThrowIfNull(reactiveUIBuilder);
 
-        reactiveUIBuilder.ConfigureMessageBus(configure);
+        reactiveUIBuilder.WithMessageBus(configure);
         return reactiveUIBuilder;
     }
 
@@ -392,6 +408,22 @@ public static IReactiveUIBuilder RegisterViewModel<TViewModel>(this IReactiveUIB
         return reactiveUIBuilder;
     }
 
+    /// <summary>
+    /// Registers a constant instance of the specified view model type for use with the ReactiveUI builder.
+    /// </summary>
+    /// <typeparam name="TViewModel">The type of the view model to register. Must be a class that implements IReactiveObject and has a parameterless
+    /// constructor.</typeparam>
+    /// <param name="reactiveUIBuilder">The ReactiveUI builder to configure. Cannot be null.</param>
+    /// <returns>The same ReactiveUI builder instance, to allow for method chaining.</returns>
+    public static IReactiveUIBuilder RegisterConstantViewModel<TViewModel>(this IReactiveUIBuilder reactiveUIBuilder)
+        where TViewModel : class, IReactiveObject, new()
+    {
+        ArgumentExceptionHelper.ThrowIfNull(reactiveUIBuilder);
+
+        reactiveUIBuilder.RegisterConstantViewModel<TViewModel>();
+        return reactiveUIBuilder;
+    }
+
     /// <summary>
     /// Registers a custom view model with the dependency resolver.
     /// </summary>
diff --git a/src/examples/ReactiveUI.Builder.BlazorServer/Program.cs b/src/examples/ReactiveUI.Builder.BlazorServer/Program.cs
index 4d22fce0c5..13b903a00c 100644
--- a/src/examples/ReactiveUI.Builder.BlazorServer/Program.cs
+++ b/src/examples/ReactiveUI.Builder.BlazorServer/Program.cs
@@ -8,8 +8,6 @@
 using ReactiveUI.Builder.BlazorServer.Components;
 using ReactiveUI.Builder.BlazorServer.Services;
 using ReactiveUI.Builder.BlazorServer.ViewModels;
-using ReactiveUI.Builder.BlazorServer.Views;
-using Splat;
 using Splat.Microsoft.Extensions.DependencyInjection;
 
 var builder = WebApplication.CreateBuilder(args);
@@ -30,14 +28,8 @@
 
 RxAppBuilder.CreateReactiveUIBuilder()
    .WithBlazor()
+   .WithMessageBus()
    .WithViewsFromAssembly(typeof(Program).Assembly)
-   .WithRegistration(locator =>
-   {
-       if (Locator.Current.GetService<IMessageBus>() is null)
-       {
-           locator.RegisterConstant(MessageBus.Current);
-       }
-   })
    .BuildApp();
 
 var app = builder.Build();
diff --git a/src/examples/ReactiveUI.Builder.BlazorServer/ReactiveUI.Builder.BlazorServer.csproj b/src/examples/ReactiveUI.Builder.BlazorServer/ReactiveUI.Builder.BlazorServer.csproj
index ba1f0c80ad..4396b7a43b 100644
--- a/src/examples/ReactiveUI.Builder.BlazorServer/ReactiveUI.Builder.BlazorServer.csproj
+++ b/src/examples/ReactiveUI.Builder.BlazorServer/ReactiveUI.Builder.BlazorServer.csproj
@@ -4,6 +4,7 @@
     <TargetFramework>net10.0</TargetFramework>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
+    <IsPackable>false</IsPackable>
     <BlazorDisableThrowNavigationException>true</BlazorDisableThrowNavigationException>
     <DefaultPackageDescription>Blazor Server example app for ReactiveUI Builder.</DefaultPackageDescription>
   </PropertyGroup>
diff --git a/src/examples/ReactiveUI.Builder.BlazorServer/Services/FileJsonSuspensionDriver.cs b/src/examples/ReactiveUI.Builder.BlazorServer/Services/FileJsonSuspensionDriver.cs
index 41c69399f2..9dd1112f77 100644
--- a/src/examples/ReactiveUI.Builder.BlazorServer/Services/FileJsonSuspensionDriver.cs
+++ b/src/examples/ReactiveUI.Builder.BlazorServer/Services/FileJsonSuspensionDriver.cs
@@ -3,7 +3,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for full license information.
 
-using System.IO;
 using System.Reactive;
 using System.Reactive.Linq;
 using System.Text.Json;
@@ -70,7 +69,7 @@ public IObservable<Unit> InvalidateState() => Observable.Start(
     {
         if (!File.Exists(path))
         {
-            return default(T);
+            return default;
         }
 
         var json = File.ReadAllText(path);
diff --git a/src/examples/ReactiveUI.Builder.BlazorServer/Services/ReactiveUiAppHostedService.cs b/src/examples/ReactiveUI.Builder.BlazorServer/Services/ReactiveUiAppHostedService.cs
index 2312cf22c3..417d9d48e6 100644
--- a/src/examples/ReactiveUI.Builder.BlazorServer/Services/ReactiveUiAppHostedService.cs
+++ b/src/examples/ReactiveUI.Builder.BlazorServer/Services/ReactiveUiAppHostedService.cs
@@ -5,8 +5,6 @@
 
 using System.Diagnostics;
 using System.Reactive.Linq;
-using Microsoft.Extensions.Hosting;
-using ReactiveUI;
 using ReactiveUI.Builder.BlazorServer.Models;
 using Splat;
 
diff --git a/src/examples/ReactiveUI.Builder.BlazorServer/Views/LobbyView.razor.cs b/src/examples/ReactiveUI.Builder.BlazorServer/Views/LobbyView.razor.cs
index 601db78183..48ff0058a7 100644
--- a/src/examples/ReactiveUI.Builder.BlazorServer/Views/LobbyView.razor.cs
+++ b/src/examples/ReactiveUI.Builder.BlazorServer/Views/LobbyView.razor.cs
@@ -5,7 +5,6 @@
 
 using System.Reactive.Linq;
 using Microsoft.AspNetCore.Components.Web;
-using ReactiveUI;
 using ReactiveUI.Blazor;
 using ReactiveUI.Builder.BlazorServer.Models;
 using ReactiveUI.Builder.BlazorServer.ViewModels;
diff --git a/src/examples/ReactiveUI.Builder.WpfApp/App.xaml.cs b/src/examples/ReactiveUI.Builder.WpfApp/App.xaml.cs
index 1bb3998849..1437956d78 100644
--- a/src/examples/ReactiveUI.Builder.WpfApp/App.xaml.cs
+++ b/src/examples/ReactiveUI.Builder.WpfApp/App.xaml.cs
@@ -35,7 +35,7 @@ protected override void OnStartup(StartupEventArgs e)
         base.OnStartup(e);
 
         // Initialize ReactiveUI via the Builder only
-        RxAppBuilder.CreateReactiveUIBuilder()
+        var app = RxAppBuilder.CreateReactiveUIBuilder()
             .WithWpf()
             .WithViewsFromAssembly(typeof(App).Assembly) // auto-register all IViewFor in this assembly
                                                          ////.RegisterView<MainWindow, ViewModels.AppBootstrapper>()
@@ -52,17 +52,12 @@ protected override void OnStartup(StartupEventArgs e)
                     Debugger.Break();
                 }
             }))
+            .WithMessageBus()
             .WithRegistration(static r =>
             {
                 // Register IScreen as a singleton so all resolutions share the same Router
                 r.RegisterLazySingleton<IScreen>(static () => new ViewModels.AppBootstrapper());
 
-                // Register MessageBus as a singleton if not already
-                if (Locator.Current.GetService<IMessageBus>() is null)
-                {
-                    r.RegisterConstant(MessageBus.Current);
-                }
-
                 // Cross-process instance lifetime coordination
                 r.RegisterLazySingleton(static () => new Services.AppLifetimeCoordinator());
 
diff --git a/src/examples/ReactiveUI.Builder.WpfApp/Models/RoomEventMessage.cs b/src/examples/ReactiveUI.Builder.WpfApp/Models/RoomEventMessage.cs
index eb32360736..ba4080e590 100644
--- a/src/examples/ReactiveUI.Builder.WpfApp/Models/RoomEventMessage.cs
+++ b/src/examples/ReactiveUI.Builder.WpfApp/Models/RoomEventMessage.cs
@@ -3,7 +3,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for full license information.
 
-namespace ReactiveUI.Builder.WpfApp.Services;
+using ReactiveUI.Builder.WpfApp.Services;
+
+namespace ReactiveUI.Builder.WpfApp.Models;
 
 /// <summary>
 /// Network event describing a change in the rooms list.
diff --git a/src/examples/ReactiveUI.Builder.WpfApp/ReactiveUI.Builder.WpfApp.csproj b/src/examples/ReactiveUI.Builder.WpfApp/ReactiveUI.Builder.WpfApp.csproj
index 173a47585f..52e24c8998 100644
--- a/src/examples/ReactiveUI.Builder.WpfApp/ReactiveUI.Builder.WpfApp.csproj
+++ b/src/examples/ReactiveUI.Builder.WpfApp/ReactiveUI.Builder.WpfApp.csproj
@@ -19,6 +19,14 @@
 
   <ItemGroup>
     <Using Include="ReactiveUI.Helpers" />
+    <Using Include="System.Collections.ObjectModel" />
+    <Using Include="System.IO.MemoryMappedFiles" />
+    <Using Include="System.Diagnostics" />
+    <Using Include="System.Net" />
+    <Using Include="System.Net.Sockets" />
+    <Using Include="System.Reactive" />
+    <Using Include="System.Reactive.Linq" />
+    <Using Include="System.Text.Json" />
   </ItemGroup>
 
 </Project>
diff --git a/src/examples/ReactiveUI.Builder.WpfApp/ViewModels/LobbyViewModel.cs b/src/examples/ReactiveUI.Builder.WpfApp/ViewModels/LobbyViewModel.cs
index 1c5b7e9e78..5a6943dd1d 100644
--- a/src/examples/ReactiveUI.Builder.WpfApp/ViewModels/LobbyViewModel.cs
+++ b/src/examples/ReactiveUI.Builder.WpfApp/ViewModels/LobbyViewModel.cs
@@ -46,7 +46,7 @@ public LobbyViewModel(IScreen hostScreen)
 
         // Remote changes and sync (ignore own events)
         var remoteRoomsChanged = MessageBus.Current
-            .Listen<Services.RoomEventMessage>(contract: "__rooms__")
+            .Listen<RoomEventMessage>(contract: "__rooms__")
             .Where(m => m.InstanceId != Services.AppInstance.Id)
             .Do(evt =>
             {
@@ -56,7 +56,7 @@ public LobbyViewModel(IScreen hostScreen)
                     case Services.RoomEventKind.SyncRequest:
                         // Respond with our snapshot of room names
                         var snapshot = GetState().Rooms.ConvertAll(r => r.Name);
-                        var response = new Services.RoomEventMessage(Services.RoomEventKind.Add, string.Empty)
+                        var response = new RoomEventMessage(Services.RoomEventKind.Add, string.Empty)
                         {
                             Snapshot = snapshot,
                             InstanceId = Services.AppInstance.Id,
@@ -82,7 +82,7 @@ public LobbyViewModel(IScreen hostScreen)
         // Request a snapshot from peers shortly after activation
         RxSchedulers.MainThreadScheduler.Schedule(Unit.Default, TimeSpan.FromMilliseconds(500), (s, __) =>
         {
-            var req = new Services.RoomEventMessage(Services.RoomEventKind.SyncRequest, string.Empty) { InstanceId = Services.AppInstance.Id };
+            var req = new RoomEventMessage(Services.RoomEventKind.SyncRequest, string.Empty) { InstanceId = Services.AppInstance.Id };
             Trace.WriteLine("[Lobby] Broadcasting SyncRequest");
             MessageBus.Current.SendMessage(req, contract: "__rooms__");
             return Disposable.Empty;
@@ -140,7 +140,7 @@ public string RoomName
 
     private static ChatState GetState() => RxSuspension.SuspensionHost.GetAppState<ChatState>();
 
-    private static void ApplyRoomEvent(Services.RoomEventMessage evt)
+    private static void ApplyRoomEvent(RoomEventMessage evt)
     {
         var state = GetState();
 
@@ -184,7 +184,7 @@ private void CreateRoomImpl()
             state.Rooms.Add(room);
 
             // Broadcast room add to peers
-            var evt = new Services.RoomEventMessage(Services.RoomEventKind.Add, room.Name) { InstanceId = Services.AppInstance.Id };
+            var evt = new RoomEventMessage(Services.RoomEventKind.Add, room.Name) { InstanceId = Services.AppInstance.Id };
             MessageBus.Current.SendMessage(evt, contract: "__rooms__");
             Trace.WriteLine($"[Lobby] Created room '{room.Name}'");
         }
@@ -198,7 +198,7 @@ private void DeleteRoomImpl(ChatRoom room)
         var state = GetState();
         if (state.Rooms.Remove(room))
         {
-            var evt = new Services.RoomEventMessage(Services.RoomEventKind.Remove, room.Name) { InstanceId = Services.AppInstance.Id };
+            var evt = new RoomEventMessage(Services.RoomEventKind.Remove, room.Name) { InstanceId = Services.AppInstance.Id };
             MessageBus.Current.SendMessage(evt, contract: "__rooms__");
             MessageBus.Current.SendMessage(new ChatStateChanged());
             Trace.WriteLine($"[Lobby] Deleted room '{room.Name}'");
diff --git a/src/tests/ReactiveUI.Blazor.Tests/BlazorReactiveUIBuilderExtensionsTests.cs b/src/tests/ReactiveUI.Blazor.Tests/BlazorReactiveUIBuilderExtensionsTests.cs
index c5b60ae4de..62eff81c97 100644
--- a/src/tests/ReactiveUI.Blazor.Tests/BlazorReactiveUIBuilderExtensionsTests.cs
+++ b/src/tests/ReactiveUI.Blazor.Tests/BlazorReactiveUIBuilderExtensionsTests.cs
@@ -136,8 +136,12 @@ private class TestReactiveUIBuilder : IReactiveUIBuilder
     {
         public IScheduler? MainThreadScheduler { get; private set; }
 
+        public IScheduler? TaskpoolScheduler { get; private set; }
+
         public bool MainThreadSchedulerSet { get; private set; }
 
+        public bool TaskpoolSchedulerSet { get; private set; }
+
         public bool PlatformModuleCalled { get; private set; }
 
         public IReactiveUIBuilder WithMainThreadScheduler(IScheduler scheduler, bool setRxApp = true)
@@ -165,7 +169,9 @@ public Splat.Builder.IAppBuilder UsingModule<T>(T registrationModule)
 
         public Splat.Builder.IAppBuilder WithCustomRegistration(Action<IMutableDependencyResolver> configureAction) => throw new NotImplementedException();
 
-        public IReactiveUIBuilder ConfigureMessageBus(Action<MessageBus> configure) => throw new NotImplementedException();
+        public IReactiveUIBuilder WithMessageBus() => throw new NotImplementedException();
+
+        public IReactiveUIBuilder WithMessageBus(Action<IMessageBus> configure) => throw new NotImplementedException();
 
         public IReactiveUIBuilder WithMessageBus(IMessageBus messageBus) => throw new NotImplementedException();
 
@@ -191,13 +197,21 @@ public IReactiveUIBuilder RegisterView<TView, TViewModel>()
         public IReactiveUIBuilder RegisterViewModel<TViewModel>()
             where TViewModel : class, IReactiveObject, new() => throw new NotImplementedException();
 
+        public IReactiveUIBuilder RegisterConstantViewModel<TViewModel>()
+            where TViewModel : class, IReactiveObject, new() => throw new NotImplementedException();
+
         public IReactiveUIBuilder WithPlatformServices() => throw new NotImplementedException();
 
         public IReactiveUIBuilder WithRegistration(Action<IMutableDependencyResolver> configureAction) => throw new NotImplementedException();
 
         public IReactiveUIBuilder WithRegistrationOnBuild(Action<IMutableDependencyResolver> configureAction) => throw new NotImplementedException();
 
-        public IReactiveUIBuilder WithTaskPoolScheduler(IScheduler scheduler, bool setRxApp = true) => throw new NotImplementedException();
+        public IReactiveUIBuilder WithTaskPoolScheduler(IScheduler scheduler, bool setRxApp = true)
+        {
+            TaskpoolScheduler = scheduler;
+            TaskpoolSchedulerSet = true;
+            return this;
+        }
 
         public IReactiveUIBuilder WithViewsFromAssembly(System.Reflection.Assembly assembly) => throw new NotImplementedException();
 
diff --git a/src/tests/ReactiveUI.Builder.Tests/Mixins/BuilderMixinsTests.cs b/src/tests/ReactiveUI.Builder.Tests/Mixins/BuilderMixinsTests.cs
index d233f73d38..b410776f5d 100644
--- a/src/tests/ReactiveUI.Builder.Tests/Mixins/BuilderMixinsTests.cs
+++ b/src/tests/ReactiveUI.Builder.Tests/Mixins/BuilderMixinsTests.cs
@@ -31,7 +31,7 @@ static BuilderMixinsTests()
             () => BuilderMixins.UsingSplatBuilder(null!, _ => { }),
             () => BuilderMixins.ForCustomPlatform(null!, scheduler, _ => { }),
             () => BuilderMixins.ForPlatforms(null!, _ => { }),
-            () => BuilderMixins.ConfigureMessageBus(null!, _ => { }),
+            () => BuilderMixins.WithMessageBus(null!, _ => { }),
             () => BuilderMixins.ConfigureViewLocator(null!, _ => { }),
             () => BuilderMixins.ConfigureSuspensionDriver(null!, _ => { }),
             () => BuilderMixins.RegisterViewModel<BuilderMixinsTestViewModel>(null!),
@@ -230,7 +230,7 @@ public async Task ConfigureMessageBus_registers_configured_instance()
         var builder = resolver.CreateReactiveUIBuilder();
         var configured = false;
 
-        BuilderMixins.ConfigureMessageBus(builder, _ => configured = true);
+        BuilderMixins.WithMessageBus(builder, _ => configured = true);
         builder.WithCoreServices().Build();
 
         using (Assert.Multiple())
diff --git a/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet10_0.verified.txt b/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet10_0.verified.txt
index 049acee93b..62c0950cd3 100644
--- a/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet10_0.verified.txt
+++ b/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet10_0.verified.txt
@@ -1957,11 +1957,12 @@ namespace ReactiveUI.Builder
     public static class BuilderMixins
     {
         public static ReactiveUI.Builder.IReactiveUIBuilder BuildApp(this Splat.Builder.IAppBuilder appBuilder) { }
-        public static ReactiveUI.Builder.IReactiveUIBuilder ConfigureMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.MessageBus> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ConfigureSuspensionDriver(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.ISuspensionDriver> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ConfigureViewLocator(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.DefaultViewLocator> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ForCustomPlatform(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Reactive.Concurrency.IScheduler mainThreadScheduler, System.Action<Splat.IMutableDependencyResolver> platformServices) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ForPlatforms(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, params System.Action<ReactiveUI.Builder.IReactiveUIBuilder>[] platformConfigurations) { }
+        public static ReactiveUI.Builder.IReactiveUIBuilder RegisterConstantViewModel<TViewModel>(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder)
+            where TViewModel :  class, ReactiveUI.IReactiveObject, new () { }
         public static ReactiveUI.Builder.IReactiveUIBuilder RegisterSingletonView<TView, TViewModel>(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>, new ()
             where TViewModel :  class, ReactiveUI.IReactiveObject { }
@@ -2001,7 +2002,9 @@ namespace ReactiveUI.Builder
         public static ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(this ReactiveUI.Builder.IReactiveUIInstance reactiveUIInstance, System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?> action) { }
         public static ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(this ReactiveUI.Builder.IReactiveUIInstance reactiveUIInstance, System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?, T16?> action) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithMainThreadScheduler(this ReactiveUI.Builder.IReactiveUIBuilder builder, System.Reactive.Concurrency.IScheduler scheduler, bool setRxApp = true) { }
+        public static ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, ReactiveUI.IMessageBus messageBus) { }
+        public static ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.IMessageBus> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithPlatformModule<T>(this ReactiveUI.Builder.IReactiveUIBuilder builder)
             where T : ReactiveUI.IWantsToRegisterStuff, new () { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithRegistration(this ReactiveUI.Builder.IReactiveUIBuilder builder, System.Action<Splat.IMutableDependencyResolver> configureAction) { }
@@ -2018,11 +2021,12 @@ namespace ReactiveUI.Builder
     public interface IReactiveUIBuilder : Splat.Builder.IAppBuilder
     {
         ReactiveUI.Builder.IReactiveUIInstance BuildApp();
-        ReactiveUI.Builder.IReactiveUIBuilder ConfigureMessageBus(System.Action<ReactiveUI.MessageBus> configure);
         ReactiveUI.Builder.IReactiveUIBuilder ConfigureSuspensionDriver(System.Action<ReactiveUI.ISuspensionDriver> configure);
         ReactiveUI.Builder.IReactiveUIBuilder ConfigureViewLocator(System.Action<ReactiveUI.DefaultViewLocator> configure);
         ReactiveUI.Builder.IReactiveUIBuilder ForCustomPlatform(System.Reactive.Concurrency.IScheduler mainThreadScheduler, System.Action<Splat.IMutableDependencyResolver> platformServices);
         ReactiveUI.Builder.IReactiveUIBuilder ForPlatforms(params System.Action<ReactiveUI.Builder.IReactiveUIBuilder>[] platformConfigurations);
+        ReactiveUI.Builder.IReactiveUIBuilder RegisterConstantViewModel<TViewModel>()
+            where TViewModel :  class, ReactiveUI.IReactiveObject, new ();
         ReactiveUI.Builder.IReactiveUIBuilder RegisterSingletonView<TView, TViewModel>()
             where TView :  class, ReactiveUI.IViewFor<TViewModel>, new ()
             where TViewModel :  class, ReactiveUI.IReactiveObject;
@@ -2054,7 +2058,9 @@ namespace ReactiveUI.Builder
         ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?> action);
         ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?, T16?> action);
         ReactiveUI.Builder.IReactiveUIBuilder WithMainThreadScheduler(System.Reactive.Concurrency.IScheduler scheduler, bool setRxApp = true);
+        ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus();
         ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(ReactiveUI.IMessageBus messageBus);
+        ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(System.Action<ReactiveUI.IMessageBus> configure);
         ReactiveUI.Builder.IReactiveUIBuilder WithPlatformModule<T>()
             where T : ReactiveUI.IWantsToRegisterStuff, new ();
         ReactiveUI.Builder.IReactiveUIBuilder WithPlatformServices();
@@ -2079,11 +2085,12 @@ namespace ReactiveUI.Builder
         public System.Reactive.Concurrency.IScheduler? MainThreadScheduler { get; }
         public System.Reactive.Concurrency.IScheduler? TaskpoolScheduler { get; }
         public ReactiveUI.Builder.IReactiveUIInstance BuildApp() { }
-        public ReactiveUI.Builder.IReactiveUIBuilder ConfigureMessageBus(System.Action<ReactiveUI.MessageBus> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ConfigureSuspensionDriver(System.Action<ReactiveUI.ISuspensionDriver> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ConfigureViewLocator(System.Action<ReactiveUI.DefaultViewLocator> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ForCustomPlatform(System.Reactive.Concurrency.IScheduler mainThreadScheduler, System.Action<Splat.IMutableDependencyResolver> platformServices) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ForPlatforms(params System.Action<ReactiveUI.Builder.IReactiveUIBuilder>[] platformConfigurations) { }
+        public ReactiveUI.Builder.IReactiveUIBuilder RegisterConstantViewModel<TViewModel>()
+            where TViewModel :  class, ReactiveUI.IReactiveObject, new () { }
         public ReactiveUI.Builder.IReactiveUIBuilder RegisterSingletonView<TView, TViewModel>()
             where TView :  class, ReactiveUI.IViewFor<TViewModel>, new ()
             where TViewModel :  class, ReactiveUI.IReactiveObject { }
@@ -2124,7 +2131,9 @@ namespace ReactiveUI.Builder
         public ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?> action) { }
         public ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?, T16?> action) { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithMainThreadScheduler(System.Reactive.Concurrency.IScheduler scheduler, bool setRxApp = true) { }
+        public ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus() { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(ReactiveUI.IMessageBus messageBus) { }
+        public ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(System.Action<ReactiveUI.IMessageBus> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithPlatformModule<T>()
             where T : ReactiveUI.IWantsToRegisterStuff, new () { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithPlatformServices() { }
diff --git a/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet8_0.verified.txt b/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet8_0.verified.txt
index 049acee93b..62c0950cd3 100644
--- a/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet8_0.verified.txt
+++ b/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet8_0.verified.txt
@@ -1957,11 +1957,12 @@ namespace ReactiveUI.Builder
     public static class BuilderMixins
     {
         public static ReactiveUI.Builder.IReactiveUIBuilder BuildApp(this Splat.Builder.IAppBuilder appBuilder) { }
-        public static ReactiveUI.Builder.IReactiveUIBuilder ConfigureMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.MessageBus> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ConfigureSuspensionDriver(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.ISuspensionDriver> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ConfigureViewLocator(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.DefaultViewLocator> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ForCustomPlatform(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Reactive.Concurrency.IScheduler mainThreadScheduler, System.Action<Splat.IMutableDependencyResolver> platformServices) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ForPlatforms(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, params System.Action<ReactiveUI.Builder.IReactiveUIBuilder>[] platformConfigurations) { }
+        public static ReactiveUI.Builder.IReactiveUIBuilder RegisterConstantViewModel<TViewModel>(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder)
+            where TViewModel :  class, ReactiveUI.IReactiveObject, new () { }
         public static ReactiveUI.Builder.IReactiveUIBuilder RegisterSingletonView<TView, TViewModel>(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>, new ()
             where TViewModel :  class, ReactiveUI.IReactiveObject { }
@@ -2001,7 +2002,9 @@ namespace ReactiveUI.Builder
         public static ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(this ReactiveUI.Builder.IReactiveUIInstance reactiveUIInstance, System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?> action) { }
         public static ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(this ReactiveUI.Builder.IReactiveUIInstance reactiveUIInstance, System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?, T16?> action) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithMainThreadScheduler(this ReactiveUI.Builder.IReactiveUIBuilder builder, System.Reactive.Concurrency.IScheduler scheduler, bool setRxApp = true) { }
+        public static ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, ReactiveUI.IMessageBus messageBus) { }
+        public static ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.IMessageBus> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithPlatformModule<T>(this ReactiveUI.Builder.IReactiveUIBuilder builder)
             where T : ReactiveUI.IWantsToRegisterStuff, new () { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithRegistration(this ReactiveUI.Builder.IReactiveUIBuilder builder, System.Action<Splat.IMutableDependencyResolver> configureAction) { }
@@ -2018,11 +2021,12 @@ namespace ReactiveUI.Builder
     public interface IReactiveUIBuilder : Splat.Builder.IAppBuilder
     {
         ReactiveUI.Builder.IReactiveUIInstance BuildApp();
-        ReactiveUI.Builder.IReactiveUIBuilder ConfigureMessageBus(System.Action<ReactiveUI.MessageBus> configure);
         ReactiveUI.Builder.IReactiveUIBuilder ConfigureSuspensionDriver(System.Action<ReactiveUI.ISuspensionDriver> configure);
         ReactiveUI.Builder.IReactiveUIBuilder ConfigureViewLocator(System.Action<ReactiveUI.DefaultViewLocator> configure);
         ReactiveUI.Builder.IReactiveUIBuilder ForCustomPlatform(System.Reactive.Concurrency.IScheduler mainThreadScheduler, System.Action<Splat.IMutableDependencyResolver> platformServices);
         ReactiveUI.Builder.IReactiveUIBuilder ForPlatforms(params System.Action<ReactiveUI.Builder.IReactiveUIBuilder>[] platformConfigurations);
+        ReactiveUI.Builder.IReactiveUIBuilder RegisterConstantViewModel<TViewModel>()
+            where TViewModel :  class, ReactiveUI.IReactiveObject, new ();
         ReactiveUI.Builder.IReactiveUIBuilder RegisterSingletonView<TView, TViewModel>()
             where TView :  class, ReactiveUI.IViewFor<TViewModel>, new ()
             where TViewModel :  class, ReactiveUI.IReactiveObject;
@@ -2054,7 +2058,9 @@ namespace ReactiveUI.Builder
         ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?> action);
         ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?, T16?> action);
         ReactiveUI.Builder.IReactiveUIBuilder WithMainThreadScheduler(System.Reactive.Concurrency.IScheduler scheduler, bool setRxApp = true);
+        ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus();
         ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(ReactiveUI.IMessageBus messageBus);
+        ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(System.Action<ReactiveUI.IMessageBus> configure);
         ReactiveUI.Builder.IReactiveUIBuilder WithPlatformModule<T>()
             where T : ReactiveUI.IWantsToRegisterStuff, new ();
         ReactiveUI.Builder.IReactiveUIBuilder WithPlatformServices();
@@ -2079,11 +2085,12 @@ namespace ReactiveUI.Builder
         public System.Reactive.Concurrency.IScheduler? MainThreadScheduler { get; }
         public System.Reactive.Concurrency.IScheduler? TaskpoolScheduler { get; }
         public ReactiveUI.Builder.IReactiveUIInstance BuildApp() { }
-        public ReactiveUI.Builder.IReactiveUIBuilder ConfigureMessageBus(System.Action<ReactiveUI.MessageBus> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ConfigureSuspensionDriver(System.Action<ReactiveUI.ISuspensionDriver> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ConfigureViewLocator(System.Action<ReactiveUI.DefaultViewLocator> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ForCustomPlatform(System.Reactive.Concurrency.IScheduler mainThreadScheduler, System.Action<Splat.IMutableDependencyResolver> platformServices) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ForPlatforms(params System.Action<ReactiveUI.Builder.IReactiveUIBuilder>[] platformConfigurations) { }
+        public ReactiveUI.Builder.IReactiveUIBuilder RegisterConstantViewModel<TViewModel>()
+            where TViewModel :  class, ReactiveUI.IReactiveObject, new () { }
         public ReactiveUI.Builder.IReactiveUIBuilder RegisterSingletonView<TView, TViewModel>()
             where TView :  class, ReactiveUI.IViewFor<TViewModel>, new ()
             where TViewModel :  class, ReactiveUI.IReactiveObject { }
@@ -2124,7 +2131,9 @@ namespace ReactiveUI.Builder
         public ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?> action) { }
         public ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?, T16?> action) { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithMainThreadScheduler(System.Reactive.Concurrency.IScheduler scheduler, bool setRxApp = true) { }
+        public ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus() { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(ReactiveUI.IMessageBus messageBus) { }
+        public ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(System.Action<ReactiveUI.IMessageBus> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithPlatformModule<T>()
             where T : ReactiveUI.IWantsToRegisterStuff, new () { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithPlatformServices() { }
diff --git a/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet9_0.verified.txt b/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet9_0.verified.txt
index 049acee93b..62c0950cd3 100644
--- a/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet9_0.verified.txt
+++ b/src/tests/ReactiveUI.Tests/API/ApiApprovalTests.ReactiveUI.DotNet9_0.verified.txt
@@ -1957,11 +1957,12 @@ namespace ReactiveUI.Builder
     public static class BuilderMixins
     {
         public static ReactiveUI.Builder.IReactiveUIBuilder BuildApp(this Splat.Builder.IAppBuilder appBuilder) { }
-        public static ReactiveUI.Builder.IReactiveUIBuilder ConfigureMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.MessageBus> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ConfigureSuspensionDriver(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.ISuspensionDriver> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ConfigureViewLocator(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.DefaultViewLocator> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ForCustomPlatform(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Reactive.Concurrency.IScheduler mainThreadScheduler, System.Action<Splat.IMutableDependencyResolver> platformServices) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder ForPlatforms(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, params System.Action<ReactiveUI.Builder.IReactiveUIBuilder>[] platformConfigurations) { }
+        public static ReactiveUI.Builder.IReactiveUIBuilder RegisterConstantViewModel<TViewModel>(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder)
+            where TViewModel :  class, ReactiveUI.IReactiveObject, new () { }
         public static ReactiveUI.Builder.IReactiveUIBuilder RegisterSingletonView<TView, TViewModel>(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder)
             where TView :  class, ReactiveUI.IViewFor<TViewModel>, new ()
             where TViewModel :  class, ReactiveUI.IReactiveObject { }
@@ -2001,7 +2002,9 @@ namespace ReactiveUI.Builder
         public static ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(this ReactiveUI.Builder.IReactiveUIInstance reactiveUIInstance, System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?> action) { }
         public static ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(this ReactiveUI.Builder.IReactiveUIInstance reactiveUIInstance, System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?, T16?> action) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithMainThreadScheduler(this ReactiveUI.Builder.IReactiveUIBuilder builder, System.Reactive.Concurrency.IScheduler scheduler, bool setRxApp = true) { }
+        public static ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, ReactiveUI.IMessageBus messageBus) { }
+        public static ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(this ReactiveUI.Builder.IReactiveUIBuilder reactiveUIBuilder, System.Action<ReactiveUI.IMessageBus> configure) { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithPlatformModule<T>(this ReactiveUI.Builder.IReactiveUIBuilder builder)
             where T : ReactiveUI.IWantsToRegisterStuff, new () { }
         public static ReactiveUI.Builder.IReactiveUIBuilder WithRegistration(this ReactiveUI.Builder.IReactiveUIBuilder builder, System.Action<Splat.IMutableDependencyResolver> configureAction) { }
@@ -2018,11 +2021,12 @@ namespace ReactiveUI.Builder
     public interface IReactiveUIBuilder : Splat.Builder.IAppBuilder
     {
         ReactiveUI.Builder.IReactiveUIInstance BuildApp();
-        ReactiveUI.Builder.IReactiveUIBuilder ConfigureMessageBus(System.Action<ReactiveUI.MessageBus> configure);
         ReactiveUI.Builder.IReactiveUIBuilder ConfigureSuspensionDriver(System.Action<ReactiveUI.ISuspensionDriver> configure);
         ReactiveUI.Builder.IReactiveUIBuilder ConfigureViewLocator(System.Action<ReactiveUI.DefaultViewLocator> configure);
         ReactiveUI.Builder.IReactiveUIBuilder ForCustomPlatform(System.Reactive.Concurrency.IScheduler mainThreadScheduler, System.Action<Splat.IMutableDependencyResolver> platformServices);
         ReactiveUI.Builder.IReactiveUIBuilder ForPlatforms(params System.Action<ReactiveUI.Builder.IReactiveUIBuilder>[] platformConfigurations);
+        ReactiveUI.Builder.IReactiveUIBuilder RegisterConstantViewModel<TViewModel>()
+            where TViewModel :  class, ReactiveUI.IReactiveObject, new ();
         ReactiveUI.Builder.IReactiveUIBuilder RegisterSingletonView<TView, TViewModel>()
             where TView :  class, ReactiveUI.IViewFor<TViewModel>, new ()
             where TViewModel :  class, ReactiveUI.IReactiveObject;
@@ -2054,7 +2058,9 @@ namespace ReactiveUI.Builder
         ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?> action);
         ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?, T16?> action);
         ReactiveUI.Builder.IReactiveUIBuilder WithMainThreadScheduler(System.Reactive.Concurrency.IScheduler scheduler, bool setRxApp = true);
+        ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus();
         ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(ReactiveUI.IMessageBus messageBus);
+        ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(System.Action<ReactiveUI.IMessageBus> configure);
         ReactiveUI.Builder.IReactiveUIBuilder WithPlatformModule<T>()
             where T : ReactiveUI.IWantsToRegisterStuff, new ();
         ReactiveUI.Builder.IReactiveUIBuilder WithPlatformServices();
@@ -2079,11 +2085,12 @@ namespace ReactiveUI.Builder
         public System.Reactive.Concurrency.IScheduler? MainThreadScheduler { get; }
         public System.Reactive.Concurrency.IScheduler? TaskpoolScheduler { get; }
         public ReactiveUI.Builder.IReactiveUIInstance BuildApp() { }
-        public ReactiveUI.Builder.IReactiveUIBuilder ConfigureMessageBus(System.Action<ReactiveUI.MessageBus> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ConfigureSuspensionDriver(System.Action<ReactiveUI.ISuspensionDriver> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ConfigureViewLocator(System.Action<ReactiveUI.DefaultViewLocator> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ForCustomPlatform(System.Reactive.Concurrency.IScheduler mainThreadScheduler, System.Action<Splat.IMutableDependencyResolver> platformServices) { }
         public ReactiveUI.Builder.IReactiveUIBuilder ForPlatforms(params System.Action<ReactiveUI.Builder.IReactiveUIBuilder>[] platformConfigurations) { }
+        public ReactiveUI.Builder.IReactiveUIBuilder RegisterConstantViewModel<TViewModel>()
+            where TViewModel :  class, ReactiveUI.IReactiveObject, new () { }
         public ReactiveUI.Builder.IReactiveUIBuilder RegisterSingletonView<TView, TViewModel>()
             where TView :  class, ReactiveUI.IViewFor<TViewModel>, new ()
             where TViewModel :  class, ReactiveUI.IReactiveObject { }
@@ -2124,7 +2131,9 @@ namespace ReactiveUI.Builder
         public ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?> action) { }
         public ReactiveUI.Builder.IReactiveUIInstance WithInstance<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(System.Action<T1?, T2?, T3?, T4?, T5?, T6?, T7?, T8?, T9?, T10?, T11?, T12?, T13?, T14?, T15?, T16?> action) { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithMainThreadScheduler(System.Reactive.Concurrency.IScheduler scheduler, bool setRxApp = true) { }
+        public ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus() { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(ReactiveUI.IMessageBus messageBus) { }
+        public ReactiveUI.Builder.IReactiveUIBuilder WithMessageBus(System.Action<ReactiveUI.IMessageBus> configure) { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithPlatformModule<T>()
             where T : ReactiveUI.IWantsToRegisterStuff, new () { }
         public ReactiveUI.Builder.IReactiveUIBuilder WithPlatformServices() { }