refactor(di): shared AddSharpClientViewModels registration to prevent host drift

src/SharpClient.App/MauiProgram.cs

@@ -10,6 +10,7 @@
 using SharpClient.Core.Sessions;
 using SharpClient.Core.Triggers;
 using SharpClient.Data;
+using SharpClient.UI;
 
 namespace SharpClient.App;
 
@@ -90,8 +91,6 @@ public static MauiApp CreateMauiApp()
         builder.Services.AddSingleton<ISecretStore, MauiSecretStore>();
         builder.Services.AddSingleton<INotifier, MauiNotifier>();
         builder.Services.AddSingleton<SharpClient.Core.Platform.IPreferences, MauiPreferences>();
-        builder.Services.AddSingleton<SettingsViewModel>(sp =>
-            new SettingsViewModel(sp.GetRequiredService<SharpClient.Core.Platform.IPreferences>()));
 
         // ── Data / persistence ────────────────────────────────────────────
         // AppDbContext is transient so each call gets a fresh context; this
@@ -106,27 +105,14 @@ public static MauiApp CreateMauiApp()
         builder.Services.AddSingleton<ISessionManager>(sp =>
             sp.GetRequiredService<SessionManager>());
 
-        // ── View models ───────────────────────────────────────────────────
-        builder.Services.AddSingleton<SessionsViewModel>(sp =>
-            new SessionsViewModel(sp.GetRequiredService<ISessionManager>()));
-
-        builder.Services.AddSingleton<ProtocolPanelViewModel>(sp =>
-            new ProtocolPanelViewModel(sp.GetRequiredService<ISessionManager>()));
-
-        builder.Services.AddTransient<WorldManagerViewModel>(sp =>
-            new WorldManagerViewModel(
-                sp.GetRequiredService<IWorldStore>(),
-                sp.GetRequiredService<ISecretStore>(),
-                sp.GetRequiredService<ISessionManager>(),
-                sp.GetRequiredService<ISessionLauncher>()));
-        builder.Services.AddTransient<HistorySearchViewModel>(sp =>
-            new HistorySearchViewModel(
-                sp.GetRequiredService<ISessionHistory>(),
-                sp.GetRequiredService<IWorldStore>()));
-
         // ── Session launcher (real telnet) ────────────────────────────────
         builder.Services.AddTransient<ISessionLauncher, SharpClient.Core.Sessions.TelnetSessionLauncher>();
 
+        // ── View models ───────────────────────────────────────────────────
+        // Registered via the shared extension so MAUI and Web stay in lockstep (no host drift).
+        // Per-view view models are Transient here to match MAUI's per-request-less lifetime model.
+        builder.Services.AddSharpClientViewModels(ServiceLifetime.Transient);
+
         // ── Trigger / alias engines (stateless) ──────────────────────────
         builder.Services.AddSingleton<ITriggerEngine, TriggerEngine>();
         builder.Services.AddSingleton<IAliasEngine, AliasEngine>();

src/SharpClient.UI/ServiceCollectionExtensions.cs

@@ -0,0 +1,58 @@
+using Microsoft.Extensions.DependencyInjection;
+using SharpClient.Core.Persistence;
+using SharpClient.Core.Platform;
+using SharpClient.Core.Presentation;
+using SharpClient.Core.Sessions;
+
+namespace SharpClient.UI;
+
+/// <summary>
+/// Shared DI registration for the presentation view models, referenced by BOTH the MAUI host
+/// (<c>SharpClient.App</c>) and the Web host (<c>SharpClient.Web</c>). Keeping the registrations in
+/// one place prevents host drift — previously each host registered the view models independently and
+/// they diverged (e.g. <see cref="TriggerAliasEditorViewModel"/> was registered on Web but not MAUI,
+/// crashing the Rules page on Android).
+/// </summary>
+public static class ServiceCollectionExtensions
+{
+    /// <summary>
+    /// Registers all six presentation view models. The three session/settings view models are always
+    /// singletons; the three per-view view models use <paramref name="perViewLifetime"/> (Transient
+    /// in MAUI, Scoped in Web). All constructor dependencies must already be registered by the host.
+    /// </summary>
+    public static IServiceCollection AddSharpClientViewModels(
+        this IServiceCollection services,
+        ServiceLifetime perViewLifetime)
+    {
+        // ── Shared-lifetime view models (Singleton in both hosts) ────────────
+        services.AddSingleton<SessionsViewModel>(sp =>
+            new SessionsViewModel(sp.GetRequiredService<ISessionManager>()));
+        services.AddSingleton<ProtocolPanelViewModel>(sp =>
+            new ProtocolPanelViewModel(sp.GetRequiredService<ISessionManager>()));
+        services.AddSingleton<SettingsViewModel>(sp =>
+            new SettingsViewModel(sp.GetRequiredService<IPreferences>()));
+
+        // ── Per-view view models (Transient in MAUI, Scoped in Web) ──────────
+        services.Add(new ServiceDescriptor(
+            typeof(WorldManagerViewModel),
+            sp => new WorldManagerViewModel(
+                sp.GetRequiredService<IWorldStore>(),
+                sp.GetRequiredService<ISecretStore>(),
+                sp.GetRequiredService<ISessionManager>(),
+                sp.GetRequiredService<ISessionLauncher>()),
+            perViewLifetime));
+        services.Add(new ServiceDescriptor(
+            typeof(HistorySearchViewModel),
+            sp => new HistorySearchViewModel(
+                sp.GetRequiredService<ISessionHistory>(),
+                sp.GetRequiredService<IWorldStore>()),
+            perViewLifetime));
+        services.Add(new ServiceDescriptor(
+            typeof(TriggerAliasEditorViewModel),
+            sp => new TriggerAliasEditorViewModel(
+                sp.GetRequiredService<IWorldStore>()),
+            perViewLifetime));
+
+        return services;
+    }
+}

src/SharpClient.UI/SharpClient.UI.csproj

@@ -10,6 +10,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.Components.Web" Version="10.0.8" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.8" />
   </ItemGroup>
 
   <ItemGroup>

src/SharpClient.Web/Program.cs

@@ -6,6 +6,7 @@
 using SharpClient.Core.Sessions;
 using SharpClient.Core.Triggers;
 using SharpClient.Data;
+using SharpClient.UI;
 using SharpClient.Web;
 using SharpClient.Web.Components;
 
@@ -20,8 +21,6 @@
 
 // ── Platform services ──────────────────────────────────────────────────────
 builder.Services.AddSingleton<IPreferences, WebPreferences>();
-builder.Services.AddSingleton<SettingsViewModel>(sp =>
-    new SettingsViewModel(sp.GetRequiredService<IPreferences>()));
 
 builder.Services.AddSingleton<IAppStorage, WebAppStorage>();
 builder.Services.AddSingleton<ISecretStore, WebSecretStore>();
@@ -41,10 +40,6 @@
 // ── Session management ─────────────────────────────────────────────────────
 builder.Services.AddSingleton<SessionManager>();
 builder.Services.AddSingleton<ISessionManager>(sp => sp.GetRequiredService<SessionManager>());
-builder.Services.AddSingleton<SessionsViewModel>(sp =>
-    new SessionsViewModel(sp.GetRequiredService<ISessionManager>()));
-builder.Services.AddSingleton<ProtocolPanelViewModel>(sp =>
-    new ProtocolPanelViewModel(sp.GetRequiredService<ISessionManager>()));
 
 // ── Data / persistence ─────────────────────────────────────────────────────
 builder.Services.AddScoped<AppDbContext>();
@@ -55,18 +50,9 @@
 builder.Services.AddScoped<ISessionLauncher, TelnetSessionLauncher>();
 
 // ── View models ────────────────────────────────────────────────────────────
-builder.Services.AddScoped<WorldManagerViewModel>(sp => new WorldManagerViewModel(
-    sp.GetRequiredService<IWorldStore>(),
-    sp.GetRequiredService<ISecretStore>(),
-    sp.GetRequiredService<ISessionManager>(),
-    sp.GetRequiredService<ISessionLauncher>()));
-builder.Services.AddScoped<TriggerAliasEditorViewModel>(sp =>
-    new TriggerAliasEditorViewModel(
-        sp.GetRequiredService<IWorldStore>()));
-builder.Services.AddScoped<HistorySearchViewModel>(sp =>
-    new HistorySearchViewModel(
-        sp.GetRequiredService<ISessionHistory>(),
-        sp.GetRequiredService<IWorldStore>()));
+// Registered via the shared extension so MAUI and Web stay in lockstep (no host drift).
+// Per-view view models are Scoped here to match the Web's per-request scope.
+builder.Services.AddSharpClientViewModels(ServiceLifetime.Scoped);
 
 var app = builder.Build();