0.5.20

我认为很稳定了，后面就要开始弄插件不稳定了

.github/workflows/build.yml

@@ -71,10 +71,10 @@ jobs:
           dotnet-version: ${{ env.DOTNET_VERSION }}
 
       - name: Restore
-        run: dotnet restore
+        run: dotnet restore ${{ env.Solution_Name }}
 
       - name: Build
-        run: dotnet build --no-restore -c Release -v minimal
+        run: dotnet build ${{ env.Solution_Name }} --no-restore -c Release -v minimal
 
       - name: Upload artifacts
         uses: actions/upload-artifact@v4
@@ -101,10 +101,10 @@ jobs:
           dotnet-version: ${{ env.DOTNET_VERSION }}
 
       - name: Restore
-        run: dotnet restore
+        run: dotnet restore ${{ env.Solution_Name }}
 
       - name: Build
-        run: dotnet build --no-restore -c Release -v minimal
+        run: dotnet build ${{ env.Solution_Name }} --no-restore -c Release -v minimal
 
       - name: Upload artifacts
         uses: actions/upload-artifact@v4

.gitignore

@@ -492,3 +492,23 @@ nul
 /_build_verify_plugin_services
 /LanMountainDesktop.PluginSdk/_build_verify_*/
 /_build_obj
+
+# LanMountainDesktop local workspace files
+/.arts/
+/.knox/
+/.lingma/
+/.tmp/
+/publish-test/
+/validator-restore.log
+/temp_old_main.axaml
+/temp_old_main_utf8.axaml
+
+# LanMountainDesktop local packaging outputs
+/build-installer/
+/build-deb/
+/dmg-temp/
+/release-files/
+/LanMountainDesktop.app/
+/*.deb
+/*.dmg
+/*.AppImage

LanMountainDesktop.PluginSdk/IPlugin.cs

@@ -1,6 +1,9 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
 namespace LanMountainDesktop.PluginSdk;
 
 public interface IPlugin
 {
-    void Initialize(IPluginContext context);
+    void Initialize(HostBuilderContext context, IServiceCollection services);
 }

LanMountainDesktop.PluginSdk/IPluginContext.cs

@@ -1,27 +1,6 @@
-using System.Collections.Generic;
-
 namespace LanMountainDesktop.PluginSdk;
 
-public interface IPluginContext
+[Obsolete("Plugin API 2.0.0 uses IPluginRuntimeContext and IServiceCollection-based initialization.")]
+public interface IPluginContext : IPluginRuntimeContext
 {
-    PluginManifest Manifest { get; }
-
-    string PluginDirectory { get; }
-
-    string DataDirectory { get; }
-
-    IServiceProvider Services { get; }
-
-    IReadOnlyDictionary<string, object?> Properties { get; }
-
-    T? GetService<T>();
-
-    bool TryGetProperty<T>(string key, out T? value);
-
-    void RegisterService<TService>(TService service)
-        where TService : class;
-
-    void RegisterSettingsPage(PluginSettingsPageRegistration registration);
-
-    void RegisterDesktopComponent(PluginDesktopComponentRegistration registration);
 }

LanMountainDesktop.PluginSdk/IPluginExportRegistry.cs

@@ -0,0 +1,13 @@
+namespace LanMountainDesktop.PluginSdk;
+
+public interface IPluginExportRegistry
+{
+    IReadOnlyList<PluginServiceExportDescriptor> GetExports();
+
+    IReadOnlyList<PluginServiceExportDescriptor> GetExports(Type contractType);
+
+    PluginServiceExportDescriptor? GetExport(Type contractType, string providerPluginId);
+
+    TContract? GetExport<TContract>(string providerPluginId)
+        where TContract : class;
+}

LanMountainDesktop.PluginSdk/IPluginRuntimeContext.cs

@@ -0,0 +1,18 @@
+namespace LanMountainDesktop.PluginSdk;
+
+public interface IPluginRuntimeContext
+{
+    PluginManifest Manifest { get; }
+
+    string PluginDirectory { get; }
+
+    string DataDirectory { get; }
+
+    IServiceProvider Services { get; }
+
+    IReadOnlyDictionary<string, object?> Properties { get; }
+
+    T? GetService<T>();
+
+    bool TryGetProperty<T>(string key, out T? value);
+}

LanMountainDesktop.PluginSdk/LanMountainDesktop.PluginSdk.csproj

@@ -1,15 +1,17 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFramework>net10.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
-    <Version>1.0.0</Version>
+    <Version>2.0.0</Version>
   </PropertyGroup>
 
   <ItemGroup>
     <Compile Remove="_build_verify_*\**\*.cs" />
     <PackageReference Include="Avalonia" Version="11.3.12" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="10.0.0" />
   </ItemGroup>
 
 </Project>

LanMountainDesktop.PluginSdk/PluginBase.cs

@@ -1,8 +1,11 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+
 namespace LanMountainDesktop.PluginSdk;
 
 public abstract class PluginBase : IPlugin
 {
-    public virtual void Initialize(IPluginContext context)
+    public virtual void Initialize(HostBuilderContext context, IServiceCollection services)
     {
     }
 }

LanMountainDesktop.PluginSdk/PluginDesktopComponentRegistration.cs

@@ -7,7 +7,7 @@ public sealed class PluginDesktopComponentRegistration
     public PluginDesktopComponentRegistration(
         string componentId,
         string displayName,
-        Func<PluginDesktopComponentContext, Control> controlFactory,
+        Func<IServiceProvider, PluginDesktopComponentContext, Control> controlFactory,
         string iconKey = "PuzzlePiece",
         string category = "Plugins",
         int minWidthCells = 2,
@@ -40,13 +40,42 @@ public sealed class PluginDesktopComponentRegistration
         CornerRadiusResolver = cornerRadiusResolver;
     }
 
+    public PluginDesktopComponentRegistration(
+        string componentId,
+        string displayName,
+        Func<PluginDesktopComponentContext, Control> controlFactory,
+        string iconKey = "PuzzlePiece",
+        string category = "Plugins",
+        int minWidthCells = 2,
+        int minHeightCells = 2,
+        bool allowDesktopPlacement = true,
+        bool allowStatusBarPlacement = false,
+        PluginDesktopComponentResizeMode resizeMode = PluginDesktopComponentResizeMode.Proportional,
+        string? displayNameLocalizationKey = null,
+        Func<double, double>? cornerRadiusResolver = null)
+        : this(
+            componentId,
+            displayName,
+            (_, context) => controlFactory(context),
+            iconKey,
+            category,
+            minWidthCells,
+            minHeightCells,
+            allowDesktopPlacement,
+            allowStatusBarPlacement,
+            resizeMode,
+            displayNameLocalizationKey,
+            cornerRadiusResolver)
+    {
+    }
+
     public string ComponentId { get; }
 
     public string DisplayName { get; }
 
     public string? DisplayNameLocalizationKey { get; }
 
-    public Func<PluginDesktopComponentContext, Control> ControlFactory { get; }
+    public Func<IServiceProvider, PluginDesktopComponentContext, Control> ControlFactory { get; }
 
     public string IconKey { get; }
 

LanMountainDesktop.PluginSdk/PluginLocalizer.cs

@@ -26,7 +26,7 @@ public sealed class PluginLocalizer
 
     public string LanguageCode { get; }
 
-    public static PluginLocalizer Create(IPluginContext context)
+    public static PluginLocalizer Create(IPluginRuntimeContext context)
     {
         ArgumentNullException.ThrowIfNull(context);
         return new PluginLocalizer(context.PluginDirectory, ResolveLanguageCode(context.Properties));

LanMountainDesktop.PluginSdk/PluginManifest.cs

@@ -9,7 +9,8 @@ public sealed record PluginManifest(
     string? Description = null,
     string? Author = null,
     string? Version = null,
-    string? ApiVersion = null)
+    string? ApiVersion = null,
+    IReadOnlyList<PluginSharedContractReference>? SharedContracts = null)
 {
     private static readonly JsonSerializerOptions SerializerOptions = new()
     {
@@ -57,6 +58,7 @@ public sealed record PluginManifest(
 
     private PluginManifest NormalizeAndValidate(string manifestPath)
     {
+        var normalizedSharedContracts = NormalizeSharedContracts(manifestPath, SharedContracts);
         var normalized = this with
         {
             Id = RequireValue(Id, nameof(Id), manifestPath),
@@ -65,7 +67,8 @@ public sealed record PluginManifest(
             Description = NormalizeOptionalValue(Description),
             Author = NormalizeOptionalValue(Author),
             Version = NormalizeOptionalValue(Version),
-            ApiVersion = NormalizeOptionalValue(ApiVersion) ?? PluginSdkInfo.ApiVersion
+            ApiVersion = NormalizeOptionalValue(ApiVersion) ?? PluginSdkInfo.ApiVersion,
+            SharedContracts = normalizedSharedContracts
         };
 
         if (!System.Version.TryParse(normalized.ApiVersion, out var requestedVersion))
@@ -82,7 +85,41 @@ public sealed record PluginManifest(
         if (requestedVersion.Major != currentVersion.Major)
         {
             throw new InvalidOperationException(
-                $"Plugin '{normalized.Id}' targets API version '{normalized.ApiVersion}', but the host provides '{PluginSdkInfo.ApiVersion}'.");
+                $"Plugin '{normalized.Id}' targets API version '{normalized.ApiVersion}', but the host provides '{PluginSdkInfo.ApiVersion}'. Upgrade the plugin to API {PluginSdkInfo.ApiVersion}.");
+        }
+
+        return normalized;
+    }
+
+    private static IReadOnlyList<PluginSharedContractReference> NormalizeSharedContracts(
+        string manifestPath,
+        IReadOnlyList<PluginSharedContractReference>? sharedContracts)
+    {
+        if (sharedContracts is null || sharedContracts.Count == 0)
+        {
+            return Array.Empty<PluginSharedContractReference>();
+        }
+
+        var normalized = new List<PluginSharedContractReference>(sharedContracts.Count);
+        var seenIds = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+
+        foreach (var contract in sharedContracts)
+        {
+            if (contract is null)
+            {
+                throw new InvalidOperationException(
+                    $"Plugin manifest '{manifestPath}' contains a null shared contract declaration.");
+            }
+
+            var normalizedContract = contract.NormalizeAndValidate(manifestPath);
+            var contractKey = $"{normalizedContract.Id}@{normalizedContract.Version}";
+            if (!seenIds.Add(contractKey))
+            {
+                throw new InvalidOperationException(
+                    $"Plugin manifest '{manifestPath}' declares duplicate shared contract '{contractKey}'.");
+            }
+
+            normalized.Add(normalizedContract);
         }
 
         return normalized;

LanMountainDesktop.PluginSdk/PluginSdkInfo.cs

@@ -2,7 +2,7 @@ namespace LanMountainDesktop.PluginSdk;
 
 public static class PluginSdkInfo
 {
-    public const string ApiVersion = "1.0.0";
+    public const string ApiVersion = "2.0.0";
     public const string ManifestFileName = "plugin.json";
     public const string PackageFileExtension = ".laapp";
     public const string DataDirectoryName = "Data";

LanMountainDesktop.PluginSdk/PluginServiceCollectionExtensions.cs

@@ -0,0 +1,95 @@
+using Avalonia.Controls;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace LanMountainDesktop.PluginSdk;
+
+public static class PluginServiceCollectionExtensions
+{
+    public static IServiceCollection AddPluginSettingsPage<TControl>(
+        this IServiceCollection services,
+        string id,
+        string title,
+        int sortOrder = 0)
+        where TControl : Control
+    {
+        ArgumentNullException.ThrowIfNull(services);
+
+        services.AddSingleton(new PluginSettingsPageRegistration(
+            id,
+            title,
+            provider => ActivatorUtilities.CreateInstance<TControl>(provider),
+            sortOrder));
+        return services;
+    }
+
+    public static IServiceCollection AddPluginDesktopComponent<TControl>(
+        this IServiceCollection services,
+        string componentId,
+        string displayName,
+        string iconKey = "PuzzlePiece",
+        string category = "Plugins",
+        int minWidthCells = 2,
+        int minHeightCells = 2,
+        bool allowDesktopPlacement = true,
+        bool allowStatusBarPlacement = false,
+        PluginDesktopComponentResizeMode resizeMode = PluginDesktopComponentResizeMode.Proportional,
+        string? displayNameLocalizationKey = null,
+        Func<double, double>? cornerRadiusResolver = null)
+        where TControl : Control
+    {
+        ArgumentNullException.ThrowIfNull(services);
+
+        services.AddSingleton(new PluginDesktopComponentRegistration(
+            componentId,
+            displayName,
+            (provider, context) => ActivatorUtilities.CreateInstance<TControl>(provider, context),
+            iconKey,
+            category,
+            minWidthCells,
+            minHeightCells,
+            allowDesktopPlacement,
+            allowStatusBarPlacement,
+            resizeMode,
+            displayNameLocalizationKey,
+            cornerRadiusResolver));
+        return services;
+    }
+
+    public static IServiceCollection AddPluginExport<TContract, TImplementation>(this IServiceCollection services)
+        where TContract : class
+        where TImplementation : class, TContract
+    {
+        ArgumentNullException.ThrowIfNull(services);
+
+        EnsureSingletonRegistration<TContract, TImplementation>(services);
+
+        if (!services.Any(descriptor =>
+                descriptor.ServiceType == typeof(PluginServiceExportRegistration) &&
+                descriptor.ImplementationInstance is PluginServiceExportRegistration existing &&
+                existing.ContractType == typeof(TContract) &&
+                existing.ImplementationType == typeof(TImplementation)))
+        {
+            services.AddSingleton(new PluginServiceExportRegistration(typeof(TContract), typeof(TImplementation)));
+        }
+
+        return services;
+    }
+
+    private static void EnsureSingletonRegistration<TContract, TImplementation>(IServiceCollection services)
+        where TContract : class
+        where TImplementation : class, TContract
+    {
+        var contractDescriptor = services.LastOrDefault(descriptor => descriptor.ServiceType == typeof(TContract));
+        if (contractDescriptor is null)
+        {
+            services.AddSingleton<TContract, TImplementation>();
+            return;
+        }
+
+        if (contractDescriptor.Lifetime != ServiceLifetime.Singleton)
+        {
+            throw new InvalidOperationException(
+                $"Exported contract '{typeof(TContract).FullName}' must be registered as Singleton.");
+        }
+    }
+}

LanMountainDesktop.PluginSdk/PluginServiceExportDescriptor.cs

@@ -0,0 +1,6 @@
+namespace LanMountainDesktop.PluginSdk;
+
+public sealed record PluginServiceExportDescriptor(
+    string ProviderPluginId,
+    Type ContractType,
+    object ServiceInstance);

LanMountainDesktop.PluginSdk/PluginServiceExportRegistration.cs

@@ -0,0 +1,17 @@
+namespace LanMountainDesktop.PluginSdk;
+
+public sealed class PluginServiceExportRegistration
+{
+    public PluginServiceExportRegistration(Type contractType, Type implementationType)
+    {
+        ArgumentNullException.ThrowIfNull(contractType);
+        ArgumentNullException.ThrowIfNull(implementationType);
+
+        ContractType = contractType;
+        ImplementationType = implementationType;
+    }
+
+    public Type ContractType { get; }
+
+    public Type ImplementationType { get; }
+}

LanMountainDesktop.PluginSdk/PluginSettingsPageRegistration.cs

@@ -7,7 +7,7 @@ public sealed class PluginSettingsPageRegistration
     public PluginSettingsPageRegistration(
         string id,
         string title,
-        Func<Control> contentFactory,
+        Func<IServiceProvider, Control> contentFactory,
         int sortOrder = 0)
     {
         ArgumentException.ThrowIfNullOrWhiteSpace(id);
@@ -20,11 +20,20 @@ public sealed class PluginSettingsPageRegistration
         SortOrder = sortOrder;
     }
 
+    public PluginSettingsPageRegistration(
+        string id,
+        string title,
+        Func<Control> contentFactory,
+        int sortOrder = 0)
+        : this(id, title, _ => contentFactory(), sortOrder)
+    {
+    }
+
     public string Id { get; }
 
     public string Title { get; }
 
     public int SortOrder { get; }
 
-    public Func<Control> ContentFactory { get; }
+    public Func<IServiceProvider, Control> ContentFactory { get; }
 }

LanMountainDesktop.PluginSdk/PluginSharedContractReference.cs

@@ -0,0 +1,47 @@
+using System.Text.Json.Serialization;
+
+namespace LanMountainDesktop.PluginSdk;
+
+public sealed record PluginSharedContractReference(
+    string Id,
+    string Version,
+    string AssemblyName)
+{
+    [JsonIgnore]
+    public string NormalizedId => Id.Trim();
+
+    [JsonIgnore]
+    public string NormalizedVersion => Version.Trim();
+
+    [JsonIgnore]
+    public string NormalizedAssemblyName => AssemblyName.Trim();
+
+    internal PluginSharedContractReference NormalizeAndValidate(string manifestPath)
+    {
+        var normalized = this with
+        {
+            Id = RequireValue(Id, nameof(Id), manifestPath),
+            Version = RequireValue(Version, nameof(Version), manifestPath),
+            AssemblyName = RequireValue(AssemblyName, nameof(AssemblyName), manifestPath)
+        };
+
+        if (!System.Version.TryParse(normalized.Version, out _))
+        {
+            throw new InvalidOperationException(
+                $"Plugin manifest '{manifestPath}' declares invalid shared contract version '{normalized.Version}' for '{normalized.Id}'.");
+        }
+
+        return normalized;
+    }
+
+    private static string RequireValue(string? value, string propertyName, string manifestPath)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            throw new InvalidOperationException(
+                $"Plugin manifest '{manifestPath}' is missing required shared contract property '{propertyName}'.");
+        }
+
+        return value.Trim();
+    }
+}

LanMountainDesktop.Tests/ComponentSettingsServiceTests.cs

@@ -0,0 +1,187 @@
+using System.Text.Json;
+using LanMountainDesktop.Models;
+using LanMountainDesktop.Services;
+using Xunit;
+
+namespace LanMountainDesktop.Tests;
+
+public sealed class ComponentSettingsServiceTests
+{
+    [Fact]
+    public void Load_MigratesLegacySnapshotFileToCanonicalDocument()
+    {
+        using var sandbox = new ComponentSettingsSandbox();
+        File.WriteAllText(
+            sandbox.SettingsPath,
+            """
+            {
+              "DesktopClockSecondHandMode": "Sweep",
+              "ImportedClassSchedules": [
+                {
+                  "Id": "spring-2026",
+                  "DisplayName": "Spring 2026",
+                  "FilePath": "C:\\Schedules\\spring-2026.yaml"
+                }
+              ],
+              "ActiveImportedClassScheduleId": "spring-2026"
+            }
+            """);
+
+        var service = sandbox.CreateService();
+
+        var snapshot = service.Load();
+
+        Assert.Equal("Sweep", snapshot.DesktopClockSecondHandMode);
+        Assert.Single(snapshot.ImportedClassSchedules);
+
+        using var document = JsonDocument.Parse(File.ReadAllText(sandbox.SettingsPath));
+        Assert.True(document.RootElement.TryGetProperty("defaultSettings", out var defaultSettings));
+        Assert.Equal("Sweep", defaultSettings.GetProperty("desktopClockSecondHandMode").GetString());
+        Assert.False(document.RootElement.TryGetProperty("DesktopClockSecondHandMode", out _));
+    }
+
+    [Fact]
+    public void Load_ReadsPascalCaseDocumentAndRewritesToCanonicalDocument()
+    {
+        using var sandbox = new ComponentSettingsSandbox();
+        File.WriteAllText(
+            sandbox.SettingsPath,
+            """
+            {
+              "DefaultSettings": {
+                "DesktopClockSecondHandMode": "Tick"
+              },
+              "InstanceSettings": {
+                "DesktopClock::clock-2x2": {
+                  "DesktopClockSecondHandMode": "Sweep"
+                }
+              },
+              "PluginSettings": {
+                "DesktopClock::clock-2x2": {
+                  "SampleFlag": true
+                }
+              }
+            }
+            """);
+
+        var service = sandbox.CreateService();
+
+        var snapshot = service.LoadForComponent("DesktopClock", "clock-2x2");
+        var pluginSettings = service.LoadPluginSettings<SamplePluginSettings>("DesktopClock", "clock-2x2");
+
+        Assert.Equal("Sweep", snapshot.DesktopClockSecondHandMode);
+        Assert.True(pluginSettings.SampleFlag);
+
+        using var document = JsonDocument.Parse(File.ReadAllText(sandbox.SettingsPath));
+        Assert.True(document.RootElement.TryGetProperty("instanceSettings", out var instanceSettings));
+        Assert.True(instanceSettings.TryGetProperty("DesktopClock::clock-2x2", out var clockSettings));
+        Assert.Equal("Sweep", clockSettings.GetProperty("desktopClockSecondHandMode").GetString());
+        Assert.False(document.RootElement.TryGetProperty("InstanceSettings", out _));
+    }
+
+    [Fact]
+    public void SaveForComponent_RoundTripsInstanceAndPluginSettingsAcrossNewService()
+    {
+        using var sandbox = new ComponentSettingsSandbox();
+        var service = sandbox.CreateService();
+
+        service.SaveForComponent(
+            "DesktopClock",
+            "clock-2x2",
+            new ComponentSettingsSnapshot
+            {
+                DesktopClockSecondHandMode = "Sweep"
+            });
+        service.SaveForComponent(
+            "DesktopClassSchedule",
+            "class-schedule-2x2",
+            new ComponentSettingsSnapshot
+            {
+                ImportedClassSchedules =
+                [
+                    new ImportedClassScheduleSnapshot
+                    {
+                        Id = "spring-2026",
+                        DisplayName = "Spring 2026",
+                        FilePath = "C:\\Schedules\\spring-2026.yaml"
+                    }
+                ],
+                ActiveImportedClassScheduleId = "spring-2026"
+            });
+        service.SavePluginSettings(
+            "DesktopClassSchedule",
+            "class-schedule-2x2",
+            new SamplePluginSettings
+            {
+                SampleFlag = true,
+                Title = "schedule-settings"
+            });
+
+        ComponentSettingsService.ResetCacheForTests();
+        var reloadedService = sandbox.CreateService();
+
+        var clockSnapshot = reloadedService.LoadForComponent("DesktopClock", "clock-2x2");
+        var classScheduleSnapshot = reloadedService.LoadForComponent("DesktopClassSchedule", "class-schedule-2x2");
+        var pluginSettings = reloadedService.LoadPluginSettings<SamplePluginSettings>(
+            "DesktopClassSchedule",
+            "class-schedule-2x2");
+
+        Assert.Equal("Sweep", clockSnapshot.DesktopClockSecondHandMode);
+        Assert.Single(classScheduleSnapshot.ImportedClassSchedules);
+        Assert.Equal("spring-2026", classScheduleSnapshot.ActiveImportedClassScheduleId);
+        Assert.True(pluginSettings.SampleFlag);
+        Assert.Equal("schedule-settings", pluginSettings.Title);
+
+        using var document = JsonDocument.Parse(File.ReadAllText(sandbox.SettingsPath));
+        Assert.True(document.RootElement.TryGetProperty("instanceSettings", out var instanceSettings));
+        Assert.True(instanceSettings.TryGetProperty("DesktopClock::clock-2x2", out _));
+        Assert.True(instanceSettings.TryGetProperty("DesktopClassSchedule::class-schedule-2x2", out _));
+        Assert.True(document.RootElement.TryGetProperty("pluginSettings", out var pluginSettingsNode));
+        Assert.True(pluginSettingsNode.TryGetProperty("DesktopClassSchedule::class-schedule-2x2", out _));
+    }
+
+    private sealed class ComponentSettingsSandbox : IDisposable
+    {
+        private readonly string _directoryPath = Path.Combine(
+            Path.GetTempPath(),
+            "LanMountainDesktop.ComponentSettingsTests",
+            Guid.NewGuid().ToString("N"));
+
+        public ComponentSettingsSandbox()
+        {
+            Directory.CreateDirectory(_directoryPath);
+            ComponentSettingsService.ResetCacheForTests();
+        }
+
+        public string SettingsPath => Path.Combine(_directoryPath, "component-settings.json");
+
+        public ComponentSettingsService CreateService()
+        {
+            return new ComponentSettingsService(_directoryPath);
+        }
+
+        public void Dispose()
+        {
+            ComponentSettingsService.ResetCacheForTests();
+
+            try
+            {
+                if (Directory.Exists(_directoryPath))
+                {
+                    Directory.Delete(_directoryPath, true);
+                }
+            }
+            catch
+            {
+                // Temporary test directories are best-effort cleanup.
+            }
+        }
+    }
+
+    private sealed class SamplePluginSettings
+    {
+        public bool SampleFlag { get; set; }
+
+        public string Title { get; set; } = string.Empty;
+    }
+}

LanMountainDesktop.Tests/LanMountainDesktop.Tests.csproj

@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\LanMountainDesktop\LanMountainDesktop.csproj" />
+  </ItemGroup>
+</Project>

LanMountainDesktop.Tests/UiExceptionGuardTests.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Threading.Tasks;
+using LanMountainDesktop.Services;
+using Xunit;
+
+namespace LanMountainDesktop.Tests;
+
+public sealed class UiExceptionGuardTests
+{
+    [Fact]
+    public async Task RunGuardedUiActionAsync_SwallowsNonFatalException_AndInvokesHandler()
+    {
+        var handlerCalled = false;
+
+        await UiExceptionGuard.RunGuardedUiActionAsync(
+            () => throw new InvalidOperationException("boom"),
+            "UnitTest.NonFatal",
+            onHandledException: ex =>
+            {
+                handlerCalled = ex is InvalidOperationException;
+                return Task.CompletedTask;
+            });
+
+        Assert.True(handlerCalled);
+    }
+
+    [Fact]
+    public async Task RunGuardedUiActionAsync_RethrowsFatalException()
+    {
+        await Assert.ThrowsAsync<OutOfMemoryException>(() =>
+            UiExceptionGuard.RunGuardedUiActionAsync(
+                () => throw new OutOfMemoryException("fatal"),
+                "UnitTest.Fatal"));
+    }
+
+    [Fact]
+    public void IsFatalException_ReturnsExpectedClassification()
+    {
+        Assert.True(UiExceptionGuard.IsFatalException(new OutOfMemoryException()));
+        Assert.True(UiExceptionGuard.IsFatalException(new AccessViolationException()));
+        Assert.False(UiExceptionGuard.IsFatalException(new InvalidOperationException()));
+    }
+}

LanMountainDesktop.slnx

@@ -1,7 +1,7 @@
 <Solution>
-  <Project Path="LanAirApp/samples/LanMountainDesktop.SamplePlugin/LanMountainDesktop.SamplePlugin.csproj" />
   <Project Path="LanAirApp/tools/LanMountainDesktop.PluginPackager/LanMountainDesktop.PluginPackager.csproj" />
   <Project Path="LanMountainDesktop.PluginSdk/LanMountainDesktop.PluginSdk.csproj" />
   <Project Path="LanMountainDesktop.PluginsInstallHelper/LanMountainDesktop.PluginsInstallHelper.csproj" />
   <Project Path="LanMountainDesktop/LanMountainDesktop.csproj" />
+  <Project Path="LanMountainDesktop.Tests/LanMountainDesktop.Tests.csproj" />
 </Solution>

LanMountainDesktop/App.axaml.cs

@@ -8,6 +8,7 @@ using System.Linq;
 using Avalonia.Markup.Xaml;
 using Avalonia.Platform;
 using Avalonia.Threading;
+using LanMountainDesktop.ComponentSystem;
 using LanMountainDesktop.Services;
 using LanMountainDesktop.ViewModels;
 using LanMountainDesktop.Views;
@@ -66,6 +67,7 @@ public partial class App : Application
                 DataContext = new MainWindowViewModel(),
             };
             AppLogger.Info("App", $"Main window created. LogFile={AppLogger.LogFilePath}");
+            LogBrowserStartupDiagnostics();
             CurrentSingleInstanceService?.StartActivationListener(ActivateMainWindow);
         }
 
@@ -268,6 +270,11 @@ public partial class App : Application
                     mainWindow.WindowState = WindowState.Normal;
                 }
 
+                if (mainWindow.WindowState != WindowState.FullScreen)
+                {
+                    mainWindow.WindowState = WindowState.FullScreen;
+                }
+
                 mainWindow.Activate();
                 mainWindow.Topmost = true;
                 mainWindow.Topmost = false;
@@ -335,6 +342,34 @@ public partial class App : Application
         DisposeTrayIcon();
     }
 
+    private void LogBrowserStartupDiagnostics()
+    {
+        try
+        {
+            var snapshot = new DesktopLayoutSettingsService().Load();
+            var browserPlacements = snapshot.DesktopComponentPlacements
+                .Where(placement => string.Equals(
+                    placement.ComponentId,
+                    BuiltInComponentIds.DesktopBrowser,
+                    StringComparison.OrdinalIgnoreCase))
+                .ToList();
+            var runtimeAvailability = WebView2RuntimeProbe.GetAvailability();
+
+            AppLogger.Info(
+                "StartupDiagnostics",
+                $"Browser component diagnostics. HasBrowserPlacement={browserPlacements.Count > 0}; " +
+                $"ActivePageHasBrowser={browserPlacements.Any(item => item.PageIndex == snapshot.CurrentDesktopSurfaceIndex)}; " +
+                $"CurrentDesktopSurfaceIndex={snapshot.CurrentDesktopSurfaceIndex}; " +
+                $"WebViewRuntimeAvailable={runtimeAvailability.IsAvailable}; " +
+                $"WebViewRuntimeVersion={runtimeAvailability.Version ?? string.Empty}; " +
+                $"WebViewRuntimeMessage={runtimeAvailability.Message}");
+        }
+        catch (Exception ex)
+        {
+            AppLogger.Warn("StartupDiagnostics", "Failed to log browser component diagnostics.", ex);
+        }
+    }
+
     private string L(string key, string fallback)
     {
         var snapshot = _appSettingsService.Load();

LanMountainDesktop/LanMountainDesktop.csproj

@@ -47,6 +47,8 @@
     <PackageReference Include="FluentIcons.Avalonia" Version="2.0.319" />
     <PackageReference Include="FluentIcons.Avalonia.Fluent" Version="2.0.319" />
     <PackageReference Include="Material.Icons.Avalonia" Version="2.4.1" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="10.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="10.0.0" />
     <PackageReference Include="Microsoft.Data.Sqlite" Version="10.0.0" />
     <PackageReference Include="LibVLCSharp.Avalonia" Version="3.9.5" />
     <PackageReference Include="PortAudioSharp2" Version="1.0.6" />

LanMountainDesktop/Localization/en-US.json

@@ -744,9 +744,9 @@
     "placement.stretch":  "Stretch",
     "placement.center":  "Center",
     "placement.tile":  "Tile",
-    "single_instance.notice.title":  "App already open",
-    "single_instance.notice.description":  "LanMountainDesktop is already running. Switched back to the active desktop.",
-    "single_instance.notice.button":  "Got it"
+    "single_instance.notice.title":  "App already running",
+    "single_instance.notice.description":  "The app is already running. There is no need to click multiple times to open it.",
+    "single_instance.notice.button":  "OK"
   }
 
 

LanMountainDesktop/Localization/zh-CN.json

@@ -744,9 +744,9 @@
     "placement.stretch":  "拉伸",
     "placement.center":  "居中",
     "placement.tile":  "平铺",
-    "single_instance.notice.title":  "应用已打开",
-    "single_instance.notice.description":  "阑山桌面已经在运行，已为你切换到当前正在使用的桌面。",
-    "single_instance.notice.button":  "知道了"
+    "single_instance.notice.title":  "应用已经运行",
+    "single_instance.notice.description":  "应用已经运行，无需多次点击打开。",
+    "single_instance.notice.button":  "确定"
   }
 
 

LanMountainDesktop/Program.cs

@@ -18,10 +18,19 @@ sealed class Program
     {
         AppLogger.Initialize();
         RegisterGlobalExceptionLogging();
+        var restartParentProcessId = AppRestartService.TryGetRestartParentProcessId(args);
 
-        using var singleInstance = AcquireSingleInstance(args);
+        using var singleInstance = AcquireSingleInstance(restartParentProcessId);
         if (!singleInstance.IsPrimaryInstance)
         {
+            if (restartParentProcessId is not null)
+            {
+                AppLogger.Warn(
+                    "Startup",
+                    $"Restart relaunch could not acquire the single-instance lock. pid={restartParentProcessId.Value}. Suppressing multi-open activation prompt.");
+                return;
+            }
+
             AppLogger.Warn("Startup", "A secondary launch was blocked because another instance is already running.");
             _ = singleInstance.TryNotifyPrimaryInstance(TimeSpan.FromSeconds(2));
             return;
@@ -73,9 +82,8 @@ sealed class Program
         return builder;
     }
 
-    private static SingleInstanceService AcquireSingleInstance(string[] args)
+    private static SingleInstanceService AcquireSingleInstance(int? restartParentProcessId)
     {
-        var restartParentProcessId = AppRestartService.TryGetRestartParentProcessId(args);
         var singleInstance = SingleInstanceService.CreateDefault();
         if (singleInstance.IsPrimaryInstance || restartParentProcessId is null)
         {
@@ -156,6 +164,7 @@ sealed class Program
         TaskScheduler.UnobservedTaskException += (_, eventArgs) =>
         {
             AppLogger.Error("TaskScheduler", "Unobserved task exception.", eventArgs.Exception);
+            eventArgs.SetObserved();
         };
     }
 }

LanMountainDesktop/Properties/AssemblyInfo.cs

@@ -0,0 +1,3 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("LanMountainDesktop.Tests")]

LanMountainDesktop/Services/ComponentSettingsService.cs

@@ -12,6 +12,8 @@ public sealed class ComponentSettingsService : IComponentInstanceSettingsStore
 {
     private static readonly JsonSerializerOptions SerializerOptions = new()
     {
+        PropertyNameCaseInsensitive = true,
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
         WriteIndented = true
     };
 
@@ -29,9 +31,19 @@ public sealed class ComponentSettingsService : IComponentInstanceSettingsStore
     private string _scopedPlacementId = string.Empty;
 
     public ComponentSettingsService()
+        : this(Path.Combine(
+            Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
+            "LanMountainDesktop"))
     {
-        var appData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
-        var settingsDirectory = Path.Combine(appData, "LanMountainDesktop");
+    }
+
+    internal ComponentSettingsService(string settingsDirectory)
+    {
+        if (string.IsNullOrWhiteSpace(settingsDirectory))
+        {
+            throw new ArgumentException("Settings directory cannot be null or whitespace.", nameof(settingsDirectory));
+        }
+
         _settingsPath = Path.Combine(settingsDirectory, "component-settings.json");
         _legacyAppSettingsPath = Path.Combine(settingsDirectory, "settings.json");
     }
@@ -345,10 +357,11 @@ public sealed class ComponentSettingsService : IComponentInstanceSettingsStore
         }
 
         ComponentSettingsDocumentSnapshot loadedSnapshot;
-        var loadedFromLegacy = false;
+        var loadDetails = ComponentSettingsLoadDetails.Empty;
         if (hasFile)
         {
-            loadedSnapshot = LoadSnapshotFromDisk();
+            loadDetails = LoadSnapshotFromDisk();
+            loadedSnapshot = loadDetails.Snapshot;
         }
         else if (TryLoadLegacySnapshot(out var migratedSnapshot))
         {
@@ -356,7 +369,10 @@ public sealed class ComponentSettingsService : IComponentInstanceSettingsStore
             {
                 DefaultSettings = NormalizeSnapshot(migratedSnapshot)
             };
-            loadedFromLegacy = true;
+            loadDetails = new ComponentSettingsLoadDetails(
+                loadedSnapshot,
+                ComponentSettingsDocumentFormat.LegacySnapshot,
+                true);
         }
         else
         {
@@ -364,40 +380,44 @@ public sealed class ComponentSettingsService : IComponentInstanceSettingsStore
         }
 
         var normalizedSnapshot = NormalizeDocument(loadedSnapshot);
-        if (loadedFromLegacy)
+        if (loadDetails.ShouldRewriteToCanonical)
         {
             writeTimeUtc = PersistSnapshotToDisk(normalizedSnapshot);
         }
 
+        LogLoadDetails(loadDetails.Format, loadDetails.ShouldRewriteToCanonical, normalizedSnapshot);
         UpdateCache(normalizedSnapshot, writeTimeUtc, nowUtc);
         return normalizedSnapshot.Clone();
     }
 
-    private ComponentSettingsDocumentSnapshot LoadSnapshotFromDisk()
+    private ComponentSettingsLoadDetails LoadSnapshotFromDisk()
     {
         try
         {
             var json = File.ReadAllText(_settingsPath);
             using var document = JsonDocument.Parse(json);
-            if (document.RootElement.ValueKind == JsonValueKind.Object &&
-                (document.RootElement.TryGetProperty("defaultSettings", out _) ||
-                 document.RootElement.TryGetProperty("instanceSettings", out _) ||
-                 document.RootElement.TryGetProperty("pluginSettings", out _)))
+            if (TryGetDocumentFormat(document.RootElement, out var format))
             {
                 var snapshot = JsonSerializer.Deserialize<ComponentSettingsDocumentSnapshot>(json, SerializerOptions);
-                return NormalizeDocument(snapshot);
+                return new ComponentSettingsLoadDetails(
+                    snapshot ?? new ComponentSettingsDocumentSnapshot(),
+                    format,
+                    format == ComponentSettingsDocumentFormat.PascalCaseDocument);
             }
 
             var legacySnapshot = JsonSerializer.Deserialize<ComponentSettingsSnapshot>(json, SerializerOptions);
-            return new ComponentSettingsDocumentSnapshot
-            {
-                DefaultSettings = NormalizeSnapshot(legacySnapshot)
-            };
+            return new ComponentSettingsLoadDetails(
+                new ComponentSettingsDocumentSnapshot
+                {
+                    DefaultSettings = NormalizeSnapshot(legacySnapshot)
+                },
+                ComponentSettingsDocumentFormat.LegacySnapshot,
+                true);
         }
         catch (Exception ex)
         {
             AppLogger.Warn("ComponentSettings", $"Failed to deserialize component settings from '{_settingsPath}'.", ex);
-            return new ComponentSettingsDocumentSnapshot();
+            return ComponentSettingsLoadDetails.Empty;
         }
     }
 
@@ -684,6 +704,79 @@ public sealed class ComponentSettingsService : IComponentInstanceSettingsStore
         _lastProbeUtc = probeTimeUtc;
     }
 
+    internal static void ResetCacheForTests()
+    {
+        lock (CacheGate)
+        {
+            _cachedPath = null;
+            _cachedSnapshot = null;
+            _cachedWriteTimeUtc = DateTime.MinValue;
+            _lastProbeUtc = DateTime.MinValue;
+        }
+    }
+
+    private void LogLoadDetails(
+        ComponentSettingsDocumentFormat format,
+        bool rewroteToCanonical,
+        ComponentSettingsDocumentSnapshot snapshot)
+    {
+        AppLogger.Info(
+            "ComponentSettings",
+            $"Loaded component settings document. Format={format}; RewroteToCanonical={rewroteToCanonical}; " +
+            $"InstanceSettings={snapshot.InstanceSettings.Count}; PluginSettings={snapshot.PluginSettings.Count}; Path={_settingsPath}");
+    }
+
+    private static bool TryGetDocumentFormat(
+        JsonElement rootElement,
+        out ComponentSettingsDocumentFormat format)
+    {
+        format = ComponentSettingsDocumentFormat.EmptyDocument;
+        if (rootElement.ValueKind != JsonValueKind.Object)
+        {
+            return false;
+        }
+
+        var hasDocumentProperties = false;
+        var requiresCanonicalRewrite = false;
+        foreach (var property in rootElement.EnumerateObject())
+        {
+            if (!IsDocumentPropertyName(property.Name))
+            {
+                continue;
+            }
+
+            hasDocumentProperties = true;
+            if (!IsCanonicalDocumentPropertyName(property.Name))
+            {
+                requiresCanonicalRewrite = true;
+            }
+        }
+
+        if (!hasDocumentProperties)
+        {
+            return false;
+        }
+
+        format = requiresCanonicalRewrite
+            ? ComponentSettingsDocumentFormat.PascalCaseDocument
+            : ComponentSettingsDocumentFormat.CanonicalDocument;
+        return true;
+    }
+
+    private static bool IsDocumentPropertyName(string propertyName)
+    {
+        return string.Equals(propertyName, "defaultSettings", StringComparison.OrdinalIgnoreCase) ||
+               string.Equals(propertyName, "instanceSettings", StringComparison.OrdinalIgnoreCase) ||
+               string.Equals(propertyName, "pluginSettings", StringComparison.OrdinalIgnoreCase);
+    }
+
+    private static bool IsCanonicalDocumentPropertyName(string propertyName)
+    {
+        return string.Equals(propertyName, "defaultSettings", StringComparison.Ordinal) ||
+               string.Equals(propertyName, "instanceSettings", StringComparison.Ordinal) ||
+               string.Equals(propertyName, "pluginSettings", StringComparison.Ordinal);
+    }
+
     private sealed class ComponentSettingsDocumentSnapshot
     {
         public ComponentSettingsSnapshot DefaultSettings { get; set; } = new();
@@ -771,4 +864,23 @@ public sealed class ComponentSettingsService : IComponentInstanceSettingsStore
 
         public string Stcn24ForumSourceType { get; set; } = Stcn24ForumSourceTypes.LatestCreated;
     }
+
+    private readonly record struct ComponentSettingsLoadDetails(
+        ComponentSettingsDocumentSnapshot Snapshot,
+        ComponentSettingsDocumentFormat Format,
+        bool ShouldRewriteToCanonical)
+    {
+        public static ComponentSettingsLoadDetails Empty { get; } = new(
+            new ComponentSettingsDocumentSnapshot(),
+            ComponentSettingsDocumentFormat.EmptyDocument,
+            false);
+    }
+
+    private enum ComponentSettingsDocumentFormat
+    {
+        EmptyDocument,
+        CanonicalDocument,
+        PascalCaseDocument,
+        LegacySnapshot
+    }
 }

LanMountainDesktop/Services/DesktopComponentRegistryFactory.cs

@@ -118,13 +118,13 @@ public static class DesktopComponentRegistryFactory
                 contribution.Plugin.Manifest,
                 contribution.Plugin.Context.PluginDirectory,
                 contribution.Plugin.Context.DataDirectory,
-                contribution.Plugin.Context.Services,
+                contribution.Plugin.Services,
                 contribution.Plugin.Context.Properties,
                 contribution.Registration.ComponentId,
                 context.PlacementId,
                 context.CellSize);
 
-            return contribution.Registration.ControlFactory(pluginContext);
+            return contribution.Registration.ControlFactory(contribution.Plugin.Services, pluginContext);
         }
         catch (Exception ex)
         {

LanMountainDesktop/Services/UiExceptionGuard.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Threading.Tasks;
+
+namespace LanMountainDesktop.Services;
+
+internal static class UiExceptionGuard
+{
+    public static bool IsFatalException(Exception? exception)
+    {
+        return exception is OutOfMemoryException or AccessViolationException or StackOverflowException;
+    }
+
+    public static void FireAndForgetGuarded(
+        Func<Task> action,
+        string actionName,
+        string? context = null,
+        Func<Exception, Task>? onHandledException = null)
+    {
+        _ = RunGuardedUiActionAsync(action, actionName, context, onHandledException);
+    }
+
+    public static async Task RunGuardedUiActionAsync(
+        Func<Task> action,
+        string actionName,
+        string? context = null,
+        Func<Exception, Task>? onHandledException = null)
+    {
+        ArgumentNullException.ThrowIfNull(action);
+
+        try
+        {
+            await action();
+        }
+        catch (Exception ex) when (!IsFatalException(ex))
+        {
+            LogHandledException("GuardedUiAction", actionName, ex, context, isFatal: false);
+            if (onHandledException is not null)
+            {
+                try
+                {
+                    await onHandledException(ex);
+                }
+                catch (Exception handlerEx) when (!IsFatalException(handlerEx))
+                {
+                    LogHandledException("GuardedUiActionHandler", actionName, handlerEx, context, isFatal: false);
+                }
+            }
+        }
+    }
+
+    public static string BuildContext(params (string Key, object? Value)[] parts)
+    {
+        if (parts is null || parts.Length == 0)
+        {
+            return string.Empty;
+        }
+
+        return string.Join(
+            "; ",
+            Array.ConvertAll(parts, part => $"{part.Key}={part.Value ?? "<null>"}"));
+    }
+
+    private static void LogHandledException(
+        string category,
+        string actionName,
+        Exception exception,
+        string? context,
+        bool isFatal)
+    {
+        var message =
+            $"Action={actionName}; ExceptionType={exception.GetType().FullName}; IsFatal={isFatal}; Context={context ?? string.Empty}";
+        if (isFatal)
+        {
+            AppLogger.Critical(category, message, exception);
+            return;
+        }
+
+        AppLogger.Warn(category, message, exception);
+    }
+}

LanMountainDesktop/Views/Components/BrowserWidget.axaml.cs

@@ -6,21 +6,27 @@ using Avalonia.Interactivity;
 using Avalonia.Media;
 using Avalonia.Styling;
 using AvaloniaWebView;
+using LanMountainDesktop.ComponentSystem;
 using LanMountainDesktop.Services;
 using WebViewCore.Events;
 
 namespace LanMountainDesktop.Views.Components;
 
-public partial class BrowserWidget : UserControl, IDesktopComponentWidget
-    , IDesktopPageVisibilityAwareComponentWidget, IDisposable
+public partial class BrowserWidget : UserControl, IDesktopComponentWidget,
+    IDesktopPageVisibilityAwareComponentWidget, IComponentPlacementContextAware, IDisposable
 {
     private static readonly Uri DefaultHomeUri = new("https://www.bing.com");
+
     private double _currentCellSize = 48;
+    private string _componentId = BuiltInComponentIds.DesktopBrowser;
+    private string _placementId = string.Empty;
     private bool? _isNightModeApplied;
     private Uri _lastKnownUri = DefaultHomeUri;
     private bool _isOnActiveDesktopPage;
+    private bool _isAttachedToVisualTree;
     private bool _isEditMode;
     private bool _isWebViewActive = true;
+    private bool _isWebViewFaulted;
     private readonly WebView2RuntimeAvailability _runtimeAvailability;
     private bool _isDisposed;
 
@@ -45,8 +51,8 @@ public partial class BrowserWidget : UserControl, IDesktopComponentWidget
             ApplyRuntimeUnavailableState();
         }
 
+        AddressTextBox.Text = DefaultHomeUri.ToString();
         UpdateWebViewActiveState();
-        NavigateTo(DefaultHomeUri);
     }
 
     public void Dispose()
@@ -74,17 +80,15 @@ public partial class BrowserWidget : UserControl, IDesktopComponentWidget
         _currentCellSize = Math.Max(1, cellSize);
 
         RootBorder.CornerRadius = new CornerRadius(Math.Clamp(_currentCellSize * 0.34, 12, 28));
-        RootBorder.Padding = new Thickness(
-            Math.Clamp(_currentCellSize * 0.20, 8, 18));
+        RootBorder.Padding = new Thickness(Math.Clamp(_currentCellSize * 0.20, 8, 18));
 
         WebViewHostBorder.CornerRadius = new CornerRadius(Math.Clamp(_currentCellSize * 0.24, 10, 22));
         AddressBarBorder.CornerRadius = new CornerRadius(Math.Clamp(_currentCellSize * 0.22, 10, 20));
         AddressBarBorder.Padding = new Thickness(8, 6);
 
-        var rowSpacing = 8d;
         if (RootBorder.Child is Grid rootGrid)
         {
-            rootGrid.RowSpacing = rowSpacing;
+            rootGrid.RowSpacing = 8d;
         }
 
         var buttonSize = Math.Clamp(_currentCellSize * 0.72, 30, 36);
@@ -111,16 +115,33 @@ public partial class BrowserWidget : UserControl, IDesktopComponentWidget
         AddressTextBox.Height = buttonSize;
     }
 
+    public void SetDesktopPageContext(bool isOnActivePage, bool isEditMode)
+    {
+        _isOnActiveDesktopPage = isOnActivePage;
+        _isEditMode = isEditMode;
+        UpdateWebViewActiveState();
+    }
+
+    public void SetComponentPlacementContext(string componentId, string? placementId)
+    {
+        _componentId = string.IsNullOrWhiteSpace(componentId)
+            ? BuiltInComponentIds.DesktopBrowser
+            : componentId.Trim();
+        _placementId = placementId?.Trim() ?? string.Empty;
+    }
+
     private void OnAttachedToVisualTree(object? sender, VisualTreeAttachmentEventArgs e)
     {
+        _isAttachedToVisualTree = true;
         ApplyTheme(force: true);
         UpdateWebViewActiveState();
     }
 
     private void OnDetachedFromVisualTree(object? sender, VisualTreeAttachmentEventArgs e)
     {
+        _isAttachedToVisualTree = false;
         _isOnActiveDesktopPage = false;
-        UpdateWebViewActiveState();
+        DeactivateWebView(clearUrl: false);
     }
 
     private void OnSizeChanged(object? sender, SizeChangedEventArgs e)
@@ -202,28 +223,20 @@ public partial class BrowserWidget : UserControl, IDesktopComponentWidget
 
     private void OnRefreshButtonClick(object? sender, RoutedEventArgs e)
     {
-        if (!_runtimeAvailability.IsAvailable)
+        if (!CanUseWebView())
         {
             return;
         }
 
-        if (!_isWebViewActive)
+        if (!TryReloadWebView("Refresh"))
         {
-            return;
+            TryNavigate(DefaultHomeUri, "RefreshFallback");
         }
-
-        if (BrowserWebView.Url is not null)
-        {
-            BrowserWebView.Reload();
-            return;
-        }
-
-        NavigateTo(DefaultHomeUri);
     }
 
     private void OnGoButtonClick(object? sender, RoutedEventArgs e)
     {
-        if (!_runtimeAvailability.IsAvailable)
+        if (!CanUseWebView())
         {
             return;
         }
@@ -233,7 +246,7 @@ public partial class BrowserWidget : UserControl, IDesktopComponentWidget
 
     private void OnAddressTextBoxKeyDown(object? sender, KeyEventArgs e)
     {
-        if (!_runtimeAvailability.IsAvailable)
+        if (!CanUseWebView())
         {
             return;
         }
@@ -249,7 +262,7 @@ public partial class BrowserWidget : UserControl, IDesktopComponentWidget
 
     private void NavigateFromAddressBar()
     {
-        if (!_runtimeAvailability.IsAvailable)
+        if (!CanUseWebView())
         {
             return;
         }
@@ -269,7 +282,7 @@ public partial class BrowserWidget : UserControl, IDesktopComponentWidget
         AddressTextBox.Text = uri.ToString();
         if (_isWebViewActive)
         {
-            BrowserWebView.Url = uri;
+            TryNavigate(uri, "NavigateTo");
         }
     }
 
@@ -284,25 +297,16 @@ public partial class BrowserWidget : UserControl, IDesktopComponentWidget
         AddressTextBox.Text = e.Url.ToString();
     }
 
-    public void SetDesktopPageContext(bool isOnActivePage, bool isEditMode)
-    {
-        _isOnActiveDesktopPage = isOnActivePage;
-        _isEditMode = isEditMode;
-        UpdateWebViewActiveState();
-    }
-
     private void UpdateWebViewActiveState()
     {
-        if (!_runtimeAvailability.IsAvailable)
+        if (!_runtimeAvailability.IsAvailable || _isWebViewFaulted)
         {
             _isWebViewActive = false;
-            BrowserWebView.Url = null;
-            BrowserWebView.IsVisible = false;
-            BrowserWebView.IsHitTestVisible = false;
+            ApplyRuntimeUnavailableState();
             return;
         }
 
-        var shouldBeActive = _isOnActiveDesktopPage && !_isEditMode && IsVisible;
+        var shouldBeActive = _isAttachedToVisualTree && _isOnActiveDesktopPage && !_isEditMode && IsVisible;
         if (_isWebViewActive == shouldBeActive)
         {
             return;
@@ -311,40 +315,118 @@ public partial class BrowserWidget : UserControl, IDesktopComponentWidget
         _isWebViewActive = shouldBeActive;
         if (!_isWebViewActive)
         {
-            if (BrowserWebView.Url is Uri currentUri)
-            {
-                _lastKnownUri = currentUri;
-            }
+            DeactivateWebView(clearUrl: false);
+            return;
+        }
 
-            BrowserWebView.IsHitTestVisible = false;
-            BrowserWebView.IsVisible = false;
-            BrowserWebView.Url = null;
+        ActivateWebView();
+    }
+
+    private void ActivateWebView()
+    {
+        if (_isWebViewFaulted || !_runtimeAvailability.IsAvailable)
+        {
+            ApplyRuntimeUnavailableState();
             return;
         }
 
         BrowserWebView.IsVisible = true;
         BrowserWebView.IsHitTestVisible = true;
-        BrowserWebView.Url = _lastKnownUri;
+        RefreshButton.IsEnabled = true;
+        GoButton.IsEnabled = true;
+        AddressTextBox.IsEnabled = true;
+        UnavailableOverlay.IsVisible = false;
+
+        TryNavigate(_lastKnownUri, "Activate");
+    }
+
+    private void DeactivateWebView(bool clearUrl)
+    {
+        BrowserWebView.IsHitTestVisible = false;
+        BrowserWebView.IsVisible = false;
+
+        if (clearUrl)
+        {
+            TryClearWebViewUrl();
+        }
+    }
+
+    private bool TryReloadWebView(string action)
+    {
+        try
+        {
+            BrowserWebView.Reload();
+            return true;
+        }
+        catch (Exception ex) when (!UiExceptionGuard.IsFatalException(ex))
+        {
+            EnterFaultedState(action, ex);
+            return false;
+        }
+    }
+
+    private bool TryNavigate(Uri uri, string action)
+    {
+        try
+        {
+            BrowserWebView.Url = uri;
+            return true;
+        }
+        catch (Exception ex) when (!UiExceptionGuard.IsFatalException(ex))
+        {
+            EnterFaultedState(action, ex);
+            return false;
+        }
+    }
+
+    private void TryClearWebViewUrl()
+    {
+        try
+        {
+            BrowserWebView.Url = null;
+        }
+        catch
+        {
+            // Best-effort cleanup only.
+        }
+    }
+
+    private bool CanUseWebView()
+    {
+        return _runtimeAvailability.IsAvailable && !_isWebViewFaulted && _isWebViewActive;
     }
 
     private void ApplyRuntimeUnavailableState()
     {
         _isWebViewActive = false;
-        BrowserWebView.Url = null;
         BrowserWebView.IsVisible = false;
         BrowserWebView.IsHitTestVisible = false;
 
         RefreshButton.IsEnabled = false;
         GoButton.IsEnabled = false;
         AddressTextBox.IsEnabled = false;
-        AddressTextBox.Text = string.Empty;
+        AddressTextBox.Text = _lastKnownUri.ToString();
 
-        UnavailableMessageTextBlock.Text = string.IsNullOrWhiteSpace(_runtimeAvailability.Message)
-            ? "WebView runtime unavailable."
-            : _runtimeAvailability.Message;
+        UnavailableMessageTextBlock.Text = _isWebViewFaulted
+            ? "The browser component is temporarily unavailable. Restart the app to retry."
+            : string.IsNullOrWhiteSpace(_runtimeAvailability.Message)
+                ? "WebView runtime unavailable."
+                : _runtimeAvailability.Message;
         UnavailableOverlay.IsVisible = true;
     }
 
+    private void EnterFaultedState(string action, Exception ex)
+    {
+        _isWebViewFaulted = true;
+        _isWebViewActive = false;
+        AppLogger.Warn(
+            "BrowserWidget",
+            $"Browser component faulted. Action={action}; ComponentId={_componentId}; PlacementId={_placementId}; RuntimeAvailability={_runtimeAvailability.IsAvailable}; RuntimeVersion={_runtimeAvailability.Version ?? string.Empty}; CurrentUrl={_lastKnownUri}",
+            ex);
+        TryClearWebViewUrl();
+        ApplyRuntimeUnavailableState();
+    }
+
     private static Uri? TryNormalizeUri(string? rawText)
     {
         if (string.IsNullOrWhiteSpace(rawText))

LanMountainDesktop/Views/Components/DesktopComponentFailureView.cs

@@ -0,0 +1,226 @@
+using System;
+using System.Reflection;
+using System.Text;
+using System.Threading.Tasks;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Interactivity;
+using Avalonia.Layout;
+using Avalonia.Media;
+using LanMountainDesktop.Services;
+
+namespace LanMountainDesktop.Views.Components;
+
+internal sealed class DesktopComponentFailureView : UserControl, IDesktopComponentWidget
+{
+    private readonly Border _rootBorder;
+    private readonly TextBlock _titleBlock;
+    private readonly TextBlock _summaryBlock;
+    private readonly TextBlock _statusBlock;
+    private readonly Button _toggleDetailsButton;
+    private readonly Button _copyReportButton;
+    private readonly Border _detailsBorder;
+    private readonly TextBox _reportTextBox;
+    private readonly string _componentId;
+    private readonly string? _placementId;
+    private readonly string _reportText;
+    private bool _detailsVisible;
+
+    public DesktopComponentFailureView(
+        string componentName,
+        string componentId,
+        string? placementId,
+        int? pageIndex,
+        string action,
+        Exception exception)
+    {
+        _componentId = componentId;
+        _placementId = placementId;
+        _reportText = BuildReport(componentName, componentId, placementId, pageIndex, action, exception);
+
+        _titleBlock = new TextBlock
+        {
+            Text = string.IsNullOrWhiteSpace(componentName) ? "组件暂时不可用" : componentName,
+            FontWeight = FontWeight.SemiBold,
+            TextWrapping = TextWrapping.Wrap
+        };
+
+        _summaryBlock = new TextBlock
+        {
+            Text = "该组件已临时停用，并由信息占位保留原位置。你可以展开详情或复制错误报告。",
+            Foreground = CreateBrush("#FFD6DEE9"),
+            TextWrapping = TextWrapping.Wrap
+        };
+
+        _statusBlock = new TextBlock
+        {
+            IsVisible = false,
+            Foreground = CreateBrush("#FF93C5FD"),
+            TextWrapping = TextWrapping.Wrap
+        };
+
+        _toggleDetailsButton = CreateButton("查看错误信息", OnToggleDetailsClick);
+        _copyReportButton = CreateButton("复制错误报告", OnCopyReportClick);
+
+        _reportTextBox = new TextBox
+        {
+            Text = _reportText,
+            IsReadOnly = true,
+            AcceptsReturn = true,
+            TextWrapping = TextWrapping.Wrap,
+            MinHeight = 96,
+            MaxHeight = 220,
+            Background = CreateBrush("#CC0F172A"),
+            Foreground = CreateBrush("#FFE2E8F0"),
+            BorderThickness = new Thickness(0),
+            Padding = new Thickness(8)
+        };
+
+        _detailsBorder = new Border
+        {
+            IsVisible = false,
+            Background = CreateBrush("#660F172A"),
+            BorderBrush = CreateBrush("#33475569"),
+            BorderThickness = new Thickness(1),
+            CornerRadius = new CornerRadius(12),
+            Child = _reportTextBox
+        };
+
+        _rootBorder = new Border
+        {
+            Background = CreateBrush("#D91E293B"),
+            BorderBrush = CreateBrush("#336B7280"),
+            BorderThickness = new Thickness(1),
+            CornerRadius = new CornerRadius(18),
+            Padding = new Thickness(14),
+            ClipToBounds = true,
+            Child = new StackPanel
+            {
+                Spacing = 8,
+                VerticalAlignment = VerticalAlignment.Center,
+                Children =
+                {
+                    _titleBlock,
+                    _summaryBlock,
+                    new WrapPanel
+                    {
+                        Orientation = Orientation.Horizontal,
+                        HorizontalAlignment = HorizontalAlignment.Left,
+                        ItemSpacing = 8,
+                        LineSpacing = 8,
+                        Children =
+                        {
+                            _toggleDetailsButton,
+                            _copyReportButton
+                        }
+                    },
+                    _statusBlock,
+                    _detailsBorder
+                }
+            }
+        };
+
+        Content = _rootBorder;
+        ApplyCellSize(48);
+    }
+
+    public void ApplyCellSize(double cellSize)
+    {
+        var normalized = Math.Max(1, cellSize);
+        _rootBorder.CornerRadius = new CornerRadius(Math.Clamp(normalized * 0.24, 12, 24));
+        _rootBorder.Padding = new Thickness(Math.Clamp(normalized * 0.24, 10, 18));
+        _titleBlock.FontSize = Math.Clamp(normalized * 0.36, 14, 22);
+        _summaryBlock.FontSize = Math.Clamp(normalized * 0.24, 11, 15);
+        _statusBlock.FontSize = Math.Clamp(normalized * 0.22, 10, 13);
+        _toggleDetailsButton.FontSize = Math.Clamp(normalized * 0.22, 10, 14);
+        _copyReportButton.FontSize = Math.Clamp(normalized * 0.22, 10, 14);
+        _toggleDetailsButton.Padding = new Thickness(Math.Clamp(normalized * 0.18, 8, 12), 6);
+        _copyReportButton.Padding = new Thickness(Math.Clamp(normalized * 0.18, 8, 12), 6);
+        _reportTextBox.FontSize = Math.Clamp(normalized * 0.2, 10, 13);
+        _reportTextBox.MaxHeight = Math.Clamp(normalized * 5.2, 120, 260);
+    }
+
+    private static Button CreateButton(string text, EventHandler<RoutedEventArgs> clickHandler)
+    {
+        var button = new Button
+        {
+            Content = text,
+            Background = CreateBrush("#80334155"),
+            Foreground = Brushes.White,
+            BorderBrush = CreateBrush("#335B6575"),
+            BorderThickness = new Thickness(1),
+            CornerRadius = new CornerRadius(999),
+            HorizontalAlignment = HorizontalAlignment.Left
+        };
+        button.Click += clickHandler;
+        return button;
+    }
+
+    private void OnToggleDetailsClick(object? sender, RoutedEventArgs e)
+    {
+        _detailsVisible = !_detailsVisible;
+        _detailsBorder.IsVisible = _detailsVisible;
+        _toggleDetailsButton.Content = _detailsVisible ? "隐藏错误信息" : "查看错误信息";
+        UpdateStatus(null);
+    }
+
+    private void OnCopyReportClick(object? sender, RoutedEventArgs e)
+    {
+        UiExceptionGuard.FireAndForgetGuarded(
+            CopyReportAsync,
+            "DesktopComponentFailureView.CopyReport",
+            UiExceptionGuard.BuildContext(
+                ("ComponentId", _componentId),
+                ("PlacementId", _placementId)));
+    }
+
+    private async Task CopyReportAsync()
+    {
+        var topLevel = TopLevel.GetTopLevel(this);
+        var clipboard = topLevel?.Clipboard;
+        if (clipboard is null)
+        {
+            UpdateStatus("当前环境不支持复制错误报告。");
+            return;
+        }
+
+        await clipboard.SetTextAsync(_reportText);
+        UpdateStatus("错误报告已复制到剪贴板。");
+    }
+
+    private void UpdateStatus(string? message)
+    {
+        _statusBlock.Text = message ?? string.Empty;
+        _statusBlock.IsVisible = !string.IsNullOrWhiteSpace(message);
+    }
+
+    private static string BuildReport(
+        string componentName,
+        string componentId,
+        string? placementId,
+        int? pageIndex,
+        string action,
+        Exception exception)
+    {
+        var version = Assembly.GetEntryAssembly()?.GetName().Version?.ToString() ?? "unknown";
+        var builder = new StringBuilder();
+        builder.AppendLine("LanMountainDesktop Component Failure Report");
+        builder.AppendLine($"GeneratedAt: {DateTimeOffset.Now:O}");
+        builder.AppendLine($"AppVersion: {version}");
+        builder.AppendLine($"Action: {action}");
+        builder.AppendLine($"ComponentName: {componentName}");
+        builder.AppendLine($"ComponentId: {componentId}");
+        builder.AppendLine($"PlacementId: {placementId ?? string.Empty}");
+        builder.AppendLine($"PageIndex: {pageIndex?.ToString() ?? string.Empty}");
+        builder.AppendLine($"ExceptionType: {exception.GetType().FullName}");
+        builder.AppendLine($"ExceptionMessage: {exception.Message}");
+        builder.AppendLine();
+        builder.AppendLine(exception.ToString());
+        return builder.ToString();
+    }
+
+    private static IBrush CreateBrush(string colorHex)
+    {
+        return new SolidColorBrush(Color.Parse(colorHex));
+    }
+}

LanMountainDesktop/Views/MainWindow.ComponentSystem.cs

@@ -1522,7 +1522,7 @@ public partial class MainWindow
             placement.PlacementId = Guid.NewGuid().ToString("N");
         }
 
-        var component = CreateDesktopComponentControl(placement.ComponentId, placement.PlacementId);
+        var component = CreateDesktopComponentControl(placement.ComponentId, placement.PlacementId, placement.PageIndex);
         if (component is null)
         {
             return null;
@@ -1956,23 +1956,54 @@ public partial class MainWindow
         return onLeft || onRight || onTop || onBottom;
     }
 
-    private Control? CreateDesktopComponentControl(string componentId, string? placementId = null)
+    private Control? CreateDesktopComponentControl(string componentId, string? placementId = null, int? pageIndex = null)
     {
         if (!_componentRuntimeRegistry.TryGetDescriptor(componentId, out var runtimeDescriptor))
         {
             return null;
         }
 
-        var component = runtimeDescriptor.CreateControl(
-            _currentDesktopCellSize,
-            _timeZoneService,
-            _weatherDataService,
-            _recommendationInfoService,
-            _calculatorDataService,
-            _componentSettingsService,
-            placementId);
-        component.Classes.Add(DesktopComponentClass);
-        return component;
+        return CreateDesktopComponentControl(runtimeDescriptor, _currentDesktopCellSize, placementId, pageIndex, "DesktopSurface");
+    }
+
+    private Control? CreateDesktopComponentControl(
+        DesktopComponentRuntimeDescriptor runtimeDescriptor,
+        double cellSize,
+        string? placementId,
+        int? pageIndex,
+        string action)
+    {
+        try
+        {
+            var component = runtimeDescriptor.CreateControl(
+                cellSize,
+                _timeZoneService,
+                _weatherDataService,
+                _recommendationInfoService,
+                _calculatorDataService,
+                _componentSettingsService,
+                placementId);
+            component.Classes.Add(DesktopComponentClass);
+            return component;
+        }
+        catch (Exception ex) when (!UiExceptionGuard.IsFatalException(ex))
+        {
+            AppLogger.Warn(
+                "ComponentRuntime",
+                $"Action={action}; ComponentId={runtimeDescriptor.Definition.Id}; PlacementId={placementId ?? string.Empty}; PageIndex={pageIndex?.ToString() ?? string.Empty}; ExceptionType={ex.GetType().FullName}; IsFatal=false",
+                ex);
+
+            var failureView = new DesktopComponentFailureView(
+                runtimeDescriptor.Definition.DisplayName,
+                runtimeDescriptor.Definition.Id,
+                placementId,
+                pageIndex,
+                action,
+                ex);
+            failureView.ApplyCellSize(cellSize);
+            failureView.Classes.Add(DesktopComponentClass);
+            return failureView;
+        }
     }
 
     private void CollapseComponentLibraryPanel()
@@ -3113,13 +3144,16 @@ public partial class MainWindow
             var previewHeight = previewSpan.HeightCells * previewCellSize;
             var renderCellSize = Math.Clamp(previewCellSize * 1.15, 26, 110);
 
-            var previewControl = descriptor.CreateControl(
+            var previewControl = CreateDesktopComponentControl(
+                descriptor,
                 renderCellSize,
-                _timeZoneService,
-                _weatherDataService,
-                _recommendationInfoService,
-                _calculatorDataService,
-                _componentSettingsService);
+                placementId: null,
+                pageIndex: null,
+                action: "ComponentLibraryPreview");
+            if (previewControl is null)
+            {
+                continue;
+            }
             // Component library previews must stay non-interactive so drag gesture is reliable.
             previewControl.IsHitTestVisible = false;
             previewControl.Focusable = false;

LanMountainDesktop/Views/MainWindow.SingleInstanceNotice.cs

@@ -1,59 +1,58 @@
-using System;
-using Avalonia.Interactivity;
+using System.Threading.Tasks;
 using Avalonia.Threading;
+using FluentAvalonia.UI.Controls;
+using LanMountainDesktop.Services;
 
 namespace LanMountainDesktop.Views;
 
 public partial class MainWindow
 {
-    private readonly DispatcherTimer _singleInstanceNoticeTimer = new()
-    {
-        Interval = TimeSpan.FromSeconds(6)
-    };
+    private bool _isSingleInstancePromptVisible;
 
     internal void ShowSingleInstanceNotice()
     {
+        void ShowPrompt()
+        {
+            UiExceptionGuard.FireAndForgetGuarded(
+                ShowSingleInstanceNoticeCoreAsync,
+                "MainWindow.ShowSingleInstanceNotice");
+        }
+
         if (Dispatcher.UIThread.CheckAccess())
         {
-            ShowSingleInstanceNoticeCore();
+            ShowPrompt();
             return;
         }
 
-        Dispatcher.UIThread.Post(ShowSingleInstanceNoticeCore, DispatcherPriority.Send);
+        Dispatcher.UIThread.Post(ShowPrompt, DispatcherPriority.Send);
     }
 
-    private void ShowSingleInstanceNoticeCore()
+    private async Task ShowSingleInstanceNoticeCoreAsync()
     {
-        SingleInstanceNoticeTitleTextBlock.Text = L(
-            "single_instance.notice.title",
-            "App already open");
-        SingleInstanceNoticeDescriptionTextBlock.Text = L(
-            "single_instance.notice.description",
-            "LanMountainDesktop is already running. Switched back to the active desktop.");
-        SingleInstanceNoticeButtonTextBlock.Text = L(
-            "single_instance.notice.button",
-            "Got it");
-        SingleInstanceNoticeDock.IsVisible = true;
+        if (_isSingleInstancePromptVisible)
+        {
+            return;
+        }
 
-        _singleInstanceNoticeTimer.Stop();
-        _singleInstanceNoticeTimer.Tick -= OnSingleInstanceNoticeTimerTick;
-        _singleInstanceNoticeTimer.Tick += OnSingleInstanceNoticeTimerTick;
-        _singleInstanceNoticeTimer.Start();
-    }
+        _isSingleInstancePromptVisible = true;
 
-    private void OnSingleInstanceNoticeButtonClick(object? sender, RoutedEventArgs e)
-    {
-        HideSingleInstanceNotice();
-    }
+        try
+        {
+            var dialog = new ContentDialog
+            {
+                Title = L("single_instance.notice.title", "应用已经运行"),
+                Content = L(
+                    "single_instance.notice.description",
+                    "应用已经运行，无需多次点击打开。"),
+                PrimaryButtonText = L("single_instance.notice.button", "确定"),
+                DefaultButton = ContentDialogButton.Primary
+            };
 
-    private void OnSingleInstanceNoticeTimerTick(object? sender, EventArgs e)
-    {
-        HideSingleInstanceNotice();
-    }
-
-    private void HideSingleInstanceNotice()
-    {
-        _singleInstanceNoticeTimer.Stop();
-        SingleInstanceNoticeDock.IsVisible = false;
+            await dialog.ShowAsync(this);
+        }
+        finally
+        {
+            _isSingleInstancePromptVisible = false;
+        }
     }
 }

LanMountainDesktop/Views/MainWindow.axaml

@@ -471,51 +471,6 @@
 
                         <StackPanel Grid.Row="1"
                                     Spacing="12">
-                            <Border x:Name="SingleInstanceNoticeDock"
-                                    IsVisible="False"
-                                    Classes="glass-panel"
-                                    CornerRadius="18"
-                                    Padding="14,12">
-                                <Grid ColumnDefinitions="Auto,*,Auto"
-                                      ColumnSpacing="12">
-                                    <Border Width="34"
-                                            Height="34"
-                                            CornerRadius="17"
-                                            Background="{DynamicResource AdaptiveAccentBrush}">
-                                        <fi:FluentIcon Icon="Alert"
-                                                       IconVariant="Regular"
-                                                       FontSize="16"
-                                                       Foreground="White"
-                                                       HorizontalAlignment="Center"
-                                                       VerticalAlignment="Center" />
-                                    </Border>
-                                    <StackPanel Grid.Column="1"
-                                                Spacing="2"
-                                                VerticalAlignment="Center">
-                                        <TextBlock x:Name="SingleInstanceNoticeTitleTextBlock"
-                                                   FontSize="13"
-                                                   FontWeight="SemiBold"
-                                                   Text="App already open" />
-                                        <TextBlock x:Name="SingleInstanceNoticeDescriptionTextBlock"
-                                                   TextWrapping="Wrap"
-                                                   Foreground="{DynamicResource AdaptiveTextSecondaryBrush}"
-                                                   Text="LanMountainDesktop is already running. Switched back to the active desktop." />
-                                    </StackPanel>
-                                    <Button x:Name="SingleInstanceNoticeButton"
-                                            Grid.Column="2"
-                                            Padding="14,8"
-                                            Click="OnSingleInstanceNoticeButtonClick">
-                                        <StackPanel Orientation="Horizontal" Spacing="8">
-                                            <fi:FluentIcon Icon="Checkmark"
-                                                           IconVariant="Regular" />
-                                            <TextBlock x:Name="SingleInstanceNoticeButtonTextBlock"
-                                                       VerticalAlignment="Center"
-                                                       Text="Got it" />
-                                        </StackPanel>
-                                    </Button>
-                                </Grid>
-                            </Border>
-
                             <Border x:Name="PendingRestartDock"
                                     IsVisible="False"
                                     Classes="glass-panel"

LanMountainDesktop/plugins/LoadedPlugin.cs

@@ -5,6 +5,7 @@ using System.Threading;
 using System.Threading.Tasks;
 
 using LanMountainDesktop.PluginSdk;
+using Microsoft.Extensions.Hosting;
 
 namespace LanMountainDesktop.Plugins;
 
@@ -18,9 +19,12 @@ public sealed class LoadedPlugin : IDisposable, IAsyncDisposable
         string assemblyPath,
         Assembly assembly,
         IPlugin plugin,
-        IPluginContext context,
+        IPluginRuntimeContext runtimeContext,
+        IServiceProvider services,
         IReadOnlyList<PluginSettingsPageRegistration> settingsPages,
         IReadOnlyList<PluginDesktopComponentRegistration> desktopComponents,
+        IReadOnlyList<PluginServiceExportDescriptor> exportedServices,
+        IReadOnlyList<IHostedService> hostedServices,
         PluginLoadContext loadContext)
     {
         Manifest = manifest;
@@ -28,9 +32,12 @@ public sealed class LoadedPlugin : IDisposable, IAsyncDisposable
         AssemblyPath = assemblyPath;
         Assembly = assembly;
         Plugin = plugin;
-        Context = context;
+        RuntimeContext = runtimeContext;
+        Services = services;
         SettingsPages = settingsPages;
         DesktopComponents = desktopComponents;
+        ExportedServices = exportedServices;
+        HostedServices = hostedServices;
         LoadContext = loadContext;
     }
 
@@ -44,14 +51,22 @@ public sealed class LoadedPlugin : IDisposable, IAsyncDisposable
 
     public IPlugin Plugin { get; }
 
-    public IPluginContext Context { get; }
+    public IPluginRuntimeContext RuntimeContext { get; }
+
+    public IPluginRuntimeContext Context => RuntimeContext;
+
+    public IServiceProvider Services { get; }
 
     public IReadOnlyList<PluginSettingsPageRegistration> SettingsPages { get; }
 
     public IReadOnlyList<PluginDesktopComponentRegistration> DesktopComponents { get; }
 
+    public IReadOnlyList<PluginServiceExportDescriptor> ExportedServices { get; }
+
     public PluginLoadContext LoadContext { get; }
 
+    private IReadOnlyList<IHostedService> HostedServices { get; }
+
     public void Dispose()
     {
         DisposeAsync().AsTask().GetAwaiter().GetResult();
@@ -64,6 +79,18 @@ public sealed class LoadedPlugin : IDisposable, IAsyncDisposable
             return;
         }
 
+        for (var i = HostedServices.Count - 1; i >= 0; i--)
+        {
+            try
+            {
+                await HostedServices[i].StopAsync(CancellationToken.None);
+            }
+            catch
+            {
+                // Ignore plugin hosted service shutdown failures to allow unload cleanup.
+            }
+        }
+
         if (Plugin is IAsyncDisposable asyncDisposable)
         {
             await asyncDisposable.DisposeAsync();
@@ -73,11 +100,20 @@ public sealed class LoadedPlugin : IDisposable, IAsyncDisposable
             disposable.Dispose();
         }
 
-        if (Context is IAsyncDisposable asyncContext)
+        if (Services is IAsyncDisposable asyncServices)
+        {
+            await asyncServices.DisposeAsync();
+        }
+        else if (Services is IDisposable disposableServices)
+        {
+            disposableServices.Dispose();
+        }
+
+        if (RuntimeContext is IAsyncDisposable asyncContext)
         {
             await asyncContext.DisposeAsync();
         }
-        else if (Context is IDisposable disposableContext)
+        else if (RuntimeContext is IDisposable disposableContext)
         {
             disposableContext.Dispose();
         }

LanMountainDesktop/plugins/MainWindow.PluginSettingsHost.cs

@@ -85,7 +85,7 @@ public partial class MainWindow
         Control content;
         try
         {
-            content = contribution.Registration.ContentFactory();
+            content = contribution.Registration.ContentFactory(contribution.Plugin.Services);
         }
         catch (Exception ex)
         {

LanMountainDesktop/plugins/PluginExportRegistry.cs

@@ -0,0 +1,83 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using LanMountainDesktop.PluginSdk;
+
+namespace LanMountainDesktop.Plugins;
+
+internal sealed class PluginExportRegistry : IPluginExportRegistry
+{
+    private readonly object _gate = new();
+    private readonly List<PluginServiceExportDescriptor> _exports = [];
+
+    public IReadOnlyList<PluginServiceExportDescriptor> GetExports()
+    {
+        lock (_gate)
+        {
+            return _exports.ToArray();
+        }
+    }
+
+    public IReadOnlyList<PluginServiceExportDescriptor> GetExports(Type contractType)
+    {
+        ArgumentNullException.ThrowIfNull(contractType);
+
+        lock (_gate)
+        {
+            return _exports
+                .Where(descriptor => descriptor.ContractType == contractType)
+                .ToArray();
+        }
+    }
+
+    public PluginServiceExportDescriptor? GetExport(Type contractType, string providerPluginId)
+    {
+        ArgumentNullException.ThrowIfNull(contractType);
+        ArgumentException.ThrowIfNullOrWhiteSpace(providerPluginId);
+
+        lock (_gate)
+        {
+            return _exports.FirstOrDefault(descriptor =>
+                descriptor.ContractType == contractType &&
+                string.Equals(descriptor.ProviderPluginId, providerPluginId, StringComparison.OrdinalIgnoreCase));
+        }
+    }
+
+    public TContract? GetExport<TContract>(string providerPluginId)
+        where TContract : class
+    {
+        return GetExport(typeof(TContract), providerPluginId)?.ServiceInstance as TContract;
+    }
+
+    public void ReplaceExports(string pluginId, IEnumerable<PluginServiceExportDescriptor> descriptors)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(pluginId);
+        ArgumentNullException.ThrowIfNull(descriptors);
+
+        lock (_gate)
+        {
+            _exports.RemoveAll(descriptor =>
+                string.Equals(descriptor.ProviderPluginId, pluginId, StringComparison.OrdinalIgnoreCase));
+            _exports.AddRange(descriptors);
+        }
+    }
+
+    public void RemoveExports(string pluginId)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(pluginId);
+
+        lock (_gate)
+        {
+            _exports.RemoveAll(descriptor =>
+                string.Equals(descriptor.ProviderPluginId, pluginId, StringComparison.OrdinalIgnoreCase));
+        }
+    }
+
+    public void Clear()
+    {
+        lock (_gate)
+        {
+            _exports.Clear();
+        }
+    }
+}

LanMountainDesktop/plugins/PluginLoader.cs

@@ -12,6 +12,8 @@ using System.Threading.Tasks;
 
 using LanMountainDesktop.Services;
 using LanMountainDesktop.PluginSdk;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 
 namespace LanMountainDesktop.Plugins;
 
@@ -135,19 +137,45 @@ public sealed class PluginLoader
     {
         PluginLoadContext? loadContext = null;
         IPlugin? plugin = null;
-        PluginContext? context = null;
+        PluginRuntimeContext? runtimeContext = null;
+        ServiceProvider? pluginServices = null;
+        IReadOnlyList<IHostedService> hostedServices = Array.Empty<IHostedService>();
 
         try
         {
+            Directory.CreateDirectory(dataDirectory);
+            ValidatePluginRuntimeAssets(manifest, assemblyPath, pluginDirectory);
+
             loadContext = new PluginLoadContext(assemblyPath, _options.SharedAssemblyNames);
             var assembly = loadContext.LoadFromAssemblyPath(assemblyPath);
             var pluginType = ResolvePluginType(assembly);
             plugin = CreatePluginInstance(pluginType);
-            context = CreateContext(manifest, pluginDirectory, dataDirectory, services, properties);
+            runtimeContext = CreateRuntimeContext(manifest, pluginDirectory, dataDirectory, properties);
+            var serviceCollection = CreateServiceCollection(runtimeContext, services);
+            var hostBuilderContext = CreateHostBuilderContext(runtimeContext);
 
-            plugin.Initialize(context);
-            var settingsPages = context.GetSettingsPagesSnapshot();
-            var desktopComponents = context.GetDesktopComponentsSnapshot();
+            plugin.Initialize(hostBuilderContext, serviceCollection);
+
+            pluginServices = serviceCollection.BuildServiceProvider(new ServiceProviderOptions
+            {
+                ValidateScopes = false,
+                ValidateOnBuild = true
+            });
+            runtimeContext.SetServices(pluginServices);
+
+            var settingsPages = pluginServices
+                .GetServices<PluginSettingsPageRegistration>()
+                .OrderBy(page => page.SortOrder)
+                .ThenBy(page => page.Title, StringComparer.OrdinalIgnoreCase)
+                .ToArray();
+            var desktopComponents = pluginServices
+                .GetServices<PluginDesktopComponentRegistration>()
+                .OrderBy(component => component.Category, StringComparer.OrdinalIgnoreCase)
+                .ThenBy(component => component.DisplayName, StringComparer.OrdinalIgnoreCase)
+                .ToArray();
+            var exportedServices = ResolveExports(manifest, pluginServices);
+            hostedServices = pluginServices.GetServices<IHostedService>().ToArray();
+            StartHostedServices(hostedServices);
 
             var loadedPlugin = new LoadedPlugin(
                 manifest,
@@ -155,17 +183,22 @@ public sealed class PluginLoader
                 assemblyPath,
                 assembly,
                 plugin,
-                context,
+                runtimeContext,
+                pluginServices,
                 settingsPages,
                 desktopComponents,
+                exportedServices,
+                hostedServices,
                 loadContext);
 
             return PluginLoadResult.Success(sourcePath, manifest, loadedPlugin);
         }
         catch (Exception ex)
         {
+            StopHostedServices(hostedServices);
+            DisposeInstance(pluginServices);
             DisposeInstance(plugin);
-            DisposeInstance(context);
+            DisposeInstance(runtimeContext);
             loadContext?.Unload();
             return PluginLoadResult.Failure(sourcePath, manifest, ex);
         }
@@ -243,23 +276,124 @@ public sealed class PluginLoader
         }
     }
 
-    private PluginContext CreateContext(
+    private PluginRuntimeContext CreateRuntimeContext(
         PluginManifest manifest,
         string pluginDirectory,
         string dataDirectory,
-        IServiceProvider? services,
         IReadOnlyDictionary<string, object?>? properties)
     {
-        Directory.CreateDirectory(dataDirectory);
-
-        return new PluginContext(
+        return new PluginRuntimeContext(
             manifest,
             pluginDirectory,
             dataDirectory,
-            services ?? NullServiceProvider.Instance,
             CreateReadOnlyProperties(properties));
     }
 
+    private ServiceCollection CreateServiceCollection(
+        PluginRuntimeContext runtimeContext,
+        IServiceProvider? hostServices)
+    {
+        var services = new ServiceCollection();
+        services.AddSingleton(runtimeContext);
+        services.AddSingleton<IPluginRuntimeContext>(runtimeContext);
+        services.AddSingleton(runtimeContext.Manifest);
+        services.AddSingleton<IReadOnlyDictionary<string, object?>>(runtimeContext.Properties);
+        services.AddSingleton<IPluginMessageBus, PluginMessageBus>();
+
+        RegisterHostService<IPluginPackageManager>(services, hostServices);
+        RegisterHostService<IHostApplicationLifecycle>(services, hostServices);
+        RegisterHostService<IPluginExportRegistry>(services, hostServices);
+
+        return services;
+    }
+
+    private static void RegisterHostService<TService>(IServiceCollection services, IServiceProvider? hostServices)
+        where TService : class
+    {
+        if (hostServices?.GetService(typeof(TService)) is TService service)
+        {
+            services.AddSingleton(service);
+        }
+    }
+
+    private static HostBuilderContext CreateHostBuilderContext(PluginRuntimeContext runtimeContext)
+    {
+        var hostBuilderContext = new HostBuilderContext(new Dictionary<object, object>());
+        hostBuilderContext.Properties["LanMountainDesktop.PluginManifest"] = runtimeContext.Manifest;
+        hostBuilderContext.Properties["LanMountainDesktop.PluginDirectory"] = runtimeContext.PluginDirectory;
+        hostBuilderContext.Properties["LanMountainDesktop.PluginDataDirectory"] = runtimeContext.DataDirectory;
+        hostBuilderContext.Properties["LanMountainDesktop.PluginRuntimeContext"] = runtimeContext;
+
+        foreach (var pair in runtimeContext.Properties)
+        {
+            if (pair.Value is not null)
+            {
+                hostBuilderContext.Properties[pair.Key] = pair.Value;
+            }
+        }
+
+        return hostBuilderContext;
+    }
+
+    private static IReadOnlyList<PluginServiceExportDescriptor> ResolveExports(
+        PluginManifest manifest,
+        IServiceProvider services)
+    {
+        return services
+            .GetServices<PluginServiceExportRegistration>()
+            .Select(registration =>
+            {
+                if (!IsSupportedExportContract(manifest, registration.ContractType))
+                {
+                    throw new InvalidOperationException(
+                        $"Plugin '{manifest.Id}' exported contract '{registration.ContractType.FullName}', but export contracts must come from LanMountainDesktop.PluginSdk or a manifest-declared shared contract assembly.");
+                }
+
+                return new PluginServiceExportDescriptor(
+                    manifest.Id,
+                    registration.ContractType,
+                    services.GetService(registration.ContractType)
+                        ?? throw new InvalidOperationException(
+                            $"Plugin '{manifest.Id}' exported contract '{registration.ContractType.FullName}', but no singleton service instance was registered."));
+            })
+            .ToArray();
+    }
+
+    private static bool IsSupportedExportContract(PluginManifest manifest, Type contractType)
+    {
+        if (contractType.Assembly == typeof(IPlugin).Assembly)
+        {
+            return true;
+        }
+
+        var assemblyFileName = contractType.Assembly.GetName().Name + ".dll";
+        return manifest.SharedContracts?.Any(contract =>
+            string.Equals(contract.AssemblyName, assemblyFileName, StringComparison.OrdinalIgnoreCase)) == true;
+    }
+
+    private static void StartHostedServices(IEnumerable<IHostedService> hostedServices)
+    {
+        foreach (var hostedService in hostedServices)
+        {
+            hostedService.StartAsync(CancellationToken.None).GetAwaiter().GetResult();
+        }
+    }
+
+    private static void StopHostedServices(IEnumerable<IHostedService> hostedServices)
+    {
+        foreach (var hostedService in hostedServices.Reverse())
+        {
+            try
+            {
+                hostedService.StopAsync(CancellationToken.None).GetAwaiter().GetResult();
+            }
+            catch
+            {
+                // Ignore best-effort shutdown during failed startup.
+            }
+        }
+    }
+
     private IReadOnlyList<PluginCandidate> DiscoverCandidates(
         string pluginsRootDirectory,
         List<PluginLoadResult> preparationFailures)
@@ -436,6 +570,27 @@ public sealed class PluginLoader
         return new ReadOnlyDictionary<string, object?>(map);
     }
 
+    private static void ValidatePluginRuntimeAssets(
+        PluginManifest manifest,
+        string assemblyPath,
+        string pluginDirectory)
+    {
+        var depsFilePath = Path.ChangeExtension(assemblyPath, ".deps.json");
+        if (!File.Exists(depsFilePath))
+        {
+            throw new InvalidOperationException(
+                $"Plugin '{manifest.Id}' targets API {PluginSdkInfo.ApiVersion} and must include '{Path.GetFileName(depsFilePath)}' next to its main assembly.");
+        }
+
+        var runtimesDirectory = Path.Combine(pluginDirectory, "runtimes");
+        if (Directory.Exists(runtimesDirectory) &&
+            !Directory.EnumerateFiles(runtimesDirectory, "*", SearchOption.AllDirectories).Any())
+        {
+            throw new InvalidOperationException(
+                $"Plugin '{manifest.Id}' contains an empty 'runtimes' directory. Native/runtime assets must be packaged together with the plugin.");
+        }
+    }
+
     private static Type ResolvePluginType(Assembly assembly)
     {
         var candidateTypes = GetLoadableTypes(assembly)
@@ -543,34 +698,19 @@ public sealed class PluginLoader
         }
     }
 
-    private sealed class PluginContext : IPluginContext, IDisposable, IAsyncDisposable
+    private sealed class PluginRuntimeContext : IPluginRuntimeContext
     {
-        private readonly Dictionary<string, PluginSettingsPageRegistration> _settingsPages =
-            new(StringComparer.OrdinalIgnoreCase);
-        private readonly Dictionary<string, PluginDesktopComponentRegistration> _desktopComponents =
-            new(StringComparer.OrdinalIgnoreCase);
-        private readonly Dictionary<Type, object> _registeredServices = [];
-        private readonly List<object> _serviceRegistrationOrder = [];
-        private readonly object _serviceGate = new();
-        private readonly IServiceProvider _hostServices;
-        private int _disposed;
-
-        public PluginContext(
+        public PluginRuntimeContext(
             PluginManifest manifest,
             string pluginDirectory,
             string dataDirectory,
-            IServiceProvider services,
             IReadOnlyDictionary<string, object?> properties)
         {
             Manifest = manifest;
             PluginDirectory = pluginDirectory;
             DataDirectory = dataDirectory;
-            _hostServices = services;
-            Services = new PluginCompositeServiceProvider(this);
             Properties = properties;
-
-            RegisterBuiltInService<IPluginContext>(this);
-            RegisterBuiltInService<IPluginMessageBus>(new PluginMessageBus());
+            Services = NullServiceProvider.Instance;
         }
 
         public PluginManifest Manifest { get; }
@@ -579,7 +719,7 @@ public sealed class PluginLoader
 
         public string DataDirectory { get; }
 
-        public IServiceProvider Services { get; }
+        public IServiceProvider Services { get; private set; }
 
         public IReadOnlyDictionary<string, object?> Properties { get; }
 
@@ -602,181 +742,9 @@ public sealed class PluginLoader
             return false;
         }
 
-        public void RegisterService<TService>(TService service)
-            where TService : class
+        public void SetServices(IServiceProvider services)
         {
-            RegisterServiceCore(typeof(TService), service, allowOverride: false);
-        }
-
-        public void RegisterSettingsPage(PluginSettingsPageRegistration registration)
-        {
-            ArgumentNullException.ThrowIfNull(registration);
-            ThrowIfDisposed();
-
-            if (!_settingsPages.TryAdd(registration.Id, registration))
-            {
-                throw new InvalidOperationException(
-                    $"Plugin '{Manifest.Id}' already registered a settings page with id '{registration.Id}'.");
-            }
-        }
-
-        public void RegisterDesktopComponent(PluginDesktopComponentRegistration registration)
-        {
-            ArgumentNullException.ThrowIfNull(registration);
-            ThrowIfDisposed();
-
-            if (!_desktopComponents.TryAdd(registration.ComponentId, registration))
-            {
-                throw new InvalidOperationException(
-                    $"Plugin '{Manifest.Id}' already registered a desktop component with id '{registration.ComponentId}'.");
-            }
-        }
-
-        public IReadOnlyList<PluginSettingsPageRegistration> GetSettingsPagesSnapshot()
-        {
-            ThrowIfDisposed();
-            return _settingsPages.Values
-                .OrderBy(page => page.SortOrder)
-                .ThenBy(page => page.Title, StringComparer.OrdinalIgnoreCase)
-                .ToArray();
-        }
-
-        public IReadOnlyList<PluginDesktopComponentRegistration> GetDesktopComponentsSnapshot()
-        {
-            ThrowIfDisposed();
-            return _desktopComponents.Values
-                .OrderBy(component => component.Category, StringComparer.OrdinalIgnoreCase)
-                .ThenBy(component => component.DisplayName, StringComparer.OrdinalIgnoreCase)
-                .ToArray();
-        }
-
-        internal object? ResolveService(Type serviceType)
-        {
-            if (Volatile.Read(ref _disposed) != 0)
-            {
-                return null;
-            }
-
-            if (serviceType == typeof(IServiceProvider))
-            {
-                return Services;
-            }
-
-            lock (_serviceGate)
-            {
-                if (_registeredServices.TryGetValue(serviceType, out var service))
-                {
-                    return service;
-                }
-
-                foreach (var registeredService in _registeredServices.Values)
-                {
-                    if (serviceType.IsInstanceOfType(registeredService))
-                    {
-                        return registeredService;
-                    }
-                }
-            }
-
-            return _hostServices.GetService(serviceType);
-        }
-
-        private void RegisterBuiltInService<TService>(TService service)
-            where TService : class
-        {
-            RegisterServiceCore(typeof(TService), service, allowOverride: true);
-        }
-
-        public void Dispose()
-        {
-            DisposeAsync().AsTask().GetAwaiter().GetResult();
-        }
-
-        public async ValueTask DisposeAsync()
-        {
-            if (Interlocked.Exchange(ref _disposed, 1) != 0)
-            {
-                return;
-            }
-
-            object[] services;
-            lock (_serviceGate)
-            {
-                services = _serviceRegistrationOrder.ToArray();
-                _registeredServices.Clear();
-                _serviceRegistrationOrder.Clear();
-            }
-
-            _settingsPages.Clear();
-            _desktopComponents.Clear();
-
-            var disposedServices = new HashSet<object>(ReferenceEqualityComparer.Instance);
-            for (var i = services.Length - 1; i >= 0; i--)
-            {
-                var service = services[i];
-                if (ReferenceEquals(service, this) || !disposedServices.Add(service))
-                {
-                    continue;
-                }
-
-                if (service is IAsyncDisposable asyncDisposable)
-                {
-                    await asyncDisposable.DisposeAsync();
-                }
-                else if (service is IDisposable disposable)
-                {
-                    disposable.Dispose();
-                }
-            }
-        }
-
-        private void RegisterServiceCore(Type serviceType, object service, bool allowOverride)
-        {
-            ArgumentNullException.ThrowIfNull(serviceType);
-            ArgumentNullException.ThrowIfNull(service);
-            ThrowIfDisposed();
-
-            if (!serviceType.IsInstanceOfType(service))
-            {
-                throw new InvalidOperationException(
-                    $"Service instance '{service.GetType().FullName}' is not assignable to '{serviceType.FullName}'.");
-            }
-
-            lock (_serviceGate)
-            {
-                if (!allowOverride && _registeredServices.ContainsKey(serviceType))
-                {
-                    throw new InvalidOperationException(
-                        $"Plugin '{Manifest.Id}' already registered a service for '{serviceType.FullName}'.");
-                }
-
-                _registeredServices[serviceType] = service;
-                _serviceRegistrationOrder.Add(service);
-            }
-        }
-
-        private void ThrowIfDisposed()
-        {
-            if (Volatile.Read(ref _disposed) != 0)
-            {
-                throw new ObjectDisposedException(nameof(PluginContext));
-            }
-        }
-    }
-
-    private sealed class PluginCompositeServiceProvider : IServiceProvider
-    {
-        private readonly PluginContext _context;
-
-        public PluginCompositeServiceProvider(PluginContext context)
-        {
-            _context = context;
-        }
-
-        public object? GetService(Type serviceType)
-        {
-            ArgumentNullException.ThrowIfNull(serviceType);
-            return _context.ResolveService(serviceType);
+            Services = services ?? throw new ArgumentNullException(nameof(services));
         }
     }
 

LanMountainDesktop/plugins/PluginMarketEmbeddedView.cs

@@ -3,6 +3,8 @@ using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
 using System.Linq;
+using System.Net.Http;
+using System.Threading;
 using System.Threading.Tasks;
 using Avalonia;
 using Avalonia.Controls;
@@ -37,6 +39,7 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
     private readonly AirAppMarketReadmeService _readmeService;
     private readonly AirAppMarketIconService _iconService;
     private readonly Version? _hostVersion;
+    private readonly CancellationTokenSource _lifetimeCts = new();
 
     private readonly TextBox _searchTextBox;
     private readonly Button _refreshButton;
@@ -57,6 +60,8 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
     private bool _isRefreshing;
     private bool _isInstalling;
     private bool _hasLoadedOnce;
+    private bool _isDisposed;
+    private bool _isAttachedToVisualTree;
 
     public PluginMarketEmbeddedView(PluginRuntimeService runtime)
     {
@@ -106,16 +111,8 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
         _detailBorder = CreatePanelShell(18);
 
         Content = BuildLayout();
-        AttachedToVisualTree += async (_, _) =>
-        {
-            if (_hasLoadedOnce)
-            {
-                return;
-            }
-
-            _hasLoadedOnce = true;
-            await RefreshAsync();
-        };
+        AttachedToVisualTree += OnAttachedToVisualTree;
+        DetachedFromVisualTree += OnDetachedFromVisualTree;
     }
 
     public void RefreshInstalledSnapshot()
@@ -134,18 +131,47 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
 
     public void Dispose()
     {
+        if (_isDisposed)
+        {
+            return;
+        }
+
+        _isDisposed = true;
+        _lifetimeCts.Cancel();
+
         foreach (var bitmap in _iconBitmaps.Values)
         {
             bitmap?.Dispose();
         }
 
         _iconBitmaps.Clear();
+        _lifetimeCts.Dispose();
         _iconService.Dispose();
         _readmeService.Dispose();
         _installService.Dispose();
         _indexService.Dispose();
     }
 
+    private void OnAttachedToVisualTree(object? sender, VisualTreeAttachmentEventArgs e)
+    {
+        _isAttachedToVisualTree = true;
+        if (_hasLoadedOnce)
+        {
+            return;
+        }
+
+        _hasLoadedOnce = true;
+        UiExceptionGuard.FireAndForgetGuarded(
+            RefreshAsync,
+            "PluginMarket.InitialLoad",
+            BuildMarketContext());
+    }
+
+    private void OnDetachedFromVisualTree(object? sender, VisualTreeAttachmentEventArgs e)
+    {
+        _isAttachedToVisualTree = false;
+    }
+
     private Control BuildLayout()
     {
         var root = new Grid
@@ -197,14 +223,23 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
         return root;
     }
 
-    private async void OnRefreshClick(object? sender, RoutedEventArgs e)
+    private void OnRefreshClick(object? sender, RoutedEventArgs e)
     {
-        await RefreshAsync();
+        UiExceptionGuard.FireAndForgetGuarded(
+            RefreshAsync,
+            "PluginMarket.Refresh",
+            BuildMarketContext(),
+            ex => HandleTopLevelUiActionExceptionAsync(
+                ex,
+                F(
+                    "market.status.load_failed_format",
+                    "Failed to load the plugin market: {0}",
+                    DescribeException(ex))));
     }
 
     private async Task RefreshAsync()
     {
-        if (_isRefreshing)
+        if (_isRefreshing || _isDisposed || _lifetimeCts.IsCancellationRequested)
         {
             return;
         }
@@ -217,11 +252,19 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
         {
             RefreshInstalledSnapshot();
 
-            var result = await _indexService.LoadAsync();
+            var result = await _indexService.LoadAsync(_lifetimeCts.Token);
+            if (!CanUpdateUi())
+            {
+                return;
+            }
+
             if (!result.Success || result.Document is null)
             {
                 _document = null;
                 _selectedPlugin = null;
+                AppLogger.Warn(
+                    "PluginMarket",
+                    $"Refresh failed. Source=None; Warning={result.WarningMessage ?? string.Empty}; Error={result.ErrorMessage ?? string.Empty}; Context={BuildMarketContext()}");
                 SetStatus(
                     F(
                         "market.status.load_failed_format",
@@ -235,6 +278,9 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
             _document = result.Document;
             _marketSourceDisplay = result.SourceLocation ?? AirAppMarketDefaults.DefaultIndexUrl;
             _selectedPlugin = ResolveSelectedPlugin(_selectedPlugin?.Id, result.Document.Plugins);
+            AppLogger.Info(
+                "PluginMarket",
+                $"Refresh completed. Source={result.Source}; PluginCount={result.Document.Plugins.Count}; SourceLocation={result.SourceLocation ?? string.Empty}; Warning={result.WarningMessage ?? string.Empty}; Context={BuildMarketContext()}");
 
             var statusMessage = result.Source == AirAppMarketLoadSource.Cache
                 ? F(
@@ -251,15 +297,43 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
             RebuildSurface();
             await EnsureReadmeLoadedAsync(_selectedPlugin);
         }
+        catch (OperationCanceledException) when (_lifetimeCts.IsCancellationRequested)
+        {
+            AppLogger.Info("PluginMarket", $"Refresh canceled because the view is being disposed. Context={BuildMarketContext()}");
+        }
+        catch (Exception ex)
+        {
+            AppLogger.Warn(
+                "PluginMarket",
+                $"Refresh threw unexpectedly. ExceptionType={ex.GetType().FullName}; Classification={ClassifyException(ex)}; Context={BuildMarketContext()}",
+                ex);
+            if (CanUpdateUi())
+            {
+                SetStatus(
+                    F(
+                        "market.status.load_failed_format",
+                        "Failed to load the plugin market: {0}",
+                        DescribeException(ex)),
+                    ErrorBrush);
+                _document = null;
+                _selectedPlugin = null;
+                RebuildSurface();
+            }
+        }
         finally
         {
             _isRefreshing = false;
-            _refreshButton.IsEnabled = true;
+            _refreshButton.IsEnabled = !_isDisposed;
         }
     }
 
     private void RebuildSurface()
     {
+        if (_isDisposed)
+        {
+            return;
+        }
+
         var filteredPlugins = GetFilteredPlugins();
         _selectedPlugin = filteredPlugins.Count > 0
             ? ResolveSelectedPlugin(_selectedPlugin?.Id, filteredPlugins)
@@ -396,7 +470,10 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
             HorizontalContentAlignment = HorizontalAlignment.Stretch,
             Content = selectGrid
         };
-        selectButton.Click += async (_, _) => await SelectPluginAsync(plugin);
+        selectButton.Click += (_, _) => UiExceptionGuard.FireAndForgetGuarded(
+            () => SelectPluginAsync(plugin),
+            "PluginMarket.SelectPlugin",
+            BuildMarketContext(plugin));
 
         var rightPanel = new StackPanel
         {
@@ -623,13 +700,22 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
             HorizontalAlignment = HorizontalAlignment.Right
         };
 
-        button.Click += async (_, _) =>
-        {
-            _selectedPlugin = plugin;
-            RebuildSurface();
-            await EnsureReadmeLoadedAsync(plugin);
-            await InstallSelectedPluginAsync(plugin);
-        };
+        button.Click += (_, _) => UiExceptionGuard.FireAndForgetGuarded(
+            async () =>
+            {
+                _selectedPlugin = plugin;
+                RebuildSurface();
+                await EnsureReadmeLoadedAsync(plugin);
+                await InstallSelectedPluginAsync(plugin);
+            },
+            "PluginMarket.InstallPlugin",
+            BuildMarketContext(plugin),
+            ex => HandleTopLevelUiActionExceptionAsync(
+                ex,
+                F(
+                    "market.status.install_failed_format",
+                    "Failed to install plugin: {0}",
+                    DescribeException(ex))));
 
         return button;
     }
@@ -643,7 +729,7 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
 
     private async Task InstallSelectedPluginAsync(AirAppMarketPluginEntry plugin)
     {
-        if (_isInstalling)
+        if (_isInstalling || _isDisposed || _lifetimeCts.IsCancellationRequested)
         {
             return;
         }
@@ -658,7 +744,12 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
 
         try
         {
-            var result = await _installService.InstallAsync(plugin);
+            var result = await _installService.InstallAsync(plugin, _lifetimeCts.Token);
+            if (!CanUpdateUi())
+            {
+                return;
+            }
+
             if (!result.Success || result.Manifest is null)
             {
                 SetStatus(
@@ -679,6 +770,12 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
                 SuccessBrush);
             RebuildSurface();
         }
+        catch (OperationCanceledException) when (_lifetimeCts.IsCancellationRequested)
+        {
+            AppLogger.Info(
+                "PluginMarket",
+                $"Install canceled because the view is being disposed. PluginId={plugin.Id}; Context={BuildMarketContext(plugin)}");
+        }
         finally
         {
             _isInstalling = false;
@@ -690,6 +787,7 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
     private async Task EnsureReadmeLoadedAsync(AirAppMarketPluginEntry? plugin)
     {
         if (plugin is null ||
+            _isDisposed ||
             _readmeContents.ContainsKey(plugin.Id) ||
             string.Equals(_loadingReadmePluginId, plugin.Id, StringComparison.OrdinalIgnoreCase))
         {
@@ -702,19 +800,30 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
 
         try
         {
-            var readme = await _readmeService.LoadAsync(plugin);
+            var readme = await _readmeService.LoadAsync(plugin, _lifetimeCts.Token);
             _readmeContents[plugin.Id] = string.IsNullOrWhiteSpace(readme)
                 ? T("market.detail.readme_empty", "README is empty.")
                 : readme.Trim();
         }
+        catch (OperationCanceledException) when (_lifetimeCts.IsCancellationRequested)
+        {
+            AppLogger.Info(
+                "PluginMarket",
+                $"README load canceled because the view is being disposed. PluginId={plugin.Id}; Context={BuildMarketContext(plugin)}");
+        }
         catch (Exception ex)
         {
+            AppLogger.Warn(
+                "PluginMarket",
+                $"README load failed. PluginId={plugin.Id}; ExceptionType={ex.GetType().FullName}; Classification={ClassifyException(ex)}; Context={BuildMarketContext(plugin)}",
+                ex);
             _readmeErrors[plugin.Id] = ex.Message;
         }
         finally
         {
             _loadingReadmePluginId = null;
-            if (string.Equals(_selectedPlugin?.Id, plugin.Id, StringComparison.OrdinalIgnoreCase))
+            if (CanUpdateUi() &&
+                string.Equals(_selectedPlugin?.Id, plugin.Id, StringComparison.OrdinalIgnoreCase))
             {
                 BuildDetailPanel();
             }
@@ -724,6 +833,7 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
     private async Task EnsureIconLoadedAsync(AirAppMarketPluginEntry? plugin)
     {
         if (plugin is null ||
+            _isDisposed ||
             _iconBitmaps.ContainsKey(plugin.Id) ||
             !_loadingIconPluginIds.Add(plugin.Id))
         {
@@ -732,7 +842,13 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
 
         try
         {
-            _iconBitmaps[plugin.Id] = await _iconService.LoadAsync(plugin);
+            _iconBitmaps[plugin.Id] = await _iconService.LoadAsync(plugin, _lifetimeCts.Token);
+        }
+        catch (OperationCanceledException) when (_lifetimeCts.IsCancellationRequested)
+        {
+            AppLogger.Info(
+                "PluginMarket",
+                $"Icon load canceled because the view is being disposed. PluginId={plugin.Id}; Context={BuildMarketContext(plugin)}");
         }
         catch
         {
@@ -741,8 +857,61 @@ internal sealed class PluginMarketEmbeddedView : UserControl, IDisposable
         finally
         {
             _loadingIconPluginIds.Remove(plugin.Id);
+            if (CanUpdateUi())
+            {
+                RebuildSurface();
+            }
+        }
+    }
+
+    private Task HandleTopLevelUiActionExceptionAsync(Exception ex, string fallbackStatus)
+    {
+        if (CanUpdateUi())
+        {
+            SetStatus(fallbackStatus, ErrorBrush);
             RebuildSurface();
         }
+
+        return Task.CompletedTask;
+    }
+
+    private bool CanUpdateUi()
+    {
+        return !_isDisposed && _isAttachedToVisualTree && !_lifetimeCts.IsCancellationRequested;
+    }
+
+    private string BuildMarketContext(AirAppMarketPluginEntry? plugin = null)
+    {
+        return UiExceptionGuard.BuildContext(
+            ("SelectedPluginId", _selectedPlugin?.Id),
+            ("PluginId", plugin?.Id),
+            ("Source", _marketSourceDisplay),
+            ("IsRefreshing", _isRefreshing),
+            ("IsInstalling", _isInstalling),
+            ("IsDisposed", _isDisposed));
+    }
+
+    private static string ClassifyException(Exception ex)
+    {
+        return ex switch
+        {
+            OperationCanceledException => "Canceled",
+            TimeoutException => "Timeout",
+            HttpRequestException => "Network",
+            IOException => "IO",
+            _ => "Unexpected"
+        };
+    }
+
+    private static string DescribeException(Exception ex)
+    {
+        return ex switch
+        {
+            OperationCanceledException => "The request timed out or was canceled.",
+            TimeoutException => "The request timed out.",
+            HttpRequestException => ex.Message,
+            _ => ex.Message
+        };
     }
 
     private string GetReadmeContent(AirAppMarketPluginEntry plugin)

LanMountainDesktop/plugins/PluginMarketIndexService.cs

@@ -43,10 +43,14 @@ internal sealed class AirAppMarketIndexService : IDisposable
                     null,
                     null);
             }
-            catch (OperationCanceledException)
+            catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
             {
                 throw;
             }
+            catch (OperationCanceledException ex)
+            {
+                networkError = ex;
+            }
             catch (Exception ex)
             {
                 networkError = ex;
@@ -71,10 +75,14 @@ internal sealed class AirAppMarketIndexService : IDisposable
                 null,
                 null);
         }
-        catch (OperationCanceledException)
+        catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
         {
             throw;
         }
+        catch (OperationCanceledException ex)
+        {
+            networkError = ex;
+        }
         catch (Exception ex)
         {
             networkError = ex;

LanMountainDesktop/plugins/PluginMarketInstallService.cs

@@ -78,6 +78,7 @@ internal sealed class AirAppMarketInstallService : IDisposable
                 }
             }
 
+            var actualSize = new FileInfo(downloadPath).Length;
             string actualHash;
             await using (var hashStream = File.OpenRead(downloadPath))
             {
@@ -87,11 +88,14 @@ internal sealed class AirAppMarketInstallService : IDisposable
 
             if (!string.Equals(actualHash, plugin.Sha256, StringComparison.OrdinalIgnoreCase))
             {
+                AppLogger.Error(
+                    "PluginMarket",
+                    $"SHA-256 verification failed. PluginId='{plugin.Id}'; Version='{plugin.Version}'; DownloadUrl='{resolvedDownloadUrl}'; DownloadPath='{downloadPath}'; ExpectedHash='{plugin.Sha256}'; ActualHash='{actualHash}'; ExpectedSize='{plugin.PackageSizeBytes}'; ActualSize='{actualSize}'.");
                 File.Delete(downloadPath);
                 return new AirAppMarketInstallResult(
                     false,
                     null,
-                    $"SHA-256 mismatch. Expected {plugin.Sha256}, actual {actualHash}.");
+                    $"SHA-256 mismatch. Expected {plugin.Sha256}, actual {actualHash}. Expected size {plugin.PackageSizeBytes}, actual size {actualSize}. Source {resolvedDownloadUrl}.");
             }
 
             PluginManifest manifest;

LanMountainDesktop/plugins/PluginMarketModels.cs

@@ -215,6 +215,8 @@ internal sealed class AirAppMarketIndexDocument
 
     public DateTimeOffset GeneratedAt { get; init; }
 
+    public List<AirAppMarketSharedContractEntry> Contracts { get; init; } = [];
+
     public List<AirAppMarketPluginEntry> Plugins { get; init; } = [];
 
     public static AirAppMarketIndexDocument Load(string json, string sourceName)
@@ -236,6 +238,23 @@ internal sealed class AirAppMarketIndexDocument
 
     private AirAppMarketIndexDocument ValidateAndNormalize(string sourceName)
     {
+        var contracts = Contracts ?? [];
+        var normalizedContracts = new List<AirAppMarketSharedContractEntry>(contracts.Count);
+        var seenContracts = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+
+        foreach (var contract in contracts)
+        {
+            var normalizedContract = contract.ValidateAndNormalize(sourceName);
+            var contractKey = $"{normalizedContract.Id}@{normalizedContract.Version}";
+            if (!seenContracts.Add(contractKey))
+            {
+                throw new InvalidOperationException(
+                    $"Market index '{sourceName}' contains duplicate shared contract '{contractKey}'.");
+            }
+
+            normalizedContracts.Add(normalizedContract);
+        }
+
         var plugins = Plugins ?? [];
         var normalizedPlugins = new List<AirAppMarketPluginEntry>(plugins.Count);
         var seenIds = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
@@ -260,6 +279,10 @@ internal sealed class AirAppMarketIndexDocument
             GeneratedAt = GeneratedAt == default
                 ? throw new InvalidOperationException($"Market index '{sourceName}' is missing a valid generatedAt timestamp.")
                 : GeneratedAt,
+            Contracts = normalizedContracts
+                .OrderBy(contract => contract.Id, StringComparer.OrdinalIgnoreCase)
+                .ThenBy(contract => contract.Version, StringComparer.OrdinalIgnoreCase)
+                .ToList(),
             Plugins = normalizedPlugins
                 .OrderBy(plugin => plugin.Name, StringComparer.OrdinalIgnoreCase)
                 .ToList()
@@ -373,6 +396,56 @@ internal sealed class AirAppMarketIndexDocument
     }
 }
 
+internal sealed class AirAppMarketSharedContractEntry
+{
+    public string Id { get; init; } = string.Empty;
+
+    public string Version { get; init; } = string.Empty;
+
+    public string AssemblyName { get; init; } = string.Empty;
+
+    public string DownloadUrl { get; init; } = string.Empty;
+
+    public string Sha256 { get; init; } = string.Empty;
+
+    public long PackageSizeBytes { get; init; }
+
+    public AirAppMarketSharedContractEntry ValidateAndNormalize(string sourceName)
+    {
+        var normalizedSha = AirAppMarketIndexDocument.NormalizeValue(Sha256)?.ToLowerInvariant()
+            ?? throw new InvalidOperationException(
+                $"Market index '{sourceName}' is missing required property '{nameof(Sha256)}' for a shared contract.");
+        if (normalizedSha.Length != 64 || normalizedSha.Any(ch => !Uri.IsHexDigit(ch)))
+        {
+            throw new InvalidOperationException(
+                $"Market index '{sourceName}' declares invalid SHA-256 '{normalizedSha}' for shared contract '{Id}'.");
+        }
+
+        var normalizedDownloadUrl = AirAppMarketIndexDocument.NormalizeValue(DownloadUrl)
+            ?? throw new InvalidOperationException(
+                $"Market index '{sourceName}' is missing required property '{nameof(DownloadUrl)}' for shared contract '{Id}'.");
+        AirAppMarketIndexDocument.EnsureUrl(normalizedDownloadUrl, nameof(DownloadUrl), sourceName);
+
+        if (PackageSizeBytes <= 0)
+        {
+            throw new InvalidOperationException(
+                $"Market index '{sourceName}' declares invalid packageSizeBytes '{PackageSizeBytes}' for shared contract '{Id}'.");
+        }
+
+        return new AirAppMarketSharedContractEntry
+        {
+            Id = AirAppMarketIndexDocument.NormalizeValue(Id)
+                ?? throw new InvalidOperationException($"Market index '{sourceName}' is missing a shared contract id."),
+            Version = AirAppMarketIndexDocument.NormalizeVersion(Version, nameof(Version), sourceName),
+            AssemblyName = AirAppMarketIndexDocument.NormalizeValue(AssemblyName)
+                ?? throw new InvalidOperationException($"Market index '{sourceName}' is missing assemblyName for shared contract '{Id}'."),
+            DownloadUrl = normalizedDownloadUrl,
+            Sha256 = normalizedSha,
+            PackageSizeBytes = PackageSizeBytes
+        };
+    }
+}
+
 internal sealed class AirAppMarketPluginEntry
 {
     public string Id { get; init; } = string.Empty;

LanMountainDesktop/plugins/PluginRuntimeService.cs

@@ -12,6 +12,8 @@ using Avalonia.Markup.Xaml;
 using LanMountainDesktop.Models;
 using LanMountainDesktop.Plugins;
 using LanMountainDesktop.PluginSdk;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 
 namespace LanMountainDesktop.Services;
 
@@ -19,9 +21,12 @@ public sealed class PluginRuntimeService : IDisposable
 {
     private const string PendingDeletionFileName = ".pending-plugin-deletions.json";
 
+    private readonly PluginLoaderOptions _loaderOptions;
     private readonly PluginLoader _loader;
     private readonly AppSettingsService _appSettingsService = new();
     private readonly IHostApplicationLifecycle _applicationLifecycle = new HostApplicationLifecycleService();
+    private readonly PluginExportRegistry _exportRegistry = new();
+    private readonly PluginSharedContractManager _sharedContractManager;
     private readonly IServiceProvider _hostServices;
     private readonly IPluginPackageManager _packageManager;
     private readonly List<LoadedPlugin> _loadedPlugins = [];
@@ -34,9 +39,12 @@ public sealed class PluginRuntimeService : IDisposable
     public PluginRuntimeService()
     {
         PluginsDirectory = Path.Combine(AppContext.BaseDirectory, "Extensions", "Plugins");
+        _sharedContractManager = new PluginSharedContractManager(
+            Path.Combine(GetUserDataRootDirectory(), "PluginMarket"));
         _packageManager = new PluginRuntimePackageManager(this);
-        _hostServices = new PluginHostServiceProvider(_packageManager, _applicationLifecycle);
-        _loader = new PluginLoader(CreateOptions());
+        _hostServices = new PluginHostServiceProvider(_packageManager, _applicationLifecycle, _exportRegistry);
+        _loaderOptions = CreateOptions();
+        _loader = new PluginLoader(_loaderOptions);
     }
 
     public string PluginsDirectory { get; }
@@ -51,6 +59,8 @@ public sealed class PluginRuntimeService : IDisposable
 
     public IReadOnlyList<PluginDesktopComponentContribution> DesktopComponents => _desktopComponents;
 
+    public IPluginExportRegistry ExportRegistry => _exportRegistry;
+
     public void LoadInstalledPlugins()
     {
         Directory.CreateDirectory(PluginsDirectory);
@@ -101,6 +111,27 @@ public sealed class PluginRuntimeService : IDisposable
                 continue;
             }
 
+            try
+            {
+                RegisterSharedContractsForLoad(candidate.Manifest);
+            }
+            catch (Exception ex)
+            {
+                var dependencyFailure = PluginLoadResult.Failure(candidate.SourcePath, candidate.Manifest, ex);
+                _loadResults.Add(dependencyFailure);
+                _catalog.Add(new PluginCatalogEntry(
+                    candidate.Manifest,
+                    candidate.SourcePath,
+                    candidate.SourceKind == PluginCatalogSourceKind.Package,
+                    true,
+                    false,
+                    ex.Message,
+                    0,
+                    0));
+                Debug.WriteLine($"[PluginRuntime] Failed to prepare dependencies for '{candidate.Manifest.Id}': {ex}");
+                continue;
+            }
+
             var loadResult = candidate.SourceKind switch
             {
                 PluginCatalogSourceKind.Package => _loader.LoadFromPackage(
@@ -277,6 +308,7 @@ public sealed class PluginRuntimeService : IDisposable
         Directory.CreateDirectory(PluginsDirectory);
 
         var manifest = ReadManifestFromPackage(fullPackagePath);
+        _sharedContractManager.EnsureInstalled(manifest);
         AppLogger.Info(
             "PluginRuntime",
             $"Installing package. PluginId='{manifest.Id}'; Source='{fullPackagePath}'; PluginsDirectory='{PluginsDirectory}'.");
@@ -308,6 +340,7 @@ public sealed class PluginRuntimeService : IDisposable
         }
 
         var manifest = ReadManifestFromPackage(fullPackagePath);
+        _sharedContractManager.EnsureInstalled(manifest);
         AppLogger.Info(
             "PluginRuntime",
             $"Registering externally installed package. PluginId='{manifest.Id}'; Source='{fullPackagePath}'.");
@@ -319,16 +352,19 @@ public sealed class PluginRuntimeService : IDisposable
     public void Dispose()
     {
         UnloadInstalledPlugins();
+        _sharedContractManager.Dispose();
     }
 
     private void UnloadInstalledPlugins()
     {
         for (var i = _loadedPlugins.Count - 1; i >= 0; i--)
         {
+            _exportRegistry.RemoveExports(_loadedPlugins[i].Manifest.Id);
             _loadedPlugins[i].Dispose();
         }
 
         _loadedPlugins.Clear();
+        _exportRegistry.Clear();
         _loadResults.Clear();
         _catalog.Clear();
         _settingsPages.Clear();
@@ -483,10 +519,23 @@ public sealed class PluginRuntimeService : IDisposable
             : path + Path.DirectorySeparatorChar;
     }
 
+    private static string GetUserDataRootDirectory()
+    {
+        var localAppData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
+        if (string.IsNullOrWhiteSpace(localAppData))
+        {
+            return Path.Combine(AppContext.BaseDirectory, "Data");
+        }
+
+        return Path.Combine(localAppData, "LanMountainDesktop");
+    }
+
     private static PluginLoaderOptions CreateOptions()
     {
         var options = new PluginLoaderOptions();
         AddSharedAssembly(options, typeof(App).Assembly);
+        AddSharedAssembly(options, typeof(IServiceCollection).Assembly);
+        AddSharedAssembly(options, typeof(HostBuilderContext).Assembly);
 
         foreach (var assembly in AppDomain.CurrentDomain.GetAssemblies())
         {
@@ -517,6 +566,8 @@ public sealed class PluginRuntimeService : IDisposable
 
     private void CollectContributions(LoadedPlugin loadedPlugin)
     {
+        _exportRegistry.ReplaceExports(loadedPlugin.Manifest.Id, loadedPlugin.ExportedServices);
+
         foreach (var settingsPage in loadedPlugin.SettingsPages)
         {
             _settingsPages.Add(new PluginSettingsPageContribution(loadedPlugin, settingsPage));
@@ -528,6 +579,17 @@ public sealed class PluginRuntimeService : IDisposable
         }
     }
 
+    private void RegisterSharedContractsForLoad(PluginManifest manifest)
+    {
+        foreach (var assemblyName in _sharedContractManager.PrepareForLoad(manifest))
+        {
+            if (!string.IsNullOrWhiteSpace(assemblyName))
+            {
+                _loaderOptions.SharedAssemblyNames.Add(assemblyName);
+            }
+        }
+    }
+
     private void ApplyPendingPluginDeletions()
     {
         var pendingPaths = ReadPendingPluginDeletions();
@@ -681,13 +743,16 @@ public sealed class PluginRuntimeService : IDisposable
     {
         private readonly IPluginPackageManager _packageManager;
         private readonly IHostApplicationLifecycle _applicationLifecycle;
+        private readonly IPluginExportRegistry _exportRegistry;
 
         public PluginHostServiceProvider(
             IPluginPackageManager packageManager,
-            IHostApplicationLifecycle applicationLifecycle)
+            IHostApplicationLifecycle applicationLifecycle,
+            IPluginExportRegistry exportRegistry)
         {
             _packageManager = packageManager;
             _applicationLifecycle = applicationLifecycle;
+            _exportRegistry = exportRegistry;
         }
 
         public object? GetService(Type serviceType)
@@ -702,6 +767,11 @@ public sealed class PluginRuntimeService : IDisposable
                 return _applicationLifecycle;
             }
 
+            if (serviceType == typeof(IPluginExportRegistry))
+            {
+                return _exportRegistry;
+            }
+
             return null;
         }
     }

LanMountainDesktop/plugins/PluginSettingsPage.Host.cs

@@ -130,7 +130,25 @@ public partial class PluginSettingsPage : UserControl
         };
     }
 
-    private async void OnInstallPluginPackageClick(object? sender, Avalonia.Interactivity.RoutedEventArgs e)
+    private void OnInstallPluginPackageClick(object? sender, Avalonia.Interactivity.RoutedEventArgs e)
+    {
+        UiExceptionGuard.FireAndForgetGuarded(
+            OnInstallPluginPackageAsync,
+            "PluginSettings.InstallPackage",
+            context: "Page=PluginSettings",
+            onHandledException: ex =>
+            {
+                SetPackageImportStatus(
+                    F(
+                        "settings.plugins.install_failed_format",
+                        "Failed to install plugin package: {0}",
+                        ex.Message),
+                    isError: true);
+                return Task.CompletedTask;
+            });
+    }
+
+    private async Task OnInstallPluginPackageAsync()
     {
         var runtime = (Application.Current as App)?.PluginRuntimeService;
         if (runtime is null)

LanMountainDesktop/plugins/PluginSharedContractManager.cs

@@ -0,0 +1,272 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Net.Http;
+using System.Reflection;
+using System.Runtime.Loader;
+using System.Security.Cryptography;
+using System.Threading;
+using LanMountainDesktop.PluginSdk;
+using LanMountainDesktop.Views.SettingsPages;
+
+namespace LanMountainDesktop.Plugins;
+
+internal sealed class PluginSharedContractManager : IDisposable
+{
+    private readonly string _contractsDirectory;
+    private readonly AirAppMarketIndexService _indexService;
+    private readonly HttpClient _httpClient;
+    private readonly object _gate = new();
+    private readonly Dictionary<string, LoadedSharedContract> _loadedContracts =
+        new(StringComparer.OrdinalIgnoreCase);
+
+    public PluginSharedContractManager(string cacheDirectory)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(cacheDirectory);
+
+        _contractsDirectory = Path.Combine(
+            GetSharedContractRootDirectory(),
+            "SharedContracts");
+        _indexService = new AirAppMarketIndexService(new AirAppMarketCacheService(cacheDirectory));
+        _httpClient = new HttpClient
+        {
+            Timeout = TimeSpan.FromMinutes(2)
+        };
+        _httpClient.DefaultRequestHeaders.UserAgent.ParseAdd("LanMountainDesktop-SharedContracts/1.0");
+    }
+
+    public string ContractsDirectory => _contractsDirectory;
+
+    public void EnsureInstalled(PluginManifest manifest, CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(manifest);
+
+        if (manifest.SharedContracts is not { Count: > 0 })
+        {
+            return;
+        }
+
+        var document = LoadIndex(cancellationToken);
+        foreach (var reference in manifest.SharedContracts)
+        {
+            EnsureInstalled(document, reference, cancellationToken);
+        }
+    }
+
+    public IReadOnlyList<string> PrepareForLoad(PluginManifest manifest, CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(manifest);
+
+        if (manifest.SharedContracts is not { Count: > 0 })
+        {
+            return Array.Empty<string>();
+        }
+
+        var assemblyNames = new List<string>(manifest.SharedContracts.Count);
+        foreach (var reference in manifest.SharedContracts)
+        {
+            var assemblyPath = GetInstalledAssemblyPath(reference);
+            if (!File.Exists(assemblyPath))
+            {
+                throw new InvalidOperationException(
+                    $"Plugin '{manifest.Id}' requires shared contract '{reference.Id}' version '{reference.Version}', but '{assemblyPath}' is not installed. Install the dependency from the market first.");
+            }
+
+            var loaded = LoadSharedAssembly(reference, assemblyPath);
+            assemblyNames.Add(loaded.AssemblyName);
+        }
+
+        return assemblyNames;
+    }
+
+    public void Dispose()
+    {
+        _httpClient.Dispose();
+        _indexService.Dispose();
+    }
+
+    private void EnsureInstalled(
+        AirAppMarketIndexDocument document,
+        PluginSharedContractReference reference,
+        CancellationToken cancellationToken)
+    {
+        var entry = document.Contracts.FirstOrDefault(candidate =>
+            string.Equals(candidate.Id, reference.Id, StringComparison.OrdinalIgnoreCase) &&
+            string.Equals(candidate.Version, reference.Version, StringComparison.OrdinalIgnoreCase));
+        if (entry is null)
+        {
+            throw new InvalidOperationException(
+                $"Shared contract '{reference.Id}' version '{reference.Version}' is not published in the configured market index.");
+        }
+
+        if (!string.Equals(entry.AssemblyName, reference.AssemblyName, StringComparison.OrdinalIgnoreCase))
+        {
+            throw new InvalidOperationException(
+                $"Shared contract '{reference.Id}' version '{reference.Version}' expects assembly '{reference.AssemblyName}', but the market entry provides '{entry.AssemblyName}'.");
+        }
+
+        var destinationPath = GetInstalledAssemblyPath(reference);
+        if (IsInstalledAndMatches(destinationPath, entry))
+        {
+            return;
+        }
+
+        Directory.CreateDirectory(Path.GetDirectoryName(destinationPath)!);
+
+        var temporaryPath = destinationPath + ".download";
+        try
+        {
+            if (AirAppMarketDefaults.TryResolveWorkspaceFile(entry.DownloadUrl, out var localSourcePath))
+            {
+                File.Copy(localSourcePath, temporaryPath, overwrite: true);
+            }
+            else
+            {
+                using var response = _httpClient.GetAsync(entry.DownloadUrl, cancellationToken)
+                    .GetAwaiter()
+                    .GetResult();
+                response.EnsureSuccessStatusCode();
+                using var responseStream = response.Content.ReadAsStreamAsync(cancellationToken)
+                    .GetAwaiter()
+                    .GetResult();
+                using var fileStream = File.Create(temporaryPath);
+                responseStream.CopyTo(fileStream);
+            }
+
+            ValidateInstalledFile(temporaryPath, entry);
+            File.Move(temporaryPath, destinationPath, overwrite: true);
+        }
+        finally
+        {
+            TryDeleteFile(temporaryPath);
+        }
+    }
+
+    private AirAppMarketIndexDocument LoadIndex(CancellationToken cancellationToken)
+    {
+        var result = _indexService.LoadAsync(cancellationToken).GetAwaiter().GetResult();
+        if (!result.Success || result.Document is null)
+        {
+            throw new InvalidOperationException(
+                $"Failed to load market index for shared contract resolution: {result.ErrorMessage ?? "Unknown error"}");
+        }
+
+        return result.Document;
+    }
+
+    private LoadedSharedContract LoadSharedAssembly(
+        PluginSharedContractReference reference,
+        string assemblyPath)
+    {
+        var assemblyName = AssemblyLoadContext.GetAssemblyName(assemblyPath).Name
+            ?? throw new InvalidOperationException($"Failed to determine assembly name of '{assemblyPath}'.");
+
+        lock (_gate)
+        {
+            if (_loadedContracts.TryGetValue(assemblyName, out var existing))
+            {
+                if (!string.Equals(existing.ContractId, reference.Id, StringComparison.OrdinalIgnoreCase) ||
+                    !string.Equals(existing.ContractVersion, reference.Version, StringComparison.OrdinalIgnoreCase))
+                {
+                    throw new InvalidOperationException(
+                        $"Shared contract assembly '{assemblyName}' is already loaded as '{existing.ContractId}' version '{existing.ContractVersion}', so plugin dependency '{reference.Id}' version '{reference.Version}' cannot be activated in the same host process.");
+                }
+
+                return existing;
+            }
+
+            var assembly = AssemblyLoadContext.Default.Assemblies.FirstOrDefault(candidate =>
+                string.Equals(candidate.GetName().Name, assemblyName, StringComparison.OrdinalIgnoreCase))
+                ?? AssemblyLoadContext.Default.LoadFromAssemblyPath(assemblyPath);
+
+            var loaded = new LoadedSharedContract(reference.Id, reference.Version, assemblyName, assemblyPath, assembly);
+            _loadedContracts[assemblyName] = loaded;
+            return loaded;
+        }
+    }
+
+    private static bool IsInstalledAndMatches(string assemblyPath, AirAppMarketSharedContractEntry entry)
+    {
+        if (!File.Exists(assemblyPath))
+        {
+            return false;
+        }
+
+        try
+        {
+            ValidateInstalledFile(assemblyPath, entry);
+            return true;
+        }
+        catch
+        {
+            return false;
+        }
+    }
+
+    private static void ValidateInstalledFile(string assemblyPath, AirAppMarketSharedContractEntry entry)
+    {
+        var actualSize = new FileInfo(assemblyPath).Length;
+        if (actualSize != entry.PackageSizeBytes)
+        {
+            throw new InvalidOperationException(
+                $"Shared contract '{entry.Id}' version '{entry.Version}' size mismatch. Expected {entry.PackageSizeBytes}, actual {actualSize}.");
+        }
+
+        using var stream = File.OpenRead(assemblyPath);
+        var actualHash = Convert.ToHexString(SHA256.HashData(stream)).ToLowerInvariant();
+        if (!string.Equals(actualHash, entry.Sha256, StringComparison.OrdinalIgnoreCase))
+        {
+            throw new InvalidOperationException(
+                $"Shared contract '{entry.Id}' version '{entry.Version}' hash mismatch. Expected {entry.Sha256}, actual {actualHash}.");
+        }
+    }
+
+    private string GetInstalledAssemblyPath(PluginSharedContractReference reference)
+    {
+        return Path.Combine(
+            _contractsDirectory,
+            Sanitize(reference.Id),
+            Sanitize(reference.Version),
+            reference.AssemblyName);
+    }
+
+    private static string GetSharedContractRootDirectory()
+    {
+        var localAppData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
+        if (string.IsNullOrWhiteSpace(localAppData))
+        {
+            return Path.Combine(AppContext.BaseDirectory, "Data");
+        }
+
+        return Path.Combine(localAppData, "LanMountainDesktop");
+    }
+
+    private static string Sanitize(string value)
+    {
+        var invalidChars = Path.GetInvalidFileNameChars();
+        return new string(value.Select(ch => invalidChars.Contains(ch) ? '_' : ch).ToArray());
+    }
+
+    private static void TryDeleteFile(string path)
+    {
+        try
+        {
+            if (File.Exists(path))
+            {
+                File.Delete(path);
+            }
+        }
+        catch
+        {
+            // Ignore cleanup failures.
+        }
+    }
+
+    private sealed record LoadedSharedContract(
+        string ContractId,
+        string ContractVersion,
+        string AssemblyName,
+        string AssemblyPath,
+        Assembly Assembly);
+}

LanMountainDesktop/plugins/README.md

@@ -47,6 +47,9 @@ This directory contains the host-side plugin runtime for LanMountainDesktop.
 - load plugin assemblies
 - integrate plugin settings pages and desktop components
 - expose market and plugin management in the host UI
+- build a plugin-scoped `IServiceCollection`/`ServiceProvider` for API `2.0.0` plugins
+- resolve shared contract assemblies into a version-isolated cache before plugin activation
+- expose explicit cross-plugin exports through `IPluginExportRegistry`
 
 ### Market install order
 
@@ -55,3 +58,9 @@ This directory contains the host-side plugin runtime for LanMountainDesktop.
 3. If Release resolution fails, the host falls back to the repository root `.laapp` from `downloadUrl`.
 4. Plugin details always come from the repository root `README.md`.
 5. Market installs are staged and take effect after restart.
+
+### Dependency model
+
+- Plugin-private managed and native NuGet dependencies remain plugin-local and are resolved through `AssemblyDependencyResolver`.
+- Shared contract assemblies are downloaded from the official market index, cached under `LocalAppData/LanMountainDesktop/SharedContracts/<id>/<version>/`, and loaded into the default context so host and plugins share the same contract types.
+- Different contract versions are isolated on disk. If two active plugins request incompatible versions of the same shared assembly name in one process, the host fails the later activation with a clear error instead of loading an ambiguous contract.

LanMountainDesktop/plugins/SettingsWindow.PluginSettingsHost.cs

@@ -77,7 +77,7 @@ public partial class SettingsWindow
         Control content;
         try
         {
-            content = contribution.Registration.ContentFactory();
+            content = contribution.Registration.ContentFactory(contribution.Plugin.Services);
         }
         catch (Exception ex)
         {