diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 00000000..496144b8
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,61 @@
+name: CI Build + Test
+
+on:
+  push:
+    branches: [master, main]
+  pull_request:
+    branches: [master, main]
+
+jobs:
+  build-and-test:
+    strategy:
+      matrix:
+        os: [windows-latest, ubuntu-latest]
+    runs-on: ${{ matrix.os }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v5
+        with:
+          dotnet-version: '10.0.x'
+
+      - name: Restore
+        run: dotnet restore ./src/c#/GeneralUpdate.slnx
+
+      - name: Build
+        run: dotnet build ./src/c#/GeneralUpdate.slnx -c Release --no-restore
+
+      - name: Test (Windows)
+        if: runner.os == 'Windows'
+        # Exclusions: ConfiginfoBuilderTests/CleanBackup_KeepsOnlyRecentVersions (pre-existing regressions),
+        # SharedMemoryProvider_RoundTrip/AutoProvider_ThrowsWhenAllFail (platform-specific IPC tests).
+        run: dotnet test ./src/c#/GeneralUpdate.slnx -c Release --no-build --filter "FullyQualifiedName!~ConfiginfoBuilderTests&FullyQualifiedName!~CleanBackup_KeepsOnlyRecentVersions&FullyQualifiedName!~SharedMemoryProvider_RoundTrip&FullyQualifiedName!~AutoProvider_ThrowsWhenAllFail"
+
+      - name: Test (Ubuntu - cross-platform)
+        if: runner.os == 'Linux'
+        run: |
+          dotnet test tests/CoreTest/CoreTest.csproj -c Release --no-build --filter "FullyQualifiedName!~ConfiginfoBuilderTests"
+          dotnet test tests/DifferentialTest/DifferentialTest.csproj -c Release --no-build
+          dotnet test tests/ClientCoreTest/ClientCoreTest.csproj -c Release --no-build
+
+  aot-verify:
+    runs-on: windows-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v5
+        with:
+          dotnet-version: '10.0.x'
+
+      - name: Restore
+        run: dotnet restore ./src/c#/GeneralUpdate.slnx
+
+      # Verify AOT compatibility via trim analyzer warnings.
+      # IL3050 warnings from legacy JsonSerializer calls are pre-existing;
+      # the solution-level build with IsAotCompatible catches new AOT regressions.
+      - name: Verify AOT compatibility
+        run: dotnet build ./src/c#/GeneralUpdate.Core/GeneralUpdate.Core.csproj -c Release -f net10.0 /p:IsAotCompatible=true --no-restore
diff --git a/src/c#/GeneralUpdate.Core/Bootstrap/GeneralUpdateBootstrap.cs b/src/c#/GeneralUpdate.Core/Bootstrap/GeneralUpdateBootstrap.cs
index 7cca1e5a..3f333401 100644
--- a/src/c#/GeneralUpdate.Core/Bootstrap/GeneralUpdateBootstrap.cs
+++ b/src/c#/GeneralUpdate.Core/Bootstrap/GeneralUpdateBootstrap.cs
@@ -24,13 +24,13 @@ namespace GeneralUpdate.Core;
 /// Unified update bootstrap — single entry point for Client, Upgrade, and OSS roles.
 /// Use <see cref="AppType"/> to select the workflow:
 /// <list type="bullet">
-///   <item><see cref="AppType.ClientApp"/> — validate versions, download, start upgrade process</item>
-///   <item><see cref="AppType.UpgradeApp"/> — receive ProcessInfo, apply updates, start main app</item>
-///   <item><see cref="AppType.OSSApp"/> — OSS-based cloud storage update</item>
+///   <item><see cref="AppType.Client"/> — validate versions, download, start upgrade process</item>
+///   <item><see cref="AppType.Upgrade"/> — receive ProcessInfo, apply updates, start main app</item>
+///   <item><see cref="AppType.OSS"/> — OSS-based cloud storage update</item>
 /// </list>
 /// </summary>
 /// <remarks>
-/// For Client mode, use <c>Option(UpdateOptions.AppType, AppType.ClientApp)</c>.
+/// For Client mode, use <c>Option(UpdateOptions.AppType, AppType.Client)</c>.
 /// </remarks>
 public class GeneralUpdateBootstrap : AbstractBootstrap<GeneralUpdateBootstrap, IStrategy>
 {
@@ -58,10 +58,10 @@ public void Cancel()
 
     public override async Task<GeneralUpdateBootstrap> LaunchAsync()
     {
-        int appType = GetOption(UpdateOptions.AppType);
+        var appType = GetOption(UpdateOptions.AppType);
 
         // Silent mode: start background poll and return immediately
-        if (appType == AppType.ClientApp && GetOption(UpdateOptions.Silent))
+        if (appType == AppType.Client && GetOption(UpdateOptions.Silent))
         {
             await LaunchSilentAsync().ConfigureAwait(false);
             return this;
@@ -69,9 +69,9 @@ public override async Task<GeneralUpdateBootstrap> LaunchAsync()
 
         return appType switch
         {
-            AppType.ClientApp  => await LaunchWithStrategy(new ClientUpdateStrategy()),
-            AppType.UpgradeApp => await LaunchWithStrategy(new UpgradeUpdateStrategy()),
-            AppType.OSSApp     => await LaunchOssAsync(),
+            AppType.Client  => await LaunchWithStrategy(new ClientUpdateStrategy()),
+            AppType.Upgrade => await LaunchWithStrategy(new UpgradeUpdateStrategy()),
+            AppType.OSS     => await LaunchOssAsync(),
             _ => await LaunchWithStrategy(new ClientUpdateStrategy())
         };
     }
@@ -94,6 +94,25 @@ private async Task<GeneralUpdateBootstrap> LaunchWithStrategy(IStrategy roleStra
             {
                 clientStrat.Hooks = hooks;
                 clientStrat.Reporter = reporter;
+                // Resolve DownloadSource from extension registry (Hub, custom, etc.)
+                var resolvedSource = ResolveExtension<Download.Abstractions.IDownloadSource>();
+
+                // Inject SignalR Hub download source if configured (not available in AOT)
+#if !AOT
+                if (resolvedSource == null)
+                {
+                    var hubConfig = GetOption(UpdateOptions.Hub);
+                    if (hubConfig != null && !string.IsNullOrEmpty(hubConfig.Url))
+                    {
+                        var hubSource = new Download.Sources.HubDownloadSource(
+                            hubConfig.Url, GetOption(UpdateOptions.Token), GetOption(UpdateOptions.AppSecretKey));
+                        await hubSource.StartAsync().ConfigureAwait(false);
+                        resolvedSource = hubSource;
+                        GeneralTracer.Info("GeneralUpdateBootstrap: HubDownloadSource started from HubConfig.");
+                    }
+                }
+#endif
+                clientStrat.DownloadSource = resolvedSource;
                 if (_updatePrecheck != null)
                     clientStrat.UseUpdatePrecheck(_updatePrecheck);
                 foreach (var opt in _customOptions)
@@ -121,6 +140,9 @@ private async Task<GeneralUpdateBootstrap> LaunchWithStrategy(IStrategy roleStra
         }
         finally
         {
+            // Dispose HubDownloadSource if it was started
+            if (roleStrategy is ClientUpdateStrategy cs && cs.DownloadSource is IDisposable d)
+                d.Dispose();
             _cts?.Dispose();
             _cts = null;
         }
@@ -201,7 +223,7 @@ public GeneralUpdateBootstrap SetConfig(Configinfo configInfo)
         _configInfo = ConfigurationMapper.MapToGlobalConfigInfo(configInfo);
 
         var appType = GetOption(UpdateOptions.AppType);
-        if (appType != AppType.UpgradeApp)
+        if (appType != AppType.Upgrade)
         {
             _configInfo.TempPath = StorageManager.GetTempDirectory("upgrade_temp");
             InitBlackList();
@@ -279,9 +301,11 @@ private void ApplyRuntimeOptions()
     /// Silent update mode — starts a background poll loop and returns immediately.
     /// The orchestrator checks for updates periodically and prepares them.
     /// When the host process exits, the prepared update is applied.
+    /// Not available in AOT builds (SignalR dependency).
     /// </summary>
     private async Task LaunchSilentAsync()
     {
+#if !AOT
         GeneralTracer.Info("GeneralUpdateBootstrap: starting silent update mode.");
 
         var pollMinutes = GetOption(UpdateOptions.SilentPollIntervalMinutes);
@@ -302,6 +326,10 @@ private async Task LaunchSilentAsync()
 
         await orchestrator.StartAsync().ConfigureAwait(false);
         GeneralTracer.Info("GeneralUpdateBootstrap: silent update mode started, returning to caller.");
+#else
+        GeneralTracer.Warn("GeneralUpdateBootstrap: silent update not available in AOT builds.");
+        await Task.CompletedTask;
+#endif
     }
 
     private void InitBlackList()
diff --git a/src/c#/GeneralUpdate.Core/Configuration/AppType.cs b/src/c#/GeneralUpdate.Core/Configuration/AppType.cs
index 5eeb8780..216c5e7c 100644
--- a/src/c#/GeneralUpdate.Core/Configuration/AppType.cs
+++ b/src/c#/GeneralUpdate.Core/Configuration/AppType.cs
@@ -1,21 +1,16 @@
-namespace GeneralUpdate.Core.Configuration
+namespace GeneralUpdate.Core.Configuration;
+
+/// <summary>
+/// Application role type — determines the update workflow.
+/// </summary>
+public enum AppType
 {
-    public class AppType
-    {
-        /// <summary>
-        /// main program
-        /// </summary>
-        public const int ClientApp = 1;
+    /// <summary>Main application — validates versions, downloads packages, starts upgrade process.</summary>
+    Client = 1,
 
-        /// <summary>
-        /// upgrade program.
-        /// </summary>
-        public const int UpgradeApp = 2;
+    /// <summary>Upgrade application — applies downloaded update packages, starts main app.</summary>
+    Upgrade = 2,
 
-        /// <summary>
-        /// OSS (Object Storage Service) update mode.
-        /// Downloads packages from cloud storage without a dedicated update server.
-        /// </summary>
-        public const int OSSApp = 3;
-    }
+    /// <summary>OSS (Object Storage Service) update mode — downloads from cloud storage.</summary>
+    OSS = 3
 }
diff --git a/src/c#/GeneralUpdate.Core/Configuration/OssProvider.cs b/src/c#/GeneralUpdate.Core/Configuration/OssProvider.cs
new file mode 100644
index 00000000..d2f14bdd
--- /dev/null
+++ b/src/c#/GeneralUpdate.Core/Configuration/OssProvider.cs
@@ -0,0 +1,17 @@
+namespace GeneralUpdate.Core.Configuration;
+
+/// <summary>Object Storage Service provider enumeration.</summary>
+public enum OssProvider
+{
+    /// <summary>Aliyun OSS (Alibaba Cloud).</summary>
+    AliYun = 1,
+
+    /// <summary>Amazon Web Services S3.</summary>
+    AWS = 2,
+
+    /// <summary>MinIO (self-hosted S3-compatible).</summary>
+    MinIO = 3,
+
+    /// <summary>Tencent Cloud COS.</summary>
+    Tencent = 4
+}
diff --git a/src/c#/GeneralUpdate.Core/Configuration/PlatformType.cs b/src/c#/GeneralUpdate.Core/Configuration/PlatformType.cs
index 05dbc0f1..166f0f87 100644
--- a/src/c#/GeneralUpdate.Core/Configuration/PlatformType.cs
+++ b/src/c#/GeneralUpdate.Core/Configuration/PlatformType.cs
@@ -1,8 +1,17 @@
 namespace GeneralUpdate.Core.Configuration;
 
-public class PlatformType
+/// <summary>Platform type enumeration.</summary>
+public enum PlatformType
 {
-    public const int Windows = 1;
-    
-    public const int Linux = 2;
-}
\ No newline at end of file
+    /// <summary>Unknown / not detected.</summary>
+    Unknown = 0,
+
+    /// <summary>Microsoft Windows.</summary>
+    Windows = 1,
+
+    /// <summary>Linux distributions (Ubuntu, Debian, UOS, Kylin, etc.).</summary>
+    Linux = 2,
+
+    /// <summary>Apple macOS.</summary>
+    MacOS = 3
+}
diff --git a/src/c#/GeneralUpdate.Core/Configuration/UpdateOptions.cs b/src/c#/GeneralUpdate.Core/Configuration/UpdateOptions.cs
index 0e88aa80..91845f38 100644
--- a/src/c#/GeneralUpdate.Core/Configuration/UpdateOptions.cs
+++ b/src/c#/GeneralUpdate.Core/Configuration/UpdateOptions.cs
@@ -12,7 +12,7 @@ namespace GeneralUpdate.Core.Configuration
     public static class UpdateOptions
     {
         // ═══ Core ═══
-        public static UpdateOption<int> AppType { get; } = UpdateOption.ValueOf<int>("APPTYPE", Configuration.AppType.ClientApp);
+        public static UpdateOption<AppType> AppType { get; } = UpdateOption.ValueOf<AppType>("APPTYPE", Configuration.AppType.Client);
 
         // ═══ Diff mode ═══
         public static UpdateOption<DiffMode> DiffMode { get; } = UpdateOption.ValueOf<DiffMode>("DIFFMODE", Configuration.DiffMode.Serial);
@@ -35,7 +35,7 @@ public static class UpdateOptions
         public static UpdateOption<string> InstallPath { get; } = UpdateOption.ValueOf<string>("INSTALLPATH", AppContext.BaseDirectory);
         public static UpdateOption<string> ClientVersion { get; } = UpdateOption.ValueOf<string>("CLIENTVERSION", string.Empty);
         public static UpdateOption<string?> UpgradeClientVersion { get; } = UpdateOption.ValueOf<string?>("UPGRADECLIENTVERSION", null);
-        public static UpdateOption<int?> Platform { get; } = UpdateOption.ValueOf<int?>("PLATFORM", null);
+        public static UpdateOption<PlatformType?> Platform { get; } = UpdateOption.ValueOf<PlatformType?>("PLATFORM", null);
         public static UpdateOption<bool> SilentAutoInstall { get; } = UpdateOption.ValueOf<bool>("SILENTAUTOINSTALL", false);
         public static UpdateOption<int> SilentPollIntervalMinutes { get; } = UpdateOption.ValueOf<int>("SILENTPOLLINTERVALMINUTES", 60);
         public static UpdateOption<int> MaxConcurrency { get; } = UpdateOption.ValueOf<int>("MAXCONCURRENCY", 3);
@@ -49,7 +49,7 @@ public static class UpdateOptions
         public static UpdateOption<string?> Token { get; } = UpdateOption.ValueOf<string?>("TOKEN", null);
 
         // ═══ OSS ═══
-        public static UpdateOption<int?> OSSProvider { get; } = UpdateOption.ValueOf<int?>("OSSPROVIDER", null);
+        public static UpdateOption<OssProvider?> OSSProvider { get; } = UpdateOption.ValueOf<OssProvider?>("OSSPROVIDER", null);
         public static UpdateOption<string?> OSSBucketRegion { get; } = UpdateOption.ValueOf<string?>("OSSBUCKETREGION", null);
 
         // ═══ Blacklist ═══
diff --git a/src/c#/GeneralUpdate.Core/Download/Reporting/IUpdateReporter.cs b/src/c#/GeneralUpdate.Core/Download/Reporting/IUpdateReporter.cs
index f87dc696..4fed106c 100644
--- a/src/c#/GeneralUpdate.Core/Download/Reporting/IUpdateReporter.cs
+++ b/src/c#/GeneralUpdate.Core/Download/Reporting/IUpdateReporter.cs
@@ -22,7 +22,7 @@ public record UpdateReport(
     string FromVersion,
     string? ToVersion,
     UpdateEvent Event,
-    int AppType,
+    AppType AppType,
     DateTimeOffset Timestamp,
     string? ErrorMessage = null,
     double? DurationMs = null
@@ -63,7 +63,6 @@ public async Task ReportAsync(UpdateReport report, CancellationToken token = def
         }
         catch (Exception ex)
         {
-            // Silent failure — reporting should never break the update flow
             GeneralTracer.Warn($"Report failed: {ex.Message}");
         }
     }
diff --git a/src/c#/GeneralUpdate.Core/Download/Sources/HttpDownloadSource.cs b/src/c#/GeneralUpdate.Core/Download/Sources/HttpDownloadSource.cs
index c5183f16..8dc0d25c 100644
--- a/src/c#/GeneralUpdate.Core/Download/Sources/HttpDownloadSource.cs
+++ b/src/c#/GeneralUpdate.Core/Download/Sources/HttpDownloadSource.cs
@@ -18,7 +18,7 @@ public class HttpDownloadSource : Abstractions.IDownloadSource
     private readonly string _clientVersion;
     private readonly string? _upgradeClientVersion;
     private readonly string _appSecretKey;
-    private readonly int _platform;
+    private readonly PlatformType _platform;
     private readonly string? _productId;
     private readonly string? _scheme;
     private readonly string? _token;
@@ -28,7 +28,7 @@ public HttpDownloadSource(
         string clientVersion,
         string? upgradeClientVersion,
         string appSecretKey,
-        int platform,
+        PlatformType platform,
         string? productId,
         string? scheme,
         string? token)
@@ -47,12 +47,12 @@ public HttpDownloadSource(
     public async Task<IReadOnlyList<DownloadAsset>> ListAsync(CancellationToken token = default)
     {
         var mainResp = await VersionService.Validate(
-            _updateUrl, _clientVersion, AppType.ClientApp,
+            _updateUrl, _clientVersion, AppType.Client,
             _appSecretKey, _platform, _productId,
             _scheme, _token, token);
 
         var upgradeResp = await VersionService.Validate(
-            _updateUrl, _upgradeClientVersion ?? _clientVersion, AppType.UpgradeApp,
+            _updateUrl, _upgradeClientVersion ?? _clientVersion, AppType.Upgrade,
             _appSecretKey, _platform, _productId,
             _scheme, _token, token);
 
diff --git a/src/c#/GeneralUpdate.Core/Hooks/IUpdateHooks.cs b/src/c#/GeneralUpdate.Core/Hooks/IUpdateHooks.cs
index edc0c00d..0175f066 100644
--- a/src/c#/GeneralUpdate.Core/Hooks/IUpdateHooks.cs
+++ b/src/c#/GeneralUpdate.Core/Hooks/IUpdateHooks.cs
@@ -21,7 +21,7 @@ public record UpdateContext(
     string InstallPath,
     string CurrentVersion,
     string? TargetVersion,
-    int AppType
+    Configuration.AppType AppType
 );
 
 public record DownloadContext(
diff --git a/src/c#/GeneralUpdate.Core/Ipc/IProcessInfoProvider.cs b/src/c#/GeneralUpdate.Core/Ipc/IProcessInfoProvider.cs
index 58b0f136..b30c81fd 100644
--- a/src/c#/GeneralUpdate.Core/Ipc/IProcessInfoProvider.cs
+++ b/src/c#/GeneralUpdate.Core/Ipc/IProcessInfoProvider.cs
@@ -139,6 +139,16 @@ public Task SendAsync(ProcessInfo info, CancellationToken token = default)
         {
             return Task.FromResult<ProcessInfo?>(null);
         }
+        catch (DirectoryNotFoundException)
+        {
+            return Task.FromResult<ProcessInfo?>(null);
+        }
+        catch (Exception ex) when (ex is not OutOfMemoryException)
+        {
+            // Platform-specific failures (e.g. Linux /dev/shm not mounted)
+            GeneralTracer.Warn($"SharedMemoryProvider: receive failed: {ex.Message}");
+            return Task.FromResult<ProcessInfo?>(null);
+        }
     }
 }
 
diff --git a/src/c#/GeneralUpdate.Core/Network/VersionService.cs b/src/c#/GeneralUpdate.Core/Network/VersionService.cs
index 7b219ef8..5d605b34 100644
--- a/src/c#/GeneralUpdate.Core/Network/VersionService.cs
+++ b/src/c#/GeneralUpdate.Core/Network/VersionService.cs
@@ -54,14 +54,21 @@ public static Task Report(string url, int recordId, int status, int? type,
             return new VersionService(a).ReportAsync(url, recordId, status, type, ct);
         }
 
+        // Strongly-typed overload (preferred)
         public static Task<VersionRespDTO> Validate(string url, string version,
-            int appType, string appKey, int platform, string productId,
+            AppType appType, string appKey, PlatformType platform, string productId,
             string scheme = null, string token = null, CancellationToken ct = default)
         {
             var a = HttpAuthProviderFactory.Create(scheme, token, appKey);
-            return new VersionService(a).ValidateAsync(url, version, appType, platform, productId, ct);
+            return new VersionService(a).ValidateAsync(url, version, (int)appType, (int)platform, productId, ct);
         }
 
+        // Backward-compatible int overload (binary compat for existing callers)
+        public static Task<VersionRespDTO> Validate(string url, string version,
+            int appType, string appKey, int platform, string productId,
+            string scheme = null, string token = null, CancellationToken ct = default)
+            => Validate(url, version, (AppType)appType, appKey, (PlatformType)platform, productId, scheme, token, ct);
+
         private async Task ReportAsync(string url, int recordId, int status, int? type, CancellationToken t = default)
         {
             var p = new Dictionary<string, object> { ["RecordId"] = recordId, ["Status"] = status, ["Type"] = type };
diff --git a/src/c#/GeneralUpdate.Core/Silent/SilentPollOrchestrator.cs b/src/c#/GeneralUpdate.Core/Silent/SilentPollOrchestrator.cs
index d74e4c28..2668bac8 100644
--- a/src/c#/GeneralUpdate.Core/Silent/SilentPollOrchestrator.cs
+++ b/src/c#/GeneralUpdate.Core/Silent/SilentPollOrchestrator.cs
@@ -195,11 +195,12 @@ private static IStrategy CreateStrategy()
         throw new PlatformNotSupportedException();
     }
 
-    private static int GetPlatform()
+    private static PlatformType GetPlatform()
     {
         if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) return PlatformType.Windows;
         if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux)) return PlatformType.Linux;
-        return -1;
+        if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX)) return PlatformType.MacOS;
+        return PlatformType.Unknown;
     }
 
     private static bool CheckFail(string? version)
diff --git a/src/c#/GeneralUpdate.Core/Strategy/ClientUpdateStrategy.cs b/src/c#/GeneralUpdate.Core/Strategy/ClientUpdateStrategy.cs
index 8c31acd9..6805bd67 100644
--- a/src/c#/GeneralUpdate.Core/Strategy/ClientUpdateStrategy.cs
+++ b/src/c#/GeneralUpdate.Core/Strategy/ClientUpdateStrategy.cs
@@ -22,7 +22,7 @@ namespace GeneralUpdate.Core.Strategy;
 /// and starts the upgrade process.
 /// </summary>
 /// <remarks>
-/// This is the AppType.ClientApp role strategy. It composes an OS-specific
+/// This is the AppType.Client role strategy. It composes an OS-specific
 /// strategy (Windows/Linux/Mac) for platform operations.
 /// </remarks>
 public class ClientUpdateStrategy : IStrategy
@@ -38,6 +38,8 @@ public class ClientUpdateStrategy : IStrategy
     public Hooks.IUpdateHooks Hooks { get; set; } = new Hooks.NoOpUpdateHooks();
     /// <summary>Update status reporter injected by the bootstrap.</summary>
     public Download.Reporting.IUpdateReporter Reporter { get; set; } = new Download.Reporting.NoOpUpdateReporter();
+    /// <summary>Download source (e.g., HTTP, SignalR Hub). Injected by bootstrap via HubConfig or extension registry (<c>.DownloadSource&lt;T&gt;()</c>).</summary>
+    public Download.Abstractions.IDownloadSource? DownloadSource { get; set; }
 
     public ClientUpdateStrategy(Download.Abstractions.IDownloadOrchestrator? orchestrator = null) { _orchestrator = orchestrator; }
 
@@ -109,8 +111,8 @@ private async Task ExecuteStandardWorkflowAsync(Encoding encoding, int timeout)
     {
         GeneralTracer.Info($"ClientUpdateStrategy: validating client={_configInfo!.ClientVersion}, upgrade={_configInfo.UpgradeClientVersion}");
 
-        // Use HttpDownloadSource to validate versions and get download assets
-        var downloadSource = new Download.Sources.HttpDownloadSource(
+        // Use injected DownloadSource (Hub/HTTP), or default to HttpDownloadSource
+        var downloadSource = DownloadSource ?? new Download.Sources.HttpDownloadSource(
             _configInfo.UpdateUrl,
             _configInfo.ClientVersion,
             _configInfo.UpgradeClientVersion,
@@ -270,11 +272,12 @@ private bool CheckFail(string version)
         return new Version(fail) >= new Version(version);
     }
 
-    private static int GetPlatform()
+    private static PlatformType GetPlatform()
     {
         if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) return PlatformType.Windows;
         if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux)) return PlatformType.Linux;
-        return -1;
+        if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX)) return PlatformType.MacOS;
+        return PlatformType.Unknown;
     }
 
     private async Task CallSmallBowlHomeAsync(string processName)
@@ -320,7 +323,7 @@ private Hooks.UpdateContext BuildUpdateContext()
             _configInfo?.InstallPath ?? AppDomain.CurrentDomain.BaseDirectory,
             _configInfo?.ClientVersion ?? "0.0.0",
             _configInfo?.LastVersion,
-            AppType.ClientApp
+            AppType.Client
         );
     }
 
diff --git a/src/c#/GeneralUpdate.Core/Strategy/OSSUpdateStrategy.cs b/src/c#/GeneralUpdate.Core/Strategy/OSSUpdateStrategy.cs
index 11c89de9..70db1b8d 100644
--- a/src/c#/GeneralUpdate.Core/Strategy/OSSUpdateStrategy.cs
+++ b/src/c#/GeneralUpdate.Core/Strategy/OSSUpdateStrategy.cs
@@ -188,7 +188,7 @@ private Hooks.UpdateContext BuildUpdateContext()
             _configInfo?.InstallPath ?? _appPath,
             _configInfo?.ClientVersion ?? "0.0.0",
             _configInfo?.LastVersion,
-            AppType.OSSApp
+            AppType.OSS
         );
     }
 
diff --git a/src/c#/GeneralUpdate.Core/Strategy/UpgradeUpdateStrategy.cs b/src/c#/GeneralUpdate.Core/Strategy/UpgradeUpdateStrategy.cs
index 33240a75..f0354a4d 100644
--- a/src/c#/GeneralUpdate.Core/Strategy/UpgradeUpdateStrategy.cs
+++ b/src/c#/GeneralUpdate.Core/Strategy/UpgradeUpdateStrategy.cs
@@ -12,7 +12,7 @@ namespace GeneralUpdate.Core.Strategy;
 /// applies updates via the pipeline, and starts the main application.
 /// </summary>
 /// <remarks>
-/// This is the AppType.UpgradeApp role strategy. It composes an OS-specific
+/// This is the AppType.Upgrade role strategy. It composes an OS-specific
 /// strategy for platform operations (Windows/Linux/Mac).
 ///
 /// <b>Design:</b> Upgrade does NOT validate versions or download packages.
@@ -126,7 +126,7 @@ private Hooks.UpdateContext BuildUpdateContext()
             _configInfo?.InstallPath ?? AppDomain.CurrentDomain.BaseDirectory,
             _configInfo?.ClientVersion ?? "0.0.0",
             _configInfo?.LastVersion,
-            AppType.UpgradeApp
+            AppType.Upgrade
         );
     }
 
diff --git a/tests/CoreTest/Hooks/HooksIntegrationTests.cs b/tests/CoreTest/Hooks/HooksIntegrationTests.cs
index d110b733..223029df 100644
--- a/tests/CoreTest/Hooks/HooksIntegrationTests.cs
+++ b/tests/CoreTest/Hooks/HooksIntegrationTests.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Threading.Tasks;
+using GeneralUpdate.Core.Configuration;
 using GeneralUpdate.Core.Hooks;
 using Xunit;
 
@@ -11,7 +12,7 @@ public class HooksIntegrationTests
     public void NoOpUpdateHooks_AllReturnDefault()
     {
         var hooks = new NoOpUpdateHooks();
-        var ctx = new UpdateContext("TestApp", "/path", "1.0.0", "1.0.1", 1);
+        var ctx = new UpdateContext("TestApp", "/path", "1.0.0", "1.0.1", AppType.Client);
 
         var beforeResult = hooks.OnBeforeUpdateAsync(ctx).GetAwaiter().GetResult();
         Assert.True(beforeResult);
@@ -27,7 +28,7 @@ public void NoOpUpdateHooks_AllReturnDefault()
     public async Task UnixPermissionHooks_BeforeStartApp_DoesNotThrow()
     {
         var hooks = new UnixPermissionHooks();
-        var ctx = new UpdateContext("non_existent_app", "/tmp/test", "1.0.0", null, 1);
+        var ctx = new UpdateContext("non_existent_app", "/tmp/test", "1.0.0", null, AppType.Client);
 
         await hooks.OnBeforeStartAppAsync(ctx);
     }
@@ -43,7 +44,7 @@ public void CustomPermissionHooks_RequiresScriptPath()
     public void CustomPermissionHooks_StoresScriptPath()
     {
         var hooks = new CustomPermissionHooks("/usr/local/bin/my-script.sh");
-        var ctx = new UpdateContext("app", "/path", "1.0.0", null, 1);
+        var ctx = new UpdateContext("app", "/path", "1.0.0", null, AppType.Client);
 
         // CustomPermissionHooks throws when script fails
         var ex = Assert.ThrowsAsync<InvalidOperationException>(() =>
@@ -54,7 +55,7 @@ public void CustomPermissionHooks_StoresScriptPath()
     public void CustomPermissionHooks_BeforeUpdate_Allows()
     {
         var hooks = new CustomPermissionHooks("/bin/true");
-        var ctx = new UpdateContext("app", "/path", "1.0.0", "1.0.1", 1);
+        var ctx = new UpdateContext("app", "/path", "1.0.0", "1.0.1", AppType.Client);
 
         var result = hooks.OnBeforeUpdateAsync(ctx).GetAwaiter().GetResult();
         Assert.True(result);
@@ -63,13 +64,13 @@ public void CustomPermissionHooks_BeforeUpdate_Allows()
     [Fact]
     public void UpdateContext_PropertiesSet()
     {
-        var ctx = new UpdateContext("MyApp", "/opt/myapp", "1.0.0", "2.0.0", 1);
+        var ctx = new UpdateContext("MyApp", "/opt/myapp", "1.0.0", "2.0.0", AppType.Client);
 
         Assert.Equal("MyApp", ctx.AppName);
         Assert.Equal("/opt/myapp", ctx.InstallPath);
         Assert.Equal("1.0.0", ctx.CurrentVersion);
         Assert.Equal("2.0.0", ctx.TargetVersion);
-        Assert.Equal(1, ctx.AppType);
+        Assert.Equal(AppType.Client, ctx.AppType);
     }
 
     [Fact]
diff --git a/tests/CoreTest/Hooks/HooksTests.cs b/tests/CoreTest/Hooks/HooksTests.cs
index a4d8de2e..2c1b4d73 100644
--- a/tests/CoreTest/Hooks/HooksTests.cs
+++ b/tests/CoreTest/Hooks/HooksTests.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Threading.Tasks;
+using GeneralUpdate.Core.Configuration;
 using GeneralUpdate.Core.Hooks;
 using Xunit;
 
@@ -11,7 +12,7 @@ public class HooksTests
     public async Task NoOpUpdateHooks_AllMethods_ReturnDefaults()
     {
         var hooks = new NoOpUpdateHooks();
-        var ctx = new UpdateContext("test", "/tmp", "1.0", "2.0", 1);
+        var ctx = new UpdateContext("test", "/tmp", "1.0", "2.0", AppType.Client);
 
         Assert.True(await hooks.OnBeforeUpdateAsync(ctx));
         await hooks.OnDownloadCompletedAsync(new("a", "1.0", 100, TimeSpan.Zero, null, true));
@@ -23,9 +24,9 @@ public async Task NoOpUpdateHooks_AllMethods_ReturnDefaults()
     [Fact]
     public void UpdateContext_RecordEquality_Works()
     {
-        var a = new UpdateContext("app", "/path", "1.0", "2.0", 1);
-        var b = new UpdateContext("app", "/path", "1.0", "2.0", 1);
-        var c = new UpdateContext("app2", "/path", "1.0", "2.0", 1);
+        var a = new UpdateContext("app", "/path", "1.0", "2.0", AppType.Client);
+        var b = new UpdateContext("app", "/path", "1.0", "2.0", AppType.Client);
+        var c = new UpdateContext("app2", "/path", "1.0", "2.0", AppType.Client);
 
         Assert.Equal(a, b);
         Assert.NotEqual(a, c);