试试

LanMountainDesktop/Services/PostHogUsageTelemetryService.cs

@@ -1,29 +1,23 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Net.Http;
-using System.Text;
-using System.Text.Json;
 using System.Threading;
 using LanMountainDesktop.Models;
 using LanMountainDesktop.PluginSdk;
 using LanMountainDesktop.Services.Settings;
+using PostHog;
 
 namespace LanMountainDesktop.Services;
 
 public sealed class PostHogUsageTelemetryService : IDisposable
 {
     private const string PostHogApiKey = "phc_bhQZvKDDfsEdLT6kkRFvrWMT8Pc5aCGGsnxoc5ijSf9";
-    private const string PostHogHost = "https://us.i.posthog.com/capture/";
+    private const string PostHogHostUrl = "https://us.i.posthog.com";
 
     private readonly ISettingsFacadeService _settingsFacade;
     private readonly ISettingsService _settingsService;
-    private readonly HttpClient _httpClient = new()
-    {
-        Timeout = TimeSpan.FromSeconds(10)
-    };
-    private readonly Queue<TelemetryEvent> _eventQueue = new();
-    private readonly object _queueLock = new();
+    private readonly PostHogClient _client;
+    private readonly CancellationTokenSource _cts = new();
 
     private Timer? _flushTimer;
     private bool _isInitialized;
@@ -39,6 +33,14 @@ public sealed class PostHogUsageTelemetryService : IDisposable
         _settingsFacade = settingsFacade ?? throw new ArgumentNullException(nameof(settingsFacade));
         _settingsService = settingsFacade.Settings;
         _settingsService.Changed += OnSettingsChanged;
+
+        _client = new PostHogClient(new PostHogOptions
+        {
+            ProjectApiKey = PostHogApiKey,
+            HostUrl = new Uri(PostHogHostUrl),
+            FlushAt = 20,
+            FlushInterval = TimeSpan.FromSeconds(30)
+        });
     }
 
     public bool IsUsageEnabled => _isUsageEnabled;
@@ -56,7 +58,7 @@ public sealed class PostHogUsageTelemetryService : IDisposable
         RefreshEnabledState(forceSessionStart: true);
 
         _flushTimer = new Timer(
-            _ => FlushEvents(),
+            _ => _ = _client.FlushAsync(),
             null,
             TimeSpan.FromSeconds(10),
             TimeSpan.FromSeconds(30));
@@ -88,14 +90,12 @@ public sealed class PostHogUsageTelemetryService : IDisposable
                 return;
             }
 
-            ClearQueuedEvents();
             StopSessionWithoutSending();
         }
         catch (Exception ex)
         {
             AppLogger.Warn("PostHogUsage", "Failed to refresh usage analytics enabled state.", ex);
             _isUsageEnabled = false;
-            ClearQueuedEvents();
             StopSessionWithoutSending();
         }
     }
@@ -278,7 +278,7 @@ public sealed class PostHogUsageTelemetryService : IDisposable
             EndSession(source, isRestart);
         }
 
-        FlushEvents();
+        _ = _client.FlushAsync();
         AppLogger.Info(
             "PostHogUsage",
             $"Usage telemetry shutdown complete. Source='{source}'; Restart='{isRestart}'; Enabled={_isUsageEnabled}.");
@@ -291,16 +291,13 @@ public sealed class PostHogUsageTelemetryService : IDisposable
             _flushTimer?.Dispose();
             _settingsService.Changed -= OnSettingsChanged;
             Shutdown(isRestart: false, source: "Dispose");
-            FlushEvents();
+            _cts.Cancel();
+            _client.Dispose();
         }
         catch (Exception ex)
         {
             AppLogger.Warn("PostHogUsage", "Error disposing usage telemetry service.", ex);
         }
-        finally
-        {
-            _httpClient.Dispose();
-        }
     }
 
     private void EnsureBaselineEventSent()
@@ -313,66 +310,35 @@ public sealed class PostHogUsageTelemetryService : IDisposable
                 return;
             }
 
-            var now = DateTimeOffset.UtcNow;
-            if (SendBaselineEventToPostHog(identity.InstallId, now))
+            var distinctId = identity.InstallId;
+            var personProps = new Dictionary<string, object?>
             {
-                identity.MarkBaselineReported();
-            }
-        }
-        catch (Exception ex)
-        {
-            AppLogger.Warn("PostHogUsage", "Failed to send baseline launch event.", ex);
-        }
-    }
-
-    private bool SendBaselineEventToPostHog(string installId, DateTimeOffset timestamp)
-    {
-        try
-        {
-            var requestBody = new Dictionary<string, object?>
-            {
-                ["api_key"] = PostHogApiKey,
-                ["event"] = "app_first_launch",
-                ["distinct_id"] = installId,
-                ["timestamp"] = timestamp.ToString("o"),
-                ["properties"] = new Dictionary<string, object?>
-                {
-                    ["install_id"] = installId,
-                    ["app_version"] = TelemetryEnvironmentInfo.GetAppVersion(),
-                    ["os_name"] = TelemetryEnvironmentInfo.GetOsName(),
-                    ["os_version"] = TelemetryEnvironmentInfo.GetOsVersion(),
-                    ["device_model"] = TelemetryEnvironmentInfo.GetDeviceModel(),
-                    ["device_arch"] = TelemetryEnvironmentInfo.GetDeviceArchitecture(),
-                    ["runtime_version"] = TelemetryEnvironmentInfo.GetRuntimeVersion(),
-                    ["language"] = TelemetryEnvironmentInfo.GetSystemLanguage(),
-                    ["launch_time_utc"] = timestamp.ToString("o")
-                }
+                ["install_id"] = identity.InstallId,
+                ["app_version"] = TelemetryEnvironmentInfo.GetAppVersion(),
+                ["os_name"] = TelemetryEnvironmentInfo.GetOsName(),
+                ["os_version"] = TelemetryEnvironmentInfo.GetOsVersion(),
+                ["device_model"] = TelemetryEnvironmentInfo.GetDeviceModel(),
+                ["device_arch"] = TelemetryEnvironmentInfo.GetDeviceArchitecture(),
+                ["runtime_version"] = TelemetryEnvironmentInfo.GetRuntimeVersion(),
+                ["language"] = TelemetryEnvironmentInfo.GetSystemLanguage()
             };
 
-            var json = JsonSerializer.Serialize(requestBody);
-            var bytes = Encoding.UTF8.GetBytes(json);
+            _ = _client.IdentifyAsync(distinctId, personProps, null, _cts.Token);
 
-            using var content = new ByteArrayContent(bytes);
-            content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/json");
+            _client.Capture(
+                distinctId,
+                "app_first_launch",
+                personProps,
+                groups: null,
+                sendFeatureFlags: false);
 
-            var response = _httpClient.PostAsync(PostHogHost, content).GetAwaiter().GetResult();
-            var responseBody = response.Content.ReadAsStringAsync().GetAwaiter().GetResult();
-
-            if (!response.IsSuccessStatusCode)
-            {
-                AppLogger.Warn(
-                    "PostHogUsage",
-                    $"PostHog baseline event failed: {response.StatusCode} - {responseBody}");
-                return false;
-            }
-
-            AppLogger.Info("PostHogUsage", "Sent first-launch baseline event.");
-            return true;
+            _ = _client.FlushAsync();
+            identity.MarkBaselineReported();
+            AppLogger.Info("PostHogUsage", "Sent first-launch baseline event via SDK.");
         }
         catch (Exception ex)
         {
             AppLogger.Warn("PostHogUsage", "Failed to send baseline launch event.", ex);
-            return false;
         }
     }
 
@@ -479,137 +445,60 @@ public sealed class PostHogUsageTelemetryService : IDisposable
             return;
         }
 
-        var eventData = new TelemetryEvent(
-            eventName,
-            TelemetryIdentityService.Instance.TelemetryId,
-            TelemetryIdentityService.Instance.InstallId,
-            TelemetryIdentityService.Instance.TelemetryId,
-            _sessionId,
-            Interlocked.Increment(ref _sequence),
-            DateTimeOffset.UtcNow,
-            payload ?? new Dictionary<string, object?>(),
-            stateBefore,
-            stateAfter);
+        var identity = TelemetryIdentityService.Instance;
+        var distinctId = identity.TelemetryId;
+        var seq = Interlocked.Increment(ref _sequence);
 
-        lock (_queueLock)
+        var properties = new Dictionary<string, object?>(StringComparer.OrdinalIgnoreCase)
         {
-            _eventQueue.Enqueue(eventData);
+            ["install_id"] = identity.InstallId,
+            ["telemetry_id"] = identity.TelemetryId,
+            ["session_id"] = _sessionId,
+            ["sequence"] = seq,
+            ["timestamp_utc"] = DateTimeOffset.UtcNow.ToString("o"),
+            ["app_version"] = TelemetryEnvironmentInfo.GetAppVersion(),
+            ["os_name"] = TelemetryEnvironmentInfo.GetOsName(),
+            ["os_version"] = TelemetryEnvironmentInfo.GetOsVersion(),
+            ["device_model"] = TelemetryEnvironmentInfo.GetDeviceModel(),
+            ["device_arch"] = TelemetryEnvironmentInfo.GetDeviceArchitecture(),
+            ["runtime_version"] = TelemetryEnvironmentInfo.GetRuntimeVersion(),
+            ["language"] = TelemetryEnvironmentInfo.GetSystemLanguage()
+        };
+
+        if (payload is not null)
+        {
+            foreach (var kvp in payload)
+            {
+                properties[$"payload_{kvp.Key}"] = kvp.Value;
+            }
         }
 
+        if (stateBefore is not null && stateBefore.Count > 0)
+        {
+            foreach (var kvp in stateBefore)
+            {
+                properties[$"state_before_{kvp.Key}"] = kvp.Value;
+            }
+        }
+
+        if (stateAfter is not null && stateAfter.Count > 0)
+        {
+            foreach (var kvp in stateAfter)
+            {
+                properties[$"state_after_{kvp.Key}"] = kvp.Value;
+            }
+        }
+
+        _client.Capture(
+            distinctId,
+            eventName,
+            properties,
+            groups: null,
+            sendFeatureFlags: false);
+
         if (forceFlush)
         {
-            FlushEvents();
-            return;
-        }
-
-        var shouldFlush = false;
-        lock (_queueLock)
-        {
-            shouldFlush = _eventQueue.Count >= 20;
-        }
-
-        if (shouldFlush)
-        {
-            FlushEvents();
-        }
-    }
-
-    private void FlushEvents()
-    {
-        List<TelemetryEvent> eventsToSend;
-
-        lock (_queueLock)
-        {
-            if (_eventQueue.Count == 0)
-            {
-                return;
-            }
-
-            eventsToSend = new List<TelemetryEvent>();
-            while (_eventQueue.Count > 0 && eventsToSend.Count < 20)
-            {
-                eventsToSend.Add(_eventQueue.Dequeue());
-            }
-        }
-
-        try
-        {
-            foreach (var telemetryEvent in eventsToSend)
-            {
-                if (!SendEventToPostHog(telemetryEvent, flushImmediately: false))
-                {
-                    throw new InvalidOperationException($"Failed to send PostHog event '{telemetryEvent.EventName}'.");
-                }
-            }
-        }
-        catch (Exception ex)
-        {
-            AppLogger.Warn("PostHogUsage", "Failed to send queued events to PostHog.", ex);
-
-            lock (_queueLock)
-            {
-                foreach (var evt in eventsToSend)
-                {
-                    if (_eventQueue.Count >= 100)
-                    {
-                        break;
-                    }
-
-                    _eventQueue.Enqueue(evt);
-                }
-            }
-        }
-    }
-
-    private bool SendEventToPostHog(TelemetryEvent telemetryEvent, bool flushImmediately)
-    {
-        try
-        {
-            var requestBody = new Dictionary<string, object?>
-            {
-                ["api_key"] = PostHogApiKey,
-                ["event"] = telemetryEvent.EventName,
-                ["distinct_id"] = telemetryEvent.DistinctId,
-                ["timestamp"] = telemetryEvent.Timestamp.ToString("o"),
-                ["properties"] = telemetryEvent.ToPostHogProperties()
-            };
-
-            var json = JsonSerializer.Serialize(requestBody);
-            var bytes = Encoding.UTF8.GetBytes(json);
-
-            using var content = new ByteArrayContent(bytes);
-            content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/json");
-
-            var response = _httpClient.PostAsync(PostHogHost, content).GetAwaiter().GetResult();
-            var responseBody = response.Content.ReadAsStringAsync().GetAwaiter().GetResult();
-
-            if (!response.IsSuccessStatusCode)
-            {
-                AppLogger.Warn(
-                    "PostHogUsage",
-                    $"PostHog event '{telemetryEvent.EventName}' failed: {response.StatusCode} - {responseBody}");
-                return false;
-            }
-
-            if (flushImmediately)
-            {
-                AppLogger.Info("PostHogUsage", $"Sent event '{telemetryEvent.EventName}' immediately.");
-            }
-
-            return true;
-        }
-        catch (Exception ex)
-        {
-            AppLogger.Warn("PostHogUsage", $"Failed to send PostHog event '{telemetryEvent.EventName}'.", ex);
-            return false;
-        }
-    }
-
-    private void ClearQueuedEvents()
-    {
-        lock (_queueLock)
-        {
-            _eventQueue.Clear();
+            _ = _client.FlushAsync();
         }
     }
 

LanMountainDesktop/Services/TelemetryEvent.cs

@@ -1,55 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-
-namespace LanMountainDesktop.Services;
-
-internal sealed record TelemetryEvent(
-    string EventName,
-    string DistinctId,
-    string InstallId,
-    string TelemetryId,
-    string SessionId,
-    long Sequence,
-    DateTimeOffset Timestamp,
-    IReadOnlyDictionary<string, object?> Payload,
-    IReadOnlyDictionary<string, object?>? StateBefore = null,
-    IReadOnlyDictionary<string, object?>? StateAfter = null)
-{
-    public Dictionary<string, object?> ToPostHogProperties()
-    {
-        var properties = new Dictionary<string, object?>(StringComparer.OrdinalIgnoreCase)
-        {
-            ["install_id"] = InstallId,
-            ["telemetry_id"] = TelemetryId,
-            ["session_id"] = SessionId,
-            ["sequence"] = Sequence,
-            ["timestamp_utc"] = Timestamp.ToString("o"),
-            ["app_version"] = TelemetryEnvironmentInfo.GetAppVersion(),
-            ["os_name"] = TelemetryEnvironmentInfo.GetOsName(),
-            ["os_version"] = TelemetryEnvironmentInfo.GetOsVersion(),
-            ["device_model"] = TelemetryEnvironmentInfo.GetDeviceModel(),
-            ["device_arch"] = TelemetryEnvironmentInfo.GetDeviceArchitecture(),
-            ["runtime_version"] = TelemetryEnvironmentInfo.GetRuntimeVersion(),
-            ["language"] = TelemetryEnvironmentInfo.GetSystemLanguage(),
-            ["payload"] = Copy(Payload)
-        };
-
-        if (StateBefore is not null && StateBefore.Count > 0)
-        {
-            properties["state_before"] = Copy(StateBefore);
-        }
-
-        if (StateAfter is not null && StateAfter.Count > 0)
-        {
-            properties["state_after"] = Copy(StateAfter);
-        }
-
-        return properties;
-    }
-
-    private static Dictionary<string, object?> Copy(IReadOnlyDictionary<string, object?> source)
-    {
-        return source.ToDictionary(entry => entry.Key, entry => entry.Value, StringComparer.OrdinalIgnoreCase);
-    }
-}

LanMountainDesktop/Services/UpdateWorkflowService.cs

@@ -1,8 +1,10 @@
 using System;
+using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics;
 using System.Globalization;
 using System.IO;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using LanMountainDesktop.PluginSdk;
@@ -47,6 +49,13 @@ public sealed class UpdateWorkflowService
     private readonly ISettingsFacadeService _settingsFacade;
     private readonly string _updatesDirectory;
 
+    private const string LauncherDirectoryName = ".launcher";
+    private const string UpdateDirectoryName = "update";
+    private const string IncomingDirectoryName = "incoming";
+    private const string DeltaManifestFileName = "files.json";
+    private const string DeltaSignatureFileName = "files.json.sig";
+    private const string DeltaArchiveFileName = "update.zip";
+
     public UpdateWorkflowService(ISettingsFacadeService settingsFacade)
     {
         _settingsFacade = settingsFacade ?? throw new ArgumentNullException(nameof(settingsFacade));
@@ -56,6 +65,175 @@ public sealed class UpdateWorkflowService
             "Updates");
     }
 
+    /// <summary>
+    /// Gets the path to the Launcher's incoming update directory where delta packages should be placed.
+    /// </summary>
+    public static string GetLauncherIncomingDirectory()
+    {
+        // The app runs from app-{version}/ subdirectory; Launcher root is one level up.
+        var appBaseDir = AppContext.BaseDirectory;
+        var launcherRoot = Path.GetDirectoryName(appBaseDir.TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar));
+        if (string.IsNullOrWhiteSpace(launcherRoot))
+        {
+            launcherRoot = appBaseDir;
+        }
+        return Path.Combine(launcherRoot, LauncherDirectoryName, UpdateDirectoryName, IncomingDirectoryName);
+    }
+
+    /// <summary>
+    /// Checks whether a GitHub Release contains delta update assets (files.json, files.json.sig, update.zip).
+    /// </summary>
+    public static bool IsDeltaUpdateAvailable(GitHubReleaseInfo release)
+    {
+        if (release is null || release.Assets is null || release.Assets.Count == 0)
+        {
+            return false;
+        }
+
+        var assetNames = release.Assets.Select(a => a.Name).ToHashSet(StringComparer.OrdinalIgnoreCase);
+        return assetNames.Contains(DeltaManifestFileName)
+            && assetNames.Contains(DeltaSignatureFileName)
+            && assetNames.Contains(DeltaArchiveFileName);
+    }
+
+    /// <summary>
+    /// Downloads the delta update package (files.json, files.json.sig, update.zip) from a GitHub Release
+    /// and places them in the Launcher's incoming directory for the Launcher to apply on next startup.
+    /// </summary>
+    public async Task<UpdateDownloadResult> DownloadDeltaUpdateAsync(
+        UpdateCheckResult checkResult,
+        IProgress<double>? progress = null,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(checkResult);
+
+        if (!checkResult.Success || !checkResult.IsUpdateAvailable || checkResult.Release is null)
+        {
+            return new UpdateDownloadResult(false, null, "No update available for delta download.");
+        }
+
+        if (!IsDeltaUpdateAvailable(checkResult.Release))
+        {
+            return new UpdateDownloadResult(false, null, "Release does not contain delta update assets.");
+        }
+
+        var incomingDir = GetLauncherIncomingDirectory();
+
+        try
+        {
+            Directory.CreateDirectory(incomingDir);
+        }
+        catch (Exception ex)
+        {
+            return new UpdateDownloadResult(false, null, $"Failed to create incoming directory: {ex.Message}");
+        }
+
+        var state = _settingsFacade.Update.Get();
+        var downloadSource = state.UpdateDownloadSource;
+        var downloadThreads = state.UpdateDownloadThreads;
+
+        var requiredAssets = new Dictionary<string, GitHubReleaseAsset>(StringComparer.OrdinalIgnoreCase)
+        {
+            [DeltaManifestFileName] = null!,
+            [DeltaSignatureFileName] = null!,
+            [DeltaArchiveFileName] = null!
+        };
+
+        foreach (var asset in checkResult.Release.Assets)
+        {
+            if (requiredAssets.ContainsKey(asset.Name))
+            {
+                requiredAssets[asset.Name] = asset;
+            }
+        }
+
+        if (requiredAssets.Any(kvp => kvp.Value is null))
+        {
+            return new UpdateDownloadResult(false, null, "One or more delta assets not found in release.");
+        }
+
+        var totalAssets = requiredAssets.Count;
+        var completedAssets = 0;
+
+        foreach (var (name, asset) in requiredAssets)
+        {
+            var destinationPath = Path.Combine(incomingDir, name);
+
+            // Skip if already downloaded and file exists
+            if (File.Exists(destinationPath))
+            {
+                var existingHash = await GitHubReleaseUpdateService.ComputeFileSha256Async(destinationPath, cancellationToken);
+                if (asset.Sha256 is not null && string.Equals(existingHash, asset.Sha256, StringComparison.OrdinalIgnoreCase))
+                {
+                    AppLogger.Info("UpdateWorkflow", $"Delta asset {name} already downloaded with matching hash, skipping.");
+                    completedAssets++;
+                    progress?.Report((double)completedAssets / totalAssets);
+                    continue;
+                }
+            }
+
+            var assetProgress = progress is null ? null : new Progress<double>(p =>
+            {
+                var overallProgress = ((double)completedAssets + p) / totalAssets;
+                progress.Report(overallProgress);
+            });
+
+            var result = await _settingsFacade.Update.DownloadAssetAsync(
+                asset,
+                destinationPath,
+                downloadSource,
+                downloadThreads,
+                assetProgress,
+                cancellationToken);
+
+            if (!result.Success)
+            {
+                // Clean up partially downloaded files
+                foreach (var file in requiredAssets.Keys)
+                {
+                    try { File.Delete(Path.Combine(incomingDir, file)); } catch { }
+                }
+                return new UpdateDownloadResult(false, null, $"Failed to download delta asset {name}: {result.ErrorMessage}");
+            }
+
+            completedAssets++;
+            progress?.Report((double)completedAssets / totalAssets);
+        }
+
+        // Save state indicating a delta update is pending
+        SaveState(state with
+        {
+            PendingUpdateInstallerPath = Path.Combine(incomingDir, DeltaManifestFileName),
+            PendingUpdateVersion = checkResult.LatestVersionText,
+            PendingUpdatePublishedAtUtcMs = checkResult.Release.PublishedAt == DateTimeOffset.MinValue
+                ? null
+                : checkResult.Release.PublishedAt.ToUnixTimeMilliseconds(),
+            LastUpdateCheckUtcMs = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds(),
+            PendingUpdateSha256 = null
+        });
+
+        AppLogger.Info("UpdateWorkflow", $"Delta update package downloaded to {incomingDir}. Will be applied by Launcher on next startup.");
+
+        return new UpdateDownloadResult(true, Path.Combine(incomingDir, DeltaManifestFileName), null);
+    }
+
+    /// <summary>
+    /// Checks whether the pending update is a delta update (files.json in incoming dir) vs a full installer.
+    /// </summary>
+    public bool IsPendingDeltaUpdate()
+    {
+        var state = _settingsFacade.Update.Get();
+        var pendingPath = state.PendingUpdateInstallerPath?.Trim();
+        if (string.IsNullOrWhiteSpace(pendingPath))
+        {
+            return false;
+        }
+
+        // Delta updates are identified by the manifest file path
+        return pendingPath.EndsWith(DeltaManifestFileName, StringComparison.OrdinalIgnoreCase)
+            || pendingPath.Contains(IncomingDirectoryName, StringComparison.OrdinalIgnoreCase);
+    }
+
     public UpdatePendingInfo? GetPendingUpdate()
     {
         var state = _settingsFacade.Update.Get();
@@ -261,7 +439,7 @@ public sealed class UpdateWorkflowService
         {
             // Always check for updates on startup (removed AutoCheckUpdates check)
             var result = await CheckForUpdatesAsync(currentVersion, isForce: false, cancellationToken);
-            if (!result.Success || !result.IsUpdateAvailable || result.PreferredAsset is null)
+            if (!result.Success || !result.IsUpdateAvailable || result.Release is null)
             {
                 return;
             }
@@ -272,7 +450,16 @@ public sealed class UpdateWorkflowService
             if (string.Equals(normalizedMode, UpdateSettingsValues.ModeDownloadThenConfirm, StringComparison.OrdinalIgnoreCase) ||
                 string.Equals(normalizedMode, UpdateSettingsValues.ModeSilentOnExit, StringComparison.OrdinalIgnoreCase))
             {
-                await DownloadReleaseAsync(result, cancellationToken: cancellationToken);
+                // Prefer delta update if available (smaller download, faster)
+                if (IsDeltaUpdateAvailable(result.Release))
+                {
+                    AppLogger.Info("UpdateWorkflow", "Delta update available, downloading incremental package.");
+                    await DownloadDeltaUpdateAsync(result, cancellationToken: cancellationToken);
+                }
+                else if (result.PreferredAsset is not null)
+                {
+                    await DownloadReleaseAsync(result, cancellationToken: cancellationToken);
+                }
             }
             // For "Manual" mode, just check but don't download
         }
@@ -302,6 +489,15 @@ public sealed class UpdateWorkflowService
             return false;
         }
 
+        // For delta updates, the files are already in .launcher/update/incoming/.
+        // Just exit the app - the Launcher will detect and apply the update on next startup.
+        if (IsPendingDeltaUpdate())
+        {
+            AppLogger.Info("UpdateWorkflow", "Delta update pending in incoming directory. Exiting to let Launcher apply on next startup.");
+            ClearPendingUpdate();
+            return true;
+        }
+
         var result = LaunchPendingInstaller(silent: true, exitApplicationAfterLaunch: false);
         if (!result.Success && !string.IsNullOrWhiteSpace(result.ErrorMessage))
         {