feat: wire UpdateOptions configuration to runtime behavior

src/c#/GeneralUpdate.Core/Bootstrap/GeneralUpdateBootstrap.cs

@@ -285,6 +285,18 @@ private void ApplyRuntimeOptions()
         _configInfo.Encoding = GetOption(UpdateOptions.Encoding);
         _configInfo.Format = GetOption(UpdateOptions.Format);
         _configInfo.DownloadTimeOut = GetOption(UpdateOptions.DownloadTimeout) ?? 60;
+
+        // Download behaviour
+        _configInfo.MaxConcurrency = GetOption(UpdateOptions.MaxConcurrency);
+        _configInfo.EnableResume = GetOption(UpdateOptions.EnableResume);
+        _configInfo.RetryCount = GetOption(UpdateOptions.RetryCount);
+        _configInfo.RetryInterval = GetOption(UpdateOptions.RetryInterval);
+        _configInfo.VerifyChecksum = GetOption(UpdateOptions.VerifyChecksum);
+
+        // Update behaviour
+        _configInfo.BackupEnabled = GetOption(UpdateOptions.BackupEnabled);
+        _configInfo.PatchEnabled = GetOption(UpdateOptions.PatchEnabled);
+        _configInfo.DiffMode = GetOption(UpdateOptions.DiffMode);
     }
 
     /// <summary>

src/c#/GeneralUpdate.Core/Configuration/GlobalConfigInfo.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Text;
 
@@ -104,7 +105,7 @@
     /// Directory path containing driver files for update.
     /// Used when DriveEnabled is true to locate driver files for installation.
     /// </summary>
     public string DriverDirectory { get; set; }
 
     /// <summary>
     /// Indicates whether differential patch update is enabled.
@@ -112,9 +113,54 @@
     /// </summary>
     public bool? PatchEnabled { get; set; }
 
+    /// <summary>
+    /// Whether to back up the current version before applying an update.
+    /// Computed from UpdateOption.BackupEnabled, defaults to true.
+    /// </summary>
+    public bool? BackupEnabled { get; set; }
+
     /// <summary>
     /// Directory path where the current version files are backed up before update.
     /// Computed by combining InstallPath with a versioned directory name.
     /// </summary>
     public string BackupDirectory { get; set; }
-}
+
+    // ═══ Download/update behaviour options (wired from UpdateOptions) ═══
+
+    /// <summary>
+    /// Maximum number of concurrent download operations.
+    /// Computed from UpdateOption.MaxConcurrency, defaults to 3.
+    /// Valid range: 1 to <see cref="Environment.ProcessorCount"/> * 2.
+    /// </summary>
+    public int MaxConcurrency { get; set; } = 3;
+
+    /// <summary>
+    /// Whether to resume interrupted downloads via HTTP Range requests.
+    /// Computed from UpdateOption.EnableResume, defaults to true.
+    /// </summary>
+    public bool EnableResume { get; set; } = true;
+
+    /// <summary>
+    /// Maximum number of retry attempts for failed download operations.
+    /// Computed from UpdateOption.RetryCount, defaults to 3.
+    /// </summary>
+    public int RetryCount { get; set; } = 3;
+
+    /// <summary>
+    /// Initial retry interval for exponential back-off.
+    /// Computed from UpdateOption.RetryInterval, defaults to 1 second.
+    /// </summary>
+    public TimeSpan RetryInterval { get; set; } = TimeSpan.FromSeconds(1);
+
+    /// <summary>
+    /// Whether to perform SHA256 checksum verification after download.
+    /// Computed from UpdateOption.VerifyChecksum, defaults to true.
+    /// </summary>
+    public bool VerifyChecksum { get; set; } = true;
+
+    /// <summary>
+    /// Diff/patch generation mode — Serial or Parallel.
+    /// Computed from UpdateOption.DiffMode, defaults to <see cref="Configuration.DiffMode.Serial"/>.
+    /// </summary>
+    public DiffMode DiffMode { get; set; } = DiffMode.Serial;
+}

src/c#/GeneralUpdate.Core/Download/Executors/HttpDownloadExecutor.cs

@@ -10,18 +10,20 @@
 namespace GeneralUpdate.Core.Download.Executors;
 
 /// <summary>
-/// HTTP-based download executor with Range/resume support.
+/// HTTP-based download executor with optional Range/resume support.
 /// Uses the shared HttpClient from VersionService for consistent SSL/auth handling.
 /// </summary>
 public class HttpDownloadExecutor : IDownloadExecutor
 {
     private readonly HttpClient _client;
     private readonly TimeSpan _timeout;
+    private readonly bool _enableResume;
 
-    public HttpDownloadExecutor(HttpClient client, TimeSpan? timeout = null)
+    public HttpDownloadExecutor(HttpClient client, TimeSpan? timeout = null, bool enableResume = true)
     {
         _client = client ?? throw new ArgumentNullException(nameof(client));
         _timeout = timeout ?? TimeSpan.FromSeconds(30);
+        _enableResume = enableResume;
     }
 
     public async Task<DownloadResult> ExecuteAsync(
@@ -34,8 +36,8 @@ public async Task<DownloadResult> ExecuteAsync(
         long totalBytes = -1;
         long existingBytes = 0;
 
-        // Check for existing partial file (resume support)
-        if (File.Exists(destPath))
+        // Check for existing partial file (resume support; skip when disabled)
+        if (_enableResume && File.Exists(destPath))
         {
             existingBytes = new FileInfo(destPath).Length;
         }
@@ -44,8 +46,8 @@ public async Task<DownloadResult> ExecuteAsync(
         {
             using var request = new HttpRequestMessage(HttpMethod.Get, url);
 
-            // Request resume from existing position
-            if (existingBytes > 0)
+            // Request resume from existing position (skip when resume is disabled)
+            if (_enableResume && existingBytes > 0)
                 request.Headers.Range = new System.Net.Http.Headers.RangeHeaderValue(existingBytes, null);
 
             using var cts = CancellationTokenSource.CreateLinkedTokenSource(token);
@@ -56,7 +58,7 @@ public async Task<DownloadResult> ExecuteAsync(
                 .ConfigureAwait(false);
 
             // If server doesn't support Range, discard partial file
-            if (existingBytes > 0 && response.StatusCode != System.Net.HttpStatusCode.PartialContent)
+            if (_enableResume && existingBytes > 0 && response.StatusCode != System.Net.HttpStatusCode.PartialContent)
             {
                 existingBytes = 0;
                 File.Delete(destPath);

src/c#/GeneralUpdate.Core/Download/Models/DownloadOrchestratorOptions.cs

@@ -0,0 +1,82 @@
+using System;
+
+namespace GeneralUpdate.Core.Download.Models;
+
+/// <summary>
+/// Bundles all configurable download behaviour options into a single value object.
+/// Used by <see cref="Orchestrators.DefaultDownloadOrchestrator"/> and
+/// <see cref="Executors.HttpDownloadExecutor"/> to avoid constructor parameter explosion.
+/// </summary>
+public class DownloadOrchestratorOptions
+{
+    /// <summary>
+    /// Maximum number of concurrent download operations.
+    /// Valid range: 1 to <see cref="Environment.ProcessorCount"/> * 2.
+    /// Default: 3.
+    /// </summary>
+    public int MaxConcurrency { get; set; } = 3;
+
+    /// <summary>
+    /// Whether to resume interrupted downloads via HTTP Range requests.
+    /// Default: true.
+    /// </summary>
+    public bool EnableResume { get; set; } = true;
+
+    /// <summary>
+    /// Maximum number of retry attempts for failed download operations.
+    /// Default: 3.
+    /// </summary>
+    public int RetryCount { get; set; } = 3;
+
+    /// <summary>
+    /// Initial retry interval for exponential back-off.
+    /// Actual delay before N-th retry = <c>RetryInterval * 2^(N-1)</c>.
+    /// Default: 1 second.
+    /// </summary>
+    public TimeSpan RetryInterval { get; set; } = TimeSpan.FromSeconds(1);
+
+    /// <summary>
+    /// Whether to perform SHA256 checksum verification after download.
+    /// Default: true.
+    /// </summary>
+    public bool VerifyChecksum { get; set; } = true;
+
+    /// <summary>
+    /// Diff/patch generation mode — Serial or Parallel.
+    /// When <see cref="Configuration.DiffMode.Serial"/>, <see cref="MaxConcurrency"/> is forced to 1.
+    /// Default: <see cref="Configuration.DiffMode.Serial"/>.
+    /// </summary>
+    public Configuration.DiffMode DiffMode { get; set; } = Configuration.DiffMode.Serial;
+
+    /// <summary>
+    /// HTTP download timeout duration.
+    /// Default: 30 seconds.
+    /// </summary>
+    public TimeSpan DownloadTimeout { get; set; } = TimeSpan.FromSeconds(30);
+
+    /// <summary>
+    /// Creates a <see cref="DownloadOrchestratorOptions"/> from <see cref="Configuration.GlobalConfigInfo"/>.
+    /// </summary>
+    public static DownloadOrchestratorOptions From(Configuration.GlobalConfigInfo config)
+    {
+        return new DownloadOrchestratorOptions
+        {
+            MaxConcurrency = SanitizeMaxConcurrency(config.MaxConcurrency),
+            EnableResume = config.EnableResume,
+            RetryCount = Math.Max(0, config.RetryCount),
+            RetryInterval = config.RetryInterval,
+            VerifyChecksum = config.VerifyChecksum,
+            DiffMode = config.DiffMode,
+            DownloadTimeout = TimeSpan.FromSeconds(config.DownloadTimeOut > 0 ? config.DownloadTimeOut : 30),
+        };
+    }
+
+    /// <summary>Clamps <paramref name="value"/> to [1, ProcessorCount * 2].</summary>
+    public static int SanitizeMaxConcurrency(int value)
+    {
+        var max = Math.Max(1, Environment.ProcessorCount * 2);
+        if (value < 1) return 1;
+        if (value > max) return max;
+        return value;
+    }
+}

src/c#/GeneralUpdate.Core/Download/Orchestrators/DefaultDownloadOrchestrator.cs

@@ -6,6 +6,7 @@
 using System.Net.Http;
 using System.Threading;
 using System.Threading.Tasks;
+using GeneralUpdate.Core.Configuration;
 using GeneralUpdate.Core.Download.Abstractions;
 using GeneralUpdate.Core.Download.Executors;
 using GeneralUpdate.Core.Download.Policy;
@@ -16,17 +17,22 @@ namespace GeneralUpdate.Core.Download.Orchestrators;
 
 /// <summary>
 /// Default download orchestrator with parallel execution, concurrency limit,
-/// SHA256 verification, and progress reporting.
+/// SHA256 verification, resume support, and progress reporting.
+///
+/// All configurable behaviour is driven by <see cref="DownloadOrchestratorOptions"/>,
+/// which maps to the <see cref="UpdateOptions"/> defined in the bootstrap layer.
 /// </summary>
 public class DefaultDownloadOrchestrator : IDownloadOrchestrator
 {
     private readonly HttpClient _httpClient;
     private readonly IDownloadPolicy _policy;
+    private readonly DownloadOrchestratorOptions _options;
 
-    public DefaultDownloadOrchestrator(HttpClient httpClient, IDownloadPolicy? policy = null)
+    public DefaultDownloadOrchestrator(HttpClient httpClient, DownloadOrchestratorOptions? options = null, IDownloadPolicy? policy = null)
     {
         _httpClient = httpClient ?? throw new ArgumentNullException(nameof(httpClient));
-        _policy = policy ?? new DefaultRetryPolicy();
+        _options = options ?? new DownloadOrchestratorOptions();
+        _policy = policy ?? new DefaultRetryPolicy(_options.RetryCount, _options.RetryInterval);
     }
 
     /// <summary>Execute downloads for all assets in the plan.</summary>
@@ -42,9 +48,20 @@ public async Task<DownloadReport> ExecuteAsync(
 
         Directory.CreateDirectory(destDir);
 
+        // Resolve effective concurrency: Serial mode forces 1.
+        // Uses _options.MaxConcurrency as primary value; the method parameter
+        // maxConcurrency acts as an override (default 3).
+        var baseConcurrency = maxConcurrency > 0 ? maxConcurrency : _options.MaxConcurrency;
+        var effectiveConcurrency = _options.DiffMode == DiffMode.Serial
+            ? 1
+            : DownloadOrchestratorOptions.SanitizeMaxConcurrency(Math.Max(1, baseConcurrency));
+
+        GeneralTracer.Info($"DefaultDownloadOrchestrator.ExecuteAsync: concurrency={effectiveConcurrency}, " +
+            $"resume={_options.EnableResume}, verifyChecksum={_options.VerifyChecksum}, diffMode={_options.DiffMode}");
+
         var sw = Stopwatch.StartNew();
         var results = new List<DownloadResult>();
-        using var sem = new SemaphoreSlim(maxConcurrency);
+        using var sem = new SemaphoreSlim(effectiveConcurrency);
         long totalBytes = 0;
 
         var tasks = plan.Assets.Select(async asset =>
@@ -55,7 +72,7 @@ public async Task<DownloadReport> ExecuteAsync(
                 var fileName = GetFileName(asset);
                 var destPath = Path.Combine(destDir, fileName);
 
-                var executor = new HttpDownloadExecutor(_httpClient);
+                var executor = new HttpDownloadExecutor(_httpClient, _options.DownloadTimeout, _options.EnableResume);
                 var pipeline = new DefaultDownloadPipeline(asset.SHA256);
 
                 var result = await _policy.ExecuteAsync(async ct =>
@@ -69,7 +86,13 @@ public async Task<DownloadReport> ExecuteAsync(
                     if (!downloadResult.Success)
                         return downloadResult;
 
-                    // Verify (SHA256)
+                    // Verify (SHA256) — conditionally skipped when VerifyChecksum is false
+                    if (!_options.VerifyChecksum)
+                    {
+                        GeneralTracer.Info($"DefaultDownloadOrchestrator: checksum verification skipped for {asset.Name} (VerifyChecksum=false).");
+                        return downloadResult;
+                    }
+
                     try
                     {
                         await pipeline.ProcessAsync(destPath, ct).ConfigureAwait(false);

src/c#/GeneralUpdate.Core/Strategy/ClientUpdateStrategy.cs

@@ -183,12 +183,20 @@ private async Task ExecuteStandardWorkflowAsync(Encoding encoding, int timeout)
                 BlackListManager.Instance.SkipDirectorys.ToList()),
             ProcessInfoJsonContext.Default.ProcessInfo);
 
-        // Backup
-        Backup();
+        // Backup — conditionally skipped when BackupEnabled is false
+        if (_configInfo.BackupEnabled != false)
+        {
+            Backup();
+        }
+        else
+        {
+            GeneralTracer.Info("ClientUpdateStrategy: backup skipped (BackupEnabled=false).");
+        }
 
         _osStrategy!.Create(_configInfo);
 
-        // Download via orchestrator
+        // Download via orchestrator — wired with options from GlobalConfigInfo
+        var orchOptions = Download.Models.DownloadOrchestratorOptions.From(_configInfo);
         GeneralTracer.Info($"ClientUpdateStrategy: downloading {downloadPlan.Assets.Count} asset(s).");
         if (_orchestrator != null)
         {
@@ -199,7 +207,7 @@ private async Task ExecuteStandardWorkflowAsync(Encoding encoding, int timeout)
             var httpClient = new System.Net.Http.HttpClient();
             try
             {
-                var orchestrator = new Download.Orchestrators.DefaultDownloadOrchestrator(httpClient);
+                var orchestrator = new Download.Orchestrators.DefaultDownloadOrchestrator(httpClient, orchOptions);
                 await orchestrator.ExecuteAsync(downloadPlan, _configInfo.TempPath).ConfigureAwait(false);
             }
             finally { httpClient.Dispose(); }