diff --git a/docs/knowledgebase/gui-architecture-deferred.md b/docs/knowledgebase/gui-architecture-deferred.md
index 02d3d143..f765e78a 100644
--- a/docs/knowledgebase/gui-architecture-deferred.md
+++ b/docs/knowledgebase/gui-architecture-deferred.md
@@ -62,6 +62,7 @@ Plans: `docs/plans/2026-06-03-012`, `021`–`029`, `033`–`057`. Surface refere
 | Directory picker init/sync → `SettingsService` | Done | plan `075`, PR #123 |
 | Mod context menu + global flyout → `MenuBuilderService` | Done | plan `072`, PR #130 |
 
+**Headless tests:** `dotnet test src/ModSync.Tests/ModSync.Tests.csproj --filter SettingsService` (plan `077`); `--filter MenuBuilderService` (plan `072`); `--filter DownloadOrchestrationService` (plan `088`).
 **Headless tests:** `dotnet test src/ModSync.Tests/ModSync.Tests.csproj --filter SettingsService` (plan `077`); `--filter MenuBuilderService` (plan `072`); `--filter DialogServiceTests` / `FileSystemServiceTests` (plan `113`).
 **Headless tests:** `dotnet test src/ModSync.Tests/ModSync.Tests.csproj --filter SettingsService` (plan `077`); `--filter MenuBuilderService` (plan `072`); `--filter FilterItemModel` (plan `112`).
 **Headless tests:** `dotnet test src/ModSync.Tests/ModSync.Tests.csproj --filter SettingsService` (plan `077`); `--filter MenuBuilderService` (plan `072`); `--filter FileTreeNode` (plan `111`).
diff --git a/docs/plans/2026-06-04-088-test-download-orchestration-service-headless-plan.md b/docs/plans/2026-06-04-088-test-download-orchestration-service-headless-plan.md
new file mode 100644
index 00000000..8f5c41f3
--- /dev/null
+++ b/docs/plans/2026-06-04-088-test-download-orchestration-service-headless-plan.md
@@ -0,0 +1,19 @@
+---
+title: "test: headless DownloadOrchestrationService coverage"
+status: shipped
+pr: pending
+---
+
+# test: headless DownloadOrchestrationService coverage
+
+## Problem
+
+`DownloadOrchestrationService` coordinates GUI download sessions but had no dedicated headless tests. `DownloadQueueHeadlessTests` covers `DownloadProgressWindow` queue behavior only.
+
+## Solution
+
+Add `DownloadOrchestrationServiceTests` for constructor guards, idle initial state, cancel state-change signaling, no-URL single-component guard, and null-safe single-component entry points.
+
+## Verification
+
+`dotnet test src/ModSync.Tests/ModSync.Tests.csproj --filter DownloadOrchestrationService`
diff --git a/src/ModSync.Tests/DownloadOrchestrationServiceTests.cs b/src/ModSync.Tests/DownloadOrchestrationServiceTests.cs
new file mode 100644
index 00000000..c216af6f
--- /dev/null
+++ b/src/ModSync.Tests/DownloadOrchestrationServiceTests.cs
@@ -0,0 +1,168 @@
+// Copyright 2021-2025 ModSync
+// Licensed under the Business Source License 1.1 (BSL 1.1).
+// See LICENSE.txt file in the project root for full license information.
+
+using System;
+using System.Threading.Tasks;
+using Avalonia.Controls;
+using Avalonia.Headless.XUnit;
+using Avalonia.Threading;
+using ModSync.Core;
+using ModSync.Core.Services;
+using ModSync.Services;
+using Xunit;
+
+namespace ModSync.Tests
+{
+    [Collection(HeadlessTestApp.CollectionName)]
+    public sealed class DownloadOrchestrationServiceTests
+    {
+        [AvaloniaFact(DisplayName = "Constructor rejects null DownloadCacheService")]
+        public void Constructor_NullCacheService_Throws()
+        {
+            Window window = new Window();
+            var config = new MainConfig();
+
+            Assert.Throws<ArgumentNullException>(() =>
+                new DownloadOrchestrationService(null, config, window));
+        }
+
+        [AvaloniaFact(DisplayName = "Constructor rejects null MainConfig")]
+        public void Constructor_NullMainConfig_Throws()
+        {
+            Window window = new Window();
+            var cacheService = new DownloadCacheService();
+
+            Assert.Throws<ArgumentNullException>(() =>
+                new DownloadOrchestrationService(cacheService, null, window));
+        }
+
+        [AvaloniaFact(DisplayName = "Constructor rejects null parent window")]
+        public void Constructor_NullParentWindow_Throws()
+        {
+            var cacheService = new DownloadCacheService();
+            var config = new MainConfig();
+
+            Assert.Throws<ArgumentNullException>(() =>
+                new DownloadOrchestrationService(cacheService, config, null));
+        }
+
+        [AvaloniaFact(DisplayName = "Initial download state is idle with zero counters")]
+        public void InitialState_IsIdleWithZeroCounters()
+        {
+            DownloadOrchestrationService service = CreateService(out Window window);
+
+            try
+            {
+                Assert.False(service.IsDownloadInProgress);
+                Assert.Equal(0, service.TotalComponentsToDownload);
+                Assert.Equal(0, service.CompletedComponents);
+            }
+            finally
+            {
+                window.Close();
+            }
+        }
+
+        [AvaloniaFact(DisplayName = "CancelAllDownloadsAsync raises DownloadStateChanged and stays idle")]
+        public async Task CancelAllDownloadsAsync_RaisesStateChangedAndClearsInProgress()
+        {
+            DownloadOrchestrationService service = CreateService(out Window window);
+            int stateChangeCount = 0;
+            service.DownloadStateChanged += (_, _) => stateChangeCount++;
+
+            try
+            {
+                await service.CancelAllDownloadsAsync();
+                await PumpEventsAsync();
+
+                Assert.False(service.IsDownloadInProgress);
+                Assert.Equal(1, stateChangeCount);
+            }
+            finally
+            {
+                window.Close();
+            }
+        }
+
+        [AvaloniaFact(DisplayName = "DownloadSingleComponentAsync without URLs does not mark download in progress")]
+        public async Task DownloadSingleComponentAsync_NoUrls_DoesNotStartDownload()
+        {
+            DownloadOrchestrationService service = CreateService(out Window window);
+            DownloadProgressWindow progressWindow = await CreateProgressWindowAsync();
+            var component = new ModComponent { Name = "No Urls Mod" };
+
+            try
+            {
+                await service.DownloadSingleComponentAsync(component, progressWindow);
+                await PumpEventsAsync();
+
+                Assert.False(service.IsDownloadInProgress);
+            }
+            finally
+            {
+                progressWindow.Close();
+                window.Close();
+            }
+        }
+
+        [AvaloniaFact(DisplayName = "DownloadSingleComponentAsync ignores null component")]
+        public async Task DownloadSingleComponentAsync_NullComponent_ReturnsWithoutThrow()
+        {
+            DownloadOrchestrationService service = CreateService(out Window window);
+            DownloadProgressWindow progressWindow = await CreateProgressWindowAsync();
+
+            try
+            {
+                await service.DownloadSingleComponentAsync(null, progressWindow);
+                await PumpEventsAsync();
+            }
+            finally
+            {
+                progressWindow.Close();
+                window.Close();
+            }
+        }
+
+        [AvaloniaFact(DisplayName = "DownloadSingleComponentAsync ignores null progress window")]
+        public async Task DownloadSingleComponentAsync_NullProgressWindow_ReturnsWithoutThrow()
+        {
+            DownloadOrchestrationService service = CreateService(out Window window);
+            var component = new ModComponent { Name = "Test Mod" };
+
+            try
+            {
+                await service.DownloadSingleComponentAsync(component, null);
+                await PumpEventsAsync();
+            }
+            finally
+            {
+                window.Close();
+            }
+        }
+
+        private static DownloadOrchestrationService CreateService(out Window window)
+        {
+            window = new Window { Width = 400, Height = 300 };
+            var config = new MainConfig();
+            var cacheService = new DownloadCacheService();
+            cacheService.SetDownloadManager();
+            return new DownloadOrchestrationService(cacheService, config, window);
+        }
+
+        private static async Task<DownloadProgressWindow> CreateProgressWindowAsync()
+        {
+            DownloadProgressWindow window = await Dispatcher.UIThread.InvokeAsync(
+                () => new DownloadProgressWindow(),
+                DispatcherPriority.Background);
+            await PumpEventsAsync();
+            return window;
+        }
+
+        private static async Task PumpEventsAsync()
+        {
+            await Dispatcher.UIThread.InvokeAsync(() => { }, DispatcherPriority.Background);
+            await Dispatcher.UIThread.InvokeAsync(() => { }, DispatcherPriority.ApplicationIdle);
+        }
+    }
+}