diff --git a/MSIXplainer/App.xaml.cs b/MSIXplainer/App.xaml.cs
index 1550b83..3bc68a9 100644
--- a/MSIXplainer/App.xaml.cs
+++ b/MSIXplainer/App.xaml.cs
@@ -4,6 +4,7 @@
 using Microsoft.UI.Xaml.Input;
 using Microsoft.UI.Xaml.Media;
 using Microsoft.UI.Xaml.Navigation;
+using System.Linq;
 
 // To learn more about WinUI, the WinUI project structure,
 // and more about our project templates, see: http://aka.ms/winui-project-info.
@@ -59,12 +60,29 @@ private void OnUnhandledException(object sender, Microsoft.UI.Xaml.UnhandledExce
         e.Handled = true;
     }
 
+    /// <summary>
+    /// File path provided via file activation (right-click → Open with
+    /// MSIXplainer). MainPage reads this on construction and loads the
+    /// package. Null when the app was launched normally.
+    /// </summary>
+    public static string? PendingFileActivationPath { get; private set; }
+
+    /// <summary>
+    /// Clears the pending file-activation path. Call after the path has been
+    /// loaded so it isn't re-applied on subsequent page reloads.
+    /// </summary>
+    public static void ConsumePendingFileActivationPath() => PendingFileActivationPath = null;
+
     /// <summary>
     /// Invoked when the application is launched.
     /// </summary>
     /// <param name="args">Details about the launch request and process.</param>
     protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs args)
     {
+        // Capture file-activation arg BEFORE MainWindow is constructed so
+        // MainPage can pick it up during its own construction. See #20.
+        PendingFileActivationPath = TryGetFileActivationPath();
+
         Window = new MainWindow();
         DispatcherQueue = Microsoft.UI.Dispatching.DispatcherQueue.GetForCurrentThread();
         Window.Activate();
@@ -72,4 +90,41 @@ protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs ar
         // root exists. ThemeService.Apply no-ops if Content is still null.
         MSIXplainer.Services.ThemeService.Apply(MSIXplainer.Services.ThemeService.LoadPreference());
     }
+
+    /// <summary>
+    /// If the app was launched via a file activation, return the first file's
+    /// path; otherwise return null. Safe to call early in OnLaunched.
+    /// </summary>
+    private static string? TryGetFileActivationPath()
+    {
+        try
+        {
+            var activated = Microsoft.Windows.AppLifecycle.AppInstance
+                .GetCurrent()
+                .GetActivatedEventArgs();
+
+            System.Diagnostics.Debug.WriteLine(
+                $"[MSIXplainer] Activation kind: {activated.Kind}");
+
+            if (activated.Kind != Microsoft.Windows.AppLifecycle.ExtendedActivationKind.File)
+                return null;
+
+            if (activated.Data is not Windows.ApplicationModel.Activation.IFileActivatedEventArgs fileArgs)
+            {
+                System.Diagnostics.Debug.WriteLine(
+                    $"[MSIXplainer] Activation data is {activated.Data?.GetType().FullName ?? "null"}, not IFileActivatedEventArgs");
+                return null;
+            }
+
+            var firstFile = fileArgs.Files.FirstOrDefault();
+            System.Diagnostics.Debug.WriteLine(
+                $"[MSIXplainer] File activation path: {firstFile?.Path ?? "<null>"}");
+            return firstFile?.Path;
+        }
+        catch (System.Exception ex)
+        {
+            System.Diagnostics.Debug.WriteLine($"[MSIXplainer] File activation failed: {ex.Message}");
+            return null;
+        }
+    }
 }
diff --git a/MSIXplainer/MainPage.xaml.cs b/MSIXplainer/MainPage.xaml.cs
index 879ae5e..b61f4e4 100644
--- a/MSIXplainer/MainPage.xaml.cs
+++ b/MSIXplainer/MainPage.xaml.cs
@@ -30,6 +30,21 @@ public MainPage()
         ViewModel.InstalledPackages.CollectionChanged += InstalledPackages_CollectionChanged;
         ViewModel.PropertyChanged += ViewModel_PropertyChanged;
         BuildStaticNavItems();
+        Loaded += MainPage_Loaded;
+    }
+
+    private void MainPage_Loaded(object sender, RoutedEventArgs e)
+    {
+        // File activation: if the app was launched by right-clicking a .msix /
+        // .msixbundle in Explorer (see App.PendingFileActivationPath / issue #20),
+        // load it now that the page is fully wired up. Consume the path so a
+        // page reload doesn't reopen it.
+        var path = App.PendingFileActivationPath;
+        if (!string.IsNullOrEmpty(path))
+        {
+            App.ConsumePendingFileActivationPath();
+            ViewModel.LoadPackageFromPath(path);
+        }
     }
 
     private void BuildStaticNavItems()
@@ -212,10 +227,9 @@ private void OnCloseFindingClick(object sender, RoutedEventArgs e)
     }
 
     /// <summary>
-    /// Copies a manifest property value to the clipboard. Wraps the clipboard
-    /// call in try/catch so a transient clipboard failure never bubbles up as
-    /// an unhandled exception. Bug fix for #10 — the built-in TextBlock
-    /// context-menu Copy was crashing the app on some Windows builds.
+    /// Copies a manifest property value to the clipboard. The 3-line WinUI
+    /// pattern works as long as the process's Main is marked [STAThread] —
+    /// see Program.cs and the comment there about issue #21.
     /// </summary>
     private void CopyPropertyValue_Click(object sender, RoutedEventArgs e)
     {
@@ -224,13 +238,14 @@ private void CopyPropertyValue_Click(object sender, RoutedEventArgs e)
 
         try
         {
-            var package = new Windows.ApplicationModel.DataTransfer.DataPackage();
-            package.SetText(value);
-            Windows.ApplicationModel.DataTransfer.Clipboard.SetContent(package);
+            var pkg = new Windows.ApplicationModel.DataTransfer.DataPackage();
+            pkg.SetText(value);
+            Windows.ApplicationModel.DataTransfer.Clipboard.SetContent(pkg);
         }
         catch (System.Exception ex)
         {
-            System.Diagnostics.Debug.WriteLine($"[MSIXplainer] Clipboard copy failed: {ex.Message}");
+            System.Diagnostics.Debug.WriteLine(
+                $"[MSIXplainer] Clipboard copy failed: {ex.GetType().Name} 0x{ex.HResult:X8} {ex.Message}");
         }
     }
 
diff --git a/MSIXplainer/Package.appxmanifest b/MSIXplainer/Package.appxmanifest
index 5f32ded..a67c5ff 100644
--- a/MSIXplainer/Package.appxmanifest
+++ b/MSIXplainer/Package.appxmanifest
@@ -11,7 +11,7 @@
   <Identity
     Name="Clinick.msixplainer"
     Publisher="CN=46604BD4-AFD9-4B23-8EB3-10EAF66872A5"
-    Version="1.0.24.0" />
+    Version="1.0.27.0" />
 
   <mp:PhoneIdentity PhoneProductId="3a09e9f9-55b1-418a-9e63-9a662f1a29bc" PhonePublisherId="00000000-0000-0000-0000-000000000000"/>
 
@@ -44,6 +44,20 @@
         <uap:DefaultTile Wide310x150Logo="Assets\Wide310x150Logo.png" />
         <uap:SplashScreen Image="Assets\SplashScreen.png" />
       </uap:VisualElements>
+      <Extensions>
+        <uap:Extension Category="windows.fileTypeAssociation">
+          <uap:FileTypeAssociation Name="msixplainer.packages">
+            <uap:DisplayName>MSIX Package</uap:DisplayName>
+            <uap:Logo>Assets\Square44x44Logo.png</uap:Logo>
+            <uap:SupportedFileTypes>
+              <uap:FileType>.msix</uap:FileType>
+              <uap:FileType>.msixbundle</uap:FileType>
+              <uap:FileType>.appx</uap:FileType>
+              <uap:FileType>.appxbundle</uap:FileType>
+            </uap:SupportedFileTypes>
+          </uap:FileTypeAssociation>
+        </uap:Extension>
+      </Extensions>
     </Application>
     <Application Id="Cli"
       Executable="MSIXplainer.Cli.exe"
diff --git a/MSIXplainer/Program.cs b/MSIXplainer/Program.cs
index 6cb46d3..0bdd962 100644
--- a/MSIXplainer/Program.cs
+++ b/MSIXplainer/Program.cs
@@ -8,7 +8,13 @@ namespace MSIXplainer;
 
 public static class Program
 {
-    [MTAThread]
+    // [STAThread] is REQUIRED. We disable XamlGeneratedMain
+    // (DISABLE_XAML_GENERATED_MAIN in the .csproj) and hand-write Main, so we
+    // have to set the apartment ourselves. With [MTAThread] the app appears
+    // to work — XAML, bindings, navigation, even file pickers all run — but
+    // WinRT OLE-backed APIs like Windows.ApplicationModel.DataTransfer.Clipboard
+    // throw CO_E_NOTINITIALIZED (0x800401F0). See issue #21.
+    [STAThread]
     static void Main(string[] args)
     {
         ComWrappersSupport.InitializeComWrappers();
diff --git a/MSIXplainer/ViewModels/MainPageViewModel.cs b/MSIXplainer/ViewModels/MainPageViewModel.cs
index 49e30f6..b7c60d3 100644
--- a/MSIXplainer/ViewModels/MainPageViewModel.cs
+++ b/MSIXplainer/ViewModels/MainPageViewModel.cs
@@ -180,19 +180,35 @@ private async Task OpenPackageAsync()
             var result = await picker.PickSingleFileAsync();
             if (result is null) return;
 
-            PackageFilePath = result.Path;
+            LoadPackageFromPath(result.Path);
+        }
+        catch (Exception ex)
+        {
+            ShowError($"Failed to open package: {ex.Message}");
+        }
+    }
+
+    /// <summary>
+    /// Loads and analyzes a package from a file path. Used by both the file
+    /// picker flow and the file-activation flow (right-click → Open with
+    /// MSIXplainer) — see issue #20.
+    /// </summary>
+    public void LoadPackageFromPath(string path)
+    {
+        try
+        {
+            PackageFilePath = path;
 
-            if (ManifestParserService.IsBundleFile(result.Path))
+            if (ManifestParserService.IsBundleFile(path))
             {
-                var packages = ManifestParserService.ExtractFromBundle(result.Path);
-                // Analyze the first package in the bundle (typically the current platform arch)
+                var packages = ManifestParserService.ExtractFromBundle(path);
                 var pkg = packages.First();
-                PackageFilePath = $"{result.Path} ({pkg.Label})";
+                PackageFilePath = $"{path} ({pkg.Label})";
                 AnalyzeManifest(pkg.RawXml, pkg.Info, pkg.Manifest);
             }
             else
             {
-                var (manifest, rawXml, info) = ManifestParserService.ExtractFromPackage(result.Path);
+                var (manifest, rawXml, info) = ManifestParserService.ExtractFromPackage(path);
                 AnalyzeManifest(rawXml, info, manifest);
             }
         }