[Peek] Stop fail-fast in AppWindow.Closing path; reset cached preview-handler factories on release

src/modules/peek/Peek.FilePreviewer/Previewers/ShellPreviewHandlerPreviewer/ShellPreviewHandlerPreviewer.cs

@@ -213,11 +213,29 @@
 
         public static void ReleaseHandlerFactories()
         {
-            foreach (var factory in HandlerFactories.Values)
+            // Snapshot and clear the dictionary up front so that a subsequent call
+            // or a concurrent LoadPreviewAsync can't pick up a stale RCW we are
+            // about to release. This also makes the method idempotent: a second
+            // call won't try to FinalRelease the same already-separated RCWs.
+            var factories = HandlerFactories.ToArray();
+            HandlerFactories.Clear();
+
+            foreach (var kvp in factories)
             {
+                // Mirror the LockServer(true) we did when caching, so the local
+                // server can shut down cleanly. Both calls are wrapped because the
+                // RCW may already be unreachable during process teardown.
                 try
                 {
-                    Marshal.FinalReleaseComObject(factory);
+                    kvp.Value.LockServer(false);
+                }
+                catch
+                {
+                }
+
+                try
+                {
+                    Marshal.FinalReleaseComObject(kvp.Value);
                 }
                 catch
                 {

src/modules/peek/Peek.UI/PeekXAML/MainWindow.xaml.cs

@@ -290,9 +290,22 @@
         /// <param name="args">AppWindowClosingEventArgs</param>
         private void AppWindow_Closing(AppWindow sender, AppWindowClosingEventArgs args)
         {
-            args.Cancel = true;
-            PowerToysTelemetry.Log.WriteEvent(new ClosedEvent());
-            Uninitialize();
+            // Any exception that escapes a WinRT event handler is projected back to
+            // the CsWinRT dispatcher as a failed HRESULT, and CFlat fail-fasts the
+            // process. We want a Closing handler that can never crash Peek, even if
+            // a callee (e.g., a cached preview-handler RCW that has been separated
+            // during teardown) throws InvalidComObjectException.
+            try
+            {
+                args.Cancel = true;
+                PowerToysTelemetry.Log.WriteEvent(new ClosedEvent());
+                Uninitialize();
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError("Unhandled exception in Peek MainWindow.AppWindow_Closing; suppressing to avoid fail-fast.", ex);
+                args.Cancel = true;
+            }
         }
 
         private bool IsNewSingleSelectedItem(SelectedItem selectedItem)

src/modules/registrypreview/RegistryPreview/MainWindow.Events.cs

@@ -2,6 +2,8 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
+
 using Microsoft.UI.Xaml;
 using Windows.Data.Json;
 using WinUIEx;
@@ -15,10 +17,27 @@
         /// </summary>
         private void AppWindow_Closing(Microsoft.UI.Windowing.AppWindow sender, Microsoft.UI.Windowing.AppWindowClosingEventArgs args)
         {
-            jsonWindowPlacement.SetNamedValue("appWindow.Position.X", JsonValue.CreateNumberValue(AppWindow.Position.X));
-            jsonWindowPlacement.SetNamedValue("appWindow.Position.Y", JsonValue.CreateNumberValue(AppWindow.Position.Y));
-            jsonWindowPlacement.SetNamedValue("appWindow.Size.Width", JsonValue.CreateNumberValue(AppWindow.Size.Width));
-            jsonWindowPlacement.SetNamedValue("appWindow.Size.Height", JsonValue.CreateNumberValue(AppWindow.Size.Height));
+            // Any exception that escapes a WinRT event handler is projected back to
+            // the CsWinRT dispatcher as a failed HRESULT, and CFlat fail-fasts the
+            // process. Defend the handler so a transient teardown failure (e.g.,
+            // null placement state, separated RCW during shutdown) can't terminate
+            // the editor unexpectedly.
+            try
+            {
+                if (jsonWindowPlacement == null)
+                {
+                    return;
+                }
+
+                jsonWindowPlacement.SetNamedValue("appWindow.Position.X", JsonValue.CreateNumberValue(AppWindow.Position.X));
+                jsonWindowPlacement.SetNamedValue("appWindow.Position.Y", JsonValue.CreateNumberValue(AppWindow.Position.Y));
+                jsonWindowPlacement.SetNamedValue("appWindow.Size.Width", JsonValue.CreateNumberValue(AppWindow.Size.Width));
+                jsonWindowPlacement.SetNamedValue("appWindow.Size.Height", JsonValue.CreateNumberValue(AppWindow.Size.Height));
+            }
+            catch (Exception ex)
+            {
+                ManagedCommon.Logger.LogError("Unhandled exception in RegistryPreview MainWindow.AppWindow_Closing; suppressing to avoid fail-fast.", ex);
+            }
         }
 
         /// <summary>