diff --git a/services/core/java/com/android/server/wm/ActivityStack.java b/services/core/java/com/android/server/wm/ActivityStack.java
index bcad7586b9189..d88d76c1f96f0 100644
--- a/services/core/java/com/android/server/wm/ActivityStack.java
+++ b/services/core/java/com/android/server/wm/ActivityStack.java
@@ -783,6 +783,11 @@ class ActivityStack extends Task {
         if (currentMode == WINDOWING_MODE_PINNED) {
             mAtmService.getTaskChangeNotificationController().notifyActivityUnpinned();
         }
+        if (likelyResolvedMode == WINDOWING_MODE_PINNED
+                && taskDisplayArea.getRootPinnedTask() != null) {
+            // Can only have 1 pip at a time, so replace an existing pip
+            taskDisplayArea.getRootPinnedTask().dismissPip();
+        }
         if (likelyResolvedMode != WINDOWING_MODE_FULLSCREEN
                 && topActivity != null && !topActivity.noDisplay
                 && topActivity.isNonResizableOrForcedResizable(likelyResolvedMode)) {
diff --git a/services/core/java/com/android/server/wm/DisplayContent.java b/services/core/java/com/android/server/wm/DisplayContent.java
index 80a1a4592ff3d..8d46a6769bc82 100644
--- a/services/core/java/com/android/server/wm/DisplayContent.java
+++ b/services/core/java/com/android/server/wm/DisplayContent.java
@@ -25,6 +25,7 @@ import static android.app.WindowConfiguration.ROTATION_UNDEFINED;
 import static android.app.WindowConfiguration.WINDOWING_MODE_FREEFORM;
 import static android.app.WindowConfiguration.WINDOWING_MODE_FULLSCREEN;
 import static android.app.WindowConfiguration.WINDOWING_MODE_MULTI_WINDOW;
+import static android.app.WindowConfiguration.WINDOWING_MODE_PINNED;
 import static android.app.WindowConfiguration.WINDOWING_MODE_SPLIT_SCREEN_SECONDARY;
 import static android.app.WindowConfiguration.WINDOWING_MODE_UNDEFINED;
 import static android.content.pm.ActivityInfo.SCREEN_ORIENTATION_UNSET;
@@ -5028,6 +5029,7 @@ class DisplayContent extends WindowContainer<DisplayContent.DisplayChildWindowCo
         return activityType == ACTIVITY_TYPE_STANDARD
                 && (windowingMode == WINDOWING_MODE_FULLSCREEN
                 || windowingMode == WINDOWING_MODE_FREEFORM
+                || windowingMode == WINDOWING_MODE_PINNED
                 || windowingMode == WINDOWING_MODE_SPLIT_SCREEN_SECONDARY
                 || windowingMode == WINDOWING_MODE_MULTI_WINDOW);
     }
diff --git a/services/core/java/com/android/server/wm/Task.java b/services/core/java/com/android/server/wm/Task.java
index f8ee09b7a1420..ee6cc9aa52905 100644
--- a/services/core/java/com/android/server/wm/Task.java
+++ b/services/core/java/com/android/server/wm/Task.java
@@ -3072,6 +3072,7 @@ class Task extends WindowContainer<WindowContainer> {
         mForceShowForAllUsers = forceShowForAllUsers;
     }
 
+    @Override
     public boolean isAttached() {
         final TaskDisplayArea taskDisplayArea = getDisplayArea();
         return taskDisplayArea != null && !taskDisplayArea.isRemoved();
diff --git a/services/core/java/com/android/server/wm/TaskDisplayArea.java b/services/core/java/com/android/server/wm/TaskDisplayArea.java
index ea9a3629a40f4..d71e56106e180 100644
--- a/services/core/java/com/android/server/wm/TaskDisplayArea.java
+++ b/services/core/java/com/android/server/wm/TaskDisplayArea.java
@@ -879,6 +879,11 @@ final class TaskDisplayArea extends DisplayArea<ActivityStack> {
                     + windowingMode);
         }
 
+        if (windowingMode == WINDOWING_MODE_PINNED && getRootPinnedTask() != null) {
+            // Only 1 stack can be PINNED at a time, so dismiss the existing one
+            getRootPinnedTask().dismissPip();
+        }
+
         final int stackId = getNextStackId();
         return createStackUnchecked(windowingMode, activityType, stackId, onTop, info, intent,
                 createdByOrganizer);
diff --git a/services/core/java/com/android/server/wm/WindowContainer.java b/services/core/java/com/android/server/wm/WindowContainer.java
index fba22dd4e9dfb..7219164ad2f14 100644
--- a/services/core/java/com/android/server/wm/WindowContainer.java
+++ b/services/core/java/com/android/server/wm/WindowContainer.java
@@ -737,6 +737,10 @@ class WindowContainer<E extends WindowContainer> extends ConfigurationContainer<
         return parent != null ? parent.getDisplayArea() : null;
     }
 
+    boolean isAttached() {
+        return getDisplayArea() != null;
+    }
+
     void setWaitingForDrawnIfResizingChanged() {
         for (int i = mChildren.size() - 1; i >= 0; --i) {
             final WindowContainer wc = mChildren.get(i);
diff --git a/services/core/java/com/android/server/wm/WindowOrganizerController.java b/services/core/java/com/android/server/wm/WindowOrganizerController.java
index 86bc013e36389..d9c0219c47794 100644
--- a/services/core/java/com/android/server/wm/WindowOrganizerController.java
+++ b/services/core/java/com/android/server/wm/WindowOrganizerController.java
@@ -129,6 +129,10 @@ class WindowOrganizerController extends IWindowOrganizerController.Stub
                         final Map.Entry<IBinder, WindowContainerTransaction.Change> entry =
                                 entries.next();
                         final WindowContainer wc = WindowContainer.fromBinder(entry.getKey());
+                        if (!wc.isAttached()) {
+                            Slog.e(TAG, "Attempt to operate on detached container: " + wc);
+                            continue;
+                        }
                         int containerEffect = applyWindowContainerChange(wc, entry.getValue());
                         effects |= containerEffect;
 
@@ -146,6 +150,10 @@ class WindowOrganizerController extends IWindowOrganizerController.Stub
                     for (int i = 0, n = hops.size(); i < n; ++i) {
                         final WindowContainerTransaction.HierarchyOp hop = hops.get(i);
                         final WindowContainer wc = WindowContainer.fromBinder(hop.getContainer());
+                        if (!wc.isAttached()) {
+                            Slog.e(TAG, "Attempt to operate on detached container: " + wc);
+                            continue;
+                        }
                         effects |= sanitizeAndApplyHierarchyOp(wc, hop);
                     }
                     if ((effects & TRANSACT_EFFECTS_LIFECYCLE) != 0) {
diff --git a/services/tests/wmtests/src/com/android/server/wm/TaskDisplayAreaTests.java b/services/tests/wmtests/src/com/android/server/wm/TaskDisplayAreaTests.java
index a7085334bece1..52a51875427f6 100644
--- a/services/tests/wmtests/src/com/android/server/wm/TaskDisplayAreaTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/TaskDisplayAreaTests.java
@@ -172,7 +172,7 @@ public class TaskDisplayAreaTests extends WindowTestsBase {
         assertGetOrCreateStack(WINDOWING_MODE_SPLIT_SCREEN_PRIMARY, type, candidateTask,
                 false /* reuseCandidate */);
         assertGetOrCreateStack(WINDOWING_MODE_PINNED, type, candidateTask,
-                false /* reuseCandidate */);
+                true /* reuseCandidate */);
 
         final int windowingMode = WINDOWING_MODE_FULLSCREEN;
         assertGetOrCreateStack(windowingMode, ACTIVITY_TYPE_HOME, candidateTask,