diff --git a/libs/WindowManager/Shell/Android.bp b/libs/WindowManager/Shell/Android.bp
index 7960dec..6c0ae5b 100644
--- a/libs/WindowManager/Shell/Android.bp
+++ b/libs/WindowManager/Shell/Android.bp
@@ -44,6 +44,7 @@
     srcs: [
         "src/com/android/wm/shell/util/**/*.java",
         "src/com/android/wm/shell/common/split/SplitScreenConstants.java",
+        "src/com/android/wm/shell/sysui/ShellSharedConstants.java",
     ],
     path: "src",
 }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimation.java b/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimation.java
index 86f9d5b..8cbe44b 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimation.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimation.java
@@ -29,13 +29,6 @@
 public interface BackAnimation {
 
     /**
-     * Returns a binder that can be passed to an external process to update back animations.
-     */
-    default IBackAnimation createExternalInterface() {
-        return null;
-    }
-
-    /**
      * Called when a {@link MotionEvent} is generated by a back gesture.
      *
      * @param touchX the X touch position of the {@link MotionEvent}.
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
index 33ecdd8..938189f 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
@@ -21,6 +21,7 @@
 
 import static com.android.wm.shell.common.ExecutorUtils.executeRemoteCallWithTaskPermission;
 import static com.android.wm.shell.protolog.ShellProtoLogGroup.WM_SHELL_BACK_PREVIEW;
+import static com.android.wm.shell.sysui.ShellSharedConstants.KEY_EXTRA_SHELL_BACK_ANIMATION;
 
 import android.annotation.NonNull;
 import android.annotation.Nullable;
@@ -57,10 +58,12 @@
 
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.protolog.common.ProtoLog;
+import com.android.wm.shell.common.ExternalInterfaceBinder;
 import com.android.wm.shell.common.RemoteCallable;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.annotations.ShellBackgroundThread;
 import com.android.wm.shell.common.annotations.ShellMainThread;
+import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
 
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -105,6 +108,7 @@
     private final IActivityTaskManager mActivityTaskManager;
     private final Context mContext;
     private final ContentResolver mContentResolver;
+    private final ShellController mShellController;
     private final ShellExecutor mShellExecutor;
     private final Handler mBgHandler;
     @Nullable
@@ -231,21 +235,25 @@
 
     public BackAnimationController(
             @NonNull ShellInit shellInit,
+            @NonNull ShellController shellController,
             @NonNull @ShellMainThread ShellExecutor shellExecutor,
             @NonNull @ShellBackgroundThread Handler backgroundHandler,
             Context context) {
-        this(shellInit, shellExecutor, backgroundHandler, new SurfaceControl.Transaction(),
-                ActivityTaskManager.getService(), context, context.getContentResolver());
+        this(shellInit, shellController, shellExecutor, backgroundHandler,
+                new SurfaceControl.Transaction(), ActivityTaskManager.getService(),
+                context, context.getContentResolver());
     }
 
     @VisibleForTesting
     BackAnimationController(
             @NonNull ShellInit shellInit,
+            @NonNull ShellController shellController,
             @NonNull @ShellMainThread ShellExecutor shellExecutor,
             @NonNull @ShellBackgroundThread Handler bgHandler,
             @NonNull SurfaceControl.Transaction transaction,
             @NonNull IActivityTaskManager activityTaskManager,
             Context context, ContentResolver contentResolver) {
+        mShellController = shellController;
         mShellExecutor = shellExecutor;
         mTransaction = transaction;
         mActivityTaskManager = activityTaskManager;
@@ -257,6 +265,8 @@
 
     private void onInit() {
         setupAnimationDeveloperSettingsObserver(mContentResolver, mBgHandler);
+        mShellController.addExternalInterface(KEY_EXTRA_SHELL_BACK_ANIMATION,
+                this::createExternalInterface, this);
     }
 
     private void setupAnimationDeveloperSettingsObserver(
@@ -289,7 +299,11 @@
         return mBackAnimation;
     }
 
-    private final BackAnimation mBackAnimation = new BackAnimationImpl();
+    private ExternalInterfaceBinder createExternalInterface() {
+        return new IBackAnimationImpl(this);
+    }
+
+    private final BackAnimationImpl mBackAnimation = new BackAnimationImpl();
 
     @Override
     public Context getContext() {
@@ -302,17 +316,6 @@
     }
 
     private class BackAnimationImpl implements BackAnimation {
-        private IBackAnimationImpl mBackAnimation;
-
-        @Override
-        public IBackAnimation createExternalInterface() {
-            if (mBackAnimation != null) {
-                mBackAnimation.invalidate();
-            }
-            mBackAnimation = new IBackAnimationImpl(BackAnimationController.this);
-            return mBackAnimation;
-        }
-
         @Override
         public void onBackMotion(
                 float touchX, float touchY, int keyAction, @BackEvent.SwipeEdge int swipeEdge) {
@@ -331,7 +334,8 @@
         }
     }
 
-    private static class IBackAnimationImpl extends IBackAnimation.Stub {
+    private static class IBackAnimationImpl extends IBackAnimation.Stub
+            implements ExternalInterfaceBinder {
         private BackAnimationController mController;
 
         IBackAnimationImpl(BackAnimationController controller) {
@@ -356,7 +360,8 @@
                     (controller) -> controller.onBackToLauncherAnimationFinished());
         }
 
-        void invalidate() {
+        @Override
+        public void invalidate() {
             mController = null;
         }
     }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/common/ExternalInterfaceBinder.java b/libs/WindowManager/Shell/src/com/android/wm/shell/common/ExternalInterfaceBinder.java
new file mode 100644
index 0000000..aa5b0cb
--- /dev/null
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/common/ExternalInterfaceBinder.java
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.wm.shell.common;
+
+import android.os.IBinder;
+
+/**
+ * An interface for binders which can be registered to be sent to other processes.
+ */
+public interface ExternalInterfaceBinder {
+    /**
+     * Invalidates this binder (detaches it from the controller it would call).
+     */
+    void invalidate();
+
+    /**
+     * Returns the IBinder to send.
+     */
+    IBinder asBinder();
+}
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellBaseModule.java b/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellBaseModule.java
index 3530142..cae9d15 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellBaseModule.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellBaseModule.java
@@ -258,13 +258,14 @@
     static Optional<BackAnimationController> provideBackAnimationController(
             Context context,
             ShellInit shellInit,
+            ShellController shellController,
             @ShellMainThread ShellExecutor shellExecutor,
             @ShellBackgroundThread Handler backgroundHandler
     ) {
         if (BackAnimationController.IS_ENABLED) {
             return Optional.of(
-                    new BackAnimationController(shellInit, shellExecutor, backgroundHandler,
-                            context));
+                    new BackAnimationController(shellInit, shellController, shellExecutor,
+                            backgroundHandler, context));
         }
         return Optional.empty();
     }
@@ -468,6 +469,7 @@
     static Optional<RecentTasksController> provideRecentTasksController(
             Context context,
             ShellInit shellInit,
+            ShellController shellController,
             ShellCommandHandler shellCommandHandler,
             TaskStackListenerImpl taskStackListener,
             ActivityTaskManager activityTaskManager,
@@ -475,9 +477,9 @@
             @ShellMainThread ShellExecutor mainExecutor
     ) {
         return Optional.ofNullable(
-                RecentTasksController.create(context, shellInit, shellCommandHandler,
-                        taskStackListener, activityTaskManager, desktopModeTaskRepository,
-                        mainExecutor));
+                RecentTasksController.create(context, shellInit, shellController,
+                        shellCommandHandler, taskStackListener, activityTaskManager,
+                        desktopModeTaskRepository, mainExecutor));
     }
 
     //
@@ -494,14 +496,15 @@
     @Provides
     static Transitions provideTransitions(Context context,
             ShellInit shellInit,
+            ShellController shellController,
             ShellTaskOrganizer organizer,
             TransactionPool pool,
             DisplayController displayController,
             @ShellMainThread ShellExecutor mainExecutor,
             @ShellMainThread Handler mainHandler,
             @ShellAnimationThread ShellExecutor animExecutor) {
-        return new Transitions(context, shellInit, organizer, pool, displayController, mainExecutor,
-                mainHandler, animExecutor);
+        return new Transitions(context, shellInit, shellController, organizer, pool,
+                displayController, mainExecutor, mainHandler, animExecutor);
     }
 
     @WMSingleton
@@ -618,13 +621,15 @@
 
     @WMSingleton
     @Provides
-    static StartingWindowController provideStartingWindowController(Context context,
+    static StartingWindowController provideStartingWindowController(
+            Context context,
             ShellInit shellInit,
+            ShellController shellController,
             ShellTaskOrganizer shellTaskOrganizer,
             @ShellSplashscreenThread ShellExecutor splashScreenExecutor,
             StartingWindowTypeAlgorithm startingWindowTypeAlgorithm, IconProvider iconProvider,
             TransactionPool pool) {
-        return new StartingWindowController(context, shellInit, shellTaskOrganizer,
+        return new StartingWindowController(context, shellInit, shellController, shellTaskOrganizer,
                 splashScreenExecutor, startingWindowTypeAlgorithm, iconProvider, pool);
     }
 
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellModule.java b/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellModule.java
index 47b6659..1c3b2db 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellModule.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/dagger/WMShellModule.java
@@ -600,7 +600,9 @@
     @WMSingleton
     @Provides
     @DynamicOverride
-    static DesktopModeController provideDesktopModeController(Context context, ShellInit shellInit,
+    static DesktopModeController provideDesktopModeController(Context context,
+            ShellInit shellInit,
+            ShellController shellController,
             ShellTaskOrganizer shellTaskOrganizer,
             RootTaskDisplayAreaOrganizer rootTaskDisplayAreaOrganizer,
             Transitions transitions,
@@ -608,7 +610,7 @@
             @ShellMainThread Handler mainHandler,
             @ShellMainThread ShellExecutor mainExecutor
     ) {
-        return new DesktopModeController(context, shellInit, shellTaskOrganizer,
+        return new DesktopModeController(context, shellInit, shellController, shellTaskOrganizer,
                 rootTaskDisplayAreaOrganizer, transitions, desktopModeTaskRepository, mainHandler,
                 mainExecutor);
     }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopMode.java b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopMode.java
index ff3be38..44a467f 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopMode.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopMode.java
@@ -23,9 +23,4 @@
  */
 @ExternalThread
 public interface DesktopMode {
-
-    /** Returns a binder that can be passed to an external process to manipulate DesktopMode. */
-    default IDesktopMode createExternalInterface() {
-        return null;
-    }
 }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopModeController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopModeController.java
index 99739c4..e34c297 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopModeController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/desktopmode/DesktopModeController.java
@@ -22,6 +22,7 @@
 
 import static com.android.wm.shell.common.ExecutorUtils.executeRemoteCallWithTaskPermission;
 import static com.android.wm.shell.protolog.ShellProtoLogGroup.WM_SHELL_DESKTOP_MODE;
+import static com.android.wm.shell.sysui.ShellSharedConstants.KEY_EXTRA_SHELL_DESKTOP_MODE;
 
 import android.app.ActivityManager.RunningTaskInfo;
 import android.app.WindowConfiguration;
@@ -42,10 +43,12 @@
 import com.android.internal.protolog.common.ProtoLog;
 import com.android.wm.shell.RootTaskDisplayAreaOrganizer;
 import com.android.wm.shell.ShellTaskOrganizer;
+import com.android.wm.shell.common.ExternalInterfaceBinder;
 import com.android.wm.shell.common.RemoteCallable;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.annotations.ExternalThread;
 import com.android.wm.shell.common.annotations.ShellMainThread;
+import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
 import com.android.wm.shell.transition.Transitions;
 
@@ -58,15 +61,18 @@
 public class DesktopModeController implements RemoteCallable<DesktopModeController> {
 
     private final Context mContext;
+    private final ShellController mShellController;
     private final ShellTaskOrganizer mShellTaskOrganizer;
     private final RootTaskDisplayAreaOrganizer mRootTaskDisplayAreaOrganizer;
     private final Transitions mTransitions;
     private final DesktopModeTaskRepository mDesktopModeTaskRepository;
     private final ShellExecutor mMainExecutor;
-    private final DesktopMode mDesktopModeImpl = new DesktopModeImpl();
+    private final DesktopModeImpl mDesktopModeImpl = new DesktopModeImpl();
     private final SettingsObserver mSettingsObserver;
 
-    public DesktopModeController(Context context, ShellInit shellInit,
+    public DesktopModeController(Context context,
+            ShellInit shellInit,
+            ShellController shellController,
             ShellTaskOrganizer shellTaskOrganizer,
             RootTaskDisplayAreaOrganizer rootTaskDisplayAreaOrganizer,
             Transitions transitions,
@@ -74,6 +80,7 @@
             @ShellMainThread Handler mainHandler,
             @ShellMainThread ShellExecutor mainExecutor) {
         mContext = context;
+        mShellController = shellController;
         mShellTaskOrganizer = shellTaskOrganizer;
         mRootTaskDisplayAreaOrganizer = rootTaskDisplayAreaOrganizer;
         mTransitions = transitions;
@@ -85,6 +92,8 @@
 
     private void onInit() {
         ProtoLog.d(WM_SHELL_DESKTOP_MODE, "Initialize DesktopModeController");
+        mShellController.addExternalInterface(KEY_EXTRA_SHELL_DESKTOP_MODE,
+                this::createExternalInterface, this);
         mSettingsObserver.observe();
         if (DesktopModeStatus.isActive(mContext)) {
             updateDesktopModeActive(true);
@@ -108,6 +117,13 @@
         return mDesktopModeImpl;
     }
 
+    /**
+     * Creates a new instance of the external interface to pass to another process.
+     */
+    private ExternalInterfaceBinder createExternalInterface() {
+        return new IDesktopModeImpl(this);
+    }
+
     @VisibleForTesting
     void updateDesktopModeActive(boolean active) {
         ProtoLog.d(WM_SHELL_DESKTOP_MODE, "updateDesktopModeActive: active=%s", active);
@@ -235,24 +251,15 @@
      */
     @ExternalThread
     private final class DesktopModeImpl implements DesktopMode {
-
-        private IDesktopModeImpl mIDesktopMode;
-
-        @Override
-        public IDesktopMode createExternalInterface() {
-            if (mIDesktopMode != null) {
-                mIDesktopMode.invalidate();
-            }
-            mIDesktopMode = new IDesktopModeImpl(DesktopModeController.this);
-            return mIDesktopMode;
-        }
+        // Do nothing
     }
 
     /**
      * The interface for calls from outside the host process.
      */
     @BinderThread
-    private static class IDesktopModeImpl extends IDesktopMode.Stub {
+    private static class IDesktopModeImpl extends IDesktopMode.Stub
+            implements ExternalInterfaceBinder {
 
         private DesktopModeController mController;
 
@@ -263,7 +270,8 @@
         /**
          * Invalidates this instance, preventing future calls from updating the controller.
          */
-        void invalidate() {
+        @Override
+        public void invalidate() {
             mController = null;
         }
 
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/docs/changes.md b/libs/WindowManager/Shell/src/com/android/wm/shell/docs/changes.md
index 2aa933d..fbf326e 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/docs/changes.md
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/docs/changes.md
@@ -29,19 +29,37 @@
 ### SysUI accessible components
 In addition to doing the above, you will also need to provide an interface for calling to SysUI
 from the Shell and vice versa.  The current pattern is to have a parallel `Optional<Component name>`
-interface that the `<Component name>Controller` implements and handles on the main Shell thread.
+interface that the `<Component name>Controller` implements and handles on the main Shell thread
+(see [SysUI/Shell threading](threading.md)).
 
 In addition, because components accessible to SysUI injection are explicitly listed, you'll have to
 add an appropriate method in `WMComponent` to get the interface and update the `Builder` in
 `SysUIComponent` to take the interface so it can be injected in SysUI code.  The binding between
 the two is done in `SystemUIFactory#init()` which will need to be updated as well.
 
+Specifically, to support calling into a controller from an external process (like Launcher):
+- Create an implementation of the external interface within the controller
+- Have all incoming calls post to the main shell thread (inject @ShellMainThread Executor into the
+  controller if needed)
+- Note that callbacks into SysUI should take an associated executor to call back on
+
 ### Launcher accessible components
 Because Launcher is not a part of SystemUI and is a separate process, exposing controllers to
 Launcher requires a new AIDL interface to be created and implemented by the controller.  The
 implementation of the stub interface in the controller otherwise behaves similar to the interface
 to SysUI where it posts the work to the main Shell thread.
 
+Specifically, to support calling into a controller from an external process (like Launcher):
+- Create an implementation of the interface binder's `Stub` class within the controller, have it
+  extend `ExternalInterfaceBinder` and implement `invalidate()` to ensure it doesn't hold long
+  references to the outer controller
+- Make the controller implement `RemoteCallable<T>`, and have all incoming calls use one of
+  the `ExecutorUtils.executeRemoteCallWithTaskPermission()` calls to verify the caller's identity
+  and ensure the call happens on the main shell thread and not the binder thread
+- Inject `ShellController` and add the instance of the implementation as external interface
+- In Launcher, update `TouchInteractionService` to pass the interface to `SystemUIProxy`, and then
+  call the SystemUIProxy method as needed in that code
+
 ### Component initialization
 To initialize the component:
 - On the Shell side, you potentially need to do two things to initialize the component:
@@ -64,8 +82,9 @@
 
 ### General Do's & Dont's
 Do:
-- Do add unit tests for all new components
-- Do keep controllers simple and break them down as needed
+- Add unit tests for all new components
+- Keep controllers simple and break them down as needed
+- Any SysUI callbacks should also take an associated executor to run the callback on
 
 Don't:
 - **Don't** do initialization in the constructor, only do initialization in the init callbacks.
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/floating/FloatingTasks.java b/libs/WindowManager/Shell/src/com/android/wm/shell/floating/FloatingTasks.java
index 9356660..f86d467 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/floating/FloatingTasks.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/floating/FloatingTasks.java
@@ -33,9 +33,4 @@
      * - If there is a floating task for this intent, and it's not stashed, this stashes it.
      */
     void showOrSetStashed(Intent intent);
-
-    /** Returns a binder that can be passed to an external process to manipulate FloatingTasks. */
-    default IFloatingTasks createExternalInterface() {
-        return null;
-    }
 }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/floating/FloatingTasksController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/floating/FloatingTasksController.java
index 6755299..b3c09d3 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/floating/FloatingTasksController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/floating/FloatingTasksController.java
@@ -21,6 +21,7 @@
 
 import static com.android.wm.shell.common.ExecutorUtils.executeRemoteCallWithTaskPermission;
 import static com.android.wm.shell.protolog.ShellProtoLogGroup.WM_SHELL_FLOATING_APPS;
+import static com.android.wm.shell.sysui.ShellSharedConstants.KEY_EXTRA_SHELL_FLOATING_TASKS;
 
 import android.annotation.Nullable;
 import android.content.Context;
@@ -40,6 +41,7 @@
 import com.android.wm.shell.ShellTaskOrganizer;
 import com.android.wm.shell.TaskViewTransitions;
 import com.android.wm.shell.bubbles.BubbleController;
+import com.android.wm.shell.common.ExternalInterfaceBinder;
 import com.android.wm.shell.common.RemoteCallable;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.SyncTransactionQueue;
@@ -136,11 +138,13 @@
         if (isFloatingTasksEnabled()) {
             shellInit.addInitCallback(this::onInit, this);
         }
-        mShellCommandHandler.addDumpCallback(this::dump, this);
     }
 
     protected void onInit() {
         mShellController.addConfigurationChangeListener(this);
+        mShellController.addExternalInterface(KEY_EXTRA_SHELL_FLOATING_TASKS,
+                this::createExternalInterface, this);
+        mShellCommandHandler.addDumpCallback(this::dump, this);
     }
 
     /** Only used for testing. */
@@ -168,6 +172,10 @@
         return FLOATING_TASKS_ENABLED || mFloatingTasksEnabledForTests;
     }
 
+    private ExternalInterfaceBinder createExternalInterface() {
+        return new IFloatingTasksImpl(this);
+    }
+
     @Override
     public void onThemeChanged() {
         if (mIsFloatingLayerAdded) {
@@ -412,28 +420,18 @@
      */
     @ExternalThread
     private class FloatingTaskImpl implements FloatingTasks {
-        private IFloatingTasksImpl mIFloatingTasks;
-
         @Override
         public void showOrSetStashed(Intent intent) {
             mMainExecutor.execute(() -> FloatingTasksController.this.showOrSetStashed(intent));
         }
-
-        @Override
-        public IFloatingTasks createExternalInterface() {
-            if (mIFloatingTasks != null) {
-                mIFloatingTasks.invalidate();
-            }
-            mIFloatingTasks = new IFloatingTasksImpl(FloatingTasksController.this);
-            return mIFloatingTasks;
-        }
     }
 
     /**
      * The interface for calls from outside the host process.
      */
     @BinderThread
-    private static class IFloatingTasksImpl extends IFloatingTasks.Stub {
+    private static class IFloatingTasksImpl extends IFloatingTasks.Stub
+            implements ExternalInterfaceBinder {
         private FloatingTasksController mController;
 
         IFloatingTasksImpl(FloatingTasksController controller) {
@@ -443,7 +441,8 @@
         /**
          * Invalidates this instance, preventing future calls from updating the controller.
          */
-        void invalidate() {
+        @Override
+        public void invalidate() {
             mController = null;
         }
 
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHanded.java b/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHanded.java
index 7129165..2ee3348 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHanded.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHanded.java
@@ -30,13 +30,6 @@
             OneHandedController.SUPPORT_ONE_HANDED_MODE, false);
 
     /**
-     * Returns a binder that can be passed to an external process to manipulate OneHanded.
-     */
-    default IOneHanded createExternalInterface() {
-        return null;
-    }
-
-    /**
      * Enters one handed mode.
      */
     void startOneHanded();
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedController.java
index e0c4fe8..679d4ca 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedController.java
@@ -24,6 +24,7 @@
 import static com.android.wm.shell.onehanded.OneHandedState.STATE_ENTERING;
 import static com.android.wm.shell.onehanded.OneHandedState.STATE_EXITING;
 import static com.android.wm.shell.onehanded.OneHandedState.STATE_NONE;
+import static com.android.wm.shell.sysui.ShellSharedConstants.KEY_EXTRA_SHELL_ONE_HANDED;
 
 import android.annotation.BinderThread;
 import android.content.ComponentName;
@@ -49,6 +50,7 @@
 import com.android.wm.shell.common.DisplayChangeController;
 import com.android.wm.shell.common.DisplayController;
 import com.android.wm.shell.common.DisplayLayout;
+import com.android.wm.shell.common.ExternalInterfaceBinder;
 import com.android.wm.shell.common.RemoteCallable;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.TaskStackListenerCallback;
@@ -296,12 +298,18 @@
         mShellController.addConfigurationChangeListener(this);
         mShellController.addKeyguardChangeListener(this);
         mShellController.addUserChangeListener(this);
+        mShellController.addExternalInterface(KEY_EXTRA_SHELL_ONE_HANDED,
+                this::createExternalInterface, this);
     }
 
     public OneHanded asOneHanded() {
         return mImpl;
     }
 
+    private ExternalInterfaceBinder createExternalInterface() {
+        return new IOneHandedImpl(this);
+    }
+
     @Override
     public Context getContext() {
         return mContext;
@@ -709,17 +717,6 @@
      */
     @ExternalThread
     private class OneHandedImpl implements OneHanded {
-        private IOneHandedImpl mIOneHanded;
-
-        @Override
-        public IOneHanded createExternalInterface() {
-            if (mIOneHanded != null) {
-                mIOneHanded.invalidate();
-            }
-            mIOneHanded = new IOneHandedImpl(OneHandedController.this);
-            return mIOneHanded;
-        }
-
         @Override
         public void startOneHanded() {
             mMainExecutor.execute(() -> {
@@ -767,7 +764,7 @@
      * The interface for calls from outside the host process.
      */
     @BinderThread
-    private static class IOneHandedImpl extends IOneHanded.Stub {
+    private static class IOneHandedImpl extends IOneHanded.Stub implements ExternalInterfaceBinder {
         private OneHandedController mController;
 
         IOneHandedImpl(OneHandedController controller) {
@@ -777,7 +774,8 @@
         /**
          * Invalidates this instance, preventing future calls from updating the controller.
          */
-        void invalidate() {
+        @Override
+        public void invalidate() {
             mController = null;
         }
 
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/pip/Pip.java b/libs/WindowManager/Shell/src/com/android/wm/shell/pip/Pip.java
index 72b9dd3..f34d2a8 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/pip/Pip.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/pip/Pip.java
@@ -27,14 +27,6 @@
  */
 @ExternalThread
 public interface Pip {
-
-    /**
-     * Returns a binder that can be passed to an external process to manipulate PIP.
-     */
-    default IPip createExternalInterface() {
-        return null;
-    }
-
     /**
      * Expand PIP, it's possible that specific request to activate the window via Alt-tab.
      */
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/pip/phone/PipController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/pip/phone/PipController.java
index 3345b1b..a918559 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/pip/phone/PipController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/pip/phone/PipController.java
@@ -33,6 +33,7 @@
 import static com.android.wm.shell.pip.PipAnimationController.TRANSITION_DIRECTION_TO_PIP;
 import static com.android.wm.shell.pip.PipAnimationController.TRANSITION_DIRECTION_USER_RESIZE;
 import static com.android.wm.shell.pip.PipAnimationController.isOutPipDirection;
+import static com.android.wm.shell.sysui.ShellSharedConstants.KEY_EXTRA_SHELL_PIP;
 
 import android.app.ActivityManager;
 import android.app.ActivityTaskManager;
@@ -68,6 +69,7 @@
 import com.android.wm.shell.common.DisplayController;
 import com.android.wm.shell.common.DisplayInsetsController;
 import com.android.wm.shell.common.DisplayLayout;
+import com.android.wm.shell.common.ExternalInterfaceBinder;
 import com.android.wm.shell.common.RemoteCallable;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.SingleInstanceRemoteListener;
@@ -632,6 +634,12 @@
         mShellController.addConfigurationChangeListener(this);
         mShellController.addKeyguardChangeListener(this);
         mShellController.addUserChangeListener(this);
+        mShellController.addExternalInterface(KEY_EXTRA_SHELL_PIP,
+                this::createExternalInterface, this);
+    }
+
+    private ExternalInterfaceBinder createExternalInterface() {
+        return new IPipImpl(this);
     }
 
     @Override
@@ -1040,17 +1048,6 @@
      * The interface for calls from outside the Shell, within the host process.
      */
     private class PipImpl implements Pip {
-        private IPipImpl mIPip;
-
-        @Override
-        public IPip createExternalInterface() {
-            if (mIPip != null) {
-                mIPip.invalidate();
-            }
-            mIPip = new IPipImpl(PipController.this);
-            return mIPip;
-        }
-
         @Override
         public void expandPip() {
             mMainExecutor.execute(() -> {
@@ -1098,7 +1095,7 @@
      * The interface for calls from outside the host process.
      */
     @BinderThread
-    private static class IPipImpl extends IPip.Stub {
+    private static class IPipImpl extends IPip.Stub implements ExternalInterfaceBinder {
         private PipController mController;
         private final SingleInstanceRemoteListener<PipController,
                 IPipAnimationListener> mListener;
@@ -1129,7 +1126,8 @@
         /**
          * Invalidates this instance, preventing future calls from updating the controller.
          */
-        void invalidate() {
+        @Override
+        public void invalidate() {
             mController = null;
         }
 
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/recents/RecentTasks.java b/libs/WindowManager/Shell/src/com/android/wm/shell/recents/RecentTasks.java
index 2a62552..069066e 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/recents/RecentTasks.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/recents/RecentTasks.java
@@ -29,13 +29,6 @@
 @ExternalThread
 public interface RecentTasks {
     /**
-     * Returns a binder that can be passed to an external process to fetch recent tasks.
-     */
-    default IRecentTasks createExternalInterface() {
-        return null;
-    }
-
-    /**
      * Gets the set of recent tasks.
      */
     default void getRecentTasks(int maxNum, int flags, int userId, Executor callbackExecutor,
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/recents/RecentTasksController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/recents/RecentTasksController.java
index 02b5a35..08f3db6 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/recents/RecentTasksController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/recents/RecentTasksController.java
@@ -20,6 +20,7 @@
 import static android.content.pm.PackageManager.FEATURE_PC;
 
 import static com.android.wm.shell.common.ExecutorUtils.executeRemoteCallWithTaskPermission;
+import static com.android.wm.shell.sysui.ShellSharedConstants.KEY_EXTRA_SHELL_RECENT_TASKS;
 
 import android.app.ActivityManager;
 import android.app.ActivityTaskManager;
@@ -37,6 +38,7 @@
 import androidx.annotation.VisibleForTesting;
 
 import com.android.internal.protolog.common.ProtoLog;
+import com.android.wm.shell.common.ExternalInterfaceBinder;
 import com.android.wm.shell.common.RemoteCallable;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.SingleInstanceRemoteListener;
@@ -48,6 +50,7 @@
 import com.android.wm.shell.desktopmode.DesktopModeTaskRepository;
 import com.android.wm.shell.protolog.ShellProtoLogGroup;
 import com.android.wm.shell.sysui.ShellCommandHandler;
+import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
 import com.android.wm.shell.util.GroupedRecentTaskInfo;
 import com.android.wm.shell.util.SplitBounds;
@@ -69,11 +72,12 @@
     private static final String TAG = RecentTasksController.class.getSimpleName();
 
     private final Context mContext;
+    private final ShellController mShellController;
     private final ShellCommandHandler mShellCommandHandler;
     private final Optional<DesktopModeTaskRepository> mDesktopModeTaskRepository;
     private final ShellExecutor mMainExecutor;
     private final TaskStackListenerImpl mTaskStackListener;
-    private final RecentTasks mImpl = new RecentTasksImpl();
+    private final RecentTasksImpl mImpl = new RecentTasksImpl();
     private final ActivityTaskManager mActivityTaskManager;
     private IRecentTasksListener mListener;
     private final boolean mIsDesktopMode;
@@ -97,6 +101,7 @@
     public static RecentTasksController create(
             Context context,
             ShellInit shellInit,
+            ShellController shellController,
             ShellCommandHandler shellCommandHandler,
             TaskStackListenerImpl taskStackListener,
             ActivityTaskManager activityTaskManager,
@@ -106,18 +111,20 @@
         if (!context.getResources().getBoolean(com.android.internal.R.bool.config_hasRecents)) {
             return null;
         }
-        return new RecentTasksController(context, shellInit, shellCommandHandler, taskStackListener,
-                activityTaskManager, desktopModeTaskRepository, mainExecutor);
+        return new RecentTasksController(context, shellInit, shellController, shellCommandHandler,
+                taskStackListener, activityTaskManager, desktopModeTaskRepository, mainExecutor);
     }
 
     RecentTasksController(Context context,
             ShellInit shellInit,
+            ShellController shellController,
             ShellCommandHandler shellCommandHandler,
             TaskStackListenerImpl taskStackListener,
             ActivityTaskManager activityTaskManager,
             Optional<DesktopModeTaskRepository> desktopModeTaskRepository,
             ShellExecutor mainExecutor) {
         mContext = context;
+        mShellController = shellController;
         mShellCommandHandler = shellCommandHandler;
         mActivityTaskManager = activityTaskManager;
         mIsDesktopMode = mContext.getPackageManager().hasSystemFeature(FEATURE_PC);
@@ -131,7 +138,13 @@
         return mImpl;
     }
 
+    private ExternalInterfaceBinder createExternalInterface() {
+        return new IRecentTasksImpl(this);
+    }
+
     private void onInit() {
+        mShellController.addExternalInterface(KEY_EXTRA_SHELL_RECENT_TASKS,
+                this::createExternalInterface, this);
         mShellCommandHandler.addDumpCallback(this::dump, this);
         mTaskStackListener.addListener(this);
         mDesktopModeTaskRepository.ifPresent(it -> it.addListener(this));
@@ -366,17 +379,6 @@
      */
     @ExternalThread
     private class RecentTasksImpl implements RecentTasks {
-        private IRecentTasksImpl mIRecentTasks;
-
-        @Override
-        public IRecentTasks createExternalInterface() {
-            if (mIRecentTasks != null) {
-                mIRecentTasks.invalidate();
-            }
-            mIRecentTasks = new IRecentTasksImpl(RecentTasksController.this);
-            return mIRecentTasks;
-        }
-
         @Override
         public void getRecentTasks(int maxNum, int flags, int userId, Executor executor,
                 Consumer<List<GroupedRecentTaskInfo>> callback) {
@@ -393,7 +395,8 @@
      * The interface for calls from outside the host process.
      */
     @BinderThread
-    private static class IRecentTasksImpl extends IRecentTasks.Stub {
+    private static class IRecentTasksImpl extends IRecentTasks.Stub
+            implements ExternalInterfaceBinder {
         private RecentTasksController mController;
         private final SingleInstanceRemoteListener<RecentTasksController,
                 IRecentTasksListener> mListener;
@@ -424,7 +427,8 @@
         /**
          * Invalidates this instance, preventing future calls from updating the controller.
          */
-        void invalidate() {
+        @Override
+        public void invalidate() {
             mController = null;
         }
 
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreen.java b/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreen.java
index e73b799..d86aadc 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreen.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreen.java
@@ -70,13 +70,6 @@
     /** Unregisters listener that gets split screen callback. */
     void unregisterSplitScreenListener(@NonNull SplitScreenListener listener);
 
-    /**
-     * Returns a binder that can be passed to an external process to manipulate SplitScreen.
-     */
-    default ISplitScreen createExternalInterface() {
-        return null;
-    }
-
     /** Called when device waking up finished. */
     void onFinishedWakingUp();
 
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreenController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreenController.java
index 07a6895..eeb2c0f 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreenController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/SplitScreenController.java
@@ -29,6 +29,7 @@
 import static com.android.wm.shell.common.split.SplitScreenConstants.SPLIT_POSITION_UNDEFINED;
 import static com.android.wm.shell.splitscreen.SplitScreen.STAGE_TYPE_SIDE;
 import static com.android.wm.shell.splitscreen.SplitScreen.STAGE_TYPE_UNDEFINED;
+import static com.android.wm.shell.sysui.ShellSharedConstants.KEY_EXTRA_SHELL_SPLIT_SCREEN;
 import static com.android.wm.shell.transition.Transitions.ENABLE_SHELL_TRANSITIONS;
 
 import android.app.ActivityManager;
@@ -71,6 +72,7 @@
 import com.android.wm.shell.common.DisplayController;
 import com.android.wm.shell.common.DisplayImeController;
 import com.android.wm.shell.common.DisplayInsetsController;
+import com.android.wm.shell.common.ExternalInterfaceBinder;
 import com.android.wm.shell.common.RemoteCallable;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.SingleInstanceRemoteListener;
@@ -214,6 +216,10 @@
         return mImpl;
     }
 
+    private ExternalInterfaceBinder createExternalInterface() {
+        return new ISplitScreenImpl(this);
+    }
+
     /**
      * This will be called after ShellTaskOrganizer has initialized/registered because of the
      * dependency order.
@@ -224,6 +230,8 @@
         mShellCommandHandler.addCommandCallback("splitscreen", mSplitScreenShellCommandHandler,
                 this);
         mShellController.addKeyguardChangeListener(this);
+        mShellController.addExternalInterface(KEY_EXTRA_SHELL_SPLIT_SCREEN,
+                this::createExternalInterface, this);
         if (mStageCoordinator == null) {
             // TODO: Multi-display
             mStageCoordinator = createStageCoordinator();
@@ -658,7 +666,6 @@
      */
     @ExternalThread
     private class SplitScreenImpl implements SplitScreen {
-        private ISplitScreenImpl mISplitScreen;
         private final ArrayMap<SplitScreenListener, Executor> mExecutors = new ArrayMap<>();
         private final SplitScreen.SplitScreenListener mListener = new SplitScreenListener() {
             @Override
@@ -704,15 +711,6 @@
         };
 
         @Override
-        public ISplitScreen createExternalInterface() {
-            if (mISplitScreen != null) {
-                mISplitScreen.invalidate();
-            }
-            mISplitScreen = new ISplitScreenImpl(SplitScreenController.this);
-            return mISplitScreen;
-        }
-
-        @Override
         public void registerSplitScreenListener(SplitScreenListener listener, Executor executor) {
             if (mExecutors.containsKey(listener)) return;
 
@@ -752,7 +750,8 @@
      * The interface for calls from outside the host process.
      */
     @BinderThread
-    private static class ISplitScreenImpl extends ISplitScreen.Stub {
+    private static class ISplitScreenImpl extends ISplitScreen.Stub
+            implements ExternalInterfaceBinder {
         private SplitScreenController mController;
         private final SingleInstanceRemoteListener<SplitScreenController,
                 ISplitScreenListener> mListener;
@@ -779,7 +778,8 @@
         /**
          * Invalidates this instance, preventing future calls from updating the controller.
          */
-        void invalidate() {
+        @Override
+        public void invalidate() {
             mController = null;
         }
 
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/startingsurface/StartingSurface.java b/libs/WindowManager/Shell/src/com/android/wm/shell/startingsurface/StartingSurface.java
index 76105a3..538bbec 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/startingsurface/StartingSurface.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/startingsurface/StartingSurface.java
@@ -22,14 +22,6 @@
  * Interface to engage starting window feature.
  */
 public interface StartingSurface {
-
-    /**
-     * Returns a binder that can be passed to an external process to manipulate starting windows.
-     */
-    default IStartingWindow createExternalInterface() {
-        return null;
-    }
-
     /**
      * Returns the background color for a starting window if existing.
      */
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/startingsurface/StartingWindowController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/startingsurface/StartingWindowController.java
index 379af21..0c23f10 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/startingsurface/StartingWindowController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/startingsurface/StartingWindowController.java
@@ -23,6 +23,7 @@
 import static android.window.StartingWindowInfo.STARTING_WINDOW_TYPE_SPLASH_SCREEN;
 
 import static com.android.wm.shell.common.ExecutorUtils.executeRemoteCallWithTaskPermission;
+import static com.android.wm.shell.sysui.ShellSharedConstants.KEY_EXTRA_SHELL_STARTING_WINDOW;
 
 import android.app.ActivityManager.RunningTaskInfo;
 import android.app.TaskInfo;
@@ -43,10 +44,12 @@
 import com.android.internal.util.function.TriConsumer;
 import com.android.launcher3.icons.IconProvider;
 import com.android.wm.shell.ShellTaskOrganizer;
+import com.android.wm.shell.common.ExternalInterfaceBinder;
 import com.android.wm.shell.common.RemoteCallable;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.SingleInstanceRemoteListener;
 import com.android.wm.shell.common.TransactionPool;
+import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
 
 /**
@@ -76,6 +79,7 @@
     private TriConsumer<Integer, Integer, Integer> mTaskLaunchingCallback;
     private final StartingSurfaceImpl mImpl = new StartingSurfaceImpl();
     private final Context mContext;
+    private final ShellController mShellController;
     private final ShellTaskOrganizer mShellTaskOrganizer;
     private final ShellExecutor mSplashScreenExecutor;
     /**
@@ -86,12 +90,14 @@
 
     public StartingWindowController(Context context,
             ShellInit shellInit,
+            ShellController shellController,
             ShellTaskOrganizer shellTaskOrganizer,
             ShellExecutor splashScreenExecutor,
             StartingWindowTypeAlgorithm startingWindowTypeAlgorithm,
             IconProvider iconProvider,
             TransactionPool pool) {
         mContext = context;
+        mShellController = shellController;
         mShellTaskOrganizer = shellTaskOrganizer;
         mStartingSurfaceDrawer = new StartingSurfaceDrawer(context, splashScreenExecutor,
                 iconProvider, pool);
@@ -107,8 +113,14 @@
         return mImpl;
     }
 
+    private ExternalInterfaceBinder createExternalInterface() {
+        return new IStartingWindowImpl(this);
+    }
+
     private void onInit() {
         mShellTaskOrganizer.initStartingWindow(this);
+        mShellController.addExternalInterface(KEY_EXTRA_SHELL_STARTING_WINDOW,
+                this::createExternalInterface, this);
     }
 
     @Override
@@ -222,17 +234,6 @@
      * The interface for calls from outside the Shell, within the host process.
      */
     private class StartingSurfaceImpl implements StartingSurface {
-        private IStartingWindowImpl mIStartingWindow;
-
-        @Override
-        public IStartingWindowImpl createExternalInterface() {
-            if (mIStartingWindow != null) {
-                mIStartingWindow.invalidate();
-            }
-            mIStartingWindow = new IStartingWindowImpl(StartingWindowController.this);
-            return mIStartingWindow;
-        }
-
         @Override
         public int getBackgroundColor(TaskInfo taskInfo) {
             synchronized (mTaskBackgroundColors) {
@@ -256,7 +257,8 @@
      * The interface for calls from outside the host process.
      */
     @BinderThread
-    private static class IStartingWindowImpl extends IStartingWindow.Stub {
+    private static class IStartingWindowImpl extends IStartingWindow.Stub
+            implements ExternalInterfaceBinder {
         private StartingWindowController mController;
         private SingleInstanceRemoteListener<StartingWindowController,
                 IStartingWindowListener> mListener;
@@ -276,7 +278,8 @@
         /**
          * Invalidates this instance, preventing future calls from updating the controller.
          */
-        void invalidate() {
+        @Override
+        public void invalidate() {
             mController = null;
         }
 
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/sysui/ShellController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/sysui/ShellController.java
index 5799394..fdf073f 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/sysui/ShellController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/sysui/ShellController.java
@@ -23,23 +23,28 @@
 import static android.content.pm.ActivityInfo.CONFIG_SMALLEST_SCREEN_SIZE;
 import static android.content.pm.ActivityInfo.CONFIG_UI_MODE;
 
+import static com.android.wm.shell.protolog.ShellProtoLogGroup.WM_SHELL_INIT;
 import static com.android.wm.shell.protolog.ShellProtoLogGroup.WM_SHELL_SYSUI_EVENTS;
 
 import android.content.Context;
 import android.content.pm.ActivityInfo;
 import android.content.pm.UserInfo;
 import android.content.res.Configuration;
+import android.os.Bundle;
+import android.util.ArrayMap;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.VisibleForTesting;
 
 import com.android.internal.protolog.common.ProtoLog;
+import com.android.wm.shell.common.ExternalInterfaceBinder;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.annotations.ExternalThread;
 
 import java.io.PrintWriter;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.function.Supplier;
 
 /**
  * Handles event callbacks from SysUI that can be used within the Shell.
@@ -59,6 +64,11 @@
     private final CopyOnWriteArrayList<UserChangeListener> mUserChangeListeners =
             new CopyOnWriteArrayList<>();
 
+    private ArrayMap<String, Supplier<ExternalInterfaceBinder>> mExternalInterfaceSuppliers =
+            new ArrayMap<>();
+    // References to the existing interfaces, to be invalidated when they are recreated
+    private ArrayMap<String, ExternalInterfaceBinder> mExternalInterfaces = new ArrayMap<>();
+
     private Configuration mLastConfiguration;
 
 
@@ -67,6 +77,11 @@
         mShellInit = shellInit;
         mShellCommandHandler = shellCommandHandler;
         mMainExecutor = mainExecutor;
+        shellInit.addInitCallback(this::onInit, this);
+    }
+
+    private void onInit() {
+        mShellCommandHandler.addDumpCallback(this::dump, this);
     }
 
     /**
@@ -124,6 +139,47 @@
         mUserChangeListeners.remove(listener);
     }
 
+    /**
+     * Adds an interface that can be called from a remote process. This method takes a supplier
+     * because each binder reference is valid for a single process, and in multi-user mode, SysUI
+     * will request new binder instances for each instance of Launcher that it provides binders
+     * to.
+     *
+     * @param extra the key for the interface, {@see ShellSharedConstants}
+     * @param binderSupplier the supplier of the binder to pass to the external process
+     * @param callerInstance the instance of the caller, purely for logging
+     */
+    public void addExternalInterface(String extra, Supplier<ExternalInterfaceBinder> binderSupplier,
+            Object callerInstance) {
+        ProtoLog.v(WM_SHELL_INIT, "Adding external interface from %s with key %s",
+                callerInstance.getClass().getSimpleName(), extra);
+        if (mExternalInterfaceSuppliers.containsKey(extra)) {
+            throw new IllegalArgumentException("Supplier with same key already exists: "
+                    + extra);
+        }
+        mExternalInterfaceSuppliers.put(extra, binderSupplier);
+    }
+
+    /**
+     * Updates the given bundle with the set of external interfaces, invalidating the old set of
+     * binders.
+     */
+    private void createExternalInterfaces(Bundle output) {
+        // Invalidate the old binders
+        for (int i = 0; i < mExternalInterfaces.size(); i++) {
+            mExternalInterfaces.valueAt(i).invalidate();
+        }
+        mExternalInterfaces.clear();
+
+        // Create new binders for each key
+        for (int i = 0; i < mExternalInterfaceSuppliers.size(); i++) {
+            final String key = mExternalInterfaceSuppliers.keyAt(i);
+            final ExternalInterfaceBinder b = mExternalInterfaceSuppliers.valueAt(i).get();
+            mExternalInterfaces.put(key, b);
+            output.putBinder(key, b.asBinder());
+        }
+    }
+
     @VisibleForTesting
     void onConfigurationChanged(Configuration newConfig) {
         // The initial config is send on startup and doesn't trigger listener callbacks
@@ -204,6 +260,14 @@
         pw.println(innerPrefix + "mLastConfiguration=" + mLastConfiguration);
         pw.println(innerPrefix + "mKeyguardChangeListeners=" + mKeyguardChangeListeners.size());
         pw.println(innerPrefix + "mUserChangeListeners=" + mUserChangeListeners.size());
+
+        if (!mExternalInterfaces.isEmpty()) {
+            pw.println(innerPrefix + "mExternalInterfaces={");
+            for (String key : mExternalInterfaces.keySet()) {
+                pw.println(innerPrefix + "\t" + key + ": " + mExternalInterfaces.get(key));
+            }
+            pw.println(innerPrefix + "}");
+        }
     }
 
     /**
@@ -211,7 +275,6 @@
      */
     @ExternalThread
     private class ShellInterfaceImpl implements ShellInterface {
-
         @Override
         public void onInit() {
             try {
@@ -222,28 +285,6 @@
         }
 
         @Override
-        public void dump(PrintWriter pw) {
-            try {
-                mMainExecutor.executeBlocking(() -> mShellCommandHandler.dump(pw));
-            } catch (InterruptedException e) {
-                throw new RuntimeException("Failed to dump the Shell in 2s", e);
-            }
-        }
-
-        @Override
-        public boolean handleCommand(String[] args, PrintWriter pw) {
-            try {
-                boolean[] result = new boolean[1];
-                mMainExecutor.executeBlocking(() -> {
-                    result[0] = mShellCommandHandler.handleCommand(args, pw);
-                });
-                return result[0];
-            } catch (InterruptedException e) {
-                throw new RuntimeException("Failed to handle Shell command in 2s", e);
-            }
-        }
-
-        @Override
         public void onConfigurationChanged(Configuration newConfiguration) {
             mMainExecutor.execute(() ->
                     ShellController.this.onConfigurationChanged(newConfiguration));
@@ -274,5 +315,38 @@
             mMainExecutor.execute(() ->
                     ShellController.this.onUserProfilesChanged(profiles));
         }
+
+        @Override
+        public boolean handleCommand(String[] args, PrintWriter pw) {
+            try {
+                boolean[] result = new boolean[1];
+                mMainExecutor.executeBlocking(() -> {
+                    result[0] = mShellCommandHandler.handleCommand(args, pw);
+                });
+                return result[0];
+            } catch (InterruptedException e) {
+                throw new RuntimeException("Failed to handle Shell command in 2s", e);
+            }
+        }
+
+        @Override
+        public void createExternalInterfaces(Bundle bundle) {
+            try {
+                mMainExecutor.executeBlocking(() -> {
+                    ShellController.this.createExternalInterfaces(bundle);
+                });
+            } catch (InterruptedException e) {
+                throw new RuntimeException("Failed to get Shell command in 2s", e);
+            }
+        }
+
+        @Override
+        public void dump(PrintWriter pw) {
+            try {
+                mMainExecutor.executeBlocking(() -> mShellCommandHandler.dump(pw));
+            } catch (InterruptedException e) {
+                throw new RuntimeException("Failed to dump the Shell in 2s", e);
+            }
+        }
     }
 }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/sysui/ShellInterface.java b/libs/WindowManager/Shell/src/com/android/wm/shell/sysui/ShellInterface.java
index 2108c82..bc5dd11 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/sysui/ShellInterface.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/sysui/ShellInterface.java
@@ -19,6 +19,7 @@
 import android.content.Context;
 import android.content.pm.UserInfo;
 import android.content.res.Configuration;
+import android.os.Bundle;
 
 import androidx.annotation.NonNull;
 
@@ -37,18 +38,6 @@
     default void onInit() {}
 
     /**
-     * Dumps the shell state.
-     */
-    default void dump(PrintWriter pw) {}
-
-    /**
-     * Handles a shell command.
-     */
-    default boolean handleCommand(final String[] args, PrintWriter pw) {
-        return false;
-    }
-
-    /**
      * Notifies the Shell that the configuration has changed.
      */
     default void onConfigurationChanged(Configuration newConfiguration) {}
@@ -74,4 +63,21 @@
      * Notifies the Shell when a profile belonging to the user changes.
      */
     default void onUserProfilesChanged(@NonNull List<UserInfo> profiles) {}
+
+    /**
+     * Handles a shell command.
+     */
+    default boolean handleCommand(final String[] args, PrintWriter pw) {
+        return false;
+    }
+
+    /**
+     * Updates the given {@param bundle} with the set of exposed interfaces.
+     */
+    default void createExternalInterfaces(Bundle bundle) {}
+
+    /**
+     * Dumps the shell state.
+     */
+    default void dump(PrintWriter pw) {}
 }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/sysui/ShellSharedConstants.java b/libs/WindowManager/Shell/src/com/android/wm/shell/sysui/ShellSharedConstants.java
new file mode 100644
index 0000000..bdda6a8
--- /dev/null
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/sysui/ShellSharedConstants.java
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.wm.shell.sysui;
+
+/**
+ * General shell-related constants that are shared with users of the library.
+ */
+public class ShellSharedConstants {
+    // See IPip.aidl
+    public static final String KEY_EXTRA_SHELL_PIP = "extra_shell_pip";
+    // See ISplitScreen.aidl
+    public static final String KEY_EXTRA_SHELL_SPLIT_SCREEN = "extra_shell_split_screen";
+    // See IOneHanded.aidl
+    public static final String KEY_EXTRA_SHELL_ONE_HANDED = "extra_shell_one_handed";
+    // See IShellTransitions.aidl
+    public static final String KEY_EXTRA_SHELL_SHELL_TRANSITIONS =
+            "extra_shell_shell_transitions";
+    // See IStartingWindow.aidl
+    public static final String KEY_EXTRA_SHELL_STARTING_WINDOW =
+            "extra_shell_starting_window";
+    // See IRecentTasks.aidl
+    public static final String KEY_EXTRA_SHELL_RECENT_TASKS = "extra_shell_recent_tasks";
+    // See IBackAnimation.aidl
+    public static final String KEY_EXTRA_SHELL_BACK_ANIMATION = "extra_shell_back_animation";
+    // See IFloatingTasks.aidl
+    public static final String KEY_EXTRA_SHELL_FLOATING_TASKS = "extra_shell_floating_tasks";
+    // See IDesktopMode.aidl
+    public static final String KEY_EXTRA_SHELL_DESKTOP_MODE = "extra_shell_desktop_mode";
+}
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/ShellTransitions.java b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/ShellTransitions.java
index b34049d..da39017 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/ShellTransitions.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/ShellTransitions.java
@@ -27,14 +27,6 @@
  */
 @ExternalThread
 public interface ShellTransitions {
-
-    /**
-     * Returns a binder that can be passed to an external process to manipulate remote transitions.
-     */
-    default IShellTransitions createExternalInterface() {
-        return null;
-    }
-
     /**
      * Registers a remote transition.
      */
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
index 29d25bc..e26f1be 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/transition/Transitions.java
@@ -29,6 +29,7 @@
 import static android.window.TransitionInfo.FLAG_STARTING_WINDOW_TRANSFER_RECIPIENT;
 
 import static com.android.wm.shell.common.ExecutorUtils.executeRemoteCallWithTaskPermission;
+import static com.android.wm.shell.sysui.ShellSharedConstants.KEY_EXTRA_SHELL_SHELL_TRANSITIONS;
 
 import android.annotation.NonNull;
 import android.annotation.Nullable;
@@ -61,11 +62,13 @@
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.protolog.common.ProtoLog;
 import com.android.wm.shell.common.DisplayController;
+import com.android.wm.shell.common.ExternalInterfaceBinder;
 import com.android.wm.shell.common.RemoteCallable;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.TransactionPool;
 import com.android.wm.shell.common.annotations.ExternalThread;
 import com.android.wm.shell.protolog.ShellProtoLogGroup;
+import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
 
 import java.util.ArrayList;
@@ -115,6 +118,7 @@
     private final DefaultTransitionHandler mDefaultTransitionHandler;
     private final RemoteTransitionHandler mRemoteTransitionHandler;
     private final DisplayController mDisplayController;
+    private final ShellController mShellController;
     private final ShellTransitionImpl mImpl = new ShellTransitionImpl();
 
     /** List of possible handlers. Ordered by specificity (eg. tapped back to front). */
@@ -142,6 +146,7 @@
 
     public Transitions(@NonNull Context context,
             @NonNull ShellInit shellInit,
+            @NonNull ShellController shellController,
             @NonNull WindowOrganizer organizer,
             @NonNull TransactionPool pool,
             @NonNull DisplayController displayController,
@@ -156,10 +161,14 @@
         mDefaultTransitionHandler = new DefaultTransitionHandler(context, shellInit,
                 displayController, pool, mainExecutor, mainHandler, animExecutor);
         mRemoteTransitionHandler = new RemoteTransitionHandler(mMainExecutor);
+        mShellController = shellController;
         shellInit.addInitCallback(this::onInit, this);
     }
 
     private void onInit() {
+        mShellController.addExternalInterface(KEY_EXTRA_SHELL_SHELL_TRANSITIONS,
+                this::createExternalInterface, this);
+
         // The very last handler (0 in the list) should be the default one.
         mHandlers.add(mDefaultTransitionHandler);
         ProtoLog.v(ShellProtoLogGroup.WM_SHELL_TRANSITIONS, "addHandler: Default");
@@ -193,6 +202,10 @@
         return mImpl;
     }
 
+    private ExternalInterfaceBinder createExternalInterface() {
+        return new IShellTransitionsImpl(this);
+    }
+
     @Override
     public Context getContext() {
         return mContext;
@@ -897,17 +910,6 @@
      */
     @ExternalThread
     private class ShellTransitionImpl implements ShellTransitions {
-        private IShellTransitionsImpl mIShellTransitions;
-
-        @Override
-        public IShellTransitions createExternalInterface() {
-            if (mIShellTransitions != null) {
-                mIShellTransitions.invalidate();
-            }
-            mIShellTransitions = new IShellTransitionsImpl(Transitions.this);
-            return mIShellTransitions;
-        }
-
         @Override
         public void registerRemote(@NonNull TransitionFilter filter,
                 @NonNull RemoteTransition remoteTransition) {
@@ -928,7 +930,8 @@
      * The interface for calls from outside the host process.
      */
     @BinderThread
-    private static class IShellTransitionsImpl extends IShellTransitions.Stub {
+    private static class IShellTransitionsImpl extends IShellTransitions.Stub
+            implements ExternalInterfaceBinder {
         private Transitions mTransitions;
 
         IShellTransitionsImpl(Transitions transitions) {
@@ -938,7 +941,8 @@
         /**
          * Invalidates this instance, preventing future calls from updating the controller.
          */
-        void invalidate() {
+        @Override
+        public void invalidate() {
             mTransitions = null;
         }
 
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java
index 90a3773..077e9ca 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java
@@ -63,7 +63,9 @@
 import com.android.internal.util.test.FakeSettingsProvider;
 import com.android.wm.shell.ShellTestCase;
 import com.android.wm.shell.TestShellExecutor;
+import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
+import com.android.wm.shell.sysui.ShellSharedConstants;
 
 import org.junit.Before;
 import org.junit.Ignore;
@@ -102,6 +104,9 @@
     @Mock
     private IBackNaviAnimationController mIBackNaviAnimationController;
 
+    @Mock
+    private ShellController mShellController;
+
     private BackAnimationController mController;
 
     private int mEventTime = 0;
@@ -118,7 +123,7 @@
                 ANIMATION_ENABLED);
         mTestableLooper = TestableLooper.get(this);
         mShellInit = spy(new ShellInit(mShellExecutor));
-        mController = new BackAnimationController(mShellInit,
+        mController = new BackAnimationController(mShellInit, mShellController,
                 mShellExecutor, new Handler(mTestableLooper.getLooper()), mTransaction,
                 mActivityTaskManager, mContext,
                 mContentResolver);
@@ -175,6 +180,12 @@
     }
 
     @Test
+    public void instantiateController_addExternalInterface() {
+        verify(mShellController, times(1)).addExternalInterface(
+                eq(ShellSharedConstants.KEY_EXTRA_SHELL_BACK_ANIMATION), any(), any());
+    }
+
+    @Test
     @Ignore("b/207481538")
     public void crossActivity_screenshotAttachedAndVisible() {
         SurfaceControl screenshotSurface = new SurfaceControl();
@@ -250,7 +261,7 @@
         // Toggle the setting off
         Settings.Global.putString(mContentResolver, Settings.Global.ENABLE_BACK_ANIMATION, "0");
         ShellInit shellInit = new ShellInit(mShellExecutor);
-        mController = new BackAnimationController(shellInit,
+        mController = new BackAnimationController(shellInit, mShellController,
                 mShellExecutor, new Handler(mTestableLooper.getLooper()), mTransaction,
                 mActivityTaskManager, mContext,
                 mContentResolver);
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/DesktopModeControllerTest.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/DesktopModeControllerTest.java
index dd23d97..c850a3b 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/DesktopModeControllerTest.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/desktopmode/DesktopModeControllerTest.java
@@ -52,6 +52,7 @@
 import com.android.wm.shell.TestRunningTaskInfoBuilder;
 import com.android.wm.shell.TestShellExecutor;
 import com.android.wm.shell.common.ShellExecutor;
+import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
 import com.android.wm.shell.transition.Transitions;
 
@@ -68,6 +69,8 @@
 public class DesktopModeControllerTest extends ShellTestCase {
 
     @Mock
+    private ShellController mShellController;
+    @Mock
     private ShellTaskOrganizer mShellTaskOrganizer;
     @Mock
     private RootTaskDisplayAreaOrganizer mRootTaskDisplayAreaOrganizer;
@@ -94,8 +97,8 @@
 
         mDesktopModeTaskRepository = new DesktopModeTaskRepository();
 
-        mController = new DesktopModeController(mContext, mShellInit, mShellTaskOrganizer,
-                mRootTaskDisplayAreaOrganizer, mMockTransitions,
+        mController = new DesktopModeController(mContext, mShellInit, mShellController,
+                mShellTaskOrganizer, mRootTaskDisplayAreaOrganizer, mMockTransitions,
                 mDesktopModeTaskRepository, mMockHandler, mExecutor);
 
         when(mShellTaskOrganizer.prepareClearFreeformForStandardTasks(anyInt())).thenReturn(
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/floating/FloatingTasksControllerTest.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/floating/FloatingTasksControllerTest.java
index a88c837..d378a17 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/floating/FloatingTasksControllerTest.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/floating/FloatingTasksControllerTest.java
@@ -52,6 +52,7 @@
 import com.android.wm.shell.sysui.ShellCommandHandler;
 import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
+import com.android.wm.shell.sysui.ShellSharedConstants;
 
 import org.junit.After;
 import org.junit.Before;
@@ -168,6 +169,18 @@
         }
     }
 
+    @Test
+    public void onInit_addExternalInterface() {
+        if (FLOATING_TASKS_ACTUALLY_ENABLED) {
+            createController();
+            setUpTabletConfig();
+            mController.onInit();
+
+            verify(mShellController, times(1)).addExternalInterface(
+                    ShellSharedConstants.KEY_EXTRA_SHELL_FLOATING_TASKS, any(), any());
+        }
+    }
+
     //
     // Tests for floating layer, which is only available for tablets.
     //
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/onehanded/OneHandedControllerTest.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/onehanded/OneHandedControllerTest.java
index cf8297e..8ad3d2a 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/onehanded/OneHandedControllerTest.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/onehanded/OneHandedControllerTest.java
@@ -51,6 +51,7 @@
 import com.android.wm.shell.sysui.ShellCommandHandler;
 import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
+import com.android.wm.shell.sysui.ShellSharedConstants;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -176,6 +177,12 @@
     }
 
     @Test
+    public void testControllerRegisteresExternalInterface() {
+        verify(mMockShellController, times(1)).addExternalInterface(
+                eq(ShellSharedConstants.KEY_EXTRA_SHELL_ONE_HANDED), any(), any());
+    }
+
+    @Test
     public void testDefaultShouldNotInOneHanded() {
         // Assert default transition state is STATE_NONE
         assertThat(mSpiedTransitionState.getState()).isEqualTo(STATE_NONE);
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/pip/phone/PipControllerTest.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/pip/phone/PipControllerTest.java
index 1e08f1e..d06fb55 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/pip/phone/PipControllerTest.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/pip/phone/PipControllerTest.java
@@ -20,6 +20,7 @@
 
 import static org.junit.Assert.assertNull;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
@@ -61,6 +62,7 @@
 import com.android.wm.shell.sysui.ShellCommandHandler;
 import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
+import com.android.wm.shell.sysui.ShellSharedConstants;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -152,6 +154,12 @@
     }
 
     @Test
+    public void instantiatePipController_registerExternalInterface() {
+        verify(mShellController, times(1)).addExternalInterface(
+                eq(ShellSharedConstants.KEY_EXTRA_SHELL_PIP), any(), any());
+    }
+
+    @Test
     public void instantiatePipController_registerUserChangeListener() {
         verify(mShellController, times(1)).addUserChangeListener(any());
     }
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/recents/RecentTasksControllerTest.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/recents/RecentTasksControllerTest.java
index b8aaaa7..f6ac3ee 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/recents/RecentTasksControllerTest.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/recents/RecentTasksControllerTest.java
@@ -28,6 +28,7 @@
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.ArgumentMatchers.isA;
 import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.mock;
@@ -57,7 +58,9 @@
 import com.android.wm.shell.desktopmode.DesktopModeStatus;
 import com.android.wm.shell.desktopmode.DesktopModeTaskRepository;
 import com.android.wm.shell.sysui.ShellCommandHandler;
+import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
+import com.android.wm.shell.sysui.ShellSharedConstants;
 import com.android.wm.shell.util.GroupedRecentTaskInfo;
 import com.android.wm.shell.util.SplitBounds;
 
@@ -84,6 +87,8 @@
     @Mock
     private TaskStackListenerImpl mTaskStackListener;
     @Mock
+    private ShellController mShellController;
+    @Mock
     private ShellCommandHandler mShellCommandHandler;
     @Mock
     private DesktopModeTaskRepository mDesktopModeTaskRepository;
@@ -101,7 +106,7 @@
         when(mContext.getPackageManager()).thenReturn(mock(PackageManager.class));
         mShellInit = spy(new ShellInit(mMainExecutor));
         mRecentTasksController = spy(new RecentTasksController(mContext, mShellInit,
-                mShellCommandHandler, mTaskStackListener, mActivityTaskManager,
+                mShellController, mShellCommandHandler, mTaskStackListener, mActivityTaskManager,
                 Optional.of(mDesktopModeTaskRepository), mMainExecutor));
         mShellTaskOrganizer = new ShellTaskOrganizer(mShellInit, mShellCommandHandler,
                 null /* sizeCompatUI */, Optional.empty(), Optional.of(mRecentTasksController),
@@ -121,6 +126,12 @@
     }
 
     @Test
+    public void instantiateController_addExternalInterface() {
+        verify(mShellController, times(1)).addExternalInterface(
+                eq(ShellSharedConstants.KEY_EXTRA_SHELL_RECENT_TASKS), any(), any());
+    }
+
+    @Test
     public void testAddRemoveSplitNotifyChange() {
         ActivityManager.RecentTaskInfo t1 = makeTaskInfo(1);
         ActivityManager.RecentTaskInfo t2 = makeTaskInfo(2);
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/splitscreen/SplitScreenControllerTests.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/splitscreen/SplitScreenControllerTests.java
index 5a68361..55883ab 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/splitscreen/SplitScreenControllerTests.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/splitscreen/SplitScreenControllerTests.java
@@ -58,6 +58,7 @@
 import com.android.wm.shell.sysui.ShellCommandHandler;
 import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
+import com.android.wm.shell.sysui.ShellSharedConstants;
 import com.android.wm.shell.transition.Transitions;
 
 import org.junit.Before;
@@ -133,6 +134,15 @@
     }
 
     @Test
+    public void instantiateController_addExternalInterface() {
+        doReturn(mMainExecutor).when(mTaskOrganizer).getExecutor();
+        when(mDisplayController.getDisplayLayout(anyInt())).thenReturn(new DisplayLayout());
+        mSplitScreenController.onInit();
+        verify(mShellController, times(1)).addExternalInterface(
+                eq(ShellSharedConstants.KEY_EXTRA_SHELL_SPLIT_SCREEN), any(), any());
+    }
+
+    @Test
     public void testShouldAddMultipleTaskFlag_notInSplitScreen() {
         doReturn(false).when(mSplitScreenController).isSplitScreenVisible();
         doReturn(true).when(mSplitScreenController).isValidToEnterSplitScreen(any());
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/startingsurface/StartingWindowControllerTests.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/startingsurface/StartingWindowControllerTests.java
index 35515e3..90165d1 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/startingsurface/StartingWindowControllerTests.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/startingsurface/StartingWindowControllerTests.java
@@ -21,6 +21,7 @@
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 
@@ -36,7 +37,9 @@
 import com.android.wm.shell.ShellTestCase;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.TransactionPool;
+import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
+import com.android.wm.shell.sysui.ShellSharedConstants;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -56,25 +59,34 @@
 
     private @Mock Context mContext;
     private @Mock DisplayManager mDisplayManager;
-    private @Mock ShellInit mShellInit;
+    private @Mock ShellController mShellController;
     private @Mock ShellTaskOrganizer mTaskOrganizer;
     private @Mock ShellExecutor mMainExecutor;
     private @Mock StartingWindowTypeAlgorithm mTypeAlgorithm;
     private @Mock IconProvider mIconProvider;
     private @Mock TransactionPool mTransactionPool;
     private StartingWindowController mController;
+    private ShellInit mShellInit;
 
     @Before
     public void setUp() {
         MockitoAnnotations.initMocks(this);
         doReturn(mock(Display.class)).when(mDisplayManager).getDisplay(anyInt());
         doReturn(mDisplayManager).when(mContext).getSystemService(eq(DisplayManager.class));
-        mController = new StartingWindowController(mContext, mShellInit, mTaskOrganizer,
-                mMainExecutor, mTypeAlgorithm, mIconProvider, mTransactionPool);
+        mShellInit = spy(new ShellInit(mMainExecutor));
+        mController = new StartingWindowController(mContext, mShellInit, mShellController,
+                mTaskOrganizer, mMainExecutor, mTypeAlgorithm, mIconProvider, mTransactionPool);
+        mShellInit.init();
     }
 
     @Test
-    public void instantiate_addInitCallback() {
+    public void instantiateController_addInitCallback() {
         verify(mShellInit, times(1)).addInitCallback(any(), any());
     }
+
+    @Test
+    public void instantiateController_addExternalInterface() {
+        verify(mShellController, times(1)).addExternalInterface(
+                eq(ShellSharedConstants.KEY_EXTRA_SHELL_STARTING_WINDOW), any(), any());
+    }
 }
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/sysui/ShellControllerTest.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/sysui/ShellControllerTest.java
index d6ddba9..fbc50c6 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/sysui/ShellControllerTest.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/sysui/ShellControllerTest.java
@@ -16,12 +16,16 @@
 
 package com.android.wm.shell.sysui;
 
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.mock;
 
 import android.content.Context;
 import android.content.pm.UserInfo;
 import android.content.res.Configuration;
+import android.os.Binder;
+import android.os.Bundle;
+import android.os.IBinder;
 import android.testing.AndroidTestingRunner;
 import android.testing.TestableLooper;
 
@@ -30,6 +34,7 @@
 import androidx.test.platform.app.InstrumentationRegistry;
 
 import com.android.wm.shell.ShellTestCase;
+import com.android.wm.shell.common.ExternalInterfaceBinder;
 import com.android.wm.shell.common.ShellExecutor;
 
 import org.junit.After;
@@ -49,6 +54,7 @@
 public class ShellControllerTest extends ShellTestCase {
 
     private static final int TEST_USER_ID = 100;
+    private static final String EXTRA_TEST_BINDER = "test_binder";
 
     @Mock
     private ShellInit mShellInit;
@@ -81,6 +87,47 @@
     }
 
     @Test
+    public void testAddExternalInterface_ensureCallback() {
+        Binder callback = new Binder();
+        ExternalInterfaceBinder wrapper = new ExternalInterfaceBinder() {
+            @Override
+            public void invalidate() {
+                // Do nothing
+            }
+
+            @Override
+            public IBinder asBinder() {
+                return callback;
+            }
+        };
+        mController.addExternalInterface(EXTRA_TEST_BINDER, () -> wrapper, this);
+
+        Bundle b = new Bundle();
+        mController.asShell().createExternalInterfaces(b);
+        assertTrue(b.getIBinder(EXTRA_TEST_BINDER) == callback);
+    }
+
+    @Test
+    public void testAddExternalInterface_disallowDuplicateKeys() {
+        Binder callback = new Binder();
+        ExternalInterfaceBinder wrapper = new ExternalInterfaceBinder() {
+            @Override
+            public void invalidate() {
+                // Do nothing
+            }
+
+            @Override
+            public IBinder asBinder() {
+                return callback;
+            }
+        };
+        mController.addExternalInterface(EXTRA_TEST_BINDER, () -> wrapper, this);
+        assertThrows(IllegalArgumentException.class, () -> {
+            mController.addExternalInterface(EXTRA_TEST_BINDER, () -> wrapper, this);
+        });
+    }
+
+    @Test
     public void testAddUserChangeListener_ensureCallback() {
         mController.addUserChangeListener(mUserChangeListener);
 
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/transition/ShellTransitionTests.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/transition/ShellTransitionTests.java
index c6492be..d888b79 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/transition/ShellTransitionTests.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/transition/ShellTransitionTests.java
@@ -86,7 +86,9 @@
 import com.android.wm.shell.common.DisplayLayout;
 import com.android.wm.shell.common.ShellExecutor;
 import com.android.wm.shell.common.TransactionPool;
+import com.android.wm.shell.sysui.ShellController;
 import com.android.wm.shell.sysui.ShellInit;
+import com.android.wm.shell.sysui.ShellSharedConstants;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -123,12 +125,25 @@
     @Test
     public void instantiate_addInitCallback() {
         ShellInit shellInit = mock(ShellInit.class);
-        final Transitions t = new Transitions(mContext, shellInit, mOrganizer, mTransactionPool,
-                createTestDisplayController(), mMainExecutor, mMainHandler, mAnimExecutor);
+        final Transitions t = new Transitions(mContext, shellInit, mock(ShellController.class),
+                mOrganizer, mTransactionPool, createTestDisplayController(), mMainExecutor,
+                mMainHandler, mAnimExecutor);
         verify(shellInit, times(1)).addInitCallback(any(), eq(t));
     }
 
     @Test
+    public void instantiateController_addExternalInterface() {
+        ShellInit shellInit = new ShellInit(mMainExecutor);
+        ShellController shellController = mock(ShellController.class);
+        final Transitions t = new Transitions(mContext, shellInit, shellController,
+                mOrganizer, mTransactionPool, createTestDisplayController(), mMainExecutor,
+                mMainHandler, mAnimExecutor);
+        shellInit.init();
+        verify(shellController, times(1)).addExternalInterface(
+                eq(ShellSharedConstants.KEY_EXTRA_SHELL_SHELL_TRANSITIONS), any(), any());
+    }
+
+    @Test
     public void testBasicTransitionFlow() {
         Transitions transitions = createTestTransitions();
         transitions.replaceDefaultHandlerForTest(mDefaultHandler);
@@ -1060,8 +1075,9 @@
 
     private Transitions createTestTransitions() {
         ShellInit shellInit = new ShellInit(mMainExecutor);
-        final Transitions t = new Transitions(mContext, shellInit, mOrganizer, mTransactionPool,
-                createTestDisplayController(), mMainExecutor, mMainHandler, mAnimExecutor);
+        final Transitions t = new Transitions(mContext, shellInit, mock(ShellController.class),
+                mOrganizer, mTransactionPool, createTestDisplayController(), mMainExecutor,
+                mMainHandler, mAnimExecutor);
         shellInit.init();
         return t;
     }