diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/common/split/SplitLayout.java b/libs/WindowManager/Shell/src/com/android/wm/shell/common/split/SplitLayout.java
index d07fff3cce79b..3579bf4413900 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/common/split/SplitLayout.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/common/split/SplitLayout.java
@@ -321,6 +321,16 @@ public final class SplitLayout implements DisplayInsetsController.OnInsetsChange
         mSplitLayoutHandler.onLayoutSizeChanged(this);
     }
 
+    /** Sets divide position base on the ratio within root bounds. */
+    public void setDivideRatio(float ratio) {
+        final int position = isLandscape()
+                ? mRootBounds.left + (int) (mRootBounds.width() * ratio)
+                : mRootBounds.top + (int) (mRootBounds.height() * ratio);
+        DividerSnapAlgorithm.SnapTarget snapTarget =
+                mDividerSnapAlgorithm.calculateNonDismissingSnapTarget(position);
+        setDividePosition(snapTarget.position);
+    }
+
     /** Resets divider position. */
     public void resetDividerPosition() {
         mDividePosition = mDividerSnapAlgorithm.getMiddleTarget().position;
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/ISplitScreen.aidl b/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/ISplitScreen.aidl
index 3d3a63057ddea..4a990975be0d4 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/ISplitScreen.aidl
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/ISplitScreen.aidl
@@ -83,14 +83,15 @@ interface ISplitScreen {
      * Starts tasks simultaneously in one transition.
      */
     oneway void startTasks(int mainTaskId, in Bundle mainOptions, int sideTaskId,
-            in Bundle sideOptions, int sidePosition, in RemoteTransition remoteTransition) = 10;
+            in Bundle sideOptions, int sidePosition, float splitRatio,
+            in RemoteTransition remoteTransition) = 10;
 
     /**
      * Version of startTasks using legacy transition system.
      */
      oneway void startTasksWithLegacyTransition(int mainTaskId, in Bundle mainOptions,
                             int sideTaskId, in Bundle sideOptions, int sidePosition,
-                            in RemoteAnimationAdapter adapter) = 11;
+                            float splitRatio, in RemoteAnimationAdapter adapter) = 11;
 
     /**
      * Blocking call that notifies and gets additional split-screen targets when entering
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 6b42ed775fb79..c754cacfc841a 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
@@ -605,21 +605,21 @@ public class SplitScreenController implements DragAndDropPolicy.Starter,
         @Override
         public void startTasksWithLegacyTransition(int mainTaskId, @Nullable Bundle mainOptions,
                 int sideTaskId, @Nullable Bundle sideOptions, @SplitPosition int sidePosition,
-                RemoteAnimationAdapter adapter) {
+                float splitRatio, RemoteAnimationAdapter adapter) {
             executeRemoteCallWithTaskPermission(mController, "startTasks",
                     (controller) -> controller.mStageCoordinator.startTasksWithLegacyTransition(
                             mainTaskId, mainOptions, sideTaskId, sideOptions, sidePosition,
-                            adapter));
+                            splitRatio, adapter));
         }
 
         @Override
         public void startTasks(int mainTaskId, @Nullable Bundle mainOptions,
                 int sideTaskId, @Nullable Bundle sideOptions,
-                @SplitPosition int sidePosition,
+                @SplitPosition int sidePosition, float splitRatio,
                 @Nullable RemoteTransition remoteTransition) {
             executeRemoteCallWithTaskPermission(mController, "startTasks",
                     (controller) -> controller.mStageCoordinator.startTasks(mainTaskId, mainOptions,
-                            sideTaskId, sideOptions, sidePosition, remoteTransition));
+                            sideTaskId, sideOptions, sidePosition, splitRatio, remoteTransition));
         }
 
         @Override
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/StageCoordinator.java b/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/StageCoordinator.java
index a3726d46d2a4a..5863f7b95b437 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/StageCoordinator.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/splitscreen/StageCoordinator.java
@@ -322,7 +322,7 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
 
     /** Starts 2 tasks in one transition. */
     void startTasks(int mainTaskId, @Nullable Bundle mainOptions, int sideTaskId,
-            @Nullable Bundle sideOptions, @SplitPosition int sidePosition,
+            @Nullable Bundle sideOptions, @SplitPosition int sidePosition, float splitRatio,
             @Nullable RemoteTransition remoteTransition) {
         final WindowContainerTransaction wct = new WindowContainerTransaction();
         mainOptions = mainOptions != null ? mainOptions : new Bundle();
@@ -334,6 +334,7 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         mMainStage.activate(getMainStageBounds(), wct, false /* reparent */);
         mSideStage.setBounds(getSideStageBounds(), wct);
 
+        mSplitLayout.setDivideRatio(splitRatio);
         // Make sure the launch options will put tasks in the corresponding split roots
         addActivityOptions(mainOptions, mMainStage);
         addActivityOptions(sideOptions, mSideStage);
@@ -349,7 +350,7 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
     /** Starts 2 tasks in one legacy transition. */
     void startTasksWithLegacyTransition(int mainTaskId, @Nullable Bundle mainOptions,
             int sideTaskId, @Nullable Bundle sideOptions, @SplitPosition int sidePosition,
-            RemoteAnimationAdapter adapter) {
+            float splitRatio, RemoteAnimationAdapter adapter) {
         final WindowContainerTransaction wct = new WindowContainerTransaction();
         // Need to add another wrapper here in shell so that we can inject the divider bar
         // and also manage the process elevation via setRunningRemote
@@ -404,6 +405,7 @@ class StageCoordinator implements SplitLayout.SplitLayoutHandler,
         sideOptions = sideOptions != null ? sideOptions : new Bundle();
         setSideStagePosition(sidePosition, wct);
 
+        mSplitLayout.setDivideRatio(splitRatio);
         // Build a request WCT that will launch both apps such that task 0 is on the main stage
         // while task 1 is on the side stage.
         mMainStage.activate(getMainStageBounds(), wct, false /* reparent */);
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/common/split/SplitLayoutTests.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/common/split/SplitLayoutTests.java
index 73eebad040d8b..453050fcfab4f 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/common/split/SplitLayoutTests.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/common/split/SplitLayoutTests.java
@@ -105,6 +105,12 @@ public class SplitLayoutTests extends ShellTestCase {
         verify(mSplitLayoutHandler).onLayoutSizeChanged(any(SplitLayout.class));
     }
 
+    @Test
+    public void testSetDivideRatio() {
+        mSplitLayout.setDivideRatio(0.5f);
+        verify(mSplitLayoutHandler).onLayoutSizeChanged(any(SplitLayout.class));
+    }
+
     @Test
     public void testOnDoubleTappedDivider() {
         mSplitLayout.onDoubleTappedDivider();