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 b2f61c2319117..5275e90b931f7 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
@@ -829,7 +829,15 @@ public class Transitions implements RemoteCallable<Transitions> {
         }
         mOrganizer.startTransition(transitionToken, wct != null && wct.isEmpty() ? null : wct);
         active.mToken = transitionToken;
-        mActiveTransitions.add(active);
+        int insertIdx = 0;
+        for (; insertIdx < mActiveTransitions.size(); ++insertIdx) {
+            if (mActiveTransitions.get(insertIdx).mInfo == null) {
+                // A `startNewTransition` was sent to WMCore, but wasn't acknowledged before WMCore
+                // made this request, so insert this request beforehand to keep order in sync.
+                break;
+            }
+        }
+        mActiveTransitions.add(insertIdx, active);
     }
 
     /** Start a new transition directly. */
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 595c3b4880df5..a9061aeb03147 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
@@ -45,6 +45,7 @@ import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyBoolean;
+import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.ArgumentMatchers.isNull;
 import static org.mockito.Mockito.clearInvocations;
@@ -119,8 +120,8 @@ public class ShellTransitionTests extends ShellTestCase {
 
     @Before
     public void setUp() {
-        doAnswer(invocation -> invocation.getArguments()[1])
-                .when(mOrganizer).startTransition(any(), any());
+        doAnswer(invocation -> new Binder())
+                .when(mOrganizer).startNewTransition(anyInt(), any());
     }
 
     @Test
@@ -561,6 +562,32 @@ public class ShellTransitionTests extends ShellTestCase {
         assertEquals(0, mDefaultHandler.activeCount());
     }
 
+    @Test
+    public void testTransitionOrderMatchesCore() {
+        Transitions transitions = createTestTransitions();
+        transitions.replaceDefaultHandlerForTest(mDefaultHandler);
+
+        IBinder transitToken = new Binder();
+        IBinder shellInit = transitions.startTransition(TRANSIT_CLOSE,
+                new WindowContainerTransaction(), null /* handler */);
+        // make sure we are testing the "New" API.
+        verify(mOrganizer, times(1)).startNewTransition(eq(TRANSIT_CLOSE), any());
+        // WMCore may not receive the new transition before requesting its own.
+        transitions.requestStartTransition(transitToken,
+                new TransitionRequestInfo(TRANSIT_OPEN, null /* trigger */, null /* remote */));
+        verify(mOrganizer, times(1)).startTransition(eq(transitToken), any());
+
+        // At this point, WM is working on its transition (the shell-initialized one is still
+        // queued), so continue the transition lifecycle for that.
+        TransitionInfo info = new TransitionInfoBuilder(TRANSIT_OPEN)
+                .addChange(TRANSIT_OPEN).addChange(TRANSIT_CLOSE).build();
+        transitions.onTransitionReady(transitToken, info, mock(SurfaceControl.Transaction.class),
+                mock(SurfaceControl.Transaction.class));
+        // At this point, if things are not working, we'd get an NPE due to attempting to merge
+        // into the shellInit transition which hasn't started yet.
+        assertEquals(1, mDefaultHandler.activeCount());
+    }
+
     @Test
     public void testShouldRotateSeamlessly() throws Exception {
         final RunningTaskInfo taskInfo =