diff --git a/services/core/java/com/android/server/wm/LetterboxUiController.java b/services/core/java/com/android/server/wm/LetterboxUiController.java
index 224be157..a961e9a 100644
--- a/services/core/java/com/android/server/wm/LetterboxUiController.java
+++ b/services/core/java/com/android/server/wm/LetterboxUiController.java
@@ -885,13 +885,11 @@
     // Note that we check the task rather than the parent as with ActivityEmbedding the parent might
     // be a TaskFragment, and its windowing mode is always MULTI_WINDOW, even if the task is
     // actually fullscreen.
-    private boolean isDisplayFullScreenAndInPosture(DeviceStateController.DeviceState state,
-            boolean isTabletop) {
+    private boolean isDisplayFullScreenAndInPosture(boolean isTabletop) {
         Task task = mActivityRecord.getTask();
-        return mActivityRecord.mDisplayContent != null
-                && mActivityRecord.mDisplayContent.getDisplayRotation().isDeviceInPosture(state,
-                    isTabletop)
-                && task != null
+        return mActivityRecord.mDisplayContent != null && task != null
+                && mActivityRecord.mDisplayContent.getDisplayRotation().isDeviceInPosture(
+                        DeviceStateController.DeviceState.HALF_FOLDED, isTabletop)
                 && task.getWindowingMode() == WINDOWING_MODE_FULLSCREEN;
     }
 
@@ -919,16 +917,14 @@
     }
 
     private boolean isFullScreenAndBookModeEnabled() {
-        return isDisplayFullScreenAndInPosture(
-                DeviceStateController.DeviceState.HALF_FOLDED, false /* isTabletop */)
+        return isDisplayFullScreenAndInPosture(/* isTabletop */ false)
                 && mLetterboxConfiguration.getIsAutomaticReachabilityInBookModeEnabled();
     }
 
     float getVerticalPositionMultiplier(Configuration parentConfiguration) {
         // Don't check resolved configuration because it may not be updated yet during
         // configuration change.
-        boolean tabletopMode = isDisplayFullScreenAndInPosture(
-                DeviceStateController.DeviceState.HALF_FOLDED, true /* isTabletop */);
+        boolean tabletopMode = isDisplayFullScreenAndInPosture(/* isTabletop */ true);
         return isVerticalReachabilityEnabled(parentConfiguration)
                 // Using the last global dynamic position to avoid "jumps" when moving
                 // between apps or activities.
@@ -961,16 +957,15 @@
     }
 
     private boolean shouldUseSplitScreenAspectRatio(@NonNull Configuration parentConfiguration) {
-        final boolean isBookMode = isDisplayFullScreenAndInPosture(
-                DeviceStateController.DeviceState.HALF_FOLDED,
-                /* isTabletop */ false);
+        final boolean isBookMode = isDisplayFullScreenAndInPosture(/* isTabletop */ false);
         final boolean isNotCenteredHorizontally = getHorizontalPositionMultiplier(
                 parentConfiguration) != LETTERBOX_POSITION_MULTIPLIER_CENTER;
-        final boolean isTabletopMode = isDisplayFullScreenAndInPosture(
-                DeviceStateController.DeviceState.HALF_FOLDED,
-                /* isTabletop */ true);
+        final boolean isTabletopMode = isDisplayFullScreenAndInPosture(/* isTabletop */ true);
+        final boolean isLandscape = isFixedOrientationLandscape(
+                mActivityRecord.getOverrideOrientation());
+
         // Don't resize to split screen size when in book mode if letterbox position is centered
-        return ((isBookMode && isNotCenteredHorizontally) || isTabletopMode)
+        return (isBookMode && isNotCenteredHorizontally || isTabletopMode && isLandscape)
                     || isCameraCompatSplitScreenAspectRatioAllowed()
                         && isCameraCompatTreatmentActive();
     }
@@ -1632,17 +1627,13 @@
         if (isHorizontalReachabilityEnabled()) {
             int letterboxPositionForHorizontalReachability = getLetterboxConfiguration()
                     .getLetterboxPositionForHorizontalReachability(
-                            isDisplayFullScreenAndInPosture(
-                                    DeviceStateController.DeviceState.HALF_FOLDED,
-                                    false /* isTabletop */));
+                            isDisplayFullScreenAndInPosture(/* isTabletop */ false));
             positionToLog = letterboxHorizontalReachabilityPositionToLetterboxPosition(
                     letterboxPositionForHorizontalReachability);
         } else if (isVerticalReachabilityEnabled()) {
             int letterboxPositionForVerticalReachability = getLetterboxConfiguration()
                     .getLetterboxPositionForVerticalReachability(
-                            isDisplayFullScreenAndInPosture(
-                                    DeviceStateController.DeviceState.HALF_FOLDED,
-                                    true /* isTabletop */));
+                            isDisplayFullScreenAndInPosture(/* isTabletop */ true));
             positionToLog = letterboxVerticalReachabilityPositionToLetterboxPosition(
                     letterboxPositionForVerticalReachability);
         }
diff --git a/services/tests/wmtests/src/com/android/server/wm/SizeCompatTests.java b/services/tests/wmtests/src/com/android/server/wm/SizeCompatTests.java
index 8641267..21c16eb 100644
--- a/services/tests/wmtests/src/com/android/server/wm/SizeCompatTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/SizeCompatTests.java
@@ -4425,6 +4425,21 @@
     }
 
     @Test
+    public void testPortraitAppInTabletop_notSplitScreen() {
+        final int dw = 2400;
+        setUpDisplaySizeWithApp(dw, 2000);
+        prepareUnresizable(mActivity, SCREEN_ORIENTATION_PORTRAIT);
+
+        final int initialWidth = mActivity.getBounds().width();
+
+        setFoldablePosture(true /* isHalfFolded */, true /* isTabletop */);
+
+        final int finalWidth = mActivity.getBounds().width();
+        assertEquals(initialWidth, finalWidth);
+        assertNotEquals(finalWidth, getExpectedSplitSize(dw));
+    }
+
+    @Test
     public void testUpdateResolvedBoundsHorizontalPosition_bookModeEnabled() {
         // Set up a display in landscape with a fixed-orientation PORTRAIT app
         setUpDisplaySizeWithApp(2800, 1400);