diff --git a/services/inputflinger/tests/InputReader_test.cpp b/services/inputflinger/tests/InputReader_test.cpp
index 9ccd965..8941d16 100644
--- a/services/inputflinger/tests/InputReader_test.cpp
+++ b/services/inputflinger/tests/InputReader_test.cpp
@@ -91,6 +91,9 @@
 static constexpr int32_t ACTION_POINTER_1_UP =
         AMOTION_EVENT_ACTION_POINTER_UP | (1 << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT);
 
+static constexpr uint32_t STYLUS_FUSION_SOURCE =
+        AINPUT_SOURCE_TOUCHSCREEN | AINPUT_SOURCE_BLUETOOTH_STYLUS;
+
 // Minimum timestamp separation between subsequent input events from a Bluetooth device.
 static constexpr nsecs_t MIN_BLUETOOTH_TIMESTAMP_DELTA = ms2ns(4);
 // Maximum smoothing time delta so that we don't generate events too far into the future.
@@ -2222,6 +2225,22 @@
 // ongoing stylus gesture that is being emitted by the touchscreen.
 using ExternalStylusIntegrationTest = BaseTouchIntegrationTest;
 
+TEST_F(ExternalStylusIntegrationTest, ExternalStylusConnectionChangesTouchscreenSource) {
+    // Create an external stylus capable of reporting pressure data that
+    // should be fused with a touch pointer.
+    std::unique_ptr<UinputExternalStylusWithPressure> stylus =
+            createUinputDevice<UinputExternalStylusWithPressure>();
+    ASSERT_NO_FATAL_FAILURE(mFakePolicy->assertInputDevicesChanged());
+    ASSERT_NO_FATAL_FAILURE(mTestListener->assertNotifyConfigurationChangedWasCalled());
+    const auto stylusInfo = findDeviceByName(stylus->getName());
+    ASSERT_TRUE(stylusInfo);
+
+    // Connecting an external stylus changes the source of the touchscreen.
+    const auto deviceInfo = findDeviceByName(mDevice->getName());
+    ASSERT_TRUE(deviceInfo);
+    ASSERT_TRUE(isFromSource(deviceInfo->getSources(), STYLUS_FUSION_SOURCE));
+}
+
 TEST_F(ExternalStylusIntegrationTest, DISABLED_FusedExternalStylusPressureReported) {
     const Point centerPoint = mDevice->getCenterPoint();
 
@@ -2251,17 +2270,17 @@
     mDevice->sendDown(centerPoint);
     mDevice->sendSync();
     ASSERT_NO_FATAL_FAILURE(mTestListener->assertNotifyMotionWasCalled(
-            AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN),
-                  WithToolType(ToolType::STYLUS), WithButtonState(0),
-                  WithDeviceId(touchscreenId), WithPressure(100.f / RAW_PRESSURE_MAX))));
+            AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN), WithToolType(ToolType::STYLUS),
+                  WithButtonState(0), WithSource(STYLUS_FUSION_SOURCE), WithDeviceId(touchscreenId),
+                  WithPressure(100.f / RAW_PRESSURE_MAX))));
 
     // Change the pressure on the external stylus, and ensure the touchscreen generates a MOVE
     // event with the updated pressure.
     stylus->setPressure(200);
     ASSERT_NO_FATAL_FAILURE(mTestListener->assertNotifyMotionWasCalled(
-            AllOf(WithMotionAction(AMOTION_EVENT_ACTION_MOVE),
-                  WithToolType(ToolType::STYLUS), WithButtonState(0),
-                  WithDeviceId(touchscreenId), WithPressure(200.f / RAW_PRESSURE_MAX))));
+            AllOf(WithMotionAction(AMOTION_EVENT_ACTION_MOVE), WithToolType(ToolType::STYLUS),
+                  WithButtonState(0), WithSource(STYLUS_FUSION_SOURCE), WithDeviceId(touchscreenId),
+                  WithPressure(200.f / RAW_PRESSURE_MAX))));
 
     // The external stylus did not generate any events.
     ASSERT_NO_FATAL_FAILURE(mTestListener->assertNotifyMotionWasNotCalled());
@@ -2306,8 +2325,8 @@
     // it shows up as a finger pointer.
     ASSERT_NO_FATAL_FAILURE(mTestListener->assertNotifyMotionWasCalled(
             AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN),
-                  WithToolType(ToolType::FINGER), WithDeviceId(touchscreenId),
-                  WithPressure(1.f))));
+                  WithSource(AINPUT_SOURCE_TOUCHSCREEN | AINPUT_SOURCE_STYLUS),
+                  WithToolType(ToolType::FINGER), WithDeviceId(touchscreenId), WithPressure(1.f))));
 
     // Change the pressure on the external stylus. Since the pressure was not present at the start
     // of the gesture, it is ignored for now.
@@ -2319,6 +2338,7 @@
     mDevice->sendSync();
     ASSERT_NO_FATAL_FAILURE(mTestListener->assertNotifyMotionWasCalled(
             AllOf(WithMotionAction(AMOTION_EVENT_ACTION_UP),
+                  WithSource(AINPUT_SOURCE_TOUCHSCREEN | AINPUT_SOURCE_STYLUS),
                   WithToolType(ToolType::FINGER))));
 
     // Start a new gesture. Since we have a valid pressure value, it shows up as a stylus.
@@ -2327,9 +2347,9 @@
     mDevice->sendDown(centerPoint);
     mDevice->sendSync();
     ASSERT_NO_FATAL_FAILURE(mTestListener->assertNotifyMotionWasCalled(
-            AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN),
-                  WithToolType(ToolType::STYLUS), WithButtonState(0),
-                  WithDeviceId(touchscreenId), WithPressure(200.f / RAW_PRESSURE_MAX))));
+            AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN), WithSource(STYLUS_FUSION_SOURCE),
+                  WithToolType(ToolType::STYLUS), WithButtonState(0), WithDeviceId(touchscreenId),
+                  WithPressure(200.f / RAW_PRESSURE_MAX))));
 
     // The external stylus did not generate any events.
     ASSERT_NO_FATAL_FAILURE(mTestListener->assertNotifyMotionWasNotCalled());
@@ -2361,14 +2381,15 @@
             std::chrono::milliseconds(ns2ms(EXTERNAL_STYLUS_DATA_TIMEOUT));
     mDevice->sendSync();
     ASSERT_NO_FATAL_FAILURE(
-            mTestListener
-                    ->assertNotifyMotionWasCalled(AllOf(WithMotionAction(AMOTION_EVENT_ACTION_DOWN),
-                                                        WithToolType(
-                                                                ToolType::FINGER),
-                                                        WithButtonState(0),
-                                                        WithDeviceId(touchscreenId),
-                                                        WithPressure(1.f)),
-                                                  waitUntil));
+            mTestListener->assertNotifyMotionWasCalled(AllOf(WithMotionAction(
+                                                                     AMOTION_EVENT_ACTION_DOWN),
+                                                             WithToolType(ToolType::FINGER),
+                                                             WithSource(AINPUT_SOURCE_TOUCHSCREEN |
+                                                                        AINPUT_SOURCE_STYLUS),
+                                                             WithButtonState(0),
+                                                             WithDeviceId(touchscreenId),
+                                                             WithPressure(1.f)),
+                                                       waitUntil));
 
     // The external stylus did not generate any events.
     ASSERT_NO_FATAL_FAILURE(mTestListener->assertNotifyMotionWasNotCalled());
@@ -7400,12 +7421,10 @@
 
 protected:
     StylusState mStylusState{};
-    static constexpr uint32_t EXPECTED_SOURCE =
-            AINPUT_SOURCE_TOUCHSCREEN | AINPUT_SOURCE_BLUETOOTH_STYLUS;
 
     void testStartFusedStylusGesture(SingleTouchInputMapper& mapper) {
         auto toolTypeSource =
-                AllOf(WithSource(EXPECTED_SOURCE), WithToolType(ToolType::STYLUS));
+                AllOf(WithSource(STYLUS_FUSION_SOURCE), WithToolType(ToolType::STYLUS));
 
         // The first pointer is withheld.
         processDown(mapper, 100, 200);
@@ -7439,7 +7458,7 @@
         processUp(mapper);
         processSync(mapper);
         ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasCalled(
-                AllOf(WithMotionAction(AMOTION_EVENT_ACTION_UP), WithSource(EXPECTED_SOURCE),
+                AllOf(WithMotionAction(AMOTION_EVENT_ACTION_UP), WithSource(STYLUS_FUSION_SOURCE),
                       WithToolType(ToolType::STYLUS))));
 
         mStylusState.pressure = 0.f;
@@ -7449,8 +7468,10 @@
     }
 
     void testUnsuccessfulFusionGesture(SingleTouchInputMapper& mapper) {
+        // When stylus fusion is not successful, events should be reported with the original source.
+        // In this case, it is from a touchscreen.
         auto toolTypeSource =
-                AllOf(WithSource(EXPECTED_SOURCE), WithToolType(ToolType::FINGER));
+                AllOf(WithSource(AINPUT_SOURCE_TOUCHSCREEN), WithToolType(ToolType::FINGER));
 
         // The first pointer is withheld when an external stylus is connected,
         // and a timeout is requested.
@@ -7490,7 +7511,7 @@
 
 TEST_F(ExternalStylusFusionTest, UsesBluetoothStylusSource) {
     SingleTouchInputMapper& mapper = initializeInputMapperWithExternalStylus();
-    ASSERT_EQ(EXPECTED_SOURCE, mapper.getSources());
+    ASSERT_EQ(STYLUS_FUSION_SOURCE, mapper.getSources());
 }
 
 TEST_F(ExternalStylusFusionTest, UnsuccessfulFusion) {
@@ -7507,8 +7528,7 @@
 // before the touch is reported by the touchscreen.
 TEST_F(ExternalStylusFusionTest, SuccessfulFusion_PressureFirst) {
     SingleTouchInputMapper& mapper = initializeInputMapperWithExternalStylus();
-    auto toolTypeSource =
-            AllOf(WithSource(EXPECTED_SOURCE), WithToolType(ToolType::STYLUS));
+    auto toolTypeSource = AllOf(WithSource(STYLUS_FUSION_SOURCE), WithToolType(ToolType::STYLUS));
 
     // The external stylus reports pressure first. It is ignored for now.
     mStylusState.pressure = 1.f;
@@ -7550,8 +7570,7 @@
 
 TEST_F(ExternalStylusFusionTest, FusedPointerReportsPressureChanges) {
     SingleTouchInputMapper& mapper = initializeInputMapperWithExternalStylus();
-    auto toolTypeSource =
-            AllOf(WithSource(EXPECTED_SOURCE), WithToolType(ToolType::STYLUS));
+    auto toolTypeSource = AllOf(WithSource(STYLUS_FUSION_SOURCE), WithToolType(ToolType::STYLUS));
 
     mStylusState.pressure = 0.8f;
     processExternalStylusState(mapper);
@@ -7612,7 +7631,7 @@
     processUp(mapper);
     processSync(mapper);
     ASSERT_NO_FATAL_FAILURE(mFakeListener->assertNotifyMotionWasCalled(
-            AllOf(WithMotionAction(AMOTION_EVENT_ACTION_UP), WithSource(EXPECTED_SOURCE),
+            AllOf(WithMotionAction(AMOTION_EVENT_ACTION_UP), WithSource(STYLUS_FUSION_SOURCE),
                   WithToolType(ToolType::STYLUS))));
 
     ASSERT_NO_FATAL_FAILURE(mReader->getContext()->assertTimeoutWasNotRequested());
@@ -7621,7 +7640,7 @@
 
 TEST_F(ExternalStylusFusionTest, FusedPointerReportsToolTypeChanges) {
     SingleTouchInputMapper& mapper = initializeInputMapperWithExternalStylus();
-    auto source = WithSource(EXPECTED_SOURCE);
+    auto source = WithSource(STYLUS_FUSION_SOURCE);
 
     mStylusState.pressure = 1.f;
     mStylusState.toolType = ToolType::ERASER;
@@ -7674,8 +7693,7 @@
 
 TEST_F(ExternalStylusFusionTest, FusedPointerReportsButtons) {
     SingleTouchInputMapper& mapper = initializeInputMapperWithExternalStylus();
-    auto toolTypeSource =
-            AllOf(WithSource(EXPECTED_SOURCE), WithToolType(ToolType::STYLUS));
+    auto toolTypeSource = AllOf(WithSource(STYLUS_FUSION_SOURCE), WithToolType(ToolType::STYLUS));
 
     ASSERT_NO_FATAL_FAILURE(testStartFusedStylusGesture(mapper));