diff --git a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
index a189c00..8566064 100644
--- a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
+++ b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
@@ -466,19 +466,18 @@
         return mFlinger->mTransactionHandler.mPendingTransactionCount.load();
     }
 
-    auto setTransactionState(const FrameTimelineInfo& frameTimelineInfo,
-                             Vector<ComposerState>& states, const Vector<DisplayState>& displays,
-                             uint32_t flags, const sp<IBinder>& applyToken,
-                             const InputWindowCommands& inputWindowCommands,
-                             int64_t desiredPresentTime, bool isAutoTimestamp,
-                             const std::vector<client_cache_t>& uncacheBuffers,
-                             bool hasListenerCallbacks,
-                             std::vector<ListenerCallbacks>& listenerCallbacks,
-                             uint64_t transactionId) {
+    auto setTransactionState(
+            const FrameTimelineInfo& frameTimelineInfo, Vector<ComposerState>& states,
+            const Vector<DisplayState>& displays, uint32_t flags, const sp<IBinder>& applyToken,
+            const InputWindowCommands& inputWindowCommands, int64_t desiredPresentTime,
+            bool isAutoTimestamp, const std::vector<client_cache_t>& uncacheBuffers,
+            bool hasListenerCallbacks, std::vector<ListenerCallbacks>& listenerCallbacks,
+            uint64_t transactionId, const std::vector<uint64_t>& mergedTransactionIds) {
         return mFlinger->setTransactionState(frameTimelineInfo, states, displays, flags, applyToken,
                                              inputWindowCommands, desiredPresentTime,
                                              isAutoTimestamp, uncacheBuffers, hasListenerCallbacks,
-                                             listenerCallbacks, transactionId);
+                                             listenerCallbacks, transactionId,
+                                             mergedTransactionIds);
     }
 
     auto setTransactionStateInternal(TransactionState& transaction) {
diff --git a/services/surfaceflinger/tests/unittests/TransactionApplicationTest.cpp b/services/surfaceflinger/tests/unittests/TransactionApplicationTest.cpp
index 6a641b3..afb8efb 100644
--- a/services/surfaceflinger/tests/unittests/TransactionApplicationTest.cpp
+++ b/services/surfaceflinger/tests/unittests/TransactionApplicationTest.cpp
@@ -73,6 +73,7 @@
         FrameTimelineInfo frameTimelineInfo;
         std::vector<client_cache_t> uncacheBuffers;
         uint64_t id = static_cast<uint64_t>(-1);
+        std::vector<uint64_t> mergedTransactionIds;
         static_assert(0xffffffffffffffff == static_cast<uint64_t>(-1));
     };
 
@@ -108,7 +109,7 @@
                                      transaction.applyToken, transaction.inputWindowCommands,
                                      transaction.desiredPresentTime, transaction.isAutoTimestamp,
                                      transaction.uncacheBuffers, mHasListenerCallbacks, mCallbacks,
-                                     transaction.id);
+                                     transaction.id, transaction.mergedTransactionIds);
 
         // If transaction is synchronous, SF applyTransactionState should time out (5s) wating for
         // SF to commit the transaction. If this is animation, it should not time out waiting.
@@ -135,7 +136,7 @@
                                      transaction.applyToken, transaction.inputWindowCommands,
                                      transaction.desiredPresentTime, transaction.isAutoTimestamp,
                                      transaction.uncacheBuffers, mHasListenerCallbacks, mCallbacks,
-                                     transaction.id);
+                                     transaction.id, transaction.mergedTransactionIds);
 
         nsecs_t returnedTime = systemTime();
         EXPECT_LE(returnedTime, applicationSentTime + TRANSACTION_TIMEOUT);
@@ -166,7 +167,7 @@
                                      transactionA.applyToken, transactionA.inputWindowCommands,
                                      transactionA.desiredPresentTime, transactionA.isAutoTimestamp,
                                      transactionA.uncacheBuffers, mHasListenerCallbacks, mCallbacks,
-                                     transactionA.id);
+                                     transactionA.id, transactionA.mergedTransactionIds);
 
         // This thread should not have been blocked by the above transaction
         // (5s is the timeout period that applyTransactionState waits for SF to
@@ -181,7 +182,7 @@
                                      transactionB.applyToken, transactionB.inputWindowCommands,
                                      transactionB.desiredPresentTime, transactionB.isAutoTimestamp,
                                      transactionB.uncacheBuffers, mHasListenerCallbacks, mCallbacks,
-                                     transactionB.id);
+                                     transactionB.id, transactionB.mergedTransactionIds);
 
         // this thread should have been blocked by the above transaction
         // if this is an animation, this thread should be blocked for 5s
@@ -218,7 +219,8 @@
                                  transactionA.displays, transactionA.flags, transactionA.applyToken,
                                  transactionA.inputWindowCommands, transactionA.desiredPresentTime,
                                  transactionA.isAutoTimestamp, transactionA.uncacheBuffers,
-                                 mHasListenerCallbacks, mCallbacks, transactionA.id);
+                                 mHasListenerCallbacks, mCallbacks, transactionA.id,
+                                 transactionA.mergedTransactionIds);
 
     auto& transactionQueue = mFlinger.getTransactionQueue();
     ASSERT_FALSE(transactionQueue.isEmpty());
@@ -238,7 +240,8 @@
                                  transactionA.displays, transactionA.flags, transactionA.applyToken,
                                  transactionA.inputWindowCommands, transactionA.desiredPresentTime,
                                  transactionA.isAutoTimestamp, transactionA.uncacheBuffers,
-                                 mHasListenerCallbacks, mCallbacks, transactionA.id);
+                                 mHasListenerCallbacks, mCallbacks, transactionA.id,
+                                 transactionA.mergedTransactionIds);
 
     auto& transactionQueue = mFlinger.getTransactionQueue();
     ASSERT_FALSE(transactionQueue.isEmpty());
@@ -251,7 +254,8 @@
     mFlinger.setTransactionState(empty.frameTimelineInfo, empty.states, empty.displays, empty.flags,
                                  empty.applyToken, empty.inputWindowCommands,
                                  empty.desiredPresentTime, empty.isAutoTimestamp,
-                                 empty.uncacheBuffers, mHasListenerCallbacks, mCallbacks, empty.id);
+                                 empty.uncacheBuffers, mHasListenerCallbacks, mCallbacks, empty.id,
+                                 empty.mergedTransactionIds);
 
     // flush transaction queue should flush as desiredPresentTime has
     // passed
@@ -388,7 +392,8 @@
                                               transaction.desiredPresentTime,
                                               transaction.isAutoTimestamp, {}, systemTime(),
                                               mHasListenerCallbacks, mCallbacks, getpid(),
-                                              static_cast<int>(getuid()), transaction.id);
+                                              static_cast<int>(getuid()), transaction.id,
+                                              transaction.mergedTransactionIds);
             mFlinger.setTransactionStateInternal(transactionState);
         }
         mFlinger.flushTransactionQueues();
@@ -1083,4 +1088,137 @@
     EXPECT_EQ(transactionsReadyToBeApplied.front().id, 42u);
 }
 
+TEST(TransactionHandlerTest, TransactionsKeepTrackOfDirectMerges) {
+    SurfaceComposerClient::Transaction transaction1, transaction2, transaction3, transaction4;
+
+    uint64_t transaction2Id = transaction2.getId();
+    uint64_t transaction3Id = transaction3.getId();
+    EXPECT_NE(transaction2Id, transaction3Id);
+
+    transaction1.merge(std::move(transaction2));
+    transaction1.merge(std::move(transaction3));
+
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 2u);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[0], transaction3Id);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[1], transaction2Id);
+}
+
+TEST(TransactionHandlerTest, TransactionsKeepTrackOfIndirectMerges) {
+    SurfaceComposerClient::Transaction transaction1, transaction2, transaction3, transaction4;
+
+    uint64_t transaction2Id = transaction2.getId();
+    uint64_t transaction3Id = transaction3.getId();
+    uint64_t transaction4Id = transaction4.getId();
+    EXPECT_NE(transaction2Id, transaction3Id);
+    EXPECT_NE(transaction2Id, transaction4Id);
+    EXPECT_NE(transaction3Id, transaction4Id);
+
+    transaction4.merge(std::move(transaction2));
+    transaction4.merge(std::move(transaction3));
+
+    EXPECT_EQ(transaction4.getMergedTransactionIds().size(), 2u);
+    EXPECT_EQ(transaction4.getMergedTransactionIds()[0], transaction3Id);
+    EXPECT_EQ(transaction4.getMergedTransactionIds()[1], transaction2Id);
+
+    transaction1.merge(std::move(transaction4));
+
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 3u);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[0], transaction4Id);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[1], transaction3Id);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[2], transaction2Id);
+}
+
+TEST(TransactionHandlerTest, TransactionMergesAreCleared) {
+    SurfaceComposerClient::Transaction transaction1, transaction2, transaction3;
+
+    transaction1.merge(std::move(transaction2));
+    transaction1.merge(std::move(transaction3));
+
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 2u);
+
+    transaction1.clear();
+
+    EXPECT_EQ(transaction1.getMergedTransactionIds().empty(), true);
+}
+
+TEST(TransactionHandlerTest, TransactionMergesAreCapped) {
+    SurfaceComposerClient::Transaction transaction;
+    std::vector<uint64_t> mergedTransactionIds;
+
+    for (uint i = 0; i < 20u; i++) {
+        SurfaceComposerClient::Transaction transactionToMerge;
+        mergedTransactionIds.push_back(transactionToMerge.getId());
+        transaction.merge(std::move(transactionToMerge));
+    }
+
+    // Keeps latest 10 merges in order of merge recency
+    EXPECT_EQ(transaction.getMergedTransactionIds().size(), 10u);
+    for (uint i = 0; i < 10u; i++) {
+        EXPECT_EQ(transaction.getMergedTransactionIds()[i],
+                  mergedTransactionIds[mergedTransactionIds.size() - 1 - i]);
+    }
+}
+
+TEST(TransactionHandlerTest, KeepsMergesFromMoreRecentMerge) {
+    SurfaceComposerClient::Transaction transaction1, transaction2, transaction3;
+    std::vector<uint64_t> mergedTransactionIds1, mergedTransactionIds2, mergedTransactionIds3;
+    uint64_t transaction2Id = transaction2.getId();
+    uint64_t transaction3Id = transaction3.getId();
+
+    for (uint i = 0; i < 20u; i++) {
+        SurfaceComposerClient::Transaction transactionToMerge;
+        mergedTransactionIds1.push_back(transactionToMerge.getId());
+        transaction1.merge(std::move(transactionToMerge));
+    }
+
+    for (uint i = 0; i < 5u; i++) {
+        SurfaceComposerClient::Transaction transactionToMerge;
+        mergedTransactionIds2.push_back(transactionToMerge.getId());
+        transaction2.merge(std::move(transactionToMerge));
+    }
+
+    transaction1.merge(std::move(transaction2));
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 10u);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[0], transaction2Id);
+    for (uint i = 0; i < 5u; i++) {
+        EXPECT_EQ(transaction1.getMergedTransactionIds()[i + 1u],
+                  mergedTransactionIds2[mergedTransactionIds2.size() - 1 - i]);
+    }
+    for (uint i = 0; i < 4u; i++) {
+        EXPECT_EQ(transaction1.getMergedTransactionIds()[i + 6u],
+                  mergedTransactionIds1[mergedTransactionIds1.size() - 1 - i]);
+    }
+
+    for (uint i = 0; i < 20u; i++) {
+        SurfaceComposerClient::Transaction transactionToMerge;
+        mergedTransactionIds3.push_back(transactionToMerge.getId());
+        transaction3.merge(std::move(transactionToMerge));
+    }
+
+    transaction1.merge(std::move(transaction3));
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 10u);
+    EXPECT_EQ(transaction1.getMergedTransactionIds()[0], transaction3Id);
+    for (uint i = 0; i < 9u; i++) {
+        EXPECT_EQ(transaction1.getMergedTransactionIds()[i + 1],
+                  mergedTransactionIds3[mergedTransactionIds3.size() - 1 - i]);
+    }
+}
+
+TEST(TransactionHandlerTest, CanAddTransactionWithFullMergedIds) {
+    SurfaceComposerClient::Transaction transaction1, transaction2;
+    for (uint i = 0; i < 20u; i++) {
+        SurfaceComposerClient::Transaction transactionToMerge;
+        transaction1.merge(std::move(transactionToMerge));
+    }
+
+    EXPECT_EQ(transaction1.getMergedTransactionIds().size(), 10u);
+
+    auto transaction1Id = transaction1.getId();
+    transaction2.merge(std::move(transaction1));
+    EXPECT_EQ(transaction2.getMergedTransactionIds().size(), 10u);
+    auto mergedTransactionIds = transaction2.getMergedTransactionIds();
+    EXPECT_TRUE(std::count(mergedTransactionIds.begin(), mergedTransactionIds.end(),
+                           transaction1Id) > 0);
+}
+
 } // namespace android
diff --git a/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp b/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
index 82aac7e..92411a7 100644
--- a/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
+++ b/services/surfaceflinger/tests/unittests/TransactionTracingTest.cpp
@@ -67,8 +67,14 @@
         ASSERT_EQ(actualProto.transactions().size(),
                   static_cast<int32_t>(expectedTransactions.size()));
         for (uint32_t i = 0; i < expectedTransactions.size(); i++) {
-            EXPECT_EQ(actualProto.transactions(static_cast<int32_t>(i)).pid(),
-                      expectedTransactions[i].originPid);
+            const auto expectedTransaction = expectedTransactions[i];
+            const auto protoTransaction = actualProto.transactions(static_cast<int32_t>(i));
+            EXPECT_EQ(protoTransaction.transaction_id(), expectedTransaction.id);
+            EXPECT_EQ(protoTransaction.pid(), expectedTransaction.originPid);
+            for (uint32_t i = 0; i < expectedTransaction.mergedTransactionIds.size(); i++) {
+                EXPECT_EQ(protoTransaction.merged_transaction_ids(static_cast<int32_t>(i)),
+                          expectedTransaction.mergedTransactionIds[i]);
+            }
         }
     }
 
@@ -92,6 +98,7 @@
         TransactionState transaction;
         transaction.id = i;
         transaction.originPid = static_cast<int32_t>(i);
+        transaction.mergedTransactionIds = std::vector<uint64_t>{i + 100, i + 102};
         transactions.emplace_back(transaction);
         mTracing.addQueuedTransaction(transaction);
     }