diff --git a/libs/gui/TransactionState.cpp b/libs/gui/TransactionState.cpp
new file mode 100644
index 0000000..9e09bc2
--- /dev/null
+++ b/libs/gui/TransactionState.cpp
@@ -0,0 +1,263 @@
+/*
+ * Copyright (C) 2025 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "TransactionState"
+#include <gui/LayerState.h>
+#include <gui/SurfaceComposerClient.h>
+#include <gui/TransactionState.h>
+#include <private/gui/ParcelUtils.h>
+#include <algorithm>
+
+namespace android {
+
+status_t TransactionState::writeToParcel(Parcel* parcel) const {
+    SAFE_PARCEL(parcel->writeUint64, mId);
+    SAFE_PARCEL(parcel->writeUint32, mFlags);
+    SAFE_PARCEL(parcel->writeInt64, mDesiredPresentTime);
+    SAFE_PARCEL(parcel->writeBool, mIsAutoTimestamp);
+    SAFE_PARCEL(parcel->writeParcelable, mFrameTimelineInfo);
+    SAFE_PARCEL(parcel->writeStrongBinder, mApplyToken);
+    SAFE_PARCEL(parcel->writeBool, mMayContainBuffer);
+    SAFE_PARCEL(parcel->writeBool, mLogCallPoints);
+
+    SAFE_PARCEL(parcel->writeUint32, static_cast<uint32_t>(mDisplayStates.size()));
+    for (auto const& displayState : mDisplayStates) {
+        displayState.write(*parcel);
+    }
+    SAFE_PARCEL(parcel->writeUint32, static_cast<uint32_t>(mComposerStates.size()));
+    for (auto const& composerState : mComposerStates) {
+        composerState.write(*parcel);
+    }
+
+    mInputWindowCommands.write(*parcel);
+    SAFE_PARCEL(parcel->writeUint32, static_cast<uint32_t>(mUncacheBuffers.size()));
+    for (const client_cache_t& uncacheBuffer : mUncacheBuffers) {
+        SAFE_PARCEL(parcel->writeStrongBinder, uncacheBuffer.token.promote());
+        SAFE_PARCEL(parcel->writeUint64, uncacheBuffer.id);
+    }
+
+    SAFE_PARCEL(parcel->writeUint32, static_cast<uint32_t>(mMergedTransactionIds.size()));
+    for (auto mergedTransactionId : mMergedTransactionIds) {
+        SAFE_PARCEL(parcel->writeUint64, mergedTransactionId);
+    }
+
+    SAFE_PARCEL(parcel->writeBool, mHasListenerCallbacks);
+    SAFE_PARCEL(parcel->writeUint32, static_cast<uint32_t>(mListenerCallbacks.size()));
+    for (const auto& [listener, callbackIds] : mListenerCallbacks) {
+        SAFE_PARCEL(parcel->writeStrongBinder, listener);
+        SAFE_PARCEL(parcel->writeParcelableVector, callbackIds);
+    }
+
+    return NO_ERROR;
+}
+
+status_t TransactionState::readFromParcel(const Parcel* parcel) {
+    SAFE_PARCEL(parcel->readUint64, &mId);
+    SAFE_PARCEL(parcel->readUint32, &mFlags);
+    SAFE_PARCEL(parcel->readInt64, &mDesiredPresentTime);
+    SAFE_PARCEL(parcel->readBool, &mIsAutoTimestamp);
+    SAFE_PARCEL(parcel->readParcelable, &mFrameTimelineInfo);
+    SAFE_PARCEL(parcel->readNullableStrongBinder, &mApplyToken);
+    SAFE_PARCEL(parcel->readBool, &mMayContainBuffer);
+    SAFE_PARCEL(parcel->readBool, &mLogCallPoints);
+
+    uint32_t count;
+    SAFE_PARCEL_READ_SIZE(parcel->readUint32, &count, parcel->dataSize())
+    mDisplayStates.clear();
+    mDisplayStates.reserve(count);
+    for (size_t i = 0; i < count; i++) {
+        DisplayState displayState;
+        if (displayState.read(*parcel) == BAD_VALUE) {
+            return BAD_VALUE;
+        }
+        mDisplayStates.emplace_back(std::move(displayState));
+    }
+
+    SAFE_PARCEL_READ_SIZE(parcel->readUint32, &count, parcel->dataSize())
+    mComposerStates.clear();
+    mComposerStates.reserve(count);
+    for (size_t i = 0; i < count; i++) {
+        ComposerState composerState;
+        if (composerState.read(*parcel) == BAD_VALUE) {
+            return BAD_VALUE;
+        }
+        mComposerStates.emplace_back(std::move(composerState));
+    }
+
+    if (status_t status = mInputWindowCommands.read(*parcel) != NO_ERROR) {
+        return status;
+    }
+
+    SAFE_PARCEL_READ_SIZE(parcel->readUint32, &count, parcel->dataSize())
+    mUncacheBuffers.clear();
+    mUncacheBuffers.reserve(count);
+    for (size_t i = 0; i < count; i++) {
+        client_cache_t client_cache;
+        sp<IBinder> tmpBinder;
+        SAFE_PARCEL(parcel->readStrongBinder, &tmpBinder);
+        client_cache.token = tmpBinder;
+        SAFE_PARCEL(parcel->readUint64, &client_cache.id);
+        mUncacheBuffers.emplace_back(std::move(client_cache));
+    }
+
+    SAFE_PARCEL_READ_SIZE(parcel->readUint32, &count, parcel->dataSize())
+    mMergedTransactionIds.clear();
+    mMergedTransactionIds.resize(count);
+    for (size_t i = 0; i < count; i++) {
+        SAFE_PARCEL(parcel->readUint64, &mMergedTransactionIds[i]);
+    }
+
+    SAFE_PARCEL(parcel->readBool, &mHasListenerCallbacks);
+    SAFE_PARCEL_READ_SIZE(parcel->readUint32, &count, parcel->dataSize());
+    mListenerCallbacks.clear();
+    mListenerCallbacks.reserve(count);
+    for (uint32_t i = 0; i < count; i++) {
+        sp<IBinder> tmpBinder;
+        SAFE_PARCEL(parcel->readStrongBinder, &tmpBinder);
+        std::vector<CallbackId> callbackIds;
+        SAFE_PARCEL(parcel->readParcelableVector, &callbackIds);
+        mListenerCallbacks.emplace_back(tmpBinder, callbackIds);
+    }
+
+    return NO_ERROR;
+}
+
+void TransactionState::merge(TransactionState&& other,
+                             const std::function<void(layer_state_t&)>& onBufferOverwrite) {
+    while (mMergedTransactionIds.size() + other.mMergedTransactionIds.size() >
+                   MAX_MERGE_HISTORY_LENGTH - 1 &&
+           mMergedTransactionIds.size() > 0) {
+        mMergedTransactionIds.pop_back();
+    }
+    if (other.mMergedTransactionIds.size() == MAX_MERGE_HISTORY_LENGTH) {
+        mMergedTransactionIds.insert(mMergedTransactionIds.begin(),
+                                     other.mMergedTransactionIds.begin(),
+                                     other.mMergedTransactionIds.end() - 1);
+    } else if (other.mMergedTransactionIds.size() > 0u) {
+        mMergedTransactionIds.insert(mMergedTransactionIds.begin(),
+                                     other.mMergedTransactionIds.begin(),
+                                     other.mMergedTransactionIds.end());
+    }
+    mMergedTransactionIds.insert(mMergedTransactionIds.begin(), other.mId);
+
+    for (auto const& otherState : other.mComposerStates) {
+        if (auto it = std::find_if(mComposerStates.begin(), mComposerStates.end(),
+                                   [&otherState](const auto& composerState) {
+                                       return composerState.state.surface ==
+                                               otherState.state.surface;
+                                   });
+            it != mComposerStates.end()) {
+            if (otherState.state.what & layer_state_t::eBufferChanged) {
+                onBufferOverwrite(it->state);
+            }
+            it->state.merge(otherState.state);
+        } else {
+            mComposerStates.push_back(otherState);
+        }
+    }
+
+    for (auto const& state : other.mDisplayStates) {
+        if (auto it = std::find_if(mDisplayStates.begin(), mDisplayStates.end(),
+                                   [&state](const auto& displayState) {
+                                       return displayState.token == state.token;
+                                   });
+            it != mDisplayStates.end()) {
+            it->merge(state);
+        } else {
+            mDisplayStates.push_back(state);
+        }
+    }
+
+    for (const auto& cacheId : other.mUncacheBuffers) {
+        mUncacheBuffers.push_back(cacheId);
+    }
+
+    mInputWindowCommands.merge(other.mInputWindowCommands);
+    // TODO(b/385156191) Consider merging desired present time.
+    mFlags |= other.mFlags;
+    mMayContainBuffer |= other.mMayContainBuffer;
+    mLogCallPoints |= other.mLogCallPoints;
+
+    // mApplyToken is explicitly not merged. Token should be set before applying the transactions to
+    // make synchronization decisions a bit simpler.
+    mergeFrameTimelineInfo(other.mFrameTimelineInfo);
+    other.clear();
+}
+
+// copied from FrameTimelineInfo::merge()
+void TransactionState::mergeFrameTimelineInfo(const FrameTimelineInfo& other) {
+    // When merging vsync Ids we take the oldest valid one
+    if (mFrameTimelineInfo.vsyncId != FrameTimelineInfo::INVALID_VSYNC_ID &&
+        other.vsyncId != FrameTimelineInfo::INVALID_VSYNC_ID) {
+        if (other.vsyncId > mFrameTimelineInfo.vsyncId) {
+            mFrameTimelineInfo = other;
+        }
+    } else if (mFrameTimelineInfo.vsyncId == FrameTimelineInfo::INVALID_VSYNC_ID) {
+        mFrameTimelineInfo = other;
+    }
+}
+
+void TransactionState::clear() {
+    mComposerStates.clear();
+    mDisplayStates.clear();
+    mListenerCallbacks.clear();
+    mHasListenerCallbacks = false;
+    mInputWindowCommands.clear();
+    mUncacheBuffers.clear();
+    mDesiredPresentTime = 0;
+    mIsAutoTimestamp = true;
+    mApplyToken = nullptr;
+    mFrameTimelineInfo = {};
+    mMergedTransactionIds.clear();
+    mFlags = 0;
+    mMayContainBuffer = false;
+    mLogCallPoints = false;
+}
+
+layer_state_t* TransactionState::getLayerState(const sp<SurfaceControl>& sc) {
+    auto handle = sc->getLayerStateHandle();
+    if (auto it = std::find_if(mComposerStates.begin(), mComposerStates.end(),
+                               [&handle](const auto& composerState) {
+                                   return composerState.state.surface == handle;
+                               });
+        it != mComposerStates.end()) {
+        return &it->state;
+    }
+
+    // we don't have it, add an initialized layer_state to our list
+    ComposerState s;
+    s.state.surface = handle;
+    s.state.layerId = sc->getLayerId();
+    mComposerStates.push_back(s);
+
+    return &mComposerStates.back().state;
+}
+
+DisplayState& TransactionState::getDisplayState(const sp<IBinder>& token) {
+    if (auto it = std::find_if(mDisplayStates.begin(), mDisplayStates.end(),
+                               [token](const auto& display) { return display.token == token; });
+        it != mDisplayStates.end()) {
+        return *it;
+    }
+
+    // If display state doesn't exist, add a new one.
+    DisplayState s;
+    s.token = token;
+    mDisplayStates.push_back(s);
+    return mDisplayStates.back();
+}
+
+}; // namespace android