diff --git a/Telegram/SourceFiles/media/streaming/media_streaming_reader.cpp b/Telegram/SourceFiles/media/streaming/media_streaming_reader.cpp
index 9d4e14a2ab..a2e1736db9 100644
--- a/Telegram/SourceFiles/media/streaming/media_streaming_reader.cpp
+++ b/Telegram/SourceFiles/media/streaming/media_streaming_reader.cpp
@@ -24,17 +24,139 @@ constexpr auto kMaxOnlyInHeader = 80 * kPartSize;
 constexpr auto kPartsOutsideFirstSliceGood = 8;
 constexpr auto kSlicesInMemory = 2;
 
-// 1 MB of header parts can be outside the first slice for us to still
-// put the whole first slice of the file in the header cache entry.
-//constexpr auto kMaxOutsideHeaderPartsForOptimizedMode = 8;
-
 // 1 MB of parts are requested from cloud ahead of reading demand.
 constexpr auto kPreloadPartsAhead = 8;
 
+using PartsMap = base::flat_map<int, QByteArray>;
+
+struct ParsedCacheEntry {
+	PartsMap parts;
+	std::optional<PartsMap> included;
+};
+
 bool IsContiguousSerialization(int serializedSize, int maxSliceSize) {
 	return !(serializedSize % kPartSize) || (serializedSize == maxSliceSize);
 }
 
+bool IsFullInHeader(int size) {
+	return (size <= kMaxOnlyInHeader);
+}
+
+bool ComputeIsGoodHeader(int size, const PartsMap &header) {
+	if (IsFullInHeader(size)) {
+		return false;
+	}
+	const auto outsideFirstSliceIt = ranges::lower_bound(
+		header,
+		kInSlice,
+		ranges::less(),
+		&PartsMap::value_type::first);
+	const auto outsideFirstSlice = end(header) - outsideFirstSliceIt;
+	return (outsideFirstSlice <= kPartsOutsideFirstSliceGood);
+}
+
+int SlicesCount(int size) {
+	return (size + kInSlice - 1) / kInSlice;
+}
+
+int MaxSliceSize(int sliceNumber, int size) {
+	return !sliceNumber
+		? size
+		: (sliceNumber == SlicesCount(size))
+		? (size - (sliceNumber - 1) * kInSlice)
+		: kInSlice;
+}
+
+bytes::const_span ParseComplexCachedMap(
+		PartsMap &result,
+		bytes::const_span data,
+		int maxSize) {
+	const auto takeInt = [&]() -> std::optional<int> {
+		if (data.size() < sizeof(int32)) {
+			return std::nullopt;
+		}
+		const auto bytes = data.data();
+		const auto result = *reinterpret_cast<const int32*>(bytes);
+		data = data.subspan(sizeof(int32));
+		return result;
+	};
+	const auto takeBytes = [&](int count) {
+		if (count <= 0 || data.size() < count) {
+			return bytes::const_span();
+		}
+		const auto result = data.subspan(0, count);
+		data = data.subspan(count);
+		return result;
+	};
+	const auto maybeCount = takeInt();
+	if (!maybeCount) {
+		return {};
+	}
+	const auto count = *maybeCount;
+	if (count < 0) {
+		return {};
+	} else if (!count) {
+		return data;
+	}
+	for (auto i = 0; i != count; ++i) {
+		const auto offset = takeInt().value_or(0);
+		const auto size = takeInt().value_or(0);
+		const auto bytes = takeBytes(size);
+		if (offset < 0
+			|| offset >= maxSize
+			|| size <= 0
+			|| size > maxSize
+			|| offset + size > maxSize
+			|| bytes.size() != size) {
+			return {};
+		}
+		result.try_emplace(
+			offset,
+			reinterpret_cast<const char*>(bytes.data()),
+			bytes.size());
+	}
+	return data;
+}
+
+bytes::const_span ParseCachedMap(
+		PartsMap &result,
+		bytes::const_span data,
+		int maxSize) {
+	const auto size = int(data.size());
+	if (IsContiguousSerialization(size, maxSize)) {
+		if (size > maxSize) {
+			return {};
+		}
+		for (auto offset = 0; offset < size; offset += kPartSize) {
+			const auto part = data.subspan(
+				offset,
+				std::min(kPartSize, size - offset));
+			result.try_emplace(
+				offset,
+				reinterpret_cast<const char*>(part.data()),
+				part.size());
+		}
+		return {};
+	}
+	return ParseComplexCachedMap(result, data, maxSize);
+}
+
+ParsedCacheEntry ParseCacheEntry(
+		bytes::const_span data,
+		int sliceNumber,
+		int size) {
+	auto result = ParsedCacheEntry();
+	const auto remaining = ParseCachedMap(
+		result.parts,
+		data,
+		MaxSliceSize(sliceNumber, size));
+	if (!sliceNumber && ComputeIsGoodHeader(size, result.parts)) {
+		result.included = PartsMap();
+		ParseCachedMap(*result.included, remaining, MaxSliceSize(1, size));
+	}
+	return result;
+}
+
 template <typename Range> // Range::value_type is Pair<int, QByteArray>
 int FindNotLoadedStart(Range &&parts, int offset) {
 	auto result = offset;
@@ -101,7 +223,7 @@ struct Reader::CacheHelper {
 	const Storage::Cache::Key baseKey;
 
 	QMutex mutex;
-	base::flat_map<int, QByteArray> results;
+	base::flat_map<int, PartsMap> results;
 	std::atomic<crl::semaphore*> waiting = nullptr;
 };
 
@@ -113,9 +235,7 @@ Storage::Cache::Key Reader::CacheHelper::key(int sliceNumber) const {
 	return Storage::Cache::Key{ baseKey.high, baseKey.low + sliceNumber };
 }
 
-bytes::const_span Reader::Slice::processCacheData(
-		bytes::const_span data,
-		int maxSize) {
+void Reader::Slice::processCacheData(PartsMap &&data) {
 	Expects((flags & Flag::LoadingFromCache) != 0);
 	Expects(!(flags & Flag::LoadedFromCache));
 
@@ -123,74 +243,13 @@ bytes::const_span Reader::Slice::processCacheData(
 		flags |= Flag::LoadedFromCache;
 		flags &= ~Flag::LoadingFromCache;
 	});
-
-	const auto size = int(data.size());
-	if (IsContiguousSerialization(size, maxSize)) {
-		if (size > maxSize) {
-			return {};
+	if (parts.empty()) {
+		parts = std::move(data);
+	} else {
+		for (auto &[offset, bytes] : data) {
+			parts.emplace(offset, std::move(bytes));
 		}
-		for (auto offset = 0; offset < size; offset += kPartSize) {
-			const auto part = data.subspan(
-				offset,
-				std::min(kPartSize, size - offset));
-			parts.try_emplace(
-				offset,
-				reinterpret_cast<const char*>(part.data()),
-				part.size());
-		}
-		return {};
 	}
-	return processComplexCacheData(bytes::make_span(data), maxSize);
-}
-
-bytes::const_span Reader::Slice::processComplexCacheData(
-		bytes::const_span data,
-		int maxSize) {
-	const auto takeInt = [&]() -> std::optional<int> {
-		if (data.size() < sizeof(int32)) {
-			return std::nullopt;
-		}
-		const auto bytes = data.data();
-		const auto result = *reinterpret_cast<const int32*>(bytes);
-		data = data.subspan(sizeof(int32));
-		return result;
-	};
-	const auto takeBytes = [&](int count) {
-		if (count <= 0 || data.size() < count) {
-			return bytes::const_span();
-		}
-		const auto result = data.subspan(0, count);
-		data = data.subspan(count);
-		return result;
-	};
-	const auto maybeCount = takeInt();
-	if (!maybeCount) {
-		return {};
-	}
-	const auto count = *maybeCount;
-	if (count < 0) {
-		return {};
-	} else if (!count) {
-		return data;
-	}
-	for (auto i = 0; i != count; ++i) {
-		const auto offset = takeInt().value_or(0);
-		const auto size = takeInt().value_or(0);
-		const auto bytes = takeBytes(size);
-		if (offset < 0
-			|| offset >= maxSize
-			|| size <= 0
-			|| size > maxSize
-			|| offset + size > maxSize
-			|| bytes.size() != size) {
-			return {};
-		}
-		parts.try_emplace(
-			offset,
-			reinterpret_cast<const char*>(bytes.data()),
-			bytes.size());
-	}
-	return data;
 }
 
 void Reader::Slice::addPart(int offset, QByteArray bytes) {
@@ -215,7 +274,7 @@ auto Reader::Slice::prepareFill(int from, int till) -> PrepareFillResult {
 		parts,
 		from,
 		ranges::less(),
-		&base::flat_map<int, QByteArray>::value_type::first);
+		&PartsMap::value_type::first);
 	if (after == begin(parts)) {
 		result.offsetsFromLoader = offsetsFromLoader(
 			fromOffset,
@@ -229,7 +288,7 @@ auto Reader::Slice::prepareFill(int from, int till) -> PrepareFillResult {
 		end(parts),
 		till,
 		ranges::less(),
-		&base::flat_map<int, QByteArray>::value_type::first);
+		&PartsMap::value_type::first);
 	const auto haveTill = FindNotLoadedStart(
 		ranges::make_iterator_range(start, finish),
 		fromOffset);
@@ -256,7 +315,7 @@ auto Reader::Slice::offsetsFromLoader(int from, int till) const
 		parts,
 		from,
 		ranges::less(),
-		&base::flat_map<int, QByteArray>::value_type::first);
+		&PartsMap::value_type::first);
 	auto check = (after == begin(parts)) ? after : (after - 1);
 	const auto end = parts.end();
 	for (auto offset = from; offset != till; offset += kPartSize) {
@@ -282,7 +341,7 @@ Reader::Slices::Slices(int size, bool useCache)
 		_headerMode = HeaderMode::NoCache;
 	}
 	if (!isFullInHeader()) {
-		_data.resize((_size + kInSlice - 1) / kInSlice);
+		_data.resize(SlicesCount(_size));
 	}
 }
 
@@ -291,7 +350,7 @@ bool Reader::Slices::headerModeUnknown() const {
 }
 
 bool Reader::Slices::isFullInHeader() const {
-	return (_size <= kMaxOnlyInHeader);
+	return IsFullInHeader(_size);
 }
 
 bool Reader::Slices::isGoodHeader() const {
@@ -299,16 +358,7 @@ bool Reader::Slices::isGoodHeader() const {
 }
 
 bool Reader::Slices::computeIsGoodHeader() const {
-	if (isFullInHeader()) {
-		return false;
-	}
-	const auto outsideFirstSliceIt = ranges::lower_bound(
-		_header.parts,
-		kInSlice,
-		ranges::less(),
-		&base::flat_map<int, QByteArray>::value_type::first);
-	const auto outsideFirstSlice = end(_header.parts) - outsideFirstSliceIt;
-	return (outsideFirstSlice <= kPartsOutsideFirstSliceGood);
+	return ComputeIsGoodHeader(_size, _header.parts);
 }
 
 void Reader::Slices::headerDone(bool fromCache) {
@@ -364,9 +414,7 @@ void Reader::Slices::applyHeaderCacheData() {
 	}
 }
 
-void Reader::Slices::processCacheResult(
-		int sliceNumber,
-		bytes::const_span result) {
+void Reader::Slices::processCacheResult(int sliceNumber, PartsMap &&result) {
 	Expects(sliceNumber >= 0 && sliceNumber <= _data.size());
 
 	auto &slice = (sliceNumber ? _data[sliceNumber - 1] : _header);
@@ -384,16 +432,13 @@ void Reader::Slices::processCacheResult(
 		// We could've already unloaded this slice using LRU _usedSlices.
 		return;
 	}
-	const auto remaining = slice.processCacheData(
-		result,
-		maxSliceSize(sliceNumber));
+	slice.processCacheData(std::move(result));
 	if (!sliceNumber) {
 		applyHeaderCacheData();
 		if (isGoodHeader()) {
 			// When we first read header we don't request the first slice.
 			// But we get it, so let's apply it anyway.
 			_data[0].flags |= Slice::Flag::LoadingFromCache;
-			processCacheResult(1, remaining);
 		}
 	}
 }
@@ -542,11 +587,7 @@ void Reader::Slices::markSliceUsed(int sliceIndex) {
 }
 
 int Reader::Slices::maxSliceSize(int sliceNumber) const {
-	return !sliceNumber
-		? _size
-		: (sliceNumber == _data.size())
-		? (_size - (sliceNumber - 1) * kInSlice)
-		: kInSlice;
+	return MaxSliceSize(sliceNumber, _size);
 }
 
 Reader::SerializedSlice Reader::Slices::serializeAndUnloadUnused() {
@@ -779,6 +820,10 @@ void Reader::processDownloaderRequests() {
 
 }
 
+void Reader::checkCacheResultsForDownloader() {
+
+}
+
 bool Reader::isRemoteLoader() const {
 	return _loader->baseCacheKey().has_value();
 }
@@ -799,17 +844,32 @@ void Reader::readFromCache(int sliceNumber) {
 	if (sliceNumber == 1 && _slices.isGoodHeader()) {
 		return readFromCache(0);
 	}
+	const auto size = _loader->size();
 	const auto key = _cacheHelper->key(sliceNumber);
-	const auto weak = std::weak_ptr<CacheHelper>(_cacheHelper);
+	const auto cache = std::weak_ptr<CacheHelper>(_cacheHelper);
+	const auto weak = base::make_weak(this);
 	_owner->cacheBigFile().get(key, [=](QByteArray &&result) {
-		if (const auto strong = weak.lock()) {
-			QMutexLocker lock(&strong->mutex);
-			strong->results.emplace(sliceNumber, std::move(result));
-			if (const auto waiting = strong->waiting.load()) {
-				strong->waiting.store(nullptr, std::memory_order_release);
-				waiting->release();
+		crl::async([=, result = std::move(result)]{
+			auto entry = ParseCacheEntry(
+				bytes::make_span(result),
+				sliceNumber,
+				size);
+			if (const auto strong = cache.lock()) {
+				QMutexLocker lock(&strong->mutex);
+				strong->results.emplace(sliceNumber, std::move(entry.parts));
+				if (!sliceNumber && entry.included) {
+					strong->results.emplace(1, std::move(*entry.included));
+				}
+				if (const auto waiting = strong->waiting.load()) {
+					strong->waiting.store(nullptr, std::memory_order_release);
+					waiting->release();
+				} else {
+					crl::on_main(weak, [=] {
+						checkCacheResultsForDownloader();
+					});
+				}
 			}
-		}
+		});
 	});
 }
 
@@ -935,11 +995,17 @@ bool Reader::processCacheResults() {
 	}
 
 	QMutexLocker lock(&_cacheHelper->mutex);
-	const auto loaded = base::take(_cacheHelper->results);
+	auto loaded = base::take(_cacheHelper->results);
 	lock.unlock();
 
-	for (const auto &[sliceNumber, result] : loaded) {
-		_slices.processCacheResult(sliceNumber, bytes::make_span(result));
+	for (auto &[sliceNumber, result] : loaded) {
+		_slices.processCacheResult(sliceNumber, std::move(result));
+	}
+	if (!loaded.empty()
+		&& (loaded.front().first == 0)
+		&& _slices.isGoodHeader()) {
+		Assert(loaded.size() > 1);
+		Assert((loaded.begin() + 1)->first == 1);
 	}
 	if (_downloaderAttached.load(std::memory_order_acquire)) {
 		for (const auto &[sliceNumber, result] : loaded) {
diff --git a/Telegram/SourceFiles/media/streaming/media_streaming_reader.h b/Telegram/SourceFiles/media/streaming/media_streaming_reader.h
index c452f29cc6..23233a62bc 100644
--- a/Telegram/SourceFiles/media/streaming/media_streaming_reader.h
+++ b/Telegram/SourceFiles/media/streaming/media_streaming_reader.h
@@ -65,6 +65,8 @@ private:
 
 	struct CacheHelper;
 
+	using PartsMap = base::flat_map<int, QByteArray>;
+
 	template <int Size>
 	class StackIntVector {
 	public:
@@ -100,17 +102,12 @@ private:
 
 		struct PrepareFillResult {
 			StackIntVector<kLoadFromRemoteMax> offsetsFromLoader;
-			base::flat_map<int, QByteArray>::const_iterator start;
-			base::flat_map<int, QByteArray>::const_iterator finish;
+			PartsMap::const_iterator start;
+			PartsMap::const_iterator finish;
 			bool ready = true;
 		};
 
-		bytes::const_span processCacheData(
-			bytes::const_span data,
-			int maxSize);
-		bytes::const_span processComplexCacheData(
-			bytes::const_span data,
-			int maxSize);
+		void processCacheData(PartsMap &&data);
 		void addPart(int offset, QByteArray bytes);
 		PrepareFillResult prepareFill(int from, int till);
 
@@ -119,7 +116,7 @@ private:
 			int from,
 			int till) const;
 
-		base::flat_map<int, QByteArray> parts;
+		PartsMap parts;
 		Flags flags;
 
 	};
@@ -134,7 +131,7 @@ private:
 		[[nodiscard]] bool isFullInHeader() const;
 		[[nodiscard]] bool isGoodHeader() const;
 
-		void processCacheResult(int sliceNumber, bytes::const_span result);
+		void processCacheResult(int sliceNumber, PartsMap &&result);
 		void processPart(int offset, QByteArray &&bytes);
 
 		[[nodiscard]] FillResult fill(int offset, bytes::span buffer);
@@ -191,6 +188,7 @@ private:
 	void finalizeCache();
 
 	void processDownloaderRequests();
+	void checkCacheResultsForDownloader();
 
 	static std::shared_ptr<CacheHelper> InitCacheHelper(
 		std::optional<Storage::Cache::Key> baseKey);