diff --git a/docs/docs/en/src/advanced/memory.md b/docs/docs/en/src/advanced/memory.md
index 7e377a775a..06079233e6 100644
--- a/docs/docs/en/src/advanced/memory.md
+++ b/docs/docs/en/src/advanced/memory.md
@@ -97,6 +97,10 @@ Properties:
   allocator overhead, scratch buffers, and any data held outside the index (e.g. user-owned input
   vectors). For SINDI in particular, call `GetMemoryUsage()` **after** the build completes to get
   a representative value.
+- For an HGraph loaded through `ReaderIO`, resident memory owned by a retained `Reader` is included
+  when the reader overrides `Reader::GetMemoryUsage()`. The default implementation returns zero;
+  custom readers with an in-memory page cache should override it. The underlying file or remote
+  data source is not part of the reported memory.
 
 See `examples/cpp/319_feature_get_memory_usage.cpp` for a runnable example, including a helper
 that compares the interface value with the process resident size.
@@ -118,8 +122,9 @@ understanding *where* the memory is going inside an index.
 
 Currently only HGraph provides a meaningful implementation, returning components such as
 `basic_flatten_codes`, `bottom_graph`, `route_graph`, `neighbors_mutex`, `pool`,
-`label_table`, `high_precise_codes`, `extra_infos`, and `raw_vector`. SINDI returns an empty
-map. Other index types throw an exception by default.
+`label_table`, `high_precise_codes`, `extra_infos`, `raw_vector`, `reader`, and
+`precise_reader`. Reader keys are present only when the corresponding retained reader exists.
+SINDI returns an empty map. Other index types throw an exception by default.
 
 ### Capability Flags
 
@@ -140,5 +145,6 @@ full control over parallelism and resource ownership. See
 ## Notes
 
 - A custom allocator must be thread-safe.
+- A custom `Reader::GetMemoryUsage()` override must be thread-safe.
 - The allocator's lifetime must outlive any index and result object referencing it.
 - If nothing is configured, VSAG falls back to a default `malloc`-based allocator.
diff --git a/docs/docs/zh/src/advanced/memory.md b/docs/docs/zh/src/advanced/memory.md
index 57b1453c13..eaeca723f5 100644
--- a/docs/docs/zh/src/advanced/memory.md
+++ b/docs/docs/zh/src/advanced/memory.md
@@ -88,6 +88,9 @@ uint64_t bytes = index->GetMemoryUsage();
   RSS 还包含 allocator 的开销、临时 scratch buffer、以及索引外部持有的数据（例如用户自有的输入
   向量缓冲）。SINDI 索引尤其建议在构建完成**之后**调用 `GetMemoryUsage()` 才能拿到具有代表性的
   数值。
+- HGraph 通过 `ReaderIO` 加载时，如果被索引持有的 `Reader` 重写了
+  `Reader::GetMemoryUsage()`，其常驻内存会计入统计。该方法默认返回 0；带内存页缓存的自定义
+  Reader 应重写此方法。底层文件或远端数据源本身不计入内存统计。
 
 可运行示例：`examples/cpp/319_feature_get_memory_usage.cpp`，其中包含一个辅助函数将接口值与进程
 驻留内存进行对照。
@@ -107,7 +110,8 @@ for (const auto& [component, bytes] : detail) {
 
 目前仅 HGraph 提供了有效实现，返回的组件包括 `basic_flatten_codes`、`bottom_graph`、
 `route_graph`、`neighbors_mutex`、`pool`、`label_table`、`high_precise_codes`、
-`extra_infos` 和 `raw_vector`。SINDI 返回空 map，其他索引类型默认抛出异常。
+`extra_infos`、`raw_vector`、`reader` 和 `precise_reader`。仅在索引持有对应 Reader 时才会
+返回 Reader 相关项。SINDI 返回空 map，其他索引类型默认抛出异常。
 
 ### 能力标志
 
@@ -127,5 +131,6 @@ for (const auto& [component, bytes] : detail) {
 ## 注意事项
 
 - 自定义 Allocator 必须是线程安全的。
+- 自定义 `Reader::GetMemoryUsage()` 实现必须是线程安全的。
 - `Allocator` 生命周期必须覆盖所有引用它的索引与结果对象。
 - 若未显式指定，VSAG 会创建一个默认的基于 `malloc` 的 allocator。
diff --git a/include/vsag/readerset.h b/include/vsag/readerset.h
index ee944240ae..c0e26821f7 100644
--- a/include/vsag/readerset.h
+++ b/include/vsag/readerset.h
@@ -131,6 +131,20 @@ class Reader {
      */
     [[nodiscard]] virtual uint64_t
     Size() const = 0;
+
+    /**
+     * @brief Returns memory owned by the reader, excluding the underlying data source.
+     *
+     * Reader implementations with resident caches should override this method so indexes that
+     * retain the reader can include that memory in their usage statistics. Overrides must be
+     * thread-safe because the method may be called concurrently with reads.
+     *
+     * @return Resident memory usage in bytes. The default implementation returns zero.
+     */
+    [[nodiscard]] virtual uint64_t
+    GetMemoryUsage() const {
+        return 0;
+    }
 };
 
 /**
diff --git a/src/algorithm/hgraph/hgraph.cpp b/src/algorithm/hgraph/hgraph.cpp
index 29d02335d0..32dccd5df6 100644
--- a/src/algorithm/hgraph/hgraph.cpp
+++ b/src/algorithm/hgraph/hgraph.cpp
@@ -538,6 +538,7 @@ HGraph::SetImmutable() {
     this->parallel_searcher_->SetMutexArray(empty_mutex);
     this->neighbors_mutex_ = empty_mutex;
     this->immutable_.store(true, std::memory_order_release);
+    this->cal_memory_usage();
 }
 
 void
@@ -549,6 +550,8 @@ HGraph::SetIO(const std::shared_ptr<Reader> reader) {
     }
     basic_flatten_codes_->InitIO(reader_param);
     bottom_graph_->InitIO(reader_param);
+    this->reader_ = reader;
+    this->precise_reader_.reset();
 }
 
 void
@@ -556,6 +559,7 @@ HGraph::SetPreciseCodesIO(const std::shared_ptr<Reader>& reader) {
     auto reader_param = std::make_shared<ReaderIOParameter>();
     reader_param->reader = reader;
     high_precise_codes_->InitIO(reader_param);
+    this->precise_reader_ = reader;
 }
 
 const static uint64_t QUERY_SAMPLE_SIZE = 10;
@@ -745,11 +749,25 @@ HGraph::GetAttributeSetByInnerId(InnerIdType inner_id, AttributeSet* attr) const
     this->attr_filter_index_->GetAttribute(0, inner_id, attr);
 }
 
+uint64_t
+HGraph::GetMemoryUsage() const {
+    auto memory = InnerIndexInterface::GetMemoryUsage();
+    if (this->pool_ != nullptr) {
+        memory += this->pool_->GetMemoryUsage();
+    }
+    if (this->reader_ != nullptr) {
+        memory += this->reader_->GetMemoryUsage();
+    }
+    if (this->precise_reader_ != nullptr && this->precise_reader_.get() != this->reader_.get()) {
+        memory += this->precise_reader_->GetMemoryUsage();
+    }
+    return memory;
+}
+
 void
 HGraph::cal_memory_usage() {
     auto memory = sizeof(HGraph);
     memory += this->neighbors_mutex_->GetMemoryUsage();
-    memory += this->pool_->GetMemoryUsage();
     memory += this->label_table_->GetMemoryUsage();
     memory += this->basic_flatten_codes_->GetMemoryUsage();
     if (this->code_slot_map_ != nullptr) {
@@ -770,7 +788,6 @@ HGraph::cal_memory_usage() {
     if (this->create_new_raw_vector_ and this->raw_vector_ != nullptr) {
         memory += raw_vector_->GetMemoryUsage();
     }
-
     std::unique_lock lock(this->memory_usage_mutex_);
     this->current_memory_usage_.store(memory);
 }
diff --git a/src/algorithm/hgraph/hgraph.h b/src/algorithm/hgraph/hgraph.h
index 427ebef1c4..540a3eb174 100644
--- a/src/algorithm/hgraph/hgraph.h
+++ b/src/algorithm/hgraph/hgraph.h
@@ -109,6 +109,9 @@ class HGraph : public InnerIndexInterface {
     uint64_t
     EstimateMemory(uint64_t num_elements) const override;
 
+    [[nodiscard]] uint64_t
+    GetMemoryUsage() const override;
+
     void
     GetAttributeSetByInnerId(InnerIdType inner_id, AttributeSet* attr) const override;
 
@@ -792,6 +795,9 @@ class HGraph : public InnerIndexInterface {
 
     std::shared_ptr<Optimizer<BasicSearcher>> optimizer_;  // search parameter optimizer
 
+    ReaderPtr reader_{nullptr};          // shared reader used by base, graph, and precise codes
+    ReaderPtr precise_reader_{nullptr};  // optional dedicated reader for precise codes
+
     bool create_new_raw_vector_{false};        // whether a separate raw vector exists
     FlattenInterfacePtr raw_vector_{nullptr};  // raw float vectors (for distance calc)
 
diff --git a/src/algorithm/hgraph/hgraph_serialize.cpp b/src/algorithm/hgraph/hgraph_serialize.cpp
index 576756a0e3..9f658095ca 100644
--- a/src/algorithm/hgraph/hgraph_serialize.cpp
+++ b/src/algorithm/hgraph/hgraph_serialize.cpp
@@ -1073,6 +1073,12 @@ HGraph::GetMemoryUsageDetail() const {
     if (this->create_new_raw_vector_ && this->raw_vector_ != nullptr) {
         memory_usage["raw_vector"] = this->raw_vector_->GetMemoryUsage();
     }
+    if (this->reader_ != nullptr) {
+        memory_usage["reader"] = this->reader_->GetMemoryUsage();
+    }
+    if (this->precise_reader_ != nullptr && this->precise_reader_.get() != this->reader_.get()) {
+        memory_usage["precise_reader"] = this->precise_reader_->GetMemoryUsage();
+    }
     return memory_usage;
 }
 
diff --git a/tests/fixtures/framework/test_reader.cpp b/tests/fixtures/framework/test_reader.cpp
index cc30739b13..ab0e582d03 100644
--- a/tests/fixtures/framework/test_reader.cpp
+++ b/tests/fixtures/framework/test_reader.cpp
@@ -18,7 +18,8 @@
 
 namespace fixtures {
 
-TestReader::TestReader(vsag::Binary binary) : binary_(std::move(binary)) {
+TestReader::TestReader(vsag::Binary binary, uint64_t memory_usage)
+    : binary_(std::move(binary)), memory_usage_(memory_usage) {
 }
 
 void
@@ -37,4 +38,9 @@ TestReader::Size() const {
     return binary_.size;
 }
 
+uint64_t
+TestReader::GetMemoryUsage() const {
+    return memory_usage_;
+}
+
 }  // namespace fixtures
diff --git a/tests/fixtures/framework/test_reader.h b/tests/fixtures/framework/test_reader.h
index 150af953af..f8bebada8d 100644
--- a/tests/fixtures/framework/test_reader.h
+++ b/tests/fixtures/framework/test_reader.h
@@ -35,7 +35,7 @@ class TestReader : public vsag::Reader {
      * @brief Constructs a TestReader from a Binary object.
      * @param binary The binary data to wrap for reading.
      */
-    explicit TestReader(vsag::Binary binary);
+    explicit TestReader(vsag::Binary binary, uint64_t memory_usage = 0);
 
     /**
      * @brief Reads data from the binary at the specified offset.
@@ -63,8 +63,12 @@ class TestReader : public vsag::Reader {
     [[nodiscard]] uint64_t
     Size() const override;
 
+    [[nodiscard]] uint64_t
+    GetMemoryUsage() const override;
+
 private:
     vsag::Binary binary_;  // The wrapped binary data.
+    uint64_t memory_usage_{0};
 };
 
 }  // namespace fixtures
diff --git a/tests/test_hgraph.cpp b/tests/test_hgraph.cpp
index 421bd4f789..8886b54f35 100644
--- a/tests/test_hgraph.cpp
+++ b/tests/test_hgraph.cpp
@@ -2312,6 +2312,67 @@ TestHGraphReaderIO(const fixtures::HGraphTestIndexPtr& test_index,
 
 HGRAPH_PR_DAILY_CASE("HGraph Reader IO", "[ft][serialize][hgraph]", TestHGraphReaderIO)
 
+TEST_CASE("HGraph Reader Memory Usage", "[ft][memory][hgraph]") {
+    constexpr uint64_t reader_memory = 64ULL * 1024ULL * 1024ULL;
+    constexpr int64_t dim = 16;
+    constexpr int64_t count = 200;
+    const auto build_param = R"({
+        "dtype": "float32",
+        "metric_type": "l2",
+        "dim": 16,
+        "index_param": {
+            "base_quantization_type": "sq8",
+            "precise_quantization_type": "fp32",
+            "use_reorder": true,
+            "max_degree": 16,
+            "ef_construction": 100
+        }
+    })";
+    const auto reader_param = R"({
+        "dtype": "float32",
+        "metric_type": "l2",
+        "dim": 16,
+        "index_param": {
+            "base_quantization_type": "sq8",
+            "precise_quantization_type": "fp32",
+            "use_reorder": true,
+            "max_degree": 16,
+            "ef_construction": 100,
+            "base_io_type": "reader_io",
+            "precise_io_type": "reader_io",
+            "graph_io_type": "reader_io"
+        }
+    })";
+
+    auto dataset = fixtures::HGraphTestIndex::pool.GetDatasetAndCreate(dim, count, "l2");
+    auto source = fixtures::TestIndex::TestFactory("hgraph", build_param, true);
+    fixtures::TestIndex::TestBuildIndex(source, dataset, true);
+    auto binary_set = source->Serialize().value();
+
+    auto restored = fixtures::TestIndex::TestFactory("hgraph", reader_param, true);
+    vsag::ReaderSet readers;
+    readers.Set("hgraph",
+                std::make_shared<fixtures::TestReader>(binary_set.Get("hgraph"), reader_memory));
+    REQUIRE(restored->Deserialize(readers).has_value());
+
+    auto detail = restored->GetMemoryUsageDetail();
+    REQUIRE(detail.at("reader") == reader_memory);
+    auto mutable_memory = restored->GetMemoryUsage();
+    REQUIRE(restored->SetImmutable().has_value());
+    auto immutable_memory = restored->GetMemoryUsage();
+    REQUIRE(immutable_memory < mutable_memory);
+
+    detail = restored->GetMemoryUsageDetail();
+    REQUIRE(detail.at("neighbors_mutex") == 0);
+    REQUIRE(detail.at("reader") == reader_memory);
+    uint64_t detail_sum = 0;
+    for (const auto& [_, memory] : detail) {
+        detail_sum += memory;
+    }
+    REQUIRE(immutable_memory >= detail_sum);
+    REQUIRE(immutable_memory - detail_sum < 4096);
+}
+
 static void
 TestHGraphClone(const fixtures::HGraphTestIndexPtr& test_index,
                 const fixtures::HGraphResourcePtr& resource) {