diff --git a/aosp/dynamic_partition_control_android.cc b/aosp/dynamic_partition_control_android.cc
index d296c53..7ccc39a 100644
--- a/aosp/dynamic_partition_control_android.cc
+++ b/aosp/dynamic_partition_control_android.cc
@@ -1256,6 +1256,18 @@
   return snapshot_->OpenSnapshotWriter(params, std::move(source_path));
 }  // namespace chromeos_update_engine
 
+FileDescriptorPtr DynamicPartitionControlAndroid::OpenCowReader(
+    const std::string& unsuffixed_partition_name,
+    const std::optional<std::string>& source_path,
+    bool is_append) {
+  auto cow_writer =
+      OpenCowWriter(unsuffixed_partition_name, source_path, is_append);
+  if (cow_writer == nullptr) {
+    return nullptr;
+  }
+  return cow_writer->OpenReader();
+}
+
 std::optional<base::FilePath> DynamicPartitionControlAndroid::GetSuperDevice() {
   std::string device_dir_str;
   if (!GetDeviceDir(&device_dir_str)) {
diff --git a/aosp/dynamic_partition_control_android.h b/aosp/dynamic_partition_control_android.h
index a4064e9..a2a42cc 100644
--- a/aosp/dynamic_partition_control_android.h
+++ b/aosp/dynamic_partition_control_android.h
@@ -89,6 +89,9 @@
       const std::string& unsuffixed_partition_name,
       const std::optional<std::string>& source_path,
       bool is_append) override;
+  FileDescriptorPtr OpenCowReader(const std::string& unsuffixed_partition_name,
+                                  const std::optional<std::string>&,
+                                  bool is_append = false) override;
 
   bool UnmapAllPartitions() override;
 
diff --git a/aosp/mock_dynamic_partition_control.h b/aosp/mock_dynamic_partition_control.h
index df7208e..d281803 100644
--- a/aosp/mock_dynamic_partition_control.h
+++ b/aosp/mock_dynamic_partition_control.h
@@ -25,6 +25,7 @@
 #include <libsnapshot/cow_writer.h>
 #include <libsnapshot/snapshot_writer.h>
 
+#include "payload_consumer/file_descriptor.h"
 #include "update_engine/aosp/dynamic_partition_control_android.h"
 #include "update_engine/common/boot_control_interface.h"
 #include "update_engine/common/dynamic_partition_control_interface.h"
@@ -90,6 +91,12 @@
                const std::optional<std::string>& source_path,
                bool is_append),
               (override));
+  MOCK_METHOD(FileDescriptorPtr,
+              OpenCowReader,
+              (const std::string& unsuffixed_partition_name,
+               const std::optional<std::string>& source_path,
+               bool is_append),
+              (override));
   MOCK_METHOD(bool, MapAllPartitions, (), (override));
   MOCK_METHOD(bool, UnmapAllPartitions, (), (override));
 
diff --git a/common/dynamic_partition_control_interface.h b/common/dynamic_partition_control_interface.h
index c8a2274..a2ebfc6 100644
--- a/common/dynamic_partition_control_interface.h
+++ b/common/dynamic_partition_control_interface.h
@@ -154,6 +154,10 @@
       const std::string& unsuffixed_partition_name,
       const std::optional<std::string>&,
       bool is_append = false) = 0;
+  virtual FileDescriptorPtr OpenCowReader(
+      const std::string& unsuffixed_partition_name,
+      const std::optional<std::string>&,
+      bool is_append = false) = 0;
 
   // Create virtual block devices for all partitions.
   virtual bool MapAllPartitions() = 0;
diff --git a/common/dynamic_partition_control_stub.cc b/common/dynamic_partition_control_stub.cc
index cfc9e2e..31975b3 100644
--- a/common/dynamic_partition_control_stub.cc
+++ b/common/dynamic_partition_control_stub.cc
@@ -96,6 +96,13 @@
   return nullptr;
 }
 
+FileDescriptorPtr DynamicPartitionControlStub::OpenCowReader(
+    const std::string& unsuffixed_partition_name,
+    const std::optional<std::string>&,
+    bool /*is_append */) {
+  return nullptr;
+}
+
 bool DynamicPartitionControlStub::MapAllPartitions() {
   return false;
 }
diff --git a/common/dynamic_partition_control_stub.h b/common/dynamic_partition_control_stub.h
index 1fc8a35..94540f4 100644
--- a/common/dynamic_partition_control_stub.h
+++ b/common/dynamic_partition_control_stub.h
@@ -62,6 +62,9 @@
       const std::string& unsuffixed_partition_name,
       const std::optional<std::string>&,
       bool is_append) override;
+  FileDescriptorPtr OpenCowReader(const std::string& unsuffixed_partition_name,
+                                  const std::optional<std::string>&,
+                                  bool is_append = false) override;
 
   bool MapAllPartitions() override;
   bool UnmapAllPartitions() override;