diff --git a/pw_software_update/BUILD.bazel b/pw_software_update/BUILD.bazel
index 5ae1d87..5dcd665 100644
--- a/pw_software_update/BUILD.bazel
+++ b/pw_software_update/BUILD.bazel
@@ -36,7 +36,9 @@
     name = "update_bundle",
     srcs = ["update_bundle.cc"],
     hdrs = [
+        "public/pw_software_update/bundled_update_backend.h",
         "public/pw_software_update/config.h",
+        "public/pw_software_update/manifest.h",
         "public/pw_software_update/update_bundle.h",
     ],
     includes = ["public"],
@@ -44,16 +46,9 @@
         "//pw_blob_store",
         "//pw_kvs",
         "//pw_log",
-    ],
-)
-
-pw_cc_library(
-    name = "update_backend",
-    hdrs = ["public/pw_software_update/update_backend.h"],
-    includes = ["public"],
-    deps = [
-        ":update_bundle_proto",
+        "//pw_protobuf",
         "//pw_status",
+        "//pw_stream",
     ],
 )
 
diff --git a/pw_software_update/BUILD.gn b/pw_software_update/BUILD.gn
index 7a8a420..63a7f9b 100644
--- a/pw_software_update/BUILD.gn
+++ b/pw_software_update/BUILD.gn
@@ -56,6 +56,28 @@
   sources = [ "docs.rst" ]
 }
 
+pw_source_set("update_bundle") {
+  public_configs = [ ":public_include_path" ]
+  public_deps = [
+    dir_pw_blob_store,
+    dir_pw_kvs,
+    dir_pw_protobuf,
+    dir_pw_status,
+    dir_pw_stream,
+  ]
+  public = [
+    "public/pw_software_update/bundled_update_backend.h",
+    "public/pw_software_update/config.h",
+    "public/pw_software_update/manifest.h",
+    "public/pw_software_update/update_bundle.h",
+  ]
+  deps = [
+    ":protos.pwpb",
+    dir_pw_log,
+  ]
+  sources = [ "update_bundle.cc" ]
+}
+
 if (dir_pw_third_party_nanopb != "" && dir_pw_third_party_protobuf != "") {
   pw_source_set("rpc_service") {
     public_configs = [ ":public_include_path" ]
@@ -66,36 +88,9 @@
       "service.cc",
     ]
   }
-
-  pw_source_set("update_backend") {
-    public_configs = [ ":public_include_path" ]
-    public_deps = [
-      ":protos.nanopb",
-      dir_pw_status,
-    ]
-    sources = [ "public/pw_software_update/update_backend.h" ]
-  }
-
-  pw_source_set("update_bundle") {
-    public_configs = [ ":public_include_path" ]
-    public_deps = [
-      ":protos.pwpb",
-      ":update_backend",
-      dir_pw_blob_store,
-      dir_pw_kvs,
-    ]
-    deps = [ dir_pw_log ]
-    public = [
-      "public/pw_software_update/config.h",
-      "public/pw_software_update/update_bundle.h",
-    ]
-    sources = [ "update_bundle.cc" ]
-  }
 } else {
   group("rpc_service") {
   }
-  group("update_bundle") {
-  }
 }
 
 pw_python_action("generate_test_bundle") {
diff --git a/pw_software_update/public/pw_software_update/update_backend.h b/pw_software_update/public/pw_software_update/bundled_update_backend.h
similarity index 88%
rename from pw_software_update/public/pw_software_update/update_backend.h
rename to pw_software_update/public/pw_software_update/bundled_update_backend.h
index c2aaf90..2a93455 100644
--- a/pw_software_update/public/pw_software_update/update_backend.h
+++ b/pw_software_update/public/pw_software_update/bundled_update_backend.h
@@ -14,8 +14,9 @@
 
 #pragma once
 
-#include "pw_software_update/update_bundle.pb.h"
+#include "pw_software_update/manifest.h"
 #include "pw_status/status.h"
+#include "pw_stream/stream.h"
 
 namespace pw::software_update {
 
@@ -37,8 +38,7 @@
 
   // Perform any product-specific bundle verification tasks (e.g. hw version
   // match check), done after TUF bundle verification process.
-  virtual Status VerifyMetadata(
-      [[maybe_unused]] const pw_software_update_Manifest& manifest) {
+  virtual Status VerifyMetadata([[maybe_unused]] const Manifest& manifest) {
     return OkStatus();
   };
 
@@ -50,7 +50,7 @@
   // (e.g. by checksum, if failed abort partial update and wipe/mark-invalid
   // running manifest)
   virtual Status VerifyTargetFile(
-      [[maybe_unused]] const pw_software_update_Manifest& manifest,
+      [[maybe_unused]] const Manifest& manifest,
       [[maybe_unused]] std::string_view target_file_name) {
     return OkStatus();
   };
@@ -64,18 +64,18 @@
   virtual int64_t GetStatus() { return 0; }
 
   // Update the specific target file on the device.
-  virtual Status ApplyTargetFile(
-      [[maybe_unused]] std::string_view target_file_name,
-      [[maybe_unused]] stream::Reader& target_payload) {
-    return OkStatus();
-  };
+  virtual Status ApplyTargetFile(std::string_view target_file_name,
+                                 stream::Reader& target_payload) = 0;
 
   // Do any work needed to finalize the update including doing a required
   // reboot of the device! This is called after all software update state and
   // breadcrumbs have been cleaned up.
   //
   // After the reboot the update is fully complete.
-  PW_NO_RETURN virtual void FinalizeUpdate() = 0;
+  //
+  // NOTE: If successful this method does not return and reboots the device, it
+  // only returns on failure to finalize.
+  virtual Status FinalizeUpdate() = 0;
 
   // Get reader of the device's current manifest.
   virtual Status GetCurrentManifestReader(
diff --git a/pw_software_update/public/pw_software_update/manifest.h b/pw_software_update/public/pw_software_update/manifest.h
new file mode 100644
index 0000000..3b9cb18
--- /dev/null
+++ b/pw_software_update/public/pw_software_update/manifest.h
@@ -0,0 +1,23 @@
+// Copyright 2021 The Pigweed Authors
+//
+// 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
+//
+//     https://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.
+
+#pragma once
+
+namespace pw::software_update {
+
+// TODO(pwbug/456): Place-holder declaration for now. To be implemented
+// and moved elsewhere.
+class Manifest {};
+
+}  // namespace pw::software_update
diff --git a/pw_software_update/public/pw_software_update/update_bundle.h b/pw_software_update/public/pw_software_update/update_bundle.h
index 17fff95..b9f85a0 100644
--- a/pw_software_update/public/pw_software_update/update_bundle.h
+++ b/pw_software_update/public/pw_software_update/update_bundle.h
@@ -19,21 +19,18 @@
 #include "pw_blob_store/blob_store.h"
 #include "pw_protobuf/map_utils.h"
 #include "pw_protobuf/message.h"
-#include "pw_software_update/update_backend.h"
+#include "pw_software_update/bundled_update_backend.h"
+#include "pw_software_update/manifest.h"
 #include "pw_stream/memory_stream.h"
 
 namespace pw::software_update {
 
-// TODO(pwbug/456): Place-holder declaration for now. To be implemented
-// and moved elsewhere.
-class Manifest {};
-
 // UpdateBundle is responsible for parsing, verifying and providing
 // target payload access of a software update bundle. It takes the following as
 // inputs:
 //
 // 1. A software update bundle via `BlobStore`.
-// 2. A `BundledUpdateHelper`, which implements project-specific update
+// 2. A `BundledUpdateBackend`, which implements project-specific update
 //    operations such as enforcing project update policies and
 //    verifying/applying target files on device.
 //
@@ -127,4 +124,4 @@
   protobuf::Message decoder_;
 };
 
-}  // namespace pw::software_update
\ No newline at end of file
+}  // namespace pw::software_update