diff --git a/payload_consumer/delta_performer.cc b/payload_consumer/delta_performer.cc
index 3263ff7..262e8bc 100644
--- a/payload_consumer/delta_performer.cc
+++ b/payload_consumer/delta_performer.cc
@@ -437,7 +437,7 @@
 
   if (!IsHeaderParsed()) {
     MetadataParseResult result =
-        payload_metadata_.ParsePayloadHeader(payload, error);
+        payload_metadata_.ParsePayloadHeader(payload, hardware_, error);
     if (result != MetadataParseResult::kSuccess)
       return result;
 
@@ -728,7 +728,8 @@
 
   // In major version 2, we don't add dummy operation to the payload.
   // If we already extracted the signature we should skip this step.
-  if (manifest_.has_signatures_offset() && manifest_.has_signatures_size() &&
+  if (major_payload_version_ == kBrilloMajorPayloadVersion &&
+      manifest_.has_signatures_offset() && manifest_.has_signatures_size() &&
       signatures_message_data_.empty()) {
     if (manifest_.signatures_offset() != buffer_offset_) {
       LOG(ERROR) << "Payload signatures offset points to blob offset "
@@ -763,11 +764,51 @@
 }
 
 bool DeltaPerformer::ParseManifestPartitions(ErrorCode* error) {
-  partitions_.clear();
-  for (const PartitionUpdate& partition : manifest_.partitions()) {
-    partitions_.push_back(partition);
+  if (major_payload_version_ == kBrilloMajorPayloadVersion) {
+    partitions_.clear();
+    for (const PartitionUpdate& partition : manifest_.partitions()) {
+      partitions_.push_back(partition);
+    }
+    manifest_.clear_partitions();
+  } else if (major_payload_version_ == kChromeOSMajorPayloadVersion) {
+    LOG(INFO) << "Converting update information from old format.";
+    PartitionUpdate root_part;
+    root_part.set_partition_name(kPartitionNameRoot);
+#ifdef __ANDROID__
+    LOG(WARNING) << "Legacy payload major version provided to an Android "
+                    "build. Assuming no post-install. Please use major version "
+                    "2 or newer.";
+    root_part.set_run_postinstall(false);
+#else
+    root_part.set_run_postinstall(true);
+#endif  // __ANDROID__
+    if (manifest_.has_old_rootfs_info()) {
+      *root_part.mutable_old_partition_info() = manifest_.old_rootfs_info();
+      manifest_.clear_old_rootfs_info();
+    }
+    if (manifest_.has_new_rootfs_info()) {
+      *root_part.mutable_new_partition_info() = manifest_.new_rootfs_info();
+      manifest_.clear_new_rootfs_info();
+    }
+    *root_part.mutable_operations() = manifest_.install_operations();
+    manifest_.clear_install_operations();
+    partitions_.push_back(std::move(root_part));
+
+    PartitionUpdate kern_part;
+    kern_part.set_partition_name(kPartitionNameKernel);
+    kern_part.set_run_postinstall(false);
+    if (manifest_.has_old_kernel_info()) {
+      *kern_part.mutable_old_partition_info() = manifest_.old_kernel_info();
+      manifest_.clear_old_kernel_info();
+    }
+    if (manifest_.has_new_kernel_info()) {
+      *kern_part.mutable_new_partition_info() = manifest_.new_kernel_info();
+      manifest_.clear_new_kernel_info();
+    }
+    *kern_part.mutable_operations() = manifest_.kernel_install_operations();
+    manifest_.clear_kernel_install_operations();
+    partitions_.push_back(std::move(kern_part));
   }
-  manifest_.clear_partitions();
 
   // Fill in the InstallPlan::partitions based on the partitions from the
   // payload.
@@ -928,6 +969,14 @@
   TEST_AND_RETURN_FALSE(buffer_offset_ == operation.data_offset());
   TEST_AND_RETURN_FALSE(buffer_.size() >= operation.data_length());
 
+  // Extract the signature message if it's in this operation.
+  if (ExtractSignatureMessageFromOperation(operation)) {
+    // If this is dummy replace operation, we ignore it after extracting the
+    // signature.
+    DiscardBuffer(true, 0);
+    return true;
+  }
+
   // Setup the ExtentWriter stack based on the operation type.
   std::unique_ptr<ExtentWriter> writer = std::make_unique<DirectExtentWriter>();
 
@@ -1378,6 +1427,19 @@
   return true;
 }
 
+bool DeltaPerformer::ExtractSignatureMessageFromOperation(
+    const InstallOperation& operation) {
+  if (operation.type() != InstallOperation::REPLACE ||
+      !manifest_.has_signatures_offset() ||
+      manifest_.signatures_offset() != operation.data_offset()) {
+    return false;
+  }
+  TEST_AND_RETURN_FALSE(manifest_.has_signatures_size() &&
+                        manifest_.signatures_size() == operation.data_length());
+  TEST_AND_RETURN_FALSE(ExtractSignatureMessage());
+  return true;
+}
+
 bool DeltaPerformer::ExtractSignatureMessage() {
   TEST_AND_RETURN_FALSE(signatures_message_data_.empty());
   TEST_AND_RETURN_FALSE(buffer_offset_ == manifest_.signatures_offset());
@@ -1429,11 +1491,11 @@
   // Perform assorted checks to sanity check the manifest, make sure it
   // matches data from other sources, and that it is a supported version.
 
-  bool has_old_fields = std::any_of(manifest_.partitions().begin(),
-                                    manifest_.partitions().end(),
-                                    [](const PartitionUpdate& partition) {
-                                      return partition.has_old_partition_info();
-                                    });
+  bool has_old_fields =
+      (manifest_.has_old_kernel_info() || manifest_.has_old_rootfs_info());
+  for (const PartitionUpdate& partition : manifest_.partitions()) {
+    has_old_fields = has_old_fields || partition.has_old_partition_info();
+  }
 
   // The presence of an old partition hash is the sole indicator for a delta
   // update.
@@ -1475,12 +1537,16 @@
     }
   }
 
-  if (manifest_.has_old_rootfs_info() || manifest_.has_new_rootfs_info() ||
-      manifest_.has_old_kernel_info() || manifest_.has_new_kernel_info() ||
-      manifest_.install_operations_size() != 0 ||
-      manifest_.kernel_install_operations_size() != 0) {
-    LOG(ERROR) << "Manifest contains deprecated fields.";
-    return ErrorCode::kPayloadMismatchedType;
+  if (major_payload_version_ != kChromeOSMajorPayloadVersion) {
+    if (manifest_.has_old_rootfs_info() || manifest_.has_new_rootfs_info() ||
+        manifest_.has_old_kernel_info() || manifest_.has_new_kernel_info() ||
+        manifest_.install_operations_size() != 0 ||
+        manifest_.kernel_install_operations_size() != 0) {
+      LOG(ERROR) << "Manifest contains deprecated field only supported in "
+                 << "major payload version 1, but the payload major version is "
+                 << major_payload_version_;
+      return ErrorCode::kPayloadMismatchedType;
+    }
   }
 
   if (manifest_.max_timestamp() < hardware_->GetBuildTimestamp()) {
@@ -1491,6 +1557,16 @@
     return ErrorCode::kPayloadTimestampError;
   }
 
+  if (major_payload_version_ == kChromeOSMajorPayloadVersion) {
+    if (manifest_.has_dynamic_partition_metadata()) {
+      LOG(ERROR)
+          << "Should not contain dynamic_partition_metadata for major version "
+          << kChromeOSMajorPayloadVersion
+          << ". Please use major version 2 or above.";
+      return ErrorCode::kPayloadMismatchedType;
+    }
+  }
+
   // TODO(crbug.com/37661) we should be adding more and more manifest checks,
   // such as partition boundaries, etc.
 
diff --git a/payload_consumer/delta_performer.h b/payload_consumer/delta_performer.h
index 7860747..4493c2a 100644
--- a/payload_consumer/delta_performer.h
+++ b/payload_consumer/delta_performer.h
@@ -237,6 +237,11 @@
   FileDescriptorPtr ChooseSourceFD(const InstallOperation& operation,
                                    ErrorCode* error);
 
+  // Extracts the payload signature message from the blob on the |operation| if
+  // the offset matches the one specified by the manifest. Returns whether the
+  // signature was extracted.
+  bool ExtractSignatureMessageFromOperation(const InstallOperation& operation);
+
   // Extracts the payload signature message from the current |buffer_| if the
   // offset matches the one specified by the manifest. Returns whether the
   // signature was extracted.
diff --git a/payload_consumer/delta_performer_integration_test.cc b/payload_consumer/delta_performer_integration_test.cc
index f1a492b..8de70e3 100644
--- a/payload_consumer/delta_performer_integration_test.cc
+++ b/payload_consumer/delta_performer_integration_test.cc
@@ -591,7 +591,8 @@
   {
     EXPECT_TRUE(utils::ReadFile(state->delta_path, &state->delta));
     PayloadMetadata payload_metadata;
-    EXPECT_TRUE(payload_metadata.ParsePayloadHeader(state->delta));
+    EXPECT_TRUE(payload_metadata.ParsePayloadHeader(state->delta,
+                                                    &state->fake_hardware_));
     state->metadata_size = payload_metadata.GetMetadataSize();
     LOG(INFO) << "Metadata size: " << state->metadata_size;
     state->metadata_signature_size =
diff --git a/payload_consumer/payload_constants.cc b/payload_consumer/payload_constants.cc
index 908a893..4015a0a 100644
--- a/payload_consumer/payload_constants.cc
+++ b/payload_consumer/payload_constants.cc
@@ -20,7 +20,7 @@
 
 namespace chromeos_update_engine {
 
-// const uint64_t kChromeOSMajorPayloadVersion = 1;  DEPRECATED
+const uint64_t kChromeOSMajorPayloadVersion = 1;
 const uint64_t kBrilloMajorPayloadVersion = 2;
 
 const uint64_t kMinSupportedMajorPayloadVersion = kBrilloMajorPayloadVersion;
diff --git a/payload_consumer/payload_constants.h b/payload_consumer/payload_constants.h
index 888fa2a..fe823f4 100644
--- a/payload_consumer/payload_constants.h
+++ b/payload_consumer/payload_constants.h
@@ -26,7 +26,7 @@
 namespace chromeos_update_engine {
 
 // The major version used by Chrome OS.
-// extern const uint64_t kChromeOSMajorPayloadVersion;  DEPRECATED
+extern const uint64_t kChromeOSMajorPayloadVersion;
 
 // The major version used by Brillo.
 extern const uint64_t kBrilloMajorPayloadVersion;
diff --git a/payload_consumer/payload_metadata.cc b/payload_consumer/payload_metadata.cc
index b83001a..69ccb46 100644
--- a/payload_consumer/payload_metadata.cc
+++ b/payload_consumer/payload_metadata.cc
@@ -20,6 +20,7 @@
 
 #include <brillo/data_encoding.h>
 
+#include "update_engine/common/hardware_interface.h"
 #include "update_engine/common/hash_calculator.h"
 #include "update_engine/common/utils.h"
 #include "update_engine/payload_consumer/payload_constants.h"
@@ -36,18 +37,36 @@
 const uint64_t PayloadMetadata::kDeltaManifestSizeSize = 8;
 const uint64_t PayloadMetadata::kDeltaMetadataSignatureSizeSize = 4;
 
-uint64_t PayloadMetadata::GetMetadataSignatureSizeOffset() const {
-  return kDeltaManifestSizeOffset + kDeltaManifestSizeSize;
+bool PayloadMetadata::GetMetadataSignatureSizeOffset(
+    uint64_t* out_offset) const {
+  if (GetMajorVersion() == kBrilloMajorPayloadVersion) {
+    *out_offset = kDeltaManifestSizeOffset + kDeltaManifestSizeSize;
+    return true;
+  }
+  return false;
 }
 
-uint64_t PayloadMetadata::GetManifestOffset() const {
-  // Actual manifest begins right after the metadata signature size field.
-  return kDeltaManifestSizeOffset + kDeltaManifestSizeSize +
-         kDeltaMetadataSignatureSizeSize;
+bool PayloadMetadata::GetManifestOffset(uint64_t* out_offset) const {
+  // Actual manifest begins right after the manifest size field or
+  // metadata signature size field if major version >= 2.
+  if (major_payload_version_ == kChromeOSMajorPayloadVersion) {
+    *out_offset = kDeltaManifestSizeOffset + kDeltaManifestSizeSize;
+    return true;
+  }
+  if (major_payload_version_ == kBrilloMajorPayloadVersion) {
+    *out_offset = kDeltaManifestSizeOffset + kDeltaManifestSizeSize +
+                  kDeltaMetadataSignatureSizeSize;
+    return true;
+  }
+  LOG(ERROR) << "Unknown major payload version: " << major_payload_version_;
+  return false;
 }
 
 MetadataParseResult PayloadMetadata::ParsePayloadHeader(
-    const brillo::Blob& payload, ErrorCode* error) {
+    const brillo::Blob& payload,
+    HardwareInterface* hardware,
+    ErrorCode* error) {
+  uint64_t manifest_offset;
   // Ensure we have data to cover the major payload version.
   if (payload.size() < kDeltaManifestSizeOffset)
     return MetadataParseResult::kInsufficientData;
@@ -59,11 +78,6 @@
     return MetadataParseResult::kError;
   }
 
-  uint64_t manifest_offset = GetManifestOffset();
-  // Check again with the manifest offset.
-  if (payload.size() < manifest_offset)
-    return MetadataParseResult::kInsufficientData;
-
   // Extract the payload version from the metadata.
   static_assert(sizeof(major_payload_version_) == kDeltaVersionSize,
                 "Major payload version size mismatch");
@@ -73,14 +87,26 @@
   // Switch big endian to host.
   major_payload_version_ = be64toh(major_payload_version_);
 
-  if (major_payload_version_ < kMinSupportedMajorPayloadVersion ||
-      major_payload_version_ > kMaxSupportedMajorPayloadVersion) {
+  // We only want to test major version 1 for test images.
+  if (major_payload_version_ == kChromeOSMajorPayloadVersion
+          ? hardware != nullptr && hardware->IsOfficialBuild()
+          : major_payload_version_ < kMinSupportedMajorPayloadVersion ||
+                major_payload_version_ > kMaxSupportedMajorPayloadVersion) {
     LOG(ERROR) << "Bad payload format -- unsupported payload version: "
                << major_payload_version_;
     *error = ErrorCode::kUnsupportedMajorPayloadVersion;
     return MetadataParseResult::kError;
   }
 
+  // Get the manifest offset now that we have payload version.
+  if (!GetManifestOffset(&manifest_offset)) {
+    *error = ErrorCode::kUnsupportedMajorPayloadVersion;
+    return MetadataParseResult::kError;
+  }
+  // Check again with the manifest offset.
+  if (payload.size() < manifest_offset)
+    return MetadataParseResult::kInsufficientData;
+
   // Next, parse the manifest size.
   static_assert(sizeof(manifest_size_) == kDeltaManifestSizeSize,
                 "manifest_size size mismatch");
@@ -97,33 +123,43 @@
     return MetadataParseResult::kError;
   }
 
-  // Parse the metadata signature size.
-  static_assert(
-      sizeof(metadata_signature_size_) == kDeltaMetadataSignatureSizeSize,
-      "metadata_signature_size size mismatch");
-  uint64_t metadata_signature_size_offset = GetMetadataSignatureSizeOffset();
-  memcpy(&metadata_signature_size_,
-         &payload[metadata_signature_size_offset],
-         kDeltaMetadataSignatureSizeSize);
-  metadata_signature_size_ = be32toh(metadata_signature_size_);
+  if (GetMajorVersion() == kBrilloMajorPayloadVersion) {
+    // Parse the metadata signature size.
+    static_assert(
+        sizeof(metadata_signature_size_) == kDeltaMetadataSignatureSizeSize,
+        "metadata_signature_size size mismatch");
+    uint64_t metadata_signature_size_offset;
+    if (!GetMetadataSignatureSizeOffset(&metadata_signature_size_offset)) {
+      *error = ErrorCode::kError;
+      return MetadataParseResult::kError;
+    }
+    memcpy(&metadata_signature_size_,
+           &payload[metadata_signature_size_offset],
+           kDeltaMetadataSignatureSizeSize);
+    metadata_signature_size_ = be32toh(metadata_signature_size_);
 
-  if (metadata_size_ + metadata_signature_size_ < metadata_size_) {
-    // Overflow detected.
-    LOG(ERROR) << "Overflow detected on metadata and signature size.";
-    *error = ErrorCode::kDownloadInvalidMetadataSize;
-    return MetadataParseResult::kError;
+    if (metadata_size_ + metadata_signature_size_ < metadata_size_) {
+      // Overflow detected.
+      LOG(ERROR) << "Overflow detected on metadata and signature size.";
+      *error = ErrorCode::kDownloadInvalidMetadataSize;
+      return MetadataParseResult::kError;
+    }
   }
   return MetadataParseResult::kSuccess;
 }
 
-bool PayloadMetadata::ParsePayloadHeader(const brillo::Blob& payload) {
+bool PayloadMetadata::ParsePayloadHeader(const brillo::Blob& payload,
+                                         HardwareInterface* hardware) {
   ErrorCode error;
-  return ParsePayloadHeader(payload, &error) == MetadataParseResult::kSuccess;
+  return ParsePayloadHeader(payload, hardware, &error) ==
+         MetadataParseResult::kSuccess;
 }
 
 bool PayloadMetadata::GetManifest(const brillo::Blob& payload,
                                   DeltaArchiveManifest* out_manifest) const {
-  uint64_t manifest_offset = GetManifestOffset();
+  uint64_t manifest_offset;
+  if (!GetManifestOffset(&manifest_offset))
+    return false;
   CHECK_GE(payload.size(), manifest_offset + manifest_size_);
   return out_manifest->ParseFromArray(&payload[manifest_offset],
                                       manifest_size_);
@@ -145,7 +181,7 @@
                  << metadata_signature;
       return ErrorCode::kDownloadMetadataSignatureError;
     }
-  } else {
+  } else if (major_payload_version_ == kBrilloMajorPayloadVersion) {
     metadata_signature_protobuf_blob.assign(
         payload.begin() + metadata_size_,
         payload.begin() + metadata_size_ + metadata_signature_size_);
@@ -206,7 +242,7 @@
   brillo::Blob payload;
   TEST_AND_RETURN_FALSE(
       utils::ReadFileChunk(payload_path, 0, kMaxPayloadHeaderSize, &payload));
-  TEST_AND_RETURN_FALSE(ParsePayloadHeader(payload));
+  TEST_AND_RETURN_FALSE(ParsePayloadHeader(payload, nullptr));
 
   if (manifest != nullptr) {
     TEST_AND_RETURN_FALSE(
@@ -217,7 +253,8 @@
     TEST_AND_RETURN_FALSE(GetManifest(payload, manifest));
   }
 
-  if (metadata_signatures != nullptr) {
+  if (metadata_signatures != nullptr &&
+      GetMajorVersion() >= kBrilloMajorPayloadVersion) {
     payload.clear();
     TEST_AND_RETURN_FALSE(utils::ReadFileChunk(
         payload_path, GetMetadataSize(), GetMetadataSignatureSize(), &payload));
diff --git a/payload_consumer/payload_metadata.h b/payload_consumer/payload_metadata.h
index be43c41..3292351 100644
--- a/payload_consumer/payload_metadata.h
+++ b/payload_consumer/payload_metadata.h
@@ -26,6 +26,7 @@
 #include <brillo/secure_blob.h>
 
 #include "update_engine/common/error_code.h"
+#include "update_engine/common/hardware_interface.h"
 #include "update_engine/common/platform_constants.h"
 #include "update_engine/update_metadata.pb.h"
 
@@ -54,9 +55,11 @@
   // metadata. Returns kMetadataParseError if the metadata can't be parsed given
   // the payload.
   MetadataParseResult ParsePayloadHeader(const brillo::Blob& payload,
+                                         HardwareInterface* hardware,
                                          ErrorCode* error);
   // Simpler version of the above, returns true on success.
-  bool ParsePayloadHeader(const brillo::Blob& payload);
+  bool ParsePayloadHeader(const brillo::Blob& payload,
+                          HardwareInterface* hardware);
 
   // Given the |payload|, verifies that the signed hash of its metadata matches
   // |metadata_signature| (if present) or the metadata signature in payload
@@ -94,12 +97,14 @@
                         Signatures* metadata_signatures);
 
  private:
-  // Returns the byte offset at which the manifest protobuf begins in a payload.
-  uint64_t GetManifestOffset() const;
+  // Set |*out_offset| to the byte offset at which the manifest protobuf begins
+  // in a payload. Return true on success, false if the offset is unknown.
+  bool GetManifestOffset(uint64_t* out_offset) const;
 
-  // Returns the byte offset where the size of the metadata signature is stored
-  // in a payload.
-  uint64_t GetMetadataSignatureSizeOffset() const;
+  // Set |*out_offset| to the byte offset where the size of the metadata
+  // signature is stored in a payload. Return true on success, if this field is
+  // not present in the payload, return false.
+  bool GetMetadataSignatureSizeOffset(uint64_t* out_offset) const;
 
   uint64_t metadata_size_{0};
   uint64_t manifest_size_{0};