diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index f5dfbecff..0540b847f 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -1003,15 +1003,35 @@ def MergeDynamicPartitionInfoDicts(framework_dict, vendor_dict):
   Returns:
     The merged dynamic partition info dictionary.
   """
-  merged_dict = {}
+
+  def uniq_concat(a, b):
+    combined = set(a.split(" "))
+    combined.update(set(b.split(" ")))
+    combined = [item.strip() for item in combined if item.strip()]
+    return " ".join(sorted(combined))
+
+  if (framework_dict.get("use_dynamic_partitions") !=
+      "true") or (vendor_dict.get("use_dynamic_partitions") != "true"):
+    raise ValueError("Both dictionaries must have use_dynamic_partitions=true")
+
+  merged_dict = {"use_dynamic_partitions": "true"}
+
+  merged_dict["dynamic_partition_list"] = uniq_concat(
+      framework_dict.get("dynamic_partition_list", ""),
+      vendor_dict.get("dynamic_partition_list", ""))
+
+  # Super block devices are defined by the vendor dict.
+  if "super_block_devices" in vendor_dict:
+    merged_dict["super_block_devices"] = vendor_dict["super_block_devices"]
+    for block_device in merged_dict["super_block_devices"].split(" "):
+      key = "super_%s_device_size" % block_device
+      if key not in vendor_dict:
+        raise ValueError("Vendor dict does not contain required key %s." % key)
+      merged_dict[key] = vendor_dict[key]
+
   # Partition groups and group sizes are defined by the vendor dict because
   # these values may vary for each board that uses a shared system image.
   merged_dict["super_partition_groups"] = vendor_dict["super_partition_groups"]
-  framework_dynamic_partition_list = framework_dict.get(
-      "dynamic_partition_list", "")
-  vendor_dynamic_partition_list = vendor_dict.get("dynamic_partition_list", "")
-  merged_dict["dynamic_partition_list"] = ("%s %s" % (
-      framework_dynamic_partition_list, vendor_dynamic_partition_list)).strip()
   for partition_group in merged_dict["super_partition_groups"].split(" "):
     # Set the partition group's size using the value from the vendor dict.
     key = "super_%s_group_size" % partition_group
@@ -1022,15 +1042,16 @@ def MergeDynamicPartitionInfoDicts(framework_dict, vendor_dict):
     # Set the partition group's partition list using a concatenation of the
     # framework and vendor partition lists.
     key = "super_%s_partition_list" % partition_group
-    merged_dict[key] = (
-        "%s %s" %
-        (framework_dict.get(key, ""), vendor_dict.get(key, ""))).strip()
+    merged_dict[key] = uniq_concat(
+        framework_dict.get(key, ""), vendor_dict.get(key, ""))
+
+  # Various other flags should be copied from the vendor dict, if defined.
+  for key in ("virtual_ab", "virtual_ab_retrofit", "lpmake",
+              "super_metadata_device", "super_partition_error_limit",
+              "super_partition_size"):
+    if key in vendor_dict.keys():
+      merged_dict[key] = vendor_dict[key]
 
-  # Pick virtual ab related flags from vendor dict, if defined.
-  if "virtual_ab" in vendor_dict.keys():
-    merged_dict["virtual_ab"] = vendor_dict["virtual_ab"]
-  if "virtual_ab_retrofit" in vendor_dict.keys():
-    merged_dict["virtual_ab_retrofit"] = vendor_dict["virtual_ab_retrofit"]
   return merged_dict
 
 
diff --git a/tools/releasetools/merge_target_files.py b/tools/releasetools/merge_target_files.py
index bfd2f90c4..6f414a505 100755
--- a/tools/releasetools/merge_target_files.py
+++ b/tools/releasetools/merge_target_files.py
@@ -70,6 +70,10 @@ Usage: merge_target_files.py [args]
   --rebuild_recovery
       Deprecated; does nothing.
 
+  --allow-duplicate-apkapex-keys
+      If provided, duplicate APK/APEX keys are ignored and the value from the
+      framework is used.
+
   --keep-tmp
       Keep tempoary files for debugging purposes.
 """
@@ -110,6 +114,8 @@ OPTIONS.output_img = None
 OPTIONS.output_super_empty = None
 # TODO(b/132730255): Remove this option.
 OPTIONS.rebuild_recovery = False
+# TODO(b/150582573): Remove this option.
+OPTIONS.allow_duplicate_apkapex_keys = False
 OPTIONS.keep_tmp = False
 
 # In an item list (framework or vendor), we may see entries that select whole
@@ -526,6 +532,7 @@ def item_list_to_partition_set(item_list):
 
   Args:
     item_list: A list of items in a target files package.
+
   Returns:
     A set of partitions extracted from the list of items.
   """
@@ -547,7 +554,6 @@ def process_apex_keys_apk_certs_common(framework_target_files_dir,
                                        output_target_files_dir,
                                        framework_partition_set,
                                        vendor_partition_set, file_name):
-
   """Performs special processing for META/apexkeys.txt or META/apkcerts.txt.
 
   This function merges the contents of the META/apexkeys.txt or
@@ -597,7 +603,12 @@ def process_apex_keys_apk_certs_common(framework_target_files_dir,
 
       if partition_tag in partition_set:
         if key in merged_dict:
-          raise ValueError('Duplicate key %s' % key)
+          if OPTIONS.allow_duplicate_apkapex_keys:
+            # TODO(b/150582573) Always raise on duplicates.
+            logger.warning('Duplicate key %s' % key)
+            continue
+          else:
+            raise ValueError('Duplicate key %s' % key)
 
         merged_dict[key] = value
 
@@ -647,8 +658,7 @@ def copy_file_contexts(framework_target_files_dir, vendor_target_files_dir,
 def process_special_cases(framework_target_files_temp_dir,
                           vendor_target_files_temp_dir,
                           output_target_files_temp_dir,
-                          framework_misc_info_keys,
-                          framework_partition_set,
+                          framework_misc_info_keys, framework_partition_set,
                           vendor_partition_set):
   """Performs special-case processing for certain target files items.
 
@@ -967,7 +977,7 @@ def merge_target_files(temp_dir, framework_target_files, framework_item_list,
       rebuild_recovery)
 
   if not check_target_files_vintf.CheckVintf(output_target_files_temp_dir):
-    raise RuntimeError("Incompatible VINTF metadata")
+    raise RuntimeError('Incompatible VINTF metadata')
 
   generate_images(output_target_files_temp_dir, rebuild_recovery)
 
@@ -1075,8 +1085,10 @@ def main():
       OPTIONS.output_img = a
     elif o == '--output-super-empty':
       OPTIONS.output_super_empty = a
-    elif o == '--rebuild_recovery': # TODO(b/132730255): Warn
+    elif o == '--rebuild_recovery':  # TODO(b/132730255): Warn
       OPTIONS.rebuild_recovery = True
+    elif o == '--allow-duplicate-apkapex-keys':
+      OPTIONS.allow_duplicate_apkapex_keys = True
     elif o == '--keep-tmp':
       OPTIONS.keep_tmp = True
     else:
@@ -1104,6 +1116,7 @@ def main():
           'output-img=',
           'output-super-empty=',
           'rebuild_recovery',
+          'allow-duplicate-apkapex-keys',
           'keep-tmp',
       ],
       extra_option_handler=option_handler)
diff --git a/tools/releasetools/test_common.py b/tools/releasetools/test_common.py
index 22fc85adf..ee2857187 100644
--- a/tools/releasetools/test_common.py
+++ b/tools/releasetools/test_common.py
@@ -1418,13 +1418,17 @@ class CommonUtilsTest(test_utils.ReleaseToolsTestCase):
 
   def test_MergeDynamicPartitionInfoDicts_ReturnsMergedDict(self):
     framework_dict = {
+        'use_dynamic_partitions': 'true',
         'super_partition_groups': 'group_a',
         'dynamic_partition_list': 'system',
         'super_group_a_partition_list': 'system',
     }
     vendor_dict = {
+        'use_dynamic_partitions': 'true',
         'super_partition_groups': 'group_a group_b',
         'dynamic_partition_list': 'vendor product',
+        'super_block_devices': 'super',
+        'super_super_device_size': '3000',
         'super_group_a_partition_list': 'vendor',
         'super_group_a_group_size': '1000',
         'super_group_b_partition_list': 'product',
@@ -1434,8 +1438,11 @@ class CommonUtilsTest(test_utils.ReleaseToolsTestCase):
         framework_dict=framework_dict,
         vendor_dict=vendor_dict)
     expected_merged_dict = {
+        'use_dynamic_partitions': 'true',
         'super_partition_groups': 'group_a group_b',
-        'dynamic_partition_list': 'system vendor product',
+        'dynamic_partition_list': 'product system vendor',
+        'super_block_devices': 'super',
+        'super_super_device_size': '3000',
         'super_group_a_partition_list': 'system vendor',
         'super_group_a_group_size': '1000',
         'super_group_b_partition_list': 'product',
@@ -1445,12 +1452,14 @@ class CommonUtilsTest(test_utils.ReleaseToolsTestCase):
 
   def test_MergeDynamicPartitionInfoDicts_IgnoringFrameworkGroupSize(self):
     framework_dict = {
+        'use_dynamic_partitions': 'true',
         'super_partition_groups': 'group_a',
         'dynamic_partition_list': 'system',
         'super_group_a_partition_list': 'system',
         'super_group_a_group_size': '5000',
     }
     vendor_dict = {
+        'use_dynamic_partitions': 'true',
         'super_partition_groups': 'group_a group_b',
         'dynamic_partition_list': 'vendor product',
         'super_group_a_partition_list': 'vendor',
@@ -1462,8 +1471,9 @@ class CommonUtilsTest(test_utils.ReleaseToolsTestCase):
         framework_dict=framework_dict,
         vendor_dict=vendor_dict)
     expected_merged_dict = {
+        'use_dynamic_partitions': 'true',
         'super_partition_groups': 'group_a group_b',
-        'dynamic_partition_list': 'system vendor product',
+        'dynamic_partition_list': 'product system vendor',
         'super_group_a_partition_list': 'system vendor',
         'super_group_a_group_size': '1000',
         'super_group_b_partition_list': 'product',