diff --git a/google/cloud/pubsublite/cloudpubsub/internal/single_publisher.py b/google/cloud/pubsublite/cloudpubsub/internal/single_publisher.py
index 96c03b0e..04f6e0f6 100644
--- a/google/cloud/pubsublite/cloudpubsub/internal/single_publisher.py
+++ b/google/cloud/pubsublite/cloudpubsub/internal/single_publisher.py
@@ -38,7 +38,7 @@ async def publish(
       **attrs: Additional attributes to send.
 
     Returns:
-      An ack id, which can be decoded using PublishMetadata.decode.
+      An ack id, which can be decoded using MessageMetadata.decode.
 
     Raises:
       GoogleApiCallError: On a permanent failure.
@@ -65,7 +65,7 @@ def publish(
       **attrs: Additional attributes to send.
 
     Returns:
-      A future completed with an ack id, which can be decoded using PublishMetadata.decode.
+      A future completed with an ack id, which can be decoded using MessageMetadata.decode.
 
     Raises:
       GoogleApiCallError: On a permanent failure.
diff --git a/google/cloud/pubsublite/cloudpubsub/message_transforms.py b/google/cloud/pubsublite/cloudpubsub/message_transforms.py
index e3d9a895..3eeed468 100644
--- a/google/cloud/pubsublite/cloudpubsub/message_transforms.py
+++ b/google/cloud/pubsublite/cloudpubsub/message_transforms.py
@@ -19,7 +19,7 @@
 from google.pubsub_v1 import PubsubMessage
 
 from google.cloud.pubsublite.cloudpubsub import MessageTransformer
-from google.cloud.pubsublite.types import Partition, PublishMetadata
+from google.cloud.pubsublite.types import Partition, MessageMetadata
 from google.cloud.pubsublite_v1 import AttributeValues, SequencedMessage, PubSubMessage
 
 PUBSUB_LITE_EVENT_TIME = "x-goog-pubsublite-event-time"
@@ -63,7 +63,7 @@ def add_id_to_message(source: SequencedMessage):
             raise InvalidArgument(
                 "Message after transforming has the message_id field set."
             )
-        message.message_id = PublishMetadata(partition, source.cursor).encode()
+        message.message_id = MessageMetadata(partition, source.cursor).encode()
         return message
 
     return MessageTransformer.of_callable(add_id_to_message)
diff --git a/google/cloud/pubsublite/cloudpubsub/publisher_client_interface.py b/google/cloud/pubsublite/cloudpubsub/publisher_client_interface.py
index 3b19a351..5d15a601 100644
--- a/google/cloud/pubsublite/cloudpubsub/publisher_client_interface.py
+++ b/google/cloud/pubsublite/cloudpubsub/publisher_client_interface.py
@@ -45,7 +45,7 @@ async def publish(
       **attrs: Additional attributes to send.
 
     Returns:
-      An ack id, which can be decoded using PublishMetadata.decode.
+      An ack id, which can be decoded using MessageMetadata.decode.
 
     Raises:
       GoogleApiCallError: On a permanent failure.
@@ -78,7 +78,7 @@ def publish(
       **attrs: Additional attributes to send.
 
     Returns:
-      A future completed with an ack id, which can be decoded using PublishMetadata.decode.
+      A future completed with an ack id, which can be decoded using MessageMetadata.decode.
 
     Raises:
       GoogleApiCallError: On a permanent failure.
diff --git a/google/cloud/pubsublite/internal/wire/partition_count_watching_publisher.py b/google/cloud/pubsublite/internal/wire/partition_count_watching_publisher.py
index 55618de1..ba3a962e 100644
--- a/google/cloud/pubsublite/internal/wire/partition_count_watching_publisher.py
+++ b/google/cloud/pubsublite/internal/wire/partition_count_watching_publisher.py
@@ -21,7 +21,7 @@
 )
 from google.cloud.pubsublite.internal.wire.publisher import Publisher
 from google.cloud.pubsublite.internal.wire.routing_policy import RoutingPolicy
-from google.cloud.pubsublite.types import PublishMetadata, Partition
+from google.cloud.pubsublite.types import MessageMetadata, Partition
 from google.cloud.pubsublite_v1 import PubSubMessage
 
 
@@ -87,7 +87,7 @@ async def _handle_partition_count_update(self, partition_count: int):
         self._publishers.update(new_publishers)
         self._routing_policy = routing_policy
 
-    async def publish(self, message: PubSubMessage) -> PublishMetadata:
+    async def publish(self, message: PubSubMessage) -> MessageMetadata:
         partition = self._routing_policy.route(message)
         assert partition in self._publishers
         publisher = self._publishers[partition]
diff --git a/google/cloud/pubsublite/internal/wire/publisher.py b/google/cloud/pubsublite/internal/wire/publisher.py
index d9a14a94..35b581bb 100644
--- a/google/cloud/pubsublite/internal/wire/publisher.py
+++ b/google/cloud/pubsublite/internal/wire/publisher.py
@@ -15,7 +15,7 @@
 from abc import abstractmethod
 from typing import AsyncContextManager
 from google.cloud.pubsublite_v1.types import PubSubMessage
-from google.cloud.pubsublite.types import PublishMetadata
+from google.cloud.pubsublite.types import MessageMetadata
 
 
 class Publisher(AsyncContextManager):
@@ -24,7 +24,7 @@ class Publisher(AsyncContextManager):
   """
 
     @abstractmethod
-    async def publish(self, message: PubSubMessage) -> PublishMetadata:
+    async def publish(self, message: PubSubMessage) -> MessageMetadata:
         """
     Publish the provided message.
 
diff --git a/google/cloud/pubsublite/internal/wire/routing_publisher.py b/google/cloud/pubsublite/internal/wire/routing_publisher.py
index e6db82e1..630b2712 100644
--- a/google/cloud/pubsublite/internal/wire/routing_publisher.py
+++ b/google/cloud/pubsublite/internal/wire/routing_publisher.py
@@ -17,7 +17,7 @@
 
 from google.cloud.pubsublite.internal.wire.publisher import Publisher
 from google.cloud.pubsublite.internal.wire.routing_policy import RoutingPolicy
-from google.cloud.pubsublite.types import Partition, PublishMetadata
+from google.cloud.pubsublite.types import Partition, MessageMetadata
 from google.cloud.pubsublite_v1 import PubSubMessage
 
 
@@ -42,7 +42,7 @@ async def __aexit__(self, exc_type, exc_val, exc_tb):
         for publisher in self._publishers.values():
             await publisher.__aexit__(exc_type, exc_val, exc_tb)
 
-    async def publish(self, message: PubSubMessage) -> PublishMetadata:
+    async def publish(self, message: PubSubMessage) -> MessageMetadata:
         partition = self._routing_policy.route(message)
         assert partition in self._publishers
         return await self._publishers[partition].publish(message)
diff --git a/google/cloud/pubsublite/internal/wire/single_partition_publisher.py b/google/cloud/pubsublite/internal/wire/single_partition_publisher.py
index 90f6f46a..411d9b13 100644
--- a/google/cloud/pubsublite/internal/wire/single_partition_publisher.py
+++ b/google/cloud/pubsublite/internal/wire/single_partition_publisher.py
@@ -33,7 +33,7 @@
     SerialBatcher,
     BatchTester,
 )
-from google.cloud.pubsublite.types import Partition, PublishMetadata
+from google.cloud.pubsublite.types import Partition, MessageMetadata
 from google.cloud.pubsublite_v1.types import (
     PubSubMessage,
     Cursor,
@@ -159,11 +159,11 @@ async def _flush(self):
             logging.debug(f"Failed publish on stream: {e}")
             self._fail_if_retrying_failed()
 
-    async def publish(self, message: PubSubMessage) -> PublishMetadata:
+    async def publish(self, message: PubSubMessage) -> MessageMetadata:
         cursor_future = self._batcher.add(message)
         if self._batcher.should_flush():
             await self._flush()
-        return PublishMetadata(self._partition, await cursor_future)
+        return MessageMetadata(self._partition, await cursor_future)
 
     async def reinitialize(
         self, connection: Connection[PublishRequest, PublishResponse]
diff --git a/google/cloud/pubsublite/types/__init__.py b/google/cloud/pubsublite/types/__init__.py
index d6e3e4ec..6304fd3c 100644
--- a/google/cloud/pubsublite/types/__init__.py
+++ b/google/cloud/pubsublite/types/__init__.py
@@ -16,7 +16,7 @@
 from .location import CloudRegion, CloudZone
 from .partition import Partition
 from .paths import LocationPath, TopicPath, SubscriptionPath
-from .publish_metadata import PublishMetadata
+from .message_metadata import MessageMetadata
 from .flow_control_settings import FlowControlSettings, DISABLED_FLOW_CONTROL
 
 __all__ = (
@@ -25,7 +25,7 @@
     "FlowControlSettings",
     "LocationPath",
     "Partition",
-    "PublishMetadata",
+    "MessageMetadata",
     "SubscriptionPath",
     "TopicPath",
 )
diff --git a/google/cloud/pubsublite/types/publish_metadata.py b/google/cloud/pubsublite/types/message_metadata.py
similarity index 90%
rename from google/cloud/pubsublite/types/publish_metadata.py
rename to google/cloud/pubsublite/types/message_metadata.py
index c746eda1..cd6b2dc5 100644
--- a/google/cloud/pubsublite/types/publish_metadata.py
+++ b/google/cloud/pubsublite/types/message_metadata.py
@@ -19,7 +19,7 @@
 from google.cloud.pubsublite.types.partition import Partition
 
 
-class PublishMetadata(NamedTuple):
+class MessageMetadata(NamedTuple):
     partition: Partition
     cursor: Cursor
 
@@ -29,9 +29,9 @@ def encode(self) -> str:
         )
 
     @staticmethod
-    def decode(source: str) -> "PublishMetadata":
+    def decode(source: str) -> "MessageMetadata":
         loaded = json.loads(source)
-        return PublishMetadata(
+        return MessageMetadata(
             partition=Partition(loaded["partition"]),
             cursor=Cursor(offset=loaded["offset"]),
         )
diff --git a/noxfile.py b/noxfile.py
index a2791746..776269dd 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -26,7 +26,7 @@
 BLACK_VERSION = "black==19.10b0"
 BLACK_PATHS = ["docs", "google", "tests", "noxfile.py", "setup.py"]
 
-DEFAULT_PYTHON_VERSION = "3.8"
+DEFAULT_PYTHON_VERSION = "3.6"
 SYSTEM_TEST_PYTHON_VERSIONS = ["3.8"]
 UNIT_TEST_PYTHON_VERSIONS = ["3.6", "3.7", "3.8", "3.9"]
 
@@ -45,7 +45,7 @@ def lint(session):
     session.run("flake8", "google", "tests")
 
 
-@nox.session(python="3.6")
+@nox.session(python=DEFAULT_PYTHON_VERSION)
 def blacken(session):
     """Run black.
 
diff --git a/samples/snippets/publish_with_batch_settings_example.py b/samples/snippets/publish_with_batch_settings_example.py
index 8035bbc5..5f0a1067 100644
--- a/samples/snippets/publish_with_batch_settings_example.py
+++ b/samples/snippets/publish_with_batch_settings_example.py
@@ -31,7 +31,7 @@ def publish_with_batch_settings(
     from google.cloud.pubsublite.types import (
         CloudRegion,
         CloudZone,
-        PublishMetadata,
+        MessageMetadata,
         TopicPath,
     )
 
@@ -62,9 +62,9 @@ def publish_with_batch_settings(
             api_future = publisher_client.publish(topic_path, data.encode("utf-8"))
             # result() blocks. To resolve API futures asynchronously, use add_done_callback().
             message_id = api_future.result()
-            publish_metadata = PublishMetadata.decode(message_id)
+            message_metadata = MessageMetadata.decode(message_id)
             print(
-                f"Published {data} to partition {publish_metadata.partition.value} and offset {publish_metadata.cursor.offset}."
+                f"Published {data} to partition {message_metadata.partition.value} and offset {message_metadata.cursor.offset}."
             )
 
     print(
diff --git a/samples/snippets/publish_with_custom_attributes_example.py b/samples/snippets/publish_with_custom_attributes_example.py
index 38c6b1b7..45a0ce29 100644
--- a/samples/snippets/publish_with_custom_attributes_example.py
+++ b/samples/snippets/publish_with_custom_attributes_example.py
@@ -28,7 +28,7 @@ def publish_with_custom_attributes(project_number, cloud_region, zone_id, topic_
     from google.cloud.pubsublite.types import (
         CloudRegion,
         CloudZone,
-        PublishMetadata,
+        MessageMetadata,
         TopicPath,
     )
 
@@ -49,9 +49,9 @@ def publish_with_custom_attributes(project_number, cloud_region, zone_id, topic_
         )
         # result() blocks. To resolve api futures asynchronously, use add_done_callback().
         message_id = api_future.result()
-        publish_metadata = PublishMetadata.decode(message_id)
+        message_metadata = MessageMetadata.decode(message_id)
         print(
-            f"Published {data} to partition {publish_metadata.partition.value} and offset {publish_metadata.cursor.offset}."
+            f"Published {data} to partition {message_metadata.partition.value} and offset {message_metadata.cursor.offset}."
         )
 
     print(f"Finished publishing a message with custom attributes to {str(topic_path)}.")
diff --git a/samples/snippets/publish_with_ordering_key_example.py b/samples/snippets/publish_with_ordering_key_example.py
index 54919901..5b3680e1 100644
--- a/samples/snippets/publish_with_ordering_key_example.py
+++ b/samples/snippets/publish_with_ordering_key_example.py
@@ -30,7 +30,7 @@ def publish_with_odering_key(
     from google.cloud.pubsublite.types import (
         CloudRegion,
         CloudZone,
-        PublishMetadata,
+        MessageMetadata,
         TopicPath,
     )
 
@@ -56,9 +56,9 @@ def publish_with_odering_key(
             )
             # result() blocks. To resolve api futures asynchronously, use add_done_callback().
             message_id = api_future.result()
-            publish_metadata = PublishMetadata.decode(message_id)
+            message_metadata = MessageMetadata.decode(message_id)
             print(
-                f"Published {data} to partition {publish_metadata.partition.value} and offset {publish_metadata.cursor.offset}."
+                f"Published {data} to partition {message_metadata.partition.value} and offset {message_metadata.cursor.offset}."
             )
 
     print(
diff --git a/samples/snippets/publisher_example.py b/samples/snippets/publisher_example.py
index ab240c66..04d7e713 100644
--- a/samples/snippets/publisher_example.py
+++ b/samples/snippets/publisher_example.py
@@ -28,7 +28,7 @@ def publish_messages(project_number, cloud_region, zone_id, topic_id):
     from google.cloud.pubsublite.types import (
         CloudRegion,
         CloudZone,
-        PublishMetadata,
+        MessageMetadata,
         TopicPath,
     )
 
@@ -47,9 +47,9 @@ def publish_messages(project_number, cloud_region, zone_id, topic_id):
         api_future = publisher_client.publish(topic_path, data.encode("utf-8"))
         # result() blocks. To resolve API futures asynchronously, use add_done_callback().
         message_id = api_future.result()
-        publish_metadata = PublishMetadata.decode(message_id)
+        message_metadata = MessageMetadata.decode(message_id)
         print(
-            f"Published a message to partition {publish_metadata.partition.value} and offset {publish_metadata.cursor.offset}."
+            f"Published a message to partition {message_metadata.partition.value} and offset {message_metadata.cursor.offset}."
         )
     # [END pubsublite_quickstart_publisher]
 
diff --git a/samples/snippets/subscriber_example.py b/samples/snippets/subscriber_example.py
index a8c9b5d3..5f5e2c10 100644
--- a/samples/snippets/subscriber_example.py
+++ b/samples/snippets/subscriber_example.py
@@ -21,10 +21,9 @@
 
 import argparse
 
+from google.cloud.pubsublite.types import MessageMetadata
 from google.pubsub_v1 import PubsubMessage
 
-from google.cloud.pubsublite.types import PublishMetadata
-
 
 def receive_messages(
     project_number, cloud_region, zone_id, subscription_id, timeout=90
@@ -60,7 +59,7 @@ def receive_messages(
 
     def callback(message: PubsubMessage):
         message_data = message.data.decode("utf-8")
-        metadata = PublishMetadata.decode(message.message_id)
+        metadata = MessageMetadata.decode(message.message_id)
         print(f"Received {message_data} of ordering key {message.ordering_key} with id {metadata}.")
         message.ack()
 
diff --git a/tests/unit/pubsublite/cloudpubsub/message_transforms_test.py b/tests/unit/pubsublite/cloudpubsub/message_transforms_test.py
index 43e71e90..206a228d 100644
--- a/tests/unit/pubsublite/cloudpubsub/message_transforms_test.py
+++ b/tests/unit/pubsublite/cloudpubsub/message_transforms_test.py
@@ -27,7 +27,7 @@
     from_cps_publish_message,
     add_id_to_cps_subscribe_transformer,
 )
-from google.cloud.pubsublite.types import Partition, PublishMetadata
+from google.cloud.pubsublite.types import Partition, MessageMetadata
 from google.cloud.pubsublite_v1 import (
     SequencedMessage,
     Cursor,
@@ -166,7 +166,7 @@ def test_wrapped_successful():
                 Timestamp(seconds=55).ToDatetime()
             ),
         },
-        message_id=PublishMetadata(Partition(1), Cursor(offset=10)).encode(),
+        message_id=MessageMetadata(Partition(1), Cursor(offset=10)).encode(),
         publish_time=Timestamp(seconds=10),
     )
     result = wrapped.transform(