diff --git a/google/cloud/pubsublite/cloudpubsub/internal/async_publisher_impl.py b/google/cloud/pubsublite/cloudpubsub/internal/async_publisher_impl.py
index 39b69b74..cc91e101 100644
--- a/google/cloud/pubsublite/cloudpubsub/internal/async_publisher_impl.py
+++ b/google/cloud/pubsublite/cloudpubsub/internal/async_publisher_impl.py
@@ -25,9 +25,9 @@ async def publish(
         psl_message = from_cps_publish_message(cps_message)
         return (await self._publisher.publish(psl_message)).encode()
 
-    def __aenter__(self):
-        self._publisher.__aenter__()
+    async def __aenter__(self):
+        await self._publisher.__aenter__()
         return self
 
-    def __aexit__(self, exc_type, exc_value, traceback):
-        self._publisher.__aexit__(exc_type, exc_value, traceback)
+    async def __aexit__(self, exc_type, exc_value, traceback):
+        await self._publisher.__aexit__(exc_type, exc_value, traceback)
diff --git a/google/cloud/pubsublite/internal/wire/default_routing_policy.py b/google/cloud/pubsublite/internal/wire/default_routing_policy.py
index 354bb8b2..90858ab9 100644
--- a/google/cloud/pubsublite/internal/wire/default_routing_policy.py
+++ b/google/cloud/pubsublite/internal/wire/default_routing_policy.py
@@ -17,15 +17,15 @@ class DefaultRoutingPolicy(RoutingPolicy):
 
     def __init__(self, num_partitions: int):
         self._num_partitions = num_partitions
-        self._current_round_robin = Partition(random.randint(0, num_partitions))
+        self._current_round_robin = Partition(random.randint(0, num_partitions - 1))
 
     def route(self, message: PubSubMessage) -> Partition:
         """Route the message using the key if set or round robin if unset."""
         if not message.key:
             result = Partition(self._current_round_robin.value)
-            self._current_round_robin.value = (
-                self._current_round_robin.value + 1
-            ) % self._num_partitions
+            self._current_round_robin = Partition(
+                (self._current_round_robin.value + 1) % self._num_partitions
+            )
             return result
         sha = hashlib.sha256()
         sha.update(message.key)
diff --git a/google/cloud/pubsublite/internal/wire/permanent_failable.py b/google/cloud/pubsublite/internal/wire/permanent_failable.py
index 5688e3e7..fa7fb6f2 100644
--- a/google/cloud/pubsublite/internal/wire/permanent_failable.py
+++ b/google/cloud/pubsublite/internal/wire/permanent_failable.py
@@ -9,10 +9,17 @@
 class PermanentFailable:
     """A class that can experience permanent failures, with helpers for forwarding these to client actions."""
 
-    _failure_task: asyncio.Future
+    _maybe_failure_task: Optional[asyncio.Future]
 
     def __init__(self):
-        self._failure_task = asyncio.Future()
+        self._maybe_failure_task = None
+
+    @property
+    def _failure_task(self) -> asyncio.Future:
+        """Get the failure task, initializing it lazily, since it needs to be initialized in the event loop."""
+        if self._maybe_failure_task is None:
+            self._maybe_failure_task = asyncio.Future()
+        return self._maybe_failure_task
 
     async def await_unless_failed(self, awaitable: Awaitable[T]) -> T:
         """
diff --git a/google/cloud/pubsublite/location.py b/google/cloud/pubsublite/location.py
index 6f617b8e..6bacd83a 100644
--- a/google/cloud/pubsublite/location.py
+++ b/google/cloud/pubsublite/location.py
@@ -6,6 +6,9 @@
 class CloudRegion(NamedTuple):
     name: str
 
+    def __str__(self):
+        return self.name
+
 
 class CloudZone(NamedTuple):
     region: CloudRegion
diff --git a/google/cloud/pubsublite/routing_metadata.py b/google/cloud/pubsublite/routing_metadata.py
index 59e71246..ae8e6d00 100644
--- a/google/cloud/pubsublite/routing_metadata.py
+++ b/google/cloud/pubsublite/routing_metadata.py
@@ -8,12 +8,14 @@
 
 
 def topic_routing_metadata(topic: TopicPath, partition: Partition) -> Mapping[str, str]:
-    encoded = urlencode(topic)
-    return {_PARAMS_HEADER: f"partition={partition.value}&topic={encoded}"}
+    encoded = urlencode({"partition": str(partition.value), "topic": str(topic)})
+    return {_PARAMS_HEADER: encoded}
 
 
 def subscription_routing_metadata(
     subscription: SubscriptionPath, partition: Partition
 ) -> Mapping[str, str]:
-    encoded = urlencode(subscription)
-    return {_PARAMS_HEADER: f"partition={partition.value}&subscription={encoded}"}
+    encoded = urlencode(
+        {"partition": str(partition.value), "subscription": str(subscription)}
+    )
+    return {_PARAMS_HEADER: encoded}