diff --git a/chatkit/server.py b/chatkit/server.py
index 5963ff8..c0ad3ad 100644
--- a/chatkit/server.py
+++ b/chatkit/server.py
@@ -423,7 +423,10 @@ async def _process_streaming_impl(
                     created_at=datetime.now(),
                     items=Page(),
                 )
-                await self.store.save_thread(thread, context=context)
+                await self.store.save_thread(
+                    ThreadMetadata(**thread.model_dump()),
+                    context=context,
+                )
                 yield ThreadCreatedEvent(thread=self._to_thread_response(thread))
                 user_message = await self._build_user_message_item(
                     request.params.input, thread, context