diff --git a/openhands/storage/conversation/conversation_store.py b/openhands/storage/conversation/conversation_store.py
index 8c55920efa62..efe95b1b6983 100644
--- a/openhands/storage/conversation/conversation_store.py
+++ b/openhands/storage/conversation/conversation_store.py
@@ -15,7 +15,7 @@ class ConversationStore(ABC):
     """
 
     @abstractmethod
-    async def save_metadata(self, metadata: ConversationMetadata):
+    async def save_metadata(self, metadata: ConversationMetadata) -> None:
         """Store conversation metadata"""
 
     @abstractmethod
diff --git a/openhands/storage/conversation/file_conversation_store.py b/openhands/storage/conversation/file_conversation_store.py
index 79e04921078e..0f7d1f9fa961 100644
--- a/openhands/storage/conversation/file_conversation_store.py
+++ b/openhands/storage/conversation/file_conversation_store.py
@@ -29,7 +29,7 @@
 class FileConversationStore(ConversationStore):
     file_store: FileStore
 
-    async def save_metadata(self, metadata: ConversationMetadata):
+    async def save_metadata(self, metadata: ConversationMetadata) -> None:
         json_str = conversation_metadata_type_adapter.dump_json(metadata)
         path = self.get_conversation_metadata_filename(metadata.conversation_id)
         await call_sync_from_async(self.file_store.write, path, json_str)
diff --git a/openhands/storage/google_cloud.py b/openhands/storage/google_cloud.py
index 19465c0442ce..24466e81ef8a 100644
--- a/openhands/storage/google_cloud.py
+++ b/openhands/storage/google_cloud.py
@@ -29,7 +29,7 @@ def read(self, path: str) -> str:
         blob = self.bucket.blob(path)
         try:
             with blob.open('r') as f:
-                return f.read()
+                return str(f.read())
         except NotFound as err:
             raise FileNotFoundError(err)
 
diff --git a/openhands/storage/local.py b/openhands/storage/local.py
index 38815bce1f0d..711a364cf5d1 100644
--- a/openhands/storage/local.py
+++ b/openhands/storage/local.py
@@ -17,7 +17,7 @@ def get_full_path(self, path: str) -> str:
             path = path[1:]
         return os.path.join(self.root, path)
 
-    def write(self, path: str, contents: str | bytes):
+    def write(self, path: str, contents: str | bytes) -> None:
         full_path = self.get_full_path(path)
         os.makedirs(os.path.dirname(full_path), exist_ok=True)
         mode = 'w' if isinstance(contents, str) else 'wb'
diff --git a/openhands/storage/s3.py b/openhands/storage/s3.py
index cb723355155d..4fb59b920d6c 100644
--- a/openhands/storage/s3.py
+++ b/openhands/storage/s3.py
@@ -46,7 +46,7 @@ def read(self, path: str) -> str:
         try:
             response = self.client.get_object(Bucket=self.bucket, Key=path)
             with response['Body'] as stream:
-                return stream.read().decode('utf-8')
+                return str(stream.read().decode('utf-8'))
         except botocore.exceptions.ClientError as e:
             # Catch all S3-related errors
             if e.response['Error']['Code'] == 'NoSuchBucket':
diff --git a/openhands/storage/settings/file_settings_store.py b/openhands/storage/settings/file_settings_store.py
index d3cc08677078..3c5cf9584891 100644
--- a/openhands/storage/settings/file_settings_store.py
+++ b/openhands/storage/settings/file_settings_store.py
@@ -25,7 +25,7 @@ async def load(self) -> Settings | None:
         except FileNotFoundError:
             return None
 
-    async def store(self, settings: Settings):
+    async def store(self, settings: Settings) -> None:
         json_str = settings.model_dump_json(context={'expose_secrets': True})
         await call_sync_from_async(self.file_store.write, self.path, json_str)
 
diff --git a/openhands/storage/settings/settings_store.py b/openhands/storage/settings/settings_store.py
index cd64ae8e1ea5..c9fdd093ccb9 100644
--- a/openhands/storage/settings/settings_store.py
+++ b/openhands/storage/settings/settings_store.py
@@ -16,7 +16,7 @@ async def load(self) -> Settings | None:
         """Load session init data"""
 
     @abstractmethod
-    async def store(self, settings: Settings):
+    async def store(self, settings: Settings) -> None:
         """Store session init data"""
 
     @classmethod