fix message_id not int when restoring from DDB

Author: jeromevdl

src/strands/session/dynamodb_session_manager.py

@@ -110,7 +110,10 @@ def _get_agent_sk(self, agent_id: str) -> str:
 
     def _get_message_sk(self, agent_id: str, message_id: int) -> str:
         """Get message sort key."""
-        if not isinstance(message_id, int):
+        # Convert to int to handle Decimal types from DynamoDB
+        try:
+            message_id = int(message_id)
+        except (ValueError, TypeError):
             raise ValueError(f"message_id=<{message_id}> | message id must be an integer")
         agent_id = self._validate_dynamodb_id(agent_id, _identifier.Identifier.AGENT)
         return f"agent_{agent_id}#message_{message_id}"