fix: handle empty payload gracefully (#683)

Author: nborges-aws

src/bedrock_agentcore/memory/integrations/strands/session_manager.py

@@ -322,8 +322,10 @@ def read_session(self, session_id: str, **kwargs: Any) -> Optional[Session]:
             max_results=1,
         )
         if events:
-            session_data = json.loads(events[0].get("payload", {})[0].get("blob"))
-            return Session.from_dict(session_data)
+            payload = events[0].get("payload") or []
+            if payload:
+                session_data = json.loads(payload[0].get("blob"))
+                return Session.from_dict(session_data)
 
         # 2. Fallback: check for legacy event and migrate
         legacy_actor_id = f"{LEGACY_SESSION_PREFIX}{session_id}"
@@ -335,7 +337,10 @@ def read_session(self, session_id: str, **kwargs: Any) -> Optional[Session]:
         )
         if events:
             old_event = events[0]
-            session_data = json.loads(old_event.get("payload", {})[0].get("blob"))
+            payload = old_event.get("payload") or []
+            if not payload:
+                return None
+            session_data = json.loads(payload[0].get("blob"))
             session = Session.from_dict(session_data)
             # Migrate: create new event with metadata, delete old
             if self.persistence_mode is not PersistenceMode.NONE:

tests/bedrock_agentcore/memory/integrations/strands/test_agentcore_memory_session_manager.py

@@ -207,10 +207,10 @@ def test_read_session_legacy_migration(self, session_manager, mock_memory_client
         """Test reading a legacy session event triggers migration."""
         legacy_session_data = '{"session_id": "test-session-456", "session_type": "AGENT"}'
 
-        # First call (new approach with metadata) returns empty
+        # First call returns an event whose payload is no longer available
         # Second call (legacy actor_id) returns the legacy event
         mock_memory_client.list_events.side_effect = [
-            [],  # New approach returns nothing
+            [{"eventId": "expired-session-event", "payload": []}],
             [{"eventId": "legacy-event-1", "payload": [{"blob": legacy_session_data}]}],  # Legacy approach
         ]
         mock_memory_client.gmdp_client.create_event.return_value = {"event": {"eventId": "new-event-1"}}
@@ -234,6 +234,19 @@ def test_read_session_legacy_migration(self, session_manager, mock_memory_client
         assert delete_call_kwargs["actorId"] == "session_test-session-456"
         assert delete_call_kwargs["eventId"] == "legacy-event-1"
 
+    def test_read_session_empty_payload_returns_none(self, session_manager, mock_memory_client):
+        """Test session events with empty payloads are treated as unavailable."""
+        mock_memory_client.list_events.side_effect = [
+            [{"eventId": "session-event-1", "payload": []}],
+            [{"eventId": "legacy-event-1", "payload": []}],
+        ]
+
+        result = session_manager.read_session("test-session-456")
+
+        assert result is None
+        mock_memory_client.gmdp_client.create_event.assert_not_called()
+        mock_memory_client.gmdp_client.delete_event.assert_not_called()
+
     def test_create_agent(self, session_manager):
         """Test creating an agent."""
         session_agent = SessionAgent(agent_id="test-agent-123", state={}, conversation_manager_state={})