diff --git a/api/core/app/apps/advanced_chat/generate_task_pipeline.py b/api/core/app/apps/advanced_chat/generate_task_pipeline.py
index f7b5030d33..cb7ec91115 100644
--- a/api/core/app/apps/advanced_chat/generate_task_pipeline.py
+++ b/api/core/app/apps/advanced_chat/generate_task_pipeline.py
@@ -188,6 +188,19 @@ class AdvancedChatAppGenerateTaskPipeline(GraphRuntimeStateSupport):
                 if stream_response.metadata:
                     extras["metadata"] = stream_response.metadata
 
+                answer = self._task_state.answer
+
+                # Fallback: if no text chunks were captured during streaming but the
+                # graph runtime state contains an "answer" output (set by the Answer
+                # node via _update_response_outputs), use that instead.  This covers
+                # scenarios where the response-coordinator does not emit streaming
+                # chunks for certain variable types (e.g. workflow-tool outputs fed
+                # directly into an Answer node).
+                if not answer and self._graph_runtime_state is not None:
+                    runtime_answer = self._graph_runtime_state.get_output("answer")
+                    if runtime_answer and isinstance(runtime_answer, str):
+                        answer = runtime_answer
+
                 return ChatbotAppBlockingResponse(
                     task_id=stream_response.task_id,
                     data=ChatbotAppBlockingResponse.Data(
@@ -195,7 +208,7 @@ class AdvancedChatAppGenerateTaskPipeline(GraphRuntimeStateSupport):
                         mode=self._conversation_mode,
                         conversation_id=self._conversation_id,
                         message_id=self._message_id,
-                        answer=self._task_state.answer,
+                        answer=answer,
                         created_at=self._message_created_at,
                         **extras,
                     ),
diff --git a/api/core/app/apps/base_app_queue_manager.py b/api/core/app/apps/base_app_queue_manager.py
index 5addd41815..7580b1e498 100644
--- a/api/core/app/apps/base_app_queue_manager.py
+++ b/api/core/app/apps/base_app_queue_manager.py
@@ -90,7 +90,14 @@ class AppQueueManager(ABC):
         """
         self._clear_task_belong_cache()
         self._q.put(None)
-        self._graph_runtime_state = None  # Release reference to allow GC to reclaim memory
+        # NOTE: Do NOT clear self._graph_runtime_state here.
+        # stop_listen() is called from the worker thread (via _publish) immediately
+        # after enqueueing a terminal event. The consumer thread may not have processed
+        # the preceding events yet and still needs to read graph_runtime_state via
+        # _resolve_graph_runtime_state(). Clearing it here causes a race condition
+        # where the consumer sees None and either raises ValueError or produces an
+        # empty response. The reference will be released when the queue manager is
+        # garbage-collected after both threads are done.
 
     def _clear_task_belong_cache(self) -> None:
         """