diff --git a/api/services/message_service.py b/api/services/message_service.py
index cb5ba0306f2..9b20854ab17 100644
--- a/api/services/message_service.py
+++ b/api/services/message_service.py
@@ -411,10 +411,14 @@ class MessageService:
             if suggested_questions_after_answer_config.get("enabled", False) is False:
                 raise SuggestedQuestionsAfterAnswerDisabledError()
 
-        model_instance = model_manager.get_default_model_instance(
-            tenant_id=app_model.tenant_id,
-            model_type=ModelType.LLM,
-        )
+        try:
+            model_instance = model_manager.get_default_model_instance(
+                tenant_id=app_model.tenant_id,
+                model_type=ModelType.LLM,
+            )
+        except Exception:
+            logger.exception("Failed to resolve the history model for suggested questions")
+            return []
 
         # get memory of conversation (read-only)
         memory = TokenBufferMemory(conversation=conversation, model_instance=model_instance)
diff --git a/api/tests/unit_tests/services/test_message_service.py b/api/tests/unit_tests/services/test_message_service.py
index e6e5c76a9ca..21b7093a6f7 100644
--- a/api/tests/unit_tests/services/test_message_service.py
+++ b/api/tests/unit_tests/services/test_message_service.py
@@ -950,6 +950,32 @@ class TestMessageServiceSuggestedQuestions:
             model_config=None,
         )
 
+    def test_agent_unavailable_default_model_returns_empty_questions(
+        self,
+        monkeypatch: pytest.MonkeyPatch,
+        factory: MessageServiceTestDataFactory,
+        sqlite_session: Session,
+    ) -> None:
+        conversation = factory.create_conversation()
+        conversation.mode = AppMode.AGENT
+        model_manager, memory, llm_generator = self._chat_boundaries(monkeypatch, conversation)
+        model_manager.get_default_model_instance.side_effect = ValueError("unsupported default model")
+        roster_service = MagicMock()
+        roster_service.return_value.get_published_agent_soul_for_app.return_value = self._agent_soul()
+        monkeypatch.setattr("services.agent.roster_service.AgentRosterService", roster_service)
+
+        result = MessageService.get_suggested_questions_after_answer(
+            app_model=factory.create_app(mode=AppMode.AGENT),
+            user=factory.create_end_user(),
+            message_id="msg-123",
+            invoke_from=InvokeFrom.SERVICE_API,
+            session=sqlite_session,
+        )
+
+        assert result == []
+        memory.assert_not_called()
+        llm_generator.generate_suggested_questions_after_answer.assert_not_called()
+
     def test_historical_agent_without_soul_uses_current_app_model_config(
         self,
         monkeypatch: pytest.MonkeyPatch,