fix(avatar): enforce each turn response language

digital-avatar-app/backend/tests/test_chat_orchestration.py

@@ -6,6 +6,7 @@ from fastapi import HTTPException
 
 from models import Avatar, User
 from routers.chat import (
+    _answer_requires_language_repair,
     _build_prompt,
     _iter_text_chunks,
     _match_standard_qa,
@@ -14,6 +15,7 @@ from routers.chat import (
     _qa_requires_per_turn_rendering,
     _require_owned_avatar,
     _resolve_reply,
+    _turn_language_name,
 )
 
 
@@ -107,8 +109,8 @@ class ChatOrchestrationTests(unittest.TestCase):
         messages = fake_model.call_args.kwargs["messages"]
         self.assertEqual(messages[-1], {"role": "user", "content": "Quelle est votre adresse ?"})
         self.assertEqual(messages[-2]["role"], "system")
-        self.assertIn("本轮语言覆盖指令", messages[-2]["content"])
-        self.assertIn("不要沿用上一轮语言", messages[-2]["content"])
+        self.assertIn("MANDATORY OUTPUT LANGUAGE", messages[-2]["content"])
+        self.assertIn("French", messages[-2]["content"])
 
     def test_latest_user_message_has_an_adjacent_language_override(self):
         history = [
@@ -119,8 +121,37 @@ class ChatOrchestrationTests(unittest.TestCase):
 
         self.assertEqual(messages[-1], {"role": "user", "content": "What can you help me with?"})
         self.assertEqual(messages[-2]["role"], "system")
-        self.assertIn("最新用户消息", messages[-2]["content"])
-        self.assertIn("立即切换到相同语言", messages[-2]["content"])
+        self.assertIn("MANDATORY OUTPUT LANGUAGE", messages[-2]["content"])
+        self.assertIn("English", messages[-2]["content"])
+
+    def test_reported_alzheimer_question_is_explicitly_english(self):
+        question = "I have a friend who has symptoms of Alzheimer's disease"
+
+        self.assertEqual(_turn_language_name(question), "English")
+        messages = _build_prompt(self.avatar, [], question, [])
+        self.assertIn("MANDATORY OUTPUT LANGUAGE FOR THIS TURN: English", messages[-2]["content"])
+
+    def test_non_stream_reply_repairs_a_wrong_writing_system_before_sending(self):
+        question = "I have a friend who has symptoms of Alzheimer's disease"
+        fake_model = Mock(side_effect=["建议尽快就医评估。", "Please arrange a medical assessment soon."])
+
+        result = _resolve_reply(
+            None,
+            self.avatar,
+            question,
+            [],
+            qa_pairs=[],
+            search_fn=lambda *_args, **_kwargs: [],
+            model_client=fake_model,
+            usage_source="takeover",
+        )
+
+        self.assertEqual(result["answer"], "Please arrange a medical assessment soon.")
+        self.assertEqual(fake_model.call_count, 2)
+        repair_messages = fake_model.call_args.kwargs["messages"]
+        self.assertIn("English", repair_messages[0]["content"])
+        self.assertIn("建议尽快就医评估", repair_messages[-1]["content"])
+        self.assertTrue(_answer_requires_language_repair(question, "建议尽快就医评估。"))
 
     def test_conversational_paraphrase_matches_standard_qa(self):
         for question in ("请问一下，你们公司在哪里呀？", "请问去你们那边怎么走"):