fix: remove hardcoded chinese title heuristics (#887)

* fix: remove hardcoded chinese title heuristics

* fix: use english placeholder for non-latin fallback titles

tests/test_sprint41.py

@@ -137,16 +137,21 @@ class TestIssue495TitleStreaming(unittest.TestCase):
         )
 
     def test_streaming_rejects_generic_completion_titles(self):
-        self.assertIn(
-            "测试完成",
-            STREAMING_PY,
-            "streaming.py should reject generic completion phrases as session titles",
-        )
         self.assertIn(
             "all set",
             STREAMING_PY,
             "streaming.py should reject generic English completion phrases as session titles",
         )
+        self.assertIn(
+            "completed",
+            STREAMING_PY,
+            "streaming.py should reject completion-status titles as session titles",
+        )
+        self.assertNotIn(
+            "测试完成",
+            STREAMING_PY,
+            "streaming.py title generation should stay English-only",
+        )
 
     def test_streaming_uses_reasoning_split_for_minimax_titles(self):
         self.assertIn(

tests/test_title_sanitization.py

@@ -1,6 +1,11 @@
 import unittest
+from pathlib import Path
 
-from api.streaming import _first_exchange_snippets, _sanitize_generated_title
+from api.streaming import (
+    _fallback_title_from_exchange,
+    _first_exchange_snippets,
+    _sanitize_generated_title,
+)
 
 
 class TestGeneratedTitleSanitization(unittest.TestCase):
@@ -33,3 +38,31 @@ class TestGeneratedTitleSanitization(unittest.TestCase):
             _first_exchange_snippets(messages),
             ("What time is it in San Francisco?", "It is 6:16 PM in San Francisco."),
         )
+
+    def test_fallback_title_uses_english_discussion_suffix(self):
+        self.assertEqual(
+            _fallback_title_from_exchange('Please review "random cancel"', ""),
+            "random cancel discussion",
+        )
+
+    def test_fallback_title_summary_label_is_english(self):
+        self.assertEqual(
+            _fallback_title_from_exchange("Generate a short title summary test", ""),
+            "Session title auto-summary test",
+        )
+
+    def test_fallback_title_non_latin_input_uses_english_placeholder(self):
+        self.assertEqual(
+            _fallback_title_from_exchange("讨论一下这个问题", ""),
+            "Conversation topic",
+        )
+
+    def test_fallback_title_non_latin_quoted_topic_uses_english_placeholder(self):
+        self.assertEqual(
+            _fallback_title_from_exchange('Please review "讨论主题"', ""),
+            "Conversation topic",
+        )
+
+    def test_title_generation_source_has_no_cjk_literals(self):
+        src = Path("api/streaming.py").read_text(encoding="utf-8")
+        self.assertNotRegex(src, r"[\u4e00-\u9fff]", "title generation code should stay English-only")