chore(debug): 新增对话保存写入追踪日志，捕获空覆盖调用栈

临时调试代码：每次保存对话时记录 old/new 消息数与项目内调用栈到
logs/conversation_save_debug.log（JSONL），wipe_suspect 时额外打印告警。
用于排查对话消息被清空问题，确认修复后应移除。

utils/conversation_manager/crud_mixin.py

@@ -24,6 +24,69 @@ try:
 except Exception:
     perf_log = None
 
+try:
+    from config import LOGS_DIR as _CONV_SAVE_LOG_DIR
+except Exception:
+    _CONV_SAVE_LOG_DIR = None
+
+
+def _debug_conversation_save_trace(conversation_id: str, file_path, data: Dict):
+    """[临时调试] 记录每次对话文件写入，重点捕获「非空被空覆盖」的调用栈。
+
+    输出: logs/conversation_save_debug.log （JSONL）
+    排查完「对话消息被清空」问题后应移除。
+    """
+    try:
+        import traceback
+        new_msgs = data.get("messages") if isinstance(data, dict) else None
+        new_len = len(new_msgs) if isinstance(new_msgs, list) else -1
+        old_len = None
+        try:
+            p = Path(file_path)
+            if p.exists():
+                old_data = json.loads(p.read_text(encoding="utf-8"))
+                old_msgs = old_data.get("messages")
+                old_len = len(old_msgs) if isinstance(old_msgs, list) else None
+        except Exception:
+            old_len = None
+        wipe_suspect = bool(old_len and new_len == 0)
+        # 只保留项目内调用帧，排除标准库/第三方
+        try:
+            repo_root = Path(__file__).resolve().parents[2]
+        except Exception:
+            repo_root = None
+        frames = []
+        for fr in traceback.extract_stack()[:-2]:
+            fn = str(fr.filename)
+            if repo_root and not fn.startswith(str(repo_root)):
+                continue
+            if "/.astrion/" in fn or "site-packages" in fn:
+                continue
+            rel = fn[len(str(repo_root)) + 1:] if repo_root and fn.startswith(str(repo_root)) else fn
+            frames.append(f"{rel}:{fr.lineno}:{fr.name}")
+        record = {
+            "ts": datetime.now().isoformat(),
+            "event": "conversation_save",
+            "conversation_id": conversation_id,
+            "old_msg_len": old_len,
+            "new_msg_len": new_len,
+            "wipe_suspect": wipe_suspect,
+            "title": (data.get("title") if isinstance(data, dict) else None),
+            "thread": threading.current_thread().name,
+            "stack_tail": frames[-14:],
+        }
+        if _CONV_SAVE_LOG_DIR:
+            log_dir = Path(_CONV_SAVE_LOG_DIR)
+        else:
+            log_dir = Path(DATA_DIR).parent / "logs"
+        log_dir.mkdir(parents=True, exist_ok=True)
+        with open(log_dir / "conversation_save_debug.log", "a", encoding="utf-8") as f:
+            f.write(json.dumps(record, ensure_ascii=False) + "\n")
+        if wipe_suspect:
+            print(f"🚨 [ConvSaveDebug] 对话 {conversation_id} 消息将被空列表覆盖！栈: {frames[-14:]}")
+    except Exception:
+        pass
+
 @dataclass
 class ConversationMetadata:
     """对话元数据"""
@@ -194,6 +257,7 @@ class CrudMixin:
         try:
             # 确保Token统计数据有效
             data = self._validate_token_statistics(data)
+            _debug_conversation_save_trace(conversation_id, file_path, data)
             with self._io_lock:
                 self._atomic_write_json(file_path, data)
         except Exception as e: