diff --git a/src/server/app.py b/src/server/app.py
index 4fb45c9..54a0f99 100644
--- a/src/server/app.py
+++ b/src/server/app.py
@@ -1,5 +1,6 @@
 """FastAPI 服务层."""
 import os
+import uuid
 import logging
 from pathlib import Path
 
@@ -126,7 +127,7 @@ def ingest_document(
             file_name = path.name
         else:
             # content 模式 (file_path/content 互斥由 Pydantic 校验保证)
-            file_name = req.file_name or "untitled.md"
+            file_name = req.file_name or f"untitled_{uuid.uuid4().hex[:8]}.md"
             count = ingestor.ingest_content(req.content, file_name)
         return {"status": "ok", "chunks": count, "file": file_name, "collection": ingestor.collection_name}
     except HTTPException: