diff --git a/backend/app/services/rag/indexer.py b/backend/app/services/rag/indexer.py
index 173cdc3..6d1ea48 100644
--- a/backend/app/services/rag/indexer.py
+++ b/backend/app/services/rag/indexer.py
@@ -760,8 +760,8 @@ class CodeIndexer:
 
         # 从 embedding_service 获取配置
         self.embedding_config = {
-            "provider": getattr(self.embedding_service, 'provider', 'openai'),
-            "model": getattr(self.embedding_service, 'model', 'text-embedding-3-small'),
+            "provider": getattr(self.embedding_service, 'provider', None) or 'openai',
+            "model": getattr(self.embedding_service, 'model', None) or 'text-embedding-3-small',
             "dimension": getattr(self.embedding_service, 'dimension', 1536),
             "base_url": getattr(self.embedding_service, 'base_url', None),
         }
diff --git a/backend/app/services/rag/retriever.py b/backend/app/services/rag/retriever.py
index 1400551..fcd018d 100644
--- a/backend/app/services/rag/retriever.py
+++ b/backend/app/services/rag/retriever.py
@@ -104,8 +104,8 @@ class CodeRetriever:
         """
         self.collection_name = collection_name
         self._provided_embedding_service = embedding_service  # 用户提供的 embedding 服务
-        self.embedding_service = embedding_service  # 实际使用的 embedding 服务
-        self._api_key = api_key
+        self.embedding_service = embedding_service or EmbeddingService() # 实际使用的 embedding 服务
+        self._api_key = api_key or (getattr(self.embedding_service, 'api_key', None) if self.embedding_service else None)
 
         # 创建向量存储
         if vector_store:
diff --git a/backend/app/services/rag/splitter.py b/backend/app/services/rag/splitter.py
index b29af0d..cfc6002 100644
--- a/backend/app/services/rag/splitter.py
+++ b/backend/app/services/rag/splitter.py
@@ -178,6 +178,8 @@ class TreeSitterParser:
         ".bash": "bash",
         ".zsh": "bash",
         ".sql": "sql",
+        ".md": "markdown",
+        ".markdown": "markdown",
     }
     
     # 各语言的函数/类节点类型
@@ -537,6 +539,19 @@ class CodeSplitter:
             if not chunks:
                 chunks = self._split_by_lines(content, file_path, language)
             
+            # 🔥 最后一道防线：如果文件不为空但没有产生任何块（比如文件内容太短被过滤了）
+            # 我们强制创建一个文件级别的块，以确保该文件在索引中“挂名”，避免增量索引一直提示它是“新增”
+            if not chunks and content.strip():
+                chunks.append(CodeChunk(
+                    id="",
+                    content=content,
+                    file_path=file_path,
+                    language=language,
+                    chunk_type=ChunkType.FILE,
+                    line_start=1,
+                    line_end=len(content.split('\n')),
+                ))
+            
             # 后处理：提取安全指标
             for chunk in chunks:
                 chunk.security_indicators = self._extract_security_indicators(