Fix 法规对话

backend/app/shared/bootstrap.py

@@ -19,6 +19,7 @@ from app.infrastructure.storage.json_document_repository import JsonDocumentRepo
 from app.infrastructure.storage.minio_binary_store import MinioDocumentBinaryStore
 from app.infrastructure.storage.postgres_document_repository import PostgresDocumentRepository
 from app.infrastructure.storage.postgres_parse_artifact_store import PostgresParseArtifactStore
+from app.infrastructure.vectorstore.bm25_retriever import BM25Retriever
 from app.infrastructure.vectorstore.dense_retriever import DenseRetriever
 from app.infrastructure.vectorstore.milvus_vector_index import MilvusVectorIndex
 from app.infrastructure.vectorstore.cross_encoder_reranker import OpenAICompatibleReranker
@@ -87,6 +88,13 @@ def get_reranker():
     return None
 
 
+@lru_cache
+def get_bm25_retriever() -> BM25Retriever | None:
+    """Return BM25 retriever if rank_bm25 + jieba are installed, else None."""
+    retriever = BM25Retriever(vector_index=get_vector_index())
+    return retriever if retriever.available else None
+
+
 @lru_cache
 def get_retrieval_service() -> KnowledgeRetrievalService:
     """Return retrieval service."""
@@ -96,6 +104,7 @@ def get_retrieval_service() -> KnowledgeRetrievalService:
     )
     return KnowledgeRetrievalService(
         retriever=retriever,
+        bm25_retriever=get_bm25_retriever(),
         reranker=get_reranker(),
         reranker_top_k=settings.reranker_top_k,
     )