Update requirements.txt

requirements.txt

@@ -10,9 +10,9 @@ sentencepiece>=0.2.0
 sentence-transformers>=3.0.0
 
 # RAG / Vector store
-langchain>=0.3.0
-langchain-community>=0.3.0
-langchain-huggingface>=0.1.0
+langchain==0.1.20
+langchain-community==0.0.38
+langchain-core==0.1.52
 faiss-cpu>=1.8.0
 
 # Document loaders