Update app.py

app.py

@@ -11,6 +11,7 @@ from langchain.chains import RetrievalQA
 from langchain.llms import OpenAI
 from langchain.schema import Document
 from langchain_core.retrievers import BaseRetriever
+from pydantic import Field
 
 # --- CONFIG ---
 DB_PATH = "json_vector.db"
@@ -146,17 +147,14 @@ def query_vector_db(user_query, top_k=5):
         docs.append(Document(page_content=row[4], metadata=meta))
     return docs
 
-# --- LangChain Retriever (subclassing BaseRetriever per v0.1+) ---
-from langchain_core.retrievers import BaseRetriever
-
+# --- LangChain Retriever (BaseRetriever subclass, Pydantic v2 compliant) ---
 class SQLiteVectorRetriever(BaseRetriever):
-    def __init__(self, top_k=5):
-        self.top_k = top_k
+    top_k: int = Field(default=5)
 
     def _get_relevant_documents(self, query, run_manager=None, **kwargs):
         return query_vector_db(query, self.top_k)
 
-llm = OpenAI(model="gpt-4.1", openai_api_key=OPENAI_API_KEY, temperature=0)
+llm = OpenAI(model="gpt-4o", openai_api_key=OPENAI_API_KEY, temperature=0)
 retriever = SQLiteVectorRetriever(top_k=5)
 qa_chain = RetrievalQA.from_chain_type(
     llm=llm,