fixed tuple issue

app.py

@@ -54,14 +54,14 @@ def process_pdf(pdf_file):
     db = FAISS.from_texts(chunks, embeddings)
     db.save_local(session_path)
 
-    chat_history = [{"role": "system", "content": "Paper uploaded and processed. You can now ask questions."}]
+    chat_history = [("System", "Paper uploaded and processed. You can now ask questions.")]
     return f"Paper uploaded successfully. Session ID: {session_id}", session_id, chat_history
 
 # === QUERY FUNCTION ===
 def query_paper(session_id, user_message, chat_history):
     if not session_id or not os.path.exists(os.path.join(STORAGE_DIR, session_id)):
         chat_history = chat_history or []
-        chat_history.append({"role": "system", "content": "Session expired or not found. Upload the paper again."})
+        chat_history.append(("System", "Session expired or not found. Upload the paper again."))
         return chat_history, ""
 
     if not user_message.strip():
@@ -72,7 +72,7 @@ def query_paper(session_id, user_message, chat_history):
     db = FAISS.load_local(session_path, embeddings, allow_dangerous_deserialization=True)
     retriever = db.as_retriever(search_kwargs={"k": 3})
 
-    # Use invoke() method instead of deprecated get_relevant_documents
+    # Use invoke() instead of deprecated method
     docs = retriever.invoke(user_message)
     context = "\n\n".join([d.page_content for d in docs])
 
@@ -114,10 +114,9 @@ def query_paper(session_id, user_message, chat_history):
     except Exception as e:
         answer = f"Error: {str(e)}"
 
-    # Update chat history (Gradio expects list of dicts with role + content)
+    # Update chat history (tuple format)
     chat_history = chat_history or []
-    chat_history.append({"role": "user", "content": user_message})
-    chat_history.append({"role": "assistant", "content": answer})
+    chat_history.append((user_message, answer))
 
     return chat_history, ""
 
@@ -187,7 +186,7 @@ with gr.Blocks() as demo:
         outputs=[chatbot, state_chat]
     )
 
-    # Update chatbot display when chat history changes
+    # Sync chat state with chatbot
     state_chat.change(
         lambda chat: chat,
         inputs=[state_chat],