Chatbot loses history

Hello, I created a chatbot using Streamlit recommended tutorial, its all working nice and lovely, but for some reason the chatbot loses context in message history, what I mean by this is:

  1. Ask it a question who is the main Caracter of the book - Bot answers correctly
  2. Ask how old is he - Bot will view question as standalone questions and will not know whose age you are asking about, it loses context on question chain.

I am uncertain if Streamlit is somehow losing session data on each new question or not.

Here is the code:

def parse_pdf(file_path: str) -> List[str]:
    loader = PyMuPDFLoader(file_path)
    data = loader.load()
    output = [doc.page_content for doc in data]
    return output

def extract_text(file_path: str) -> List[str]:
        if file_path.endswith('.pdf'):
            return parse_pdf(file_path)
            print(f"Unsupported file type: {file_path}")
            return []
    except Exception as e:
        print(f"Error processing {file_path}: {e}")
        return []

def text_to_docs(text: List[str]) -> List[str]:
    combined_text = ' '.join(text)
    text_splitter = RecursiveCharacterTextSplitter(
        # separators=["\n\n", "\n", ".", "!", "?",","," "],
    return text_splitter.split_text(combined_text)

all_texts = []
for dirpath, dirnames, filenames in os.walk(data_path):
    for filename in filenames:
        file_path = os.path.join(dirpath, filename)
        print(f"processing {file_path}")
            texts = extract_text(file_path)
        except Exception as e:
            print(f"Error processing {file_path}: {e}")  # Error level log
documents = text_to_docs(all_texts)

vector_store = FAISS.from_texts(documents, embedding=embeddings)

if os.path.exists(faiss_file_path):
        vector_store = FAISS.load_local(faiss_file_path, embeddings)

 _template = """ given the following conversation and a follow up question, rephrase the follow up question to be a standalone question, in its original language.
        Chat History:
        Follow Up Input: {question}
        Standalone question:"""
    CONDENSE_QUESTION_PROMPT = PromptTemplate.from_template(_template)
    template = """You are an helpful AI assistant, if someone says HI, hello or any other greeting, try to answer in polite and mannered way as a human would.
Once asked the question try to answer with as much details as possible.
Question: {question}
Answer in Markdown:"""
    QA_PROMPT = PromptTemplate(template=template, input_variables=[
                           "question", "context"])
    memory = ConversationBufferMemory(memory_key="chat_history", return_messages=True)
    llm = ChatAnthropic(temperature=temperature, max_tokens=1000, model_name=model_name="claude-2")
    qa = ConversationalRetrievalChain.from_llm(llm=llm, retriever=vector_store.as_retriever(),condense_question_prompt=CONDENSE_QUESTION_PROMPT,memory=memory,combine_docs_chain_kwargs={"prompt": QA_PROMPT})

if "messages" not in st.session_state:
      st.session_state.messages = []

if not st.session_state.messages:
    welcome_message = {"role": "assistant", "content": "Good day I am helpful chatbot please ask me anything"}

for message in st.session_state.messages:
        with st.chat_message(message["role"]):

if prompt := st.chat_input("State your question"):
    st.session_state.messages.append({"role": "user", "content": prompt})
    with st.chat_message("user"):
    result = qa.invoke({"question": prompt, "chat_history": [(message["role"], message["content"]) for message in st.session_state.messages]})
    with st.chat_message("assistant"):
              message_placeholder = st.empty()
              full_response = result["answer"]
              message_placeholder.markdown(full_response + "|")
              col1, col2, col3, col4 = st.columns([3, 3, 0.5, 0.5])
              with col3:
                  with st.container():
                      st.button(":thumbsup:", on_click=save_likes_to_txt)
              with col4:
                  with st.container():
                      st.button(":thumbsdown:", on_click=save_dislikes_to_txt)
              col3.write(' ')
              col4.write(' ')
      st.session_state.messages.append({"role": "assistant", "content": full_response})