docs/how_to/message_history/

[giscus[bot]]

docs/how_to/message_history/

This guide assumes familiarity with the following concepts:

https://python.langchain.com/docs/how_to/message_history/

[saketh395]

TypeError: Type is not msgpack serializable: ToolMessage

[ralphy1976]

the first part of the tutorial, where the concept of checkpointer is introduced, doesn't work on vcs.

I modified the code to be able to ask questions one after the other (the while true part) and kept the original code intact.

Here is the full code:

import os
import sys

from langchain_ollama.llms import OllamaLLM
llm = OllamaLLM(temperature=0, model="gemma3:4b")

from langchain_core.messages import HumanMessage
from langgraph.checkpoint.memory import MemorySaver
from langgraph.graph import START, MessagesState, StateGraph

while True:
query = input("tell me your name-->") #this allows me to keep talking with the bot
if query == "q":
break

Define a new graph

workflow = StateGraph(state_schema=MessagesState)

Define the function that calls the model

def call_model(state: MessagesState):
    response = llm.invoke(state["messages"])
# Update message history with response:
    return {"messages": response}

Define the (single) node in the graph

workflow.add_edge(START, "model")
workflow.add_node("model", call_model)

Add memory

memory = MemorySaver()
app = workflow.compile(checkpointer=memory)

config = {"configurable": {"thread_id": "abc123"}}

input_messages = [HumanMessage(query)] #query comes from above below the while true statement
output = app.invoke({"messages": input_messages}, config)
output["messages"][-1].pretty_print()  # output contains all messages in state

After having introduced myself, when i ask the bot "what's my name" it doesn't know (see below)

(venv) PS C:\Users\emile\Desktop\test> python test2.py
tell me your name-->hi my name is bob
================================ Human Message =================================

Hi Bob! It's nice to meet you. 😊

How are you doing today?
tell me your name-->what is my name?
================================ Human Message =================================

I do not know your name. As an AI, I have no memory of past conversations and no way to access personal information about you. 😊

To tell me your name, you'll need to tell me!

Any idea why? thanks

[ralphy1976]

resolved: While statement was in wrong place!!!!