langgraph/docs/docs/how-tos/persistence.ipynb

How to add thread-level persistence to your graph

Prerequisites

This guide assumes familiarity with the following:

• Persistence
• Memory
• Chat Models

Many AI applications need memory to share context across multiple interactions. In LangGraph, this kind of memory can be added to any StateGraph using thread-level persistence .

When creating any LangGraph graph, you can set it up to persist its state by adding a checkpointer when compiling the graph:

from langgraph.checkpoint.memory import MemorySaver

checkpointer = MemorySaver()
graph.compile(checkpointer=checkpointer)

This guide shows how you can add thread-level persistence to your graph.

Note

If you need memory that is shared across multiple conversations or users (cross-thread persistence), check out this how-to guide.

Setup

First we need to install the packages required

In [1]:

%%capture --no-stderr
%pip install --quiet -U langgraph langchain_anthropic

Next, we need to set API keys for OpenAI (the LLM we will use) and Tavily (the search tool we will use)

In [2]:

import getpass
import os


def _set_env(var: str):
    if not os.environ.get(var):
        os.environ[var] = getpass.getpass(f"{var}: ")


_set_env("ANTHROPIC_API_KEY")

ANTHROPIC_API_KEY:  ········

Set up LangSmith for LangGraph development

Sign up for LangSmith to quickly spot issues and improve the performance of your LangGraph projects. LangSmith lets you use trace data to debug, test, and monitor your LLM apps built with LangGraph — read more about how to get started here.

Define graph

We will be using a single-node graph that calls a chat model.

Let's first define the model we'll be using:

In [3]:

from langchain_anthropic import ChatAnthropic

model = ChatAnthropic(model="claude-3-5-sonnet-20240620")

Now we can define our StateGraph and add our model-calling node:

In [4]:

from typing import Annotated
from typing_extensions import TypedDict

from langgraph.graph import StateGraph, MessagesState, START


def call_model(state: MessagesState):
    response = model.invoke(state["messages"])
    return {"messages": response}


builder = StateGraph(MessagesState)
builder.add_node("call_model", call_model)
builder.add_edge(START, "call_model")
graph = builder.compile()

If we try to use this graph, the context of the conversation will not be persisted across interactions:

In [5]:

input_message = {"type": "user", "content": "hi! I'm bob"}
for chunk in graph.stream({"messages": [input_message]}, stream_mode="values"):
    chunk["messages"][-1].pretty_print()

input_message = {"type": "user", "content": "what's my name?"}
for chunk in graph.stream({"messages": [input_message]}, stream_mode="values"):
    chunk["messages"][-1].pretty_print()

================================ Human Message =================================

hi! I'm bob
================================== Ai Message ==================================

Hello Bob! It's nice to meet you. How are you doing today? Is there anything I can help you with or would you like to chat about something in particular?
================================ Human Message =================================

what's my name?
================================== Ai Message ==================================

I apologize, but I don't have access to your personal information, including your name. I'm an AI language model designed to provide general information and answer questions to the best of my ability based on my training data. I don't have any information about individual users or their personal details. If you'd like to share your name, you're welcome to do so, but I won't be able to recall it in future conversations.

Add persistence

To add in persistence, we need to pass in a Checkpointer when compiling the graph.

In [6]:

from langgraph.checkpoint.memory import MemorySaver

memory = MemorySaver()
graph = builder.compile(checkpointer=memory)
# If you're using LangGraph Cloud or LangGraph Studio, you don't need to pass the checkpointer when compiling the graph, since it's done automatically.

Note

If you're using LangGraph Cloud or LangGraph Studio, you don't need to pass checkpointer when compiling the graph, since it's done automatically.

We can now interact with the agent and see that it remembers previous messages!

In [7]:

config = {"configurable": {"thread_id": "1"}}
input_message = {"type": "user", "content": "hi! I'm bob"}
for chunk in graph.stream({"messages": [input_message]}, config, stream_mode="values"):
    chunk["messages"][-1].pretty_print()

================================ Human Message =================================

hi! I'm bob
================================== Ai Message ==================================

Hello Bob! It's nice to meet you. How are you doing today? Is there anything in particular you'd like to chat about or any questions you have that I can help you with?

You can always resume previous threads:

In [8]:

input_message = {"type": "user", "content": "what's my name?"}
for chunk in graph.stream({"messages": [input_message]}, config, stream_mode="values"):
    chunk["messages"][-1].pretty_print()

================================ Human Message =================================

what's my name?
================================== Ai Message ==================================

Your name is Bob, as you introduced yourself at the beginning of our conversation.

If we want to start a new conversation, we can pass in a different thread_id. Poof! All the memories are gone!

In [9]:

input_message = {"type": "user", "content": "what's my name?"}
for chunk in graph.stream(
    {"messages": [input_message]},
    {"configurable": {"thread_id": "2"}},
    stream_mode="values",
):
    chunk["messages"][-1].pretty_print()

================================ Human Message =================================

what's is my name?
================================== Ai Message ==================================

I apologize, but I don't have access to your personal information, including your name. As an AI language model, I don't have any information about individual users unless it's provided within the conversation. If you'd like to share your name, you're welcome to do so, but otherwise, I won't be able to know or guess it.