How to add cross-thread persistence (functional API)

Prerequisites

This guide assumes familiarity with the following:

• Functional API
• Persistence
• Memory
• Chat Models

LangGraph allows you to persist data across different threads. For instance, you can store information about users (their names or preferences) in a shared (cross-thread) memory and reuse them in the new threads (e.g., new conversations).

When using the functional API, you can set it up to store and retrieve memories by using the Store interface:

1. Create an instance of a Store

   from langgraph.store.memory import InMemoryStore, BaseStore
   
   store = InMemoryStore()
   

2. Pass the store instance to the entrypoint() decorator and expose store parameter in the function signature:

   from langgraph.func import entrypoint
   
   @entrypoint(store=store)
   def workflow(inputs: dict, store: BaseStore):
       my_task(inputs).result()
       ...
   

   API Reference: entrypoint

In this guide, we will show how to construct and use a workflow that has a shared memory implemented using the Store interface.

Note

Support for the Store API that is used in this guide was added in LangGraph v0.2.32.

Support for index and query arguments of the Store API that is used in this guide was added in LangGraph v0.2.54.

Note

If you need to add cross-thread persistence to a StateGraph, check out this how-to guide.

Setup

First, let's install the required packages and set our API keys

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

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")
_set_env("OPENAI_API_KEY")

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Example: simple chatbot with long-term memory

Define store

In this example we will create a workflow that will be able to retrieve information about a user's preferences. We will do so by defining an InMemoryStore - an object that can store data in memory and query that data.

When storing objects using the Store interface you define two things:

• the namespace for the object, a tuple (similar to directories)
• the object key (similar to filenames)

In our example, we'll be using ("memories", <user_id>) as namespace and random UUID as key for each new memory.

Importantly, to determine the user, we will be passing user_id via the config keyword argument of the node function.

Let's first define our store!

from langgraph.store.memory import InMemoryStore
from langchain_openai import OpenAIEmbeddings

in_memory_store = InMemoryStore(
    index={
        "embed": OpenAIEmbeddings(model="text-embedding-3-small"),
        "dims": 1536,
    }
)

API Reference: OpenAIEmbeddings

Create workflow

import uuid

from langchain_anthropic import ChatAnthropic
from langchain_core.runnables import RunnableConfig
from langchain_core.messages import BaseMessage
from langgraph.func import entrypoint, task
from langgraph.graph import add_messages
from langgraph.checkpoint.memory import MemorySaver
from langgraph.store.base import BaseStore


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


@task
def call_model(messages: list[BaseMessage], memory_store: BaseStore, user_id: str):
    namespace = ("memories", user_id)
    last_message = messages[-1]
    memories = memory_store.search(namespace, query=str(last_message.content))
    info = "\n".join([d.value["data"] for d in memories])
    system_msg = f"You are a helpful assistant talking to the user. User info: {info}"

    # Store new memories if the user asks the model to remember
    if "remember" in last_message.content.lower():
        memory = "User name is Bob"
        memory_store.put(namespace, str(uuid.uuid4()), {"data": memory})

    response = model.invoke([{"role": "system", "content": system_msg}] + messages)
    return response


# NOTE: we're passing the store object here when creating a workflow via entrypoint()
@entrypoint(checkpointer=MemorySaver(), store=in_memory_store)
def workflow(
    inputs: list[BaseMessage],
    *,
    previous: list[BaseMessage],
    config: RunnableConfig,
    store: BaseStore,
):
    user_id = config["configurable"]["user_id"]
    previous = previous or []
    inputs = add_messages(previous, inputs)
    response = call_model(inputs, store, user_id).result()
    return entrypoint.final(value=response, save=add_messages(inputs, response))

API Reference: ChatAnthropic | RunnableConfig | BaseMessage | entrypoint | task | add_messages | MemorySaver

Note

If you're using LangGraph Cloud or LangGraph Studio, you don't need to pass store to the entrypoint decorator, since it's done automatically.

Run the workflow!

Now let's specify a user ID in the config and tell the model our name:

config = {"configurable": {"thread_id": "1", "user_id": "1"}}
input_message = {"role": "user", "content": "Hi! Remember: my name is Bob"}
for chunk in workflow.stream([input_message], config, stream_mode="values"):
    chunk.pretty_print()

================================== Ai Message ==================================

Hello Bob! Nice to meet you. I'll remember that your name is Bob. How can I help you today?

config = {"configurable": {"thread_id": "2", "user_id": "1"}}
input_message = {"role": "user", "content": "what is my name?"}
for chunk in workflow.stream([input_message], config, stream_mode="values"):
    chunk.pretty_print()

================================== Ai Message ==================================

Your name is Bob.

We can now inspect our in-memory store and verify that we have in fact saved the memories for the user:

for memory in in_memory_store.search(("memories", "1")):
    print(memory.value)

{'data': 'User name is Bob'}

Let's now run the workflow for another user to verify that the memories about the first user are self contained:

config = {"configurable": {"thread_id": "3", "user_id": "2"}}
input_message = {"role": "user", "content": "what is my name?"}
for chunk in workflow.stream([input_message], config, stream_mode="values"):
    chunk.pretty_print()

================================== Ai Message ==================================

I don't have any information about your name. I can only see our current conversation without any prior context or personal details about you. If you'd like me to know your name, feel free to tell me!

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