When the graph includes an async BaseCheckpointSaver and uses get_state_history, the program hangs

[gbaian10]

Checked other resources

• This is a bug, not a usage question. For questions, please use GitHub Discussions.
• I added a clear and detailed title that summarizes the issue.
• I read what a minimal reproducible example is (https://stackoverflow.com/help/minimal-reproducible-example).
• I included a self-contained, minimal example that demonstrates the issue INCLUDING all the relevant imports. The code run AS IS to reproduce the issue.

Example Code

import asyncio

from langgraph.checkpoint.sqlite.aio import AsyncSqliteSaver
from langgraph.graph import END, START, MessagesState, StateGraph


async def main() -> None:
    builder = StateGraph(MessagesState)
    builder.add_node("foo", lambda _: None)
    builder.add_edge(START, "foo")
    builder.add_edge("foo", END)

    async with AsyncSqliteSaver.from_conn_string(":memory:") as checkpointer:
        graph = builder.compile(checkpointer=checkpointer)
        config = {"configurable": {"thread_id": "1"}}
        await graph.ainvoke({"messages": []}, config)
        for state in graph.get_state_history(config):
            print(state)

        # async for state in graph.aget_state_history(config):
        #     print(state)


if __name__ == "__main__":
    asyncio.run(main())

Description

When using a graph with async checkpointer(sqlite / postgres) and calling sync method get_state_history, the program blocks and cannot continue running.

I expect the sync method to either throw a NotImplementedError exception or continue running, but without leveraging the benefits of async.

System Info

System Information

OS: Linux
Python Version: 3.13.1 (main, Dec 4 2024, 08:54:15) [GCC 13.2.0]

Package Information

langchain_core: 0.3.29
langgraph: 0.2.62
langgraph-checkpoint-sqlite: 2.0.1
langgraph-checkpoint-postgres: 2.0.10

[vbarda]

Thanks for flagging - fixed here #3019

[gbaian10]

I haven't tried checkpoint-duckdb, but I guess it might have the same issue?

[vbarda]

Good call -- will update that one as well. In the meantime, Sqlite/Postgres are released, so closing the issue

[gbaian10]

Thank you 😊

[hnykda]

Huh, I am getting the same with async postgres... this hangs, all on latest versions.

This works, however:

async for state in agent.checkpointer.alist(config):
    print(state)

Interestingly, after I do this, it kinda kills the whole checkpointer - getting state also hangs, even though it works before calling this (same for that alist).

[vbarda]

hm, I would double-check in fresh virtual environment with the latest versions -- the above code is supposed to raise an error

[hnykda]

And it did not raise anything? Feel free to ignore me, might be me...