cdd02084e9
DeltaChannel reconstructs its value by replaying ancestor writes through the reducer. Every saver ordered a checkpoint's writes by (task_id, idx), but live execution applies them in task-path order: apply_writes sorts a super-step's tasks by task_path_str(task.path[:3]) before calling channel.update. task_id is a hash of the path, so the two orders are unrelated, and two or more tasks writing one DeltaChannel in a single super-step replayed in an arbitrary permutation. Reducers are only required to be batching-invariant, not order-invariant, so the permutation changes the value: get_state disagreed with what invoke returned, and continuing the thread persisted the reordered replay as the base for later writes. Replay now orders by (task_path, task_id, idx), following the precedent already set for the Send channel by SELECT_PENDING_SENDS_SQL. InMemorySaver and the postgres savers already persisted task_path and only needed the sort key; sqlite accepted task_path on put_writes and dropped it, so the writes table gains the column, added by setup() to databases created by earlier versions. Writes stored without a task_path sort first within their checkpoint, which is where live execution applies the task-less input writes that carry "". Co-authored-by: ErenAta16 <149434812+ErenAta16@users.noreply.github.com> Co-authored-by: ragnarok268 <58264829+ragnarok268@users.noreply.github.com>
LangGraph Checkpoint Conformance
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Quick Install
uv add langgraph-checkpoint-conformance
🤔 What is this?
This library provides a conformance test suite for LangGraph checkpointer implementations. It validates that a BaseCheckpointSaver subclass correctly implements the checkpoint storage contract — blob round-trips, metadata preservation, namespace isolation, incremental channel updates, and more.
📖 Documentation
For full documentation, see the API reference. For conceptual guides on persistence and memory, see the LangGraph Docs.
Quick start
Register your checkpointer with @checkpointer_test and run validate():
import asyncio
from langgraph.checkpoint.conformance import checkpointer_test, validate
@checkpointer_test(name="MyCheckpointer")
async def my_checkpointer():
saver = MyCheckpointer(...)
yield saver
# cleanup runs after yield
async def main():
report = await validate(my_checkpointer)
report.print_report()
assert report.passed_all_base()
asyncio.run(main())
Or in a pytest test:
import pytest
from langgraph.checkpoint.conformance import checkpointer_test, validate
@checkpointer_test(name="MyCheckpointer")
async def my_checkpointer():
yield MyCheckpointer(...)
@pytest.mark.asyncio
async def test_conformance():
report = await validate(my_checkpointer)
report.print_report()
assert report.passed_all_base()
Capabilities
The suite tests base capabilities (required) and extended capabilities (optional, auto-detected):
| Capability | Required | Method |
|---|---|---|
put |
yes | aput |
put_writes |
yes | aput_writes |
get_tuple |
yes | aget_tuple |
list |
yes | alist |
delete_thread |
yes | adelete_thread |
delete_for_runs |
no | adelete_for_runs |
copy_thread |
no | acopy_thread |
prune |
no | aprune |
delta_channel_history |
no | aget_delta_channel_history |
Extended capabilities are detected by checking whether the method is overridden from BaseCheckpointSaver. If not overridden, those tests are skipped.
Options
Progress output
from langgraph.checkpoint.conformance.report import ProgressCallbacks
# Dot-style progress (. per pass, F per fail)
report = await validate(my_checkpointer, progress=ProgressCallbacks.default())
# Verbose (per-test names + stacktraces on failure)
report = await validate(my_checkpointer, progress=ProgressCallbacks.verbose())
Skip capabilities
@checkpointer_test(name="MyCheckpointer", skip_capabilities={"prune"})
async def my_checkpointer():
yield MyCheckpointer(...)
Run specific capabilities
report = await validate(my_checkpointer, capabilities={"put", "list"})
Lifespan (one-time setup/teardown)
For expensive setup like database creation:
async def db_lifespan():
await create_database()
yield
await drop_database()
@checkpointer_test(name="PostgresSaver", lifespan=db_lifespan)
async def pg_checkpointer():
async with PostgresSaver.from_conn_string(CONN_STRING) as saver:
yield saver
📕 Releases & Versioning
See our Releases and Versioning policies.
💁 Contributing
As an open-source project in a rapidly developing field, we are extremely open to contributions, whether it be in the form of a new feature, improved infrastructure, or better documentation.
For detailed information on how to contribute, see the Contributing Guide.