Harden HF reachability check: verify file download, not just metadata (#134)

* Harden HF reachability check: verify file download, not just metadata

model_info() can succeed while actual file downloads are blocked by
proxy or firewall. Add a config.json download probe to catch this
case and skip tests cleanly instead of failing with
LocalEntryNotFoundError.

* Harden HF reachability check: verify file download, not just metadata

model_info() can succeed while actual file downloads are blocked by
proxy or firewall. Add a config.json download probe to catch this
case and skip tests cleanly instead of failing with
LocalEntryNotFoundError.

Author: stikves

python/tests/_runner_infra/_deps.py

@@ -51,11 +51,15 @@ def _hf_hub_reachable(model_id: str = "yujiepan/qwen3-tiny-random") -> bool:
     Used as an opt-in gate for tests that call ``Model.from_hf(...)``. Any
     exception (proxy block, DNS failure, timeout, missing dep) is treated as
     "not reachable" so the test is skipped rather than failing.
+
+    Also verifies the model's config.json is downloadable — model_info()
+    can succeed while actual file downloads are blocked by proxy/firewall.
     """
     try:
         import huggingface_hub
 
         huggingface_hub.HfApi().model_info(model_id, timeout=2)
+        huggingface_hub.hf_hub_download(model_id, "config.json", timeout=5)
         return True
     except Exception:
         return False

python/tests/test_model_conversion/conftest.py

@@ -12,21 +12,32 @@
 opt-out for Core AI-export tests where the HF impl decomposes into where-ops
 the Core AI runtime can't lower.
 
-Also applies ``pytest.mark.flaky(reruns=5)`` to every test in this tree.
+Also applies ``pytest.mark.flaky(reruns=5)`` to every test in this tree
+and skips all tests when the HuggingFace Hub is unreachable (every test
+in this directory calls ``from_pretrained``).
 """
 
 import os
 from collections.abc import Iterator
 
 import pytest
 
+from tests._runner_infra._deps import _hf_hub_reachable
+
 
 def pytest_collection_modifyitems(items: list[pytest.Item]) -> None:
     """Apply flaky marker to all tests in this directory and subdirectories."""
     for item in items:
         item.add_marker(pytest.mark.flaky(reruns=5))
 
 
+@pytest.fixture(autouse=True, scope="session")
+def _skip_conversion_tests_if_offline() -> None:
+    """Skip all model conversion tests when HF Hub is unreachable."""
+    if not _hf_hub_reachable():
+        pytest.skip("HuggingFace Hub unreachable; skipping model conversion tests")
+
+
 @pytest.fixture(autouse=True, scope="module")
 def use_hf_impl() -> Iterator[None]:
     """Use HuggingFace implementation for comparison tests in this module."""