5-th DL fix

tests/test_node_startup.py

@@ -407,11 +407,11 @@ def test_download_shard_uses_huggingface_when_repo_is_assigned(tmp_path, monkeyp
     }]
 
 
-def test_download_shard_races_tracker_model_source_against_huggingface(
+def test_download_shard_prefers_tracker_model_source_over_huggingface(
     tmp_path,
     monkeypatch,
 ):
-    """Tracker-hosted model files can win while HF receives the same allow_patterns."""
+    """A working tracker model source is used exclusively — HF is never contacted."""
     source_dir = tmp_path / "source"
     source_dir.mkdir()
     (source_dir / "config.json").write_text("{}")
@@ -473,6 +473,49 @@ def test_download_shard_races_tracker_model_source_against_huggingface(
     )
 
     assert (shard_dir / "model-00002-of-00004.safetensors").read_text() == "tracker"
+    assert hf_calls == []
+
+
+def test_download_shard_falls_back_to_huggingface_when_tracker_source_fails(
+    tmp_path,
+    monkeypatch,
+):
+    """A dead tracker source falls through to HF with allow_patterns from the source files."""
+
+    def failing_urlopen(*args, **kwargs):
+        raise ConnectionResetError("tracker went away")
+
+    monkeypatch.setattr(urllib.request, "urlopen", failing_urlopen)
+    hf_calls = []
+
+    def fake_snapshot_download(**kwargs):
+        hf_calls.append(kwargs)
+        local_dir = Path(kwargs["local_dir"])
+        local_dir.mkdir(parents=True, exist_ok=True)
+        (local_dir / "model-00002-of-00004.safetensors").write_text("hf")
+        return str(local_dir)
+
+    monkeypatch.setitem(
+        sys.modules,
+        "huggingface_hub",
+        types.SimpleNamespace(snapshot_download=fake_snapshot_download),
+    )
+
+    shard_dir = download_shard(
+        "tiny-llama",
+        2,
+        3,
+        cache_dir=tmp_path / "cache",
+        hf_repo="org/tiny-llama-shards",
+        model_sources=[{
+            "type": "tracker",
+            "url": "http://tracker/v1/model-files/download?model=tiny-llama",
+            "files": ["config.json", "model-00002-of-00004.safetensors"],
+        }],
+        progress=False,
+    )
+
+    assert (shard_dir / "model-00002-of-00004.safetensors").read_text() == "hf"
     assert hf_calls[0]["allow_patterns"] == ["config.json", "model-00002-of-00004.safetensors"]