build: report cuda-bindings provenance in PEP 517 builds

cuda_core/build_hooks.py

@@ -133,6 +133,9 @@ def _build_cuda_core(debug=False):
     # This function populates "_extensions".
     global _extensions
 
+    # Resolve CUDA first so the pathfinder import repairs PEP 517 namespace shadowing before importing bindings.
+    cuda_path = _get_cuda_path()
+
     # Add cuda-bindings to sys.path so Cython can find .pxd files
     # This is needed for editable installs where meta path finders don't work for Cython
     # We need to add the directory containing the 'cuda' package so Cython can resolve
@@ -178,7 +181,7 @@ def get_sources(mod_name):
 
         return sources
 
-    all_include_dirs = [os.path.join(_get_cuda_path(), "include")]
+    all_include_dirs = [os.path.join(cuda_path, "include")]
     extra_compile_args = []
     extra_link_args = []
     extra_cythonize_kwargs = {}

cuda_core/tests/test_build_hooks.py

@@ -16,6 +16,7 @@
 These tests require Cython to be installed (build_hooks.py imports it).
 """
 
+import builtins
 import importlib.util
 import os
 import tempfile
@@ -50,6 +51,35 @@ def _load_build_hooks():
 build_hooks = _load_build_hooks()
 
 
+@pytest.mark.agent_authored(model="gpt-5.6")
+def test_cuda_path_is_resolved_before_importing_bindings(monkeypatch):
+    """PEP 517 namespace repair runs before cuda.bindings is imported."""
+    events = []
+
+    class StopBuildError(Exception):
+        pass
+
+    def get_cuda_path():
+        events.append("cuda-path")
+        return "/cuda"
+
+    original_import = builtins.__import__
+
+    def stop_at_bindings_import(name, *args, **kwargs):
+        if name == "cuda.bindings":
+            events.append("cuda-bindings")
+            raise StopBuildError
+        return original_import(name, *args, **kwargs)
+
+    monkeypatch.setattr(build_hooks, "_get_cuda_path", get_cuda_path)
+    monkeypatch.setattr(builtins, "__import__", stop_at_bindings_import)
+
+    with pytest.raises(StopBuildError):
+        build_hooks._build_cuda_core()
+
+    assert events == ["cuda-path", "cuda-bindings"]
+
+
 def _check_version_detection(
     cuda_version, expected_major, *, use_cuda_path=True, use_cuda_home=False, cuda_core_build_major=None
 ):