Make Linker.backend a classmethod

cuda_core/cuda/core/_linker.pyx

@@ -167,10 +167,22 @@ cdef class Linker:
         else:
             return as_py(self._culink_handle)
 
-    @property
-    def backend(self) -> str:
-        """Return this Linker instance's underlying backend."""
-        return "nvJitLink" if self._use_nvjitlink else "driver"
+    @classmethod
+    def backend(cls) -> str:
+        """Return which linking backend will be used.
+
+        Returns ``"nvJitLink"`` when the nvJitLink library is available
+        and meets the minimum version requirement, otherwise ``"driver"``.
+
+        .. note::
+
+            Prefer letting :class:`Linker` decide. Query ``backend()``
+            only when you need to dispatch based on input format (for
+            example: choose PTX vs. LTOIR before constructing a
+            ``Linker``). The returned string names an implementation
+            detail whose support matrix may shift across CTK releases.
+        """
+        return "driver" if _decide_nvjitlink_or_driver() else "nvJitLink"
 
 
 # =============================================================================

cuda_core/cuda/core/_program.pyx

@@ -649,7 +649,7 @@ cdef inline int Program_init(Program self, object code, str code_type, object op
         self._linker = Linker(
             ObjectCode._init(code.encode(), code_type), options=_translate_program_options(options)
         )
-        self._backend = self._linker.backend
+        self._backend = self._linker.backend()
 
     elif code_type == "nvvm":
         _get_nvvm_module()  # Validate NVVM availability

cuda_core/docs/source/release/0.8.0-notes.rst

@@ -0,0 +1,17 @@
+.. SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+.. SPDX-License-Identifier: Apache-2.0
+
+.. currentmodule:: cuda.core
+
+``cuda.core`` 0.8.0 Release Notes
+=================================
+
+
+Breaking Changes
+----------------
+
+- :meth:`Linker.backend` is now a classmethod instead of an instance property.
+  Call sites must use ``Linker.backend()`` (with parentheses) instead of
+  ``linker.backend``. This allows querying the linking backend without
+  constructing a ``Linker`` instance — for example, to choose between PTX and
+  LTOIR input before linking.

cuda_core/tests/test_linker.py

@@ -92,7 +92,7 @@ def test_linker_init(compile_ptx_functions, options):
     linker = Linker(*compile_ptx_functions, options=options)
     object_code = linker.link("cubin")
     assert isinstance(object_code, ObjectCode)
-    assert linker.backend == ("driver" if is_culink_backend else "nvJitLink")
+    assert linker.backend() == ("driver" if is_culink_backend else "nvJitLink")
 
 
 def test_linker_init_invalid_arch(compile_ptx_functions):

cuda_core/tests/test_linker_backend.py

@@ -0,0 +1,57 @@
+# SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+"""GPU-free tests for Linker.backend classmethod.
+
+These live in a separate file from test_linker.py because that module calls
+Device() at import time, which requires a GPU. These tests use monkeypatch
+to set module-level flags and never touch CUDA devices.
+"""
+
+import inspect
+
+import cuda.core._linker as _linker
+from cuda.core._linker import Linker
+
+
+class TestBackendClassmethod:
+    def test_backend_returns_nvjitlink(self, monkeypatch):
+        monkeypatch.setattr(_linker, "_use_nvjitlink_backend", True)
+        assert Linker.backend() == "nvJitLink"
+
+    def test_backend_returns_driver(self, monkeypatch):
+        monkeypatch.setattr(_linker, "_use_nvjitlink_backend", False)
+        assert Linker.backend() == "driver"
+
+    def test_backend_invokes_probe_when_not_memoised(self, monkeypatch):
+        monkeypatch.setattr(_linker, "_use_nvjitlink_backend", None)
+        called = []
+
+        def fake_decide():
+            called.append(True)
+            return False  # False = not falling back to driver = nvJitLink
+
+        monkeypatch.setattr(_linker, "_decide_nvjitlink_or_driver", fake_decide)
+        result = Linker.backend()
+        assert result == "nvJitLink"
+        assert called, "_decide_nvjitlink_or_driver was not called"
+
+    def test_backend_is_classmethod(self):
+        attr = inspect.getattr_static(Linker, "backend")
+        assert isinstance(attr, classmethod)
+
+    def test_backend_idempotent(self, monkeypatch):
+        monkeypatch.setattr(_linker, "_use_nvjitlink_backend", True)
+        results = [Linker.backend() for _ in range(3)]
+        assert results == ["nvJitLink", "nvJitLink", "nvJitLink"]
+
+    def test_backend_is_not_property(self):
+        """backend is a classmethod, not a property.
+
+        This is an intentional breaking change from the prior property API.
+        Attribute-style access (``linker.backend``) now returns a bound method,
+        not a string. All call sites must use parens: ``Linker.backend()``.
+        """
+        attr = inspect.getattr_static(Linker, "backend")
+        assert not isinstance(attr, property)