diff --git a/cuda_core/cuda/core/_utils/validators.py b/cuda_core/cuda/core/_utils/validators.py
index dac3d1c788e..fb533799e36 100644
--- a/cuda_core/cuda/core/_utils/validators.py
+++ b/cuda_core/cuda/core/_utils/validators.py
@@ -28,7 +28,11 @@ def check_str_enum(value, enum_class, *, allow_none=False):
     """
     if allow_none and value is None:
         return
-    if value not in {m.value for m in enum_class}:
+    # Membership is tested against a tuple rather than a set on purpose:
+    # ``x in {...}`` hashes ``x``, so an unhashable argument (a list, a dict,
+    # a bytearray) would raise ``TypeError: unhashable type`` from inside the
+    # check instead of the ValueError this function exists to raise.
+    if value not in tuple(m.value for m in enum_class):
         valid = sorted(m.value for m in enum_class)
         if allow_none:
             valid = [None, *valid]
diff --git a/cuda_core/docs/source/release/1.2.0-notes.rst b/cuda_core/docs/source/release/1.2.0-notes.rst
index 120d2c2a253..300249ba704 100644
--- a/cuda_core/docs/source/release/1.2.0-notes.rst
+++ b/cuda_core/docs/source/release/1.2.0-notes.rst
@@ -73,6 +73,12 @@ Fixes and enhancements
   Windows, both ``ctypes.CFUNCTYPE`` and ``ctypes.WINFUNCTYPE`` are accepted.
   (`#2439 <https://github.com/NVIDIA/cuda-python/issues/2439>`__)
 
+- String-enum options now report an unhashable argument the same way as any
+  other invalid value. Passing a ``list`` or ``dict`` where a string enum was
+  expected -- for example ``WorkqueueResourceOptions(sharing_scope=[...])`` --
+  raised ``TypeError: unhashable type`` from inside the validator instead of
+  the documented ``ValueError`` naming the accepted values.
+
 Deprecation Notices
 -------------------
 
diff --git a/cuda_core/tests/test_utils_validators.py b/cuda_core/tests/test_utils_validators.py
new file mode 100644
index 00000000000..d5047b751a5
--- /dev/null
+++ b/cuda_core/tests/test_utils_validators.py
@@ -0,0 +1,67 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+import pytest
+
+from cuda.core import WorkqueueResourceOptions
+from cuda.core._utils.validators import check_str_enum, format_or_list
+from cuda.core.typing import SourceCodeType
+
+
+@pytest.mark.agent_authored(model="claude-opus-5")
+@pytest.mark.parametrize(
+    ("values", "expected"),
+    [
+        pytest.param([], "", id="empty"),
+        pytest.param(["a"], "'a'", id="one"),
+        pytest.param(["a", "b"], "'a' or 'b'", id="two"),
+        pytest.param(["a", "b", "c"], "'a', 'b' or 'c'", id="three"),
+        pytest.param([None, "a"], "None or 'a'", id="none-first"),
+    ],
+)
+def test_format_or_list(values, expected):
+    assert format_or_list(values) == expected
+
+
+@pytest.mark.agent_authored(model="claude-opus-5")
+@pytest.mark.parametrize("value", ["c++", "ptx", "nvvm", SourceCodeType.CXX])
+def test_check_str_enum_accepts_members_and_their_values(value):
+    check_str_enum(value, SourceCodeType)
+
+
+@pytest.mark.agent_authored(model="claude-opus-5")
+def test_check_str_enum_allow_none():
+    check_str_enum(None, SourceCodeType, allow_none=True)
+
+    with pytest.raises(ValueError, match="None is not a valid SourceCodeType"):
+        check_str_enum(None, SourceCodeType)
+
+
+@pytest.mark.agent_authored(model="claude-opus-5")
+@pytest.mark.parametrize(
+    "value",
+    [
+        pytest.param("fortran", id="str"),
+        pytest.param(5, id="int"),
+        # Unhashable arguments used to blow up inside the membership test with
+        # "TypeError: unhashable type" before the ValueError was ever built.
+        pytest.param(["c++"], id="list"),
+        pytest.param({"code_type": "c++"}, id="dict"),
+        pytest.param(bytearray(b"c++"), id="bytearray"),
+    ],
+)
+def test_check_str_enum_rejects_invalid_values_with_value_error(value):
+    with pytest.raises(ValueError, match="is not a valid SourceCodeType. Must be "):
+        check_str_enum(value, SourceCodeType)
+
+
+@pytest.mark.agent_authored(model="claude-opus-5")
+def test_options_reject_an_unhashable_scope_with_value_error():
+    """A public entry point must report a bad option the same way for every
+    kind of bad value. ``WorkqueueResourceOptions.__post_init__`` validates
+    ``sharing_scope`` through ``check_str_enum``, so an unhashable argument
+    used to surface as ``TypeError: unhashable type: 'list'`` while a plain
+    string got the documented ValueError."""
+    with pytest.raises(ValueError, match="is not a valid WorkqueueSharingScopeType. Must be "):
+        WorkqueueResourceOptions(sharing_scope=["green_ctx_balanced"])