diff --git a/sdk/ml/azure-ai-ml/tests/unittests/test_defect_icm_TEST-12345.py b/sdk/ml/azure-ai-ml/tests/unittests/test_defect_icm_TEST-12345.py
new file mode 100644
index 000000000000..bb641ebecc5d
--- /dev/null
+++ b/sdk/ml/azure-ai-ml/tests/unittests/test_defect_icm_TEST-12345.py
@@ -0,0 +1,62 @@
+# ---------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# ---------------------------------------------------------
+
+import pytest
+from contextlib import nullcontext as does_not_raise
+
+from azure.ai.ml import command
+from azure.ai.ml.exceptions import ValidationException
+
+
+@pytest.mark.unittest
+@pytest.mark.defect_regression
+class TestDefectIcmTEST_12345:
+    """Tests for defect reported in IcM #TEST-12345.
+    
+    Root cause: CommandJob serialization called .lower() on compute without validating None,
+    and _validate() did not enforce compute for non-local runs, leading to AttributeError instead
+    of a clear ValidationException.
+    """
+
+    @pytest.mark.parametrize(
+        "compute_value, expected",
+        [
+            (None, pytest.raises(ValidationException)),
+            ("", pytest.raises(ValidationException)),
+            ("local", does_not_raise()),
+            ("cpu-cluster", does_not_raise()),
+        ],
+        ids=["compute_is_none", "compute_is_empty", "compute_local", "compute_valid_cluster"],
+    )
+    def test_command_job_requires_compute_or_local(self, compute_value, expected):
+        """Regression test: ensure CommandJob with missing compute fails validation with a clear error,
+        and valid compute/local values succeed without raising.
+        
+        This would have caught the AttributeError('NoneType' has no attribute 'lower') thrown during
+        _to_rest_object() when compute was None.
+        """
+        job = command(
+            command="echo hello",
+            environment="AzureML-sklearn-1.0-ubuntu20.04-py38-cpu:1",
+        )
+        job.compute = compute_value
+
+        with expected:
+            # _to_rest_object triggers _validate() and serialization
+            job._to_rest_object()
+
+    def test_error_message_is_clear_when_compute_is_none(self):
+        """Ensure the SDK raises a friendly ValidationException that mentions compute is required."""
+        job = command(
+            command="echo hello",
+            environment="AzureML-sklearn-1.0-ubuntu20.04-py38-cpu:1",
+        )
+        job.compute = None
+
+        with pytest.raises(ValidationException) as ex:
+            job._to_rest_object()
+
+        # Message should clearly indicate compute is required (non-local)
+        assert "compute" in str(ex.value).lower()
+        assert "required" in str(ex.value).lower()
diff --git a/sdk/ml/azure-ai-ml/tests/unittests/test_similar_defect_sweep_TEST-12345.py b/sdk/ml/azure-ai-ml/tests/unittests/test_similar_defect_sweep_TEST-12345.py
new file mode 100644
index 000000000000..249219fb51b5
--- /dev/null
+++ b/sdk/ml/azure-ai-ml/tests/unittests/test_similar_defect_sweep_TEST-12345.py
@@ -0,0 +1,63 @@
+# ---------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# ---------------------------------------------------------
+
+import pytest
+from contextlib import nullcontext as does_not_raise
+
+from azure.ai.ml import command
+from azure.ai.ml.exceptions import ValidationException
+from azure.ai.ml.sweep import SweepJob, Objective
+
+
+@pytest.mark.unittest
+@pytest.mark.defect_regression
+class TestSimilarDefectSweepTEST_12345:
+    """Similar defect test: SweepJob.compute=None should raise ValidationException instead of AttributeError.
+
+    Root cause pattern: unsafe .lower() normalization on compute and missing validation for non-local runs.
+    """
+
+    @pytest.mark.parametrize(
+        "compute_value, expected",
+        [
+            (None, pytest.raises(ValidationException)),
+            ("", pytest.raises(ValidationException)),
+            ("cpu-cluster", does_not_raise()),
+        ],
+        ids=["compute_none", "compute_empty", "compute_valid"],
+    )
+    def test_sweep_job_requires_compute(self, compute_value, expected):
+        # Minimal trial command job used by sweep
+        trial_cmd = command(
+            command="echo trial",
+            environment="AzureML-sklearn-1.0-ubuntu20.04-py38-cpu:1",
+        )
+
+        sweep = SweepJob(
+            trial=trial_cmd,
+            sampling_algorithm="random",
+            objective=Objective(goal="maximize", primary_metric="accuracy"),
+            compute=compute_value,
+        )
+
+        with expected:
+            sweep._to_rest_object()
+
+    def test_sweep_job_message_is_clear_when_compute_missing(self):
+        trial_cmd = command(
+            command="echo trial",
+            environment="AzureML-sklearn-1.0-ubuntu20.04-py38-cpu:1",
+        )
+        sweep = SweepJob(
+            trial=trial_cmd,
+            sampling_algorithm="random",
+            objective=Objective(goal="maximize", primary_metric="accuracy"),
+            compute=None,
+        )
+
+        with pytest.raises(ValidationException) as ex:
+            sweep._to_rest_object()
+
+        assert "compute" in str(ex.value).lower()
+        assert "required" in str(ex.value).lower()