diff --git a/optimizely/decision_service.py b/optimizely/decision_service.py
index 28275ef..86f8639 100644
--- a/optimizely/decision_service.py
+++ b/optimizely/decision_service.py
@@ -457,7 +457,10 @@ def get_variation(
             }
 
         # Check to see if user has a decision available for the given experiment
-        if user_profile_tracker is not None and not ignore_user_profile:
+        # CMAB experiments should not use UPS for sticky bucketing because UPS maintains
+        # decisions across the experiment lifetime without considering TTL or user attributes,
+        # which contradicts CMAB's dynamic nature.
+        if user_profile_tracker is not None and not ignore_user_profile and not experiment.cmab:
             variation = self.get_stored_variation(project_config, experiment, user_profile_tracker.get_user_profile())
             if variation:
                 message = f'Returning previously activated variation ID "{variation}" of experiment ' \
@@ -529,7 +532,8 @@ def get_variation(
             self.logger.info(message)
             decide_reasons.append(message)
             # Store this new decision and return the variation for the user
-            if user_profile_tracker is not None and not ignore_user_profile:
+            # CMAB experiments should not use UPS for sticky bucketing
+            if user_profile_tracker is not None and not ignore_user_profile and not experiment.cmab:
                 try:
                     user_profile_tracker.update_user_profile(experiment, variation)
                 except:
diff --git a/tests/test_decision_service.py b/tests/test_decision_service.py
index dbcb743..63a9a08 100644
--- a/tests/test_decision_service.py
+++ b/tests/test_decision_service.py
@@ -1074,6 +1074,78 @@ def test_get_variation_cmab_experiment_with_whitelisted_variation(self):
             mock_bucket.assert_not_called()
             mock_cmab_decision.assert_not_called()
 
+    def test_get_variation_cmab_experiment_excludes_user_profile_service(self):
+        """Test that CMAB experiments do not use UPS for sticky bucketing."""
+
+        # Create a user context
+        user = optimizely_user_context.OptimizelyUserContext(
+            optimizely_client=None,
+            logger=None,
+            user_id="test_user",
+            user_attributes={}
+        )
+
+        # Create a CMAB experiment
+        cmab_experiment = entities.Experiment(
+            '111150',
+            'cmab_experiment',
+            'Running',
+            '111150',
+            [],  # No audience IDs
+            {},
+            [
+                entities.Variation('111151', 'variation_1'),
+                entities.Variation('111152', 'variation_2')
+            ],
+            [
+                {'entityId': '111151', 'endOfRange': 5000},
+                {'entityId': '111152', 'endOfRange': 10000}
+            ],
+            cmab={'trafficAllocation': 5000}
+        )
+
+        # Create a user profile service and tracker
+        user_profile_service = user_profile.UserProfileService()
+        user_profile_tracker = user_profile.UserProfileTracker(user.user_id, user_profile_service)
+
+        with mock.patch('optimizely.helpers.experiment.is_experiment_running', return_value=True), \
+            mock.patch('optimizely.helpers.audience.does_user_meet_audience_conditions', return_value=[True, []]), \
+            mock.patch.object(self.decision_service.bucketer, 'bucket_to_entity_id',
+                              return_value=['$', []]), \
+            mock.patch.object(self.decision_service, 'cmab_service') as mock_cmab_service, \
+            mock.patch.object(self.project_config, 'get_variation_from_id',
+                              return_value=entities.Variation('111151', 'variation_1')), \
+            mock.patch.object(self.decision_service, 'get_stored_variation') as mock_get_stored, \
+            mock.patch.object(user_profile_tracker, 'update_user_profile') as mock_update_profile:
+
+            # Configure CMAB service to return a decision
+            mock_cmab_service.get_decision.return_value = (
+                {
+                    'variation_id': '111151',
+                    'cmab_uuid': 'test-cmab-uuid-123'
+                },
+                []  # reasons list
+            )
+
+            # Call get_variation with the CMAB experiment and UPS tracker
+            variation_result = self.decision_service.get_variation(
+                self.project_config,
+                cmab_experiment,
+                user,
+                user_profile_tracker
+            )
+            variation = variation_result['variation']
+            cmab_uuid = variation_result['cmab_uuid']
+
+            # Verify the variation and cmab_uuid
+            self.assertEqual(entities.Variation('111151', 'variation_1'), variation)
+            self.assertEqual('test-cmab-uuid-123', cmab_uuid)
+
+            # CRITICAL: Verify that UPS methods were NOT called for CMAB
+            # CMAB should not use UPS for sticky bucketing
+            mock_get_stored.assert_not_called()
+            mock_update_profile.assert_not_called()
+
 
 class FeatureFlagDecisionTests(base.BaseTest):
     def setUp(self):