diff --git a/lib/optimizely/cmab/cmab_service.rb b/lib/optimizely/cmab/cmab_service.rb
index 9254b7d3..88f2825f 100644
--- a/lib/optimizely/cmab/cmab_service.rb
+++ b/lib/optimizely/cmab/cmab_service.rb
@@ -179,12 +179,14 @@ def filter_attributes(project_config, user_context, rule_id)
       return filtered_user_attributes if experiment.nil? || experiment['cmab'].nil?
 
       cmab_attribute_ids = experiment['cmab']['attributeIds']
+      return filtered_user_attributes unless cmab_attribute_ids.is_a?(Array)
+
       cmab_attribute_ids.each do |attribute_id|
         attribute = project_config.attribute_id_map[attribute_id]
         next unless attribute
 
         attribute_key = attribute['key']
-        filtered_user_attributes[attribute_key] = user_attributes[attribute_key] if user_attributes.key?(attribute_key)
+        filtered_user_attributes[attribute_id] = user_attributes[attribute_key] if user_attributes.key?(attribute_key)
       end
 
       filtered_user_attributes
diff --git a/spec/cmab/cmab_service_spec.rb b/spec/cmab/cmab_service_spec.rb
index b4b40086..91ea37fa 100644
--- a/spec/cmab/cmab_service_spec.rb
+++ b/spec/cmab/cmab_service_spec.rb
@@ -37,7 +37,7 @@
   describe '#get_decision' do
     it 'returns decision from cache when valid' do
       expected_key = cmab_service.send(:get_cache_key, user_id, rule_id)
-      expected_attributes = {'age' => 25, 'location' => 'USA'}
+      expected_attributes = {'66' => 25, '77' => 'USA'}
       expected_hash = cmab_service.send(:hash_attributes, expected_attributes)
 
       cached_value = Optimizely::CmabCacheValue.new(
@@ -58,7 +58,7 @@
 
     it 'ignores cache when option given' do
       allow(mock_cmab_client).to receive(:fetch_decision).and_return('varB')
-      expected_attributes = {'age' => 25, 'location' => 'USA'}
+      expected_attributes = {'66' => 25, '77' => 'USA'}
 
       decision, reasons = cmab_service.get_decision(
         mock_project_config,
@@ -126,8 +126,7 @@
       allow(mock_cmab_cache).to receive(:save)
       allow(mock_cmab_client).to receive(:fetch_decision).and_return('varE')
 
-      expected_attributes = {'age' => 25, 'location' => 'USA'}
-      cmab_service.send(:hash_attributes, expected_attributes)
+      expected_attributes = {'66' => 25, '77' => 'USA'}
       expected_key = cmab_service.send(:get_cache_key, user_id, rule_id)
 
       decision, reasons = cmab_service.get_decision(mock_project_config, mock_user_context, rule_id, [])
@@ -163,11 +162,10 @@
         [Optimizely::Decide::OptimizelyDecideOption::IGNORE_CMAB_CACHE]
       )
 
-      # Verify only age and location are passed
       expect(mock_cmab_client).to have_received(:fetch_decision).with(
         rule_id,
         user_id,
-        {'age' => 25, 'location' => 'USA'},
+        {'66' => 25, '77' => 'USA'},
         decision.cmab_uuid
       )
       expect(reasons).to include(match(/Ignoring CMAB cache for user '#{user_id}' and rule '#{rule_id}'/))
@@ -178,8 +176,8 @@
     it 'returns correct subset of attributes' do
       filtered = cmab_service.send(:filter_attributes, mock_project_config, mock_user_context, rule_id)
 
-      expect(filtered['age']).to eq(25)
-      expect(filtered['location']).to eq('USA')
+      expect(filtered['66']).to eq(25)
+      expect(filtered['77']).to eq('USA')
     end
 
     it 'returns empty hash when no cmab config' do
@@ -197,6 +195,38 @@
 
       expect(filtered).to eq({})
     end
+
+    it 'skips attribute IDs not found in attribute_id_map' do
+      allow(mock_project_config).to receive(:attribute_id_map).and_return({'66' => mock_attr1})
+
+      filtered = cmab_service.send(:filter_attributes, mock_project_config, mock_user_context, rule_id)
+
+      expect(filtered).to eq({'66' => 25})
+    end
+
+    it 'returns empty hash when user has none of the CMAB attributes' do
+      allow(mock_user_context).to receive(:user_attributes).and_return({'unrelated' => 'value'})
+
+      filtered = cmab_service.send(:filter_attributes, mock_project_config, mock_user_context, rule_id)
+
+      expect(filtered).to eq({})
+    end
+
+    it 'returns empty hash when attributeIds is empty' do
+      allow(mock_project_config).to receive(:experiment_id_map).and_return({rule_id => {'cmab' => {'attributeIds' => []}}})
+
+      filtered = cmab_service.send(:filter_attributes, mock_project_config, mock_user_context, rule_id)
+
+      expect(filtered).to eq({})
+    end
+
+    it 'returns empty hash when attributeIds is nil' do
+      allow(mock_project_config).to receive(:experiment_id_map).and_return({rule_id => {'cmab' => {'attributeIds' => nil}}})
+
+      filtered = cmab_service.send(:filter_attributes, mock_project_config, mock_user_context, rule_id)
+
+      expect(filtered).to eq({})
+    end
   end
 
   describe '#hash_attributes' do