fixes

backend/igny8_core/modules/billing/serializers.py

@@ -31,15 +31,35 @@ class CreditUsageLogSerializer(serializers.ModelSerializer):
         source='get_operation_type_display', 
         read_only=True
     )
+    client_cost = serializers.SerializerMethodField(help_text='Client-facing cost (credits * price_per_credit)')
+    site_name = serializers.SerializerMethodField(help_text='Name of the associated site')
     
     class Meta:
         model = CreditUsageLog
         fields = [
             'id', 'operation_type', 'operation_type_display', 'credits_used',
-            'cost_usd', 'model_used', 'tokens_input', 'tokens_output',
-            'related_object_type', 'related_object_id', 'metadata', 'created_at'
+            'cost_usd', 'client_cost', 'model_used', 'tokens_input', 'tokens_output',
+            'related_object_type', 'related_object_id', 'site_name', 'metadata', 'created_at'
         ]
         read_only_fields = ['created_at', 'account']
+    
+    def get_client_cost(self, obj) -> str:
+        """Calculate client-facing cost from credits * default_credit_price_usd"""
+        from igny8_core.business.billing.models import BillingConfiguration
+        try:
+            config = BillingConfiguration.get_config()
+            price_per_credit = config.default_credit_price_usd
+            client_cost = Decimal(obj.credits_used) * price_per_credit
+            return str(client_cost.quantize(Decimal('0.0001')))
+        except Exception:
+            # Fallback to cost_usd if billing config unavailable
+            return str(obj.cost_usd) if obj.cost_usd else '0.0000'
+    
+    def get_site_name(self, obj) -> Optional[str]:
+        """Get the site name if available"""
+        if obj.site:
+            return obj.site.name
+        return None
 
 
 class CreditBalanceSerializer(serializers.Serializer):