diff --git a/backend/internal/service/usage_log.go b/backend/internal/service/usage_log.go
index 5a498676..576841fa 100644
--- a/backend/internal/service/usage_log.go
+++ b/backend/internal/service/usage_log.go
@@ -98,6 +98,9 @@ type UsageLog struct {
 	AccountID int64
 	RequestID string
 	Model     string
+	// RequestedModel is the client-requested model name recorded for stable user/admin display.
+	// Empty should be treated as Model for backward compatibility with historical rows.
+	RequestedModel string
 	// UpstreamModel is the actual model sent to the upstream provider after mapping.
 	// Nil means no mapping was applied (requested model was used as-is).
 	UpstreamModel *string
diff --git a/backend/internal/service/usage_log_helpers.go b/backend/internal/service/usage_log_helpers.go
index 2ab51849..57c51540 100644
--- a/backend/internal/service/usage_log_helpers.go
+++ b/backend/internal/service/usage_log_helpers.go
@@ -19,3 +19,10 @@ func optionalNonEqualStringPtr(value, compare string) *string {
 	}
 	return &value
 }
+
+func forwardResultBillingModel(requestedModel, upstreamModel string) string {
+	if trimmedUpstream := strings.TrimSpace(upstreamModel); trimmedUpstream != "" {
+		return trimmedUpstream
+	}
+	return strings.TrimSpace(requestedModel)
+}