diff --git a/internal/runtime/executor/usage_helpers.go b/internal/runtime/executor/usage_helpers.go
index 1f81c048..e0df5f3e 100644
--- a/internal/runtime/executor/usage_helpers.go
+++ b/internal/runtime/executor/usage_helpers.go
@@ -129,6 +129,21 @@ func apiKeyFromContext(ctx context.Context) string {
 
 func resolveUsageSource(auth *cliproxyauth.Auth, ctxAPIKey string) string {
 	if auth != nil {
+		provider := strings.TrimSpace(auth.Provider)
+		if strings.EqualFold(provider, "vertex") {
+			if auth.Metadata != nil {
+				if projectID, ok := auth.Metadata["project_id"].(string); ok {
+					if trimmed := strings.TrimSpace(projectID); trimmed != "" {
+						return trimmed
+					}
+				}
+				if project, ok := auth.Metadata["project"].(string); ok {
+					if trimmed := strings.TrimSpace(project); trimmed != "" {
+						return trimmed
+					}
+				}
+			}
+		}
 		if _, value := auth.AccountInfo(); value != "" {
 			return strings.TrimSpace(value)
 		}