diff --git a/src/api/errors.ts b/src/api/errors.ts
index 646b07a..af59a70 100644
--- a/src/api/errors.ts
+++ b/src/api/errors.ts
@@ -29,3 +29,5 @@ export const line_27 = 'content of src/api/errors.ts line 27 with some realistic
 export const line_28 = 'content of src/api/errors.ts line 28 with some realistic-length text padding here';
 export const line_29 = 'content of src/api/errors.ts line 29 with some realistic-length text padding here';
 export const line_30 = 'content of src/api/errors.ts line 30 with some realistic-length text padding here';
+// staged: add ErrorEnvelope type
+export interface ErrorEnvelope { code: string; message: string; requestId: string; }
diff --git a/src/utils/validation.ts b/src/utils/validation.ts
index 98a0a13..c1bc3a3 100644
--- a/src/utils/validation.ts
+++ b/src/utils/validation.ts
@@ -29,3 +29,4 @@ export const line_27 = 'content of src/utils/validation.ts line 27 with some rea
 export const line_28 = 'content of src/utils/validation.ts line 28 with some realistic-length text padding here';
 export const line_29 = 'content of src/utils/validation.ts line 29 with some realistic-length text padding here';
 export const line_30 = 'content of src/utils/validation.ts line 30 with some realistic-length text padding here';
+// staged: new validation rule for IBAN