Per RFC-WS-6 §Q3 v1.3 addition 2 + ARCH-BINDINGS §7.1 v1.2. Denormalised mirror of the FormBindingApplicatorException subclass classification, written by ApplyBindingsOnFormSubmit's outer-transaction catch block (D2) when apply_status='failed'. Drives response-shape copy. NULL when apply_status is not 'failed'. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>