The JS mock services carried MPE_TABLES.pre_edit_hook / post_edit_hook values but never acted on them, so a table configured with hooks behaved differently in the mock than in production. Add mockHookSource() to dcMockUtils (resolving a hook program name to the source of its .js counterpart on the Drive) and run the hook where the SAS backend does: - editors/getdata runs the pre-edit hook after filtering, letting it reassign visibleRows / visibleColumns (the work.OUT contract) - so an empty mirror can display the live rows of the table it points at - editors/stagedata and editors/loadfile run the post-edit hook before the MPE_SUBMIT row is written, letting it reassign libref / dsn (the call symputx contract) - so a changeset submitted against a mirror is raised against the real table Seed a demo pair in makedata (TESTDATA.DEMO_ORDERS plus an empty TESTDATA.DEMO_MIRROR with both hooks) and cover it with a Cypress spec.