- member-backfill / member-audit take their groups from the registry (TMDO_Entity_Migration_Engine::backfillable_groups(), restored orphans excluded) instead of a hard-coded list that still named the never-registered `sso`; `--all` backfills every user group (R-2.1 had to use wp eval). TMDO_Post_Migration::backfillable_groups() now delegates to it.
- member-cutover checks the Mode_Manager result with is_wp_error(): a guarded or invalid transition used to crash with a fatal (WP_Error used as an array).
- Verify: CliMemberBackfillTest (--all and the orphan filter RED before; the --group case cannot fail under the non-throwing WP_CLI stub); dev36 `member-backfill --all --reset` 9 groups, 0 errors, checker user miss/diff/extra 0; `member-cutover --confirm` exits 1 with the Guard message, mode unchanged.
- PR: PR-068
- migrate_group() REPLACEs the whole flat row; columns without a native row fell back to their DDL default (session_count / account_flags DEFAULT 0), so every backfilled user got invented zeros. Keys with no native row are now written as NULL; required NOT NULL columns keep their default.
- Covers the cron batch path (migrate_group_batch) and clears stale flat values on re-run.
- Verify: EntityMigrationEngineDefaultsTest (3 RED on main); dev36 user/activity backfill: checker extra 123 → 0 for session_count and account_flags, miss/diff unchanged.
- PR: PR-066