INSERT OR IGNORE INTO `audit_events`
  (`id`, `actor_id`, `action`, `target_type`, `target_id`, `reason`,
   `before_json`, `after_json`, `correlation_id`, `created_at`)
SELECT 'audit_slug_backfill_' || `id`,
       'system:migration',
       'tenant.slug_backfilled',
       'tenant',
       `id`,
       '旧版短租户 slug 不满足隔离域名契约，按不可变 tenant ID 扩展',
       json_object('slug', `slug`),
       json_object('slug', 'n-' || substr(`id`, -32)),
       'corr_slug_backfill_' || `id`,
       CURRENT_TIMESTAMP
FROM `tenant_instances`
WHERE `id` LIKE 'tenant_%'
  AND length(`id`) = 39
  AND (`slug` NOT LIKE 'n-%' OR length(`slug`) <> 34);--> statement-breakpoint

UPDATE `tenant_instances`
SET `slug` = 'n-' || substr(`id`, -32),
    `updated_at` = CURRENT_TIMESTAMP
WHERE `id` LIKE 'tenant_%'
  AND length(`id`) = 39
  AND (`slug` NOT LIKE 'n-%' OR length(`slug`) <> 34);