-- Apply AFTER soft_delete and BEFORE re-extraction application code. Idempotent additive migration.
-- Keep additive schema on rollback. Drain queued revisions before restoring pre-revision workers.
-- History snapshots share the original task expiry, never a renewed retention period.
SET @fa_db = DATABASE();
SET @fa_sql = IF((SELECT COUNT(*) FROM information_schema.COLUMNS WHERE TABLE_SCHEMA=@fa_db AND TABLE_NAME='zyt_followup_audio_task' AND COLUMN_NAME='extraction_revision')=0,
 'ALTER TABLE zyt_followup_audio_task ADD COLUMN extraction_revision INT UNSIGNED NOT NULL DEFAULT 0, ADD COLUMN extraction_role_override VARCHAR(20) NOT NULL DEFAULT \'\', ADD COLUMN extraction_source_version INT UNSIGNED NOT NULL DEFAULT 0, ADD COLUMN extraction_confirmed_by BIGINT UNSIGNED NOT NULL DEFAULT 0, ADD COLUMN extraction_confirmed_at BIGINT UNSIGNED NOT NULL DEFAULT 0', 'SELECT 1');
PREPARE fa_stmt FROM @fa_sql;
EXECUTE fa_stmt;
DEALLOCATE PREPARE fa_stmt;
CREATE TABLE IF NOT EXISTS zyt_followup_audio_extraction_history (
 id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
 task_id BIGINT UNSIGNED NOT NULL,
 source_version INT UNSIGNED NOT NULL,
 source_revision INT UNSIGNED NOT NULL,
 target_revision INT UNSIGNED NOT NULL,
 channel_roles VARCHAR(20) NOT NULL,
 actor_id BIGINT UNSIGNED NOT NULL,
 snapshot_cipher LONGTEXT NULL,
 created_at BIGINT UNSIGNED NOT NULL,
 expires_at BIGINT UNSIGNED NOT NULL,
 purged_at BIGINT UNSIGNED NOT NULL DEFAULT 0,
 PRIMARY KEY(id),
 UNIQUE KEY uk_task_source(task_id,source_version),
 UNIQUE KEY uk_task_revision(task_id,target_revision),
 KEY idx_expiry(expires_at,purged_at)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;