# Runbook: migration or rollback failure

## Trigger

`MIGRATION_FAILURE`, `ROLLBACK_FAILURE`, `FAILED` or `MANUAL_INTERVENTION_REQUIRED`.

## Diagnose

Review immutable plan/generation, adapter fingerprint, source/target identities, latest checkpoint,
validation snapshot, cutover journal, external-state observation and rollback retention. Never guess
external alias truth after a crash.

## Act and recover

Pause further plan actions and acknowledge the alert. Resume only idempotent backfill after source
and generation validation. Reconcile ambiguous cutover through the typed adapter. A rollback failure
is CRITICAL and requires explicit operator intervention; do not mutate production aliases manually
without preserving evidence. Recovery must retain the alert/timeline and prove exact final identity.