# ADR-0037: Migration validation and rollback retention

## Status

Accepted in M13 on 2026-08-26.

## Decision

Cutover requires an immutable validation snapshot. Technical LAB eligibility and project-production
eligibility are separate. The exact prior external identity is snapshotted before switch and remains
cleanup-blocking through the configured rollback window.

## Consequences

Completeness alone cannot promote a model. Isolated mechanics can be rehearsed despite documented
project evidence gaps, without implying production fitness or sacrificing rollback evidence.