Designs and audits compatible, staged, reversible changes to persisted or serialized data shape: database schemas, event and message schemas, API payloads, and file formats. Use when a change adds, renames, moves, narrows, reinterprets, or removes a stored or serialized element, changes a key or identity, transfers write ownership, or needs a backfill; when deciding whether old and new code versions can coexist against one schema during rollout and rollback; when planning an expand/contract transition, its reversal steps, and the evidence that permits the contract step; or when auditing never-contracted expansions, semantic drift, unowned data, and migrations without a re…
