# v2.0.0-alpha.1 — Schema migrator (apply path)

Builds on the v2.0 schema detection (`v2.0.0-alpha.0`) with a safe, opt-in
migration apply path. Deterministic, confirmation-first, no model calls.

## Added

- **Schema migrator** — `relay-baton migrate --apply [--dry-run]` applies safe
  migrations to `.ai-session` artifacts. Today's migration is **legacy
  normalization**: artifacts that predate the `schemaVersion` field get the
  current version stamped on them.
- **Safety model** — apply is opt-in (`--apply`); the default and `--check` stay
  read-only. Each change writes a timestamped `.bak.<ts>` backup first,
  `--apply --dry-run` previews the plan, and the operation is idempotent.
- **Forward-compatible** — version-to-version upgrades are reported but skipped
  until a migrator is registered, which happens with the first real schema
  version bump.

## Constraints

- Deterministic, no model calls.
- No silent mutation: apply is explicit and always backs up first.

## Next in v2.0

- Per-artifact schema v2 bumps as breaking changes require them.
- Stable desktop contract with i18n parity.
- Installer/update story finalized, public docs pass, hard constraints reaffirmed.