Self-healing Behaviour

If a stored value no longer matches the current schema (e.g. you tightened the schema after the value was stored), the registry deletes the offending record on the next read and falls back to the default. There is no migrate callback — schema evolution that needs to preserve data should be done in a Django data migration.

A read therefore never raises a validation error for stored values; either the value is good and returned, or it's silently cleaned up and the default takes over (or None if there is no default).