Why computed re-derives

A computed field reads the declared fields and is re-derived on make and update alike, rather than computed once and stored.

The alternative was tried and is quietly wrong. Deriving fullName from first + last once, then renaming the person, leaves fullName frozen at the old value — and since a derived field is not patchable, unrepairable. Every plausible use (totalCents, tier, wordCount, durationDays) has that shape.

Re-deriving also makes make self-healing: a row written before a derivation changed, or before the field existed at all, is corrected on read rather than trusted. That is why make validates against input and not output — validating stored computed values would reject exactly the rows it is meant to repair.

Why not a getter?

Because a getter carries no schema. It cannot appear in output, cannot generate JSON Schema, and is skipped by toJSON() — it lives on the prototype, not in the data. The rule:

	use
derived, needed in the response body / JSON Schema	computed
derived, domain-only behaviour	a getter

Persist and rehydrate shows the self-healing read against a real table.