ADR 0001: Nullability is opt-in

Status: accepted (2026-09-09)

Fields and results are non-null unless written Type?. GraphQL's default-nullable model pushes null handling onto every client and makes "is this really optional" a guess. Real APIs are mostly required; optional is the exception and should be spelled out.

Consequences: generated types are tighter; a resolver returning null for a non-null field is an internal error (atomic), or null plus an errors entry when the field is @partial.