LookupFieldConfig

Object

throughKey

The relation field this lookup hops through (single hop, §9.4)

targetFieldKey

Nullable to match RollupFieldConfig and the flat config under the FieldConfig union; lookup presence is enforced in createTable validation, not the GraphQL type. A non-null here makes any selection spanning Rollup and Lookup configs fail GraphQL validation (targetFieldKey String vs String!), breaking all table reads and writes.

sourceCustomFieldId

sourceCustomFieldItemType