T.record

A collection: fuzzed keys, both sides schema-driven.

T.record(
  T.string.whereby({ length: { min: 4, max: 12 } }),
  T.string.whereby({ length: { max: 40 } }),
).whereby({ size: { max: 6, minTried: 2 } });

For keys you don't know when you write the schema — a metadata bag, an i18n map, a lookup keyed by generated id. Both the keys and the values are fabricated from schemas, so a key's format is as controllable as any other value's.

size reads { max, minTried }, not { max, min } — deliberately. Keys are drawn independently, so two can come out identical and collapse into a single entry. max is a real upper bound; the lower number is only ever attempted, never guaranteed. Give the key schema enough room (a wide string, say) and collisions stop mattering in practice; make it narrow (a single digit) and you'll reliably get fewer entries than you asked for. There's no facility anywhere in this library to redraw a colliding key — the collapse is the answer, not a bug to route around.