Projections

Mark fields with Type.Readonly (output-only) and Type.Writeonly (input-only), then derive the input shape with Type.Write and the output shape with Type.Read. Both produce runtime schemas and static types, and they recurse through the whole tree: nested schemas, arrays, unions, intersections, Type.Dependent branches and Type.Cyclic definitions.

const User = Type.Object({
  id: Type.Readonly(Type.String()),
  email: Type.String({ format: 'email' }),
  password: Type.Writeonly(Type.String({ minLength: 8 })),
})

const CreateUser = Type.Write(User) // { email, password }
const PublicUser = Type.Read(User) // { id, email }

Named projections

Options clone a projection into a standalone schema. suffix renames every $id in the tree — '/user' → '/user/input', nested ids too — so read and write shapes get distinct names for doc generators. GraphQL-style naming works the same: { $id: 'User' } + suffix 'Input' → 'UserInput'. Cyclic subtrees are renamed consistently ($defs keys, $ids and $refs move together), so local resolution keeps working. Any other option overrides the root — an explicit $id wins over the suffixed one.

const UserInput = Type.Write(User, { suffix: '/input' }) // $id: '/user/input'

Partial updates

Type.Partial makes every property optional and strips property defaults. Plain TypeBox keeps default annotations on the now-optional fields, so validating a PATCH body would quietly materialize defaults — an update without status would reset it to 'draft':

const Article = Type.Object({
  title: Type.String(),
  status: Type.Union(
    [Type.Literal('draft'), Type.Literal('published')],
    { default: 'draft' },
  ),
})

const ArticlePatch = Type.Partial(Article)

validate(ArticlePatch, { title: 'New title' })
// → { success: true, data: { title: 'New title' } }
//   `status` stays absent — a missing field means "leave it unchanged"

The strip is shallow, matching Type.Partial’s own semantics: a nested object, when present in the input, still validates (and defaults) against its full schema. Explicit Type.Optional(Type.X({ default })) outside Partial keeps working — there the default is a deliberate choice:

const Query = Type.Object({
  page: Type.Optional(Type.Integer({ default: 1 })),
})

validate(Query, {}) // → { success: true, data: { page: 1 } }