Options

Options for adapterOas, with type and default in the table.

Option	Type	Default	Description
validate	boolean	true	Validate the spec before parsing
contentType	'application/json' | string	—	Preferred media type for request and response schemas
server	{ index?: number, variables?: Record<string, string> }	—	Which spec server Kubb resolves into the document baseURL
discriminator	'preserve' | 'propagate'	'preserve'	How discriminator fields are interpreted
enums	'inline' | 'root'	'inline'	Where inline enums live
dateType	false | 'string' | 'stringOffset' | 'stringLocal' | 'date'	'string'	How format: date-time schemas are represented
integerType	'number' | 'bigint'	'bigint'	How integers map to TypeScript
unknownType	'any' | 'unknown' | 'void'	'any'	Type for schemas Kubb cannot infer
emptySchemaType	'any' | 'unknown' | 'void'	unknownType | 'any'	Type for empty schemas
enumSuffix	string	'enum'	Suffix for derived enum names

validate

Validates the OpenAPI spec with @readme/openapi-parser before parsing. Set it to false only when you have a known-invalid spec that you still want to generate from.

contentType

Preferred media type when an operation defines several. Without a value, Kubb falls back to the first JSON-like media type in the spec (application/json, application/x-json, text/json, text/x-json, or any *+json), and to the first media type overall when none is JSON-like.

server

Selects which entry in the spec's servers array Kubb resolves into the document baseURL, filling in any {variable} placeholders. server.index points at one of the spec's servers, usually 0 for the primary one. server.variables supplies placeholder values, falling back to each variable's default from the spec. Omit server and baseURL resolves to null.

The resolved baseURL reaches banner functions through BannerMeta.baseURL but does not set request URLs on its own. To change where a generated client sends requests, use that plugin's own baseURL option (@kubb/plugin-fetch, @kubb/plugin-axios, @kubb/plugin-msw).

With a spec server of https://api.{env}.example.com, server: { index: 0, variables: { env: 'prod' } } resolves baseURL to https://api.prod.example.com.

discriminator

How discriminator fields on oneOf/anyOf schemas are interpreted.

• 'preserve' (default) keeps child schemas exactly as written, though the discriminator still narrows types at the call site.
• 'propagate' pushes the discriminator property with its literal value into each child schema, so each branch's type field is precisely typed.

OpenAPI spec

openapi: 3.0.3
components:
  schemas:
    Animal:
      required: [type]
      type: object
      oneOf:
        - $ref: '#/components/schemas/Cat'
        - $ref: '#/components/schemas/Dog'
      discriminator:
        propertyName: type
        mapping:
          cat: '#/components/schemas/Cat'
          dog: '#/components/schemas/Dog'
    Cat:
      type: object
      properties:
        type: { type: string }
        indoor: { type: boolean }
    Dog:
      type: object
      properties:
        type: { type: string }
        name: { type: string }

'preserve' (default)

export type Cat = { type: string; indoor?: boolean }
export type Dog = { type: string; name?: string }
export type Animal = Cat | Dog

'propagate'

export type Cat = { type: 'cat'; indoor?: boolean }
export type Dog = { type: 'dog'; name?: string }
export type Animal = Cat | Dog

enums

Where inline enums live.

• 'inline' (default) keeps each enum on the property that declares it.
• 'root' lifts every inline enum to a reusable top-level schema named after its context (for example PetStatusEnum) and references it wherever it appears.

// enum [active, inactive] on Pet.status

// 'inline' (default)
export type Pet = { status?: 'active' | 'inactive' }

// 'root'
export type PetStatusEnum = 'active' | 'inactive'
export type Pet = { status?: PetStatusEnum }

dateType

How format: date-time schemas are represented downstream.

• false falls through to a plain string with no validation.
• 'string' (default) emits an ISO 8601 datetime string.
• 'stringOffset' emits a datetime string with a timezone offset.
• 'stringLocal' emits a local datetime string with no timezone.
• 'date' emits a JavaScript Date, best for client code, though JSON needs parsing to revive it.

The string variants all emit string at the TypeScript type level. The offset and local distinction surfaces in schema output such as Zod.

integerType

How type: integer (and format: int64) maps to TypeScript.

• 'bigint' (default) is exact for 64-bit IDs, but JSON.stringify and JSON.parse cannot round-trip it. Use it only when you handle bigint serialization yourself.
• 'number' fits most JSON APIs. It loses precision above Number.MAX_SAFE_INTEGER.

unknownType

AST type used when a schema's type cannot be inferred from the spec (additionalProperties: true, a missing type, and similar). Pick 'unknown' to force callers to narrow before using the value, 'any' for the loosest option, or 'void' to match some legacy APIs.

emptySchemaType

AST type used for fully empty schemas ({}). It follows unknownType unless you set it. Override it only when empty schemas should be treated differently from unresolvable ones.

TIP

A common pairing sets unknownType: 'unknown' for safety and emptySchemaType: 'any' so empty 204 response bodies stay easy to use.

enumSuffix

Suffix appended to derived enum names when Kubb has to invent one, typically for inline enums on object properties. The derived name joins the parent schema name, the property name, and the suffix in PascalCase, so an inline enum on the status property of the Pet schema derives PetStatusEnum. Set it to 'type' and the same enum derives PetStatusType.