Props

Props define the configurable inputs of a component. Each prop has a type, a default value, and optional extensions.

type Props = Record<string, AnyProp>;
type AnyProp = BooleanProp | StringProp | EnumProp | NumberProp | SlotProp | ImageProp;

Prop Kinds

BooleanProp

Property	Type	Required	Description
`type`	`'boolean'`	Yes
`default`	`boolean`	Yes	Default value
`$extensions`	`PropExtensions`	No	Vendor extensions

EnumProp

Property	Type	Required	Description
`type`	`'string'`	Yes
`default`	`string`	Yes	Default value (must be in `enum`)
`enum`	`string[]`	Yes	Allowed values
`nullable`	`boolean`	No	Whether `null` is a valid value — absent means `false`
`$extensions`	`PropExtensions`	No	Vendor extensions

StringProp

Property	Type	Required	Description
`type`	`'string'`	Yes
`default`	`string \| null`	No	Deprecated — use `examples`
`nullable`	`boolean`	No	Whether `null` is a valid value — absent means `true`
`examples`	`string[]`	No	Example values
`$extensions`	`PropExtensions`	No	Vendor extensions

A StringProp is distinguished from an EnumProp by the absence of enum.

NumberProp

Property	Type	Required	Description
`type`	`'number'`	Yes
`default`	`number`	No	Default value
`nullable`	`boolean`	No	Whether `null` is a valid value — absent means `true` (since 0.29.0)
`examples`	`number[]`	No	Example values

Inferred from Figma variant values when inferNumberProps is enabled.

SlotProp

Property	Type	Required	Description
`type`	`'slot'`	Yes
`default`	`string \| null`	No	Default slot content
`nullable`	`boolean`	No	Whether `null` is a valid value — absent means `true`
`minChildren`	`number`	No	Minimum number of children the slot accepts (since 0.25.0)
`maxChildren`	`number`	No	Maximum number of children the slot accepts (since 0.25.0)
`anyOf`	`string[]`	No	Permitted component type names (since 0.14.0)
`$extensions`	`PropExtensions`	No	Vendor extensions

Slot constraint properties (minChildren, maxChildren, anyOf) are emitted when slotConstraints is enabled in config.

ImageProp

Property	Type	Required	Description
`type`	`'image'`	Yes
`default`	`string \| null`	No	Default image — an `images` registry reference, or null
`nullable`	`boolean`	No	Whether `null` is a valid value — absent means `true`
`$extensions`	`PropExtensions`	No	Vendor extensions

An image-valued property (e.g. a dsImage source prop). The authoring-default image rides on the ImageBinding at the binding site, not on the prop. Emitted for code-only props named in processing.images.sourceProps (since 0.28.0).

Nullability

nullable is optional on every prop kind that carries it. Its absence is meaningful, and what it means depends on whether the prop’s value set is open or closed:

Prop kind	Absent `nullable` means	Why
`StringProp`	`true`	Open value set — nothing enumerates it
`NumberProp`	`true`	Open value set
`SlotProp`	`true`	Open content set; a slot may be empty
`ImageProp`	`true`	Open value set
`EnumProp`	`false`	`enum` lists every accepted value, and `null` is not one of them
`BooleanProp`	(no field)	Booleans are never nullable

An explicit nullable: false on an open-valued prop asserts that a value always exists — useful when a code-only prop was authored with a non-empty default:

props:
  # No nullable key — accepts null
  label:
    type: string
  # Explicitly asserts a value is always present
  headingLevel:
    type: number
    default: 2
    nullable: false

Extensions

The $extensions object holds vendor-specific metadata. Currently only the com.figma extension is defined.

FigmaPropExtension

Property	Type	Description
`type`	`string`	Figma property type (e.g. `BOOLEAN`, `TEXT`, `INSTANCE_SWAP`, `VARIANT`)
`source`	`FigmaCodeOnlySource`	Present when the prop originates from a code-only prop layer

FigmaCodeOnlySource

Property	Type	Description
`kind`	`'codeOnlyProp'`	Always `'codeOnlyProp'`
`layer`	`string`	Sub-layer name in the code-only container
`instanceOf`	`string`	Component name, for enum code-only props