---
title: ChildAt
description: A type that the Authoring surface names.
---

# `ChildAt`

Type, in `@jr2/orchestrator/src/customize.ts`. It is type plumbing: it computes a type from the types of a Machine or of its parts, and a workflow module does not write it. The signature of an export, or a type that it names, names this type, so its declaration is here. The [Authoring surface](../authoring-surface.md) page lists each export.

```ts
type ChildAt<M extends AnyStateMachine, K extends string> = Extract<LogicAt<M, K>, AnyStateMachine>;
```