♻️ Reproduction Steps

A custom catalog whose list component uses a ChildList template:

const definitions = {
  PartList: { props: z.object({ items: CommonSchemas.ChildList }) },
  PartRow: { props: z.object({ name: CommonSchemas.DynamicString }) },
};

const catalog = createCatalog(definitions, {
  PartList: ({ props, children }) => (
    <ul>
      {(props.items as unknown as { id: string; basePath?: string }[]).map((node) => (
        // (a) children(node.id)                 -> compiles, renders empty
        // (b) children(node.id, node.basePath)  -> renders, fails tsc (TS2554)
        <li key={node.basePath}>{children(node.id)}</li>
      ))}
    </ul>
  ),
  PartRow: ({ props }) => <span>{String(props.name ?? "")}</span>,
});

// components: root = PartList { items: { componentId: "row", path: "/parts" } },
//             row  = PartRow  { name: { path: "name" } }
// data:       { parts: [{ name: "Bolt A" }, { name: "Bolt B" }] }

✅ Expected Behavior

The renderer can forward each item's basePath with no type error, and the list shows "Bolt A" and "Bolt B".

❌ Actual Behavior

• (a) children(node.id) compiles, but each row resolves name against the surface root, so the list renders with empty text and no error or warning.
• (b) children(node.id, node.basePath) renders correctly, but fails type-checking: TS2554: Expected 1 arguments, but got 2.

createCatalog passes A2UI's buildChild straight through as children (create-catalog.tsx:125), and buildChild is (id: string, basePath?: string) => ReactNode (a2ui-react/adapter.tsx:36). RendererProps.children (create-catalog.tsx:48) narrows it to (id: string). The built-in ChildList does pass node.basePath.

The repo's own renderers work around this with a cast, (children as any)(item.id, item.basePath): 58 call sites in 29 files, including every beautiful-chat/declarative-generative-ui/renderers.tsx in the showcase and the examples/integrations/*/declarative-generative-ui/renderers.tsx files.

Related, not part of this issue: props is typed as the schema's input (z.infer), so a ChildList prop is typed as string[] | { componentId, path }, while the renderer actually receives the resolved { id, basePath }[]. That is why the cast on props.items is needed. Happy to open a separate issue if that's useful.

Screenshots

No response

𝌚 CopilotKit Version

`@copilotkit/a2ui-renderer` 1.79.0 (`main` at c619451f); first seen on 1.67.1.

I have a fix with a test ready: type `children` as `(id: string, basePath?: string) => React.ReactNode` and document when to pass `basePath`. It's backward compatible, since existing one-argument calls still type-check. I'll open the PR and link it here.

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