Validation error for f.object(...).array() used as input field

[archasek]

I’m seeing a validation error when using f.object(...).array() for an input field.

Minimal repro (simplified)

import { ax, f } from "@ax-llm/ax";

const sig = f()
  .input(
    "items",
    f
      .object(
        {
          id: f.number("Index"),
          name: f.string("Name"),
        },
        "Item",
      )
      .array(),
  )
  .output(
    "classifiedItems",
    f
      .object(
        {
          id: f.number("Index"),
          label: f.string("Label"),
        },
        "Classification",
      )
      .array(),
  )
  .build();

const gen = ax(sig);

await gen.forward(llm, {
  items: [
    { id: 0, name: "Foo" },
    { id: 1, name: "Bar" },
  ],
});

Actual behavior

At runtime, Ax fails during validation with an error similar to:

Validation failed: Expected 'items' to be a an array of object instead got 'array' ([{"id":0,"name":"Foo"}, ...])

If I change the input field to a looser schema:

.input("items", f.json("Item {id, name}").array())

then the same payload works fine and the model call succeeds. The issue seems specific to f.object(...).array() on inputs; using f.object(...).array() on outputs works as expected.

Is f.object(...).array() for inputs supposed to be supported, or is this a current limitation/bug in the validator?

[google-labs-jules]

Jules is on it. When finished, you will see another comment and be able to review a PR.

[google-labs-jules]

Ready for a review! A PR has been created.