Architect Data Action: JSON mapping fails on nested array response

Architect & Flows
1

I’ve got a Data Action calling an external API to fetch order details. The call succeeds, but the mapping step keeps failing with a generic error.

The external response looks like this:

{
 "orderId": "12345",
 "items": [
 { "sku": "A1", "qty": 2 },
 { "sku": "B2", "qty": 1 }
 ]
}

I’m trying to map items[0].sku to a local variable OrderSKU. The mapping expression is $.items[0].sku.

The Data Action logs show the response payload is correct, but the variable ends up empty. I’ve tried $.items[0].sku and $.items[0]['sku']. Both fail silently.

Is there a specific syntax for handling arrays in the Architect JSON mapper? The documentation is vague on this.