When a batch item has completed processing, you'll get the event payload as below:
{
"event_type": "batch.item.finished",
"resource_type": "shipment_batch_item",
"resource_id": "7c16f6aa-2183-45eb-a18d-cdaf09500001",
"data": {
"batch_id": "3ed3d05f-7ba8-404d-97b1-5a50de3c00001",
"started_at": "2023-01-25T11:30:00.000Z",
"finished_at": "2023-01-25T11:31:00.000Z",
"record_type": "Shipment",
"record_id": "329c2604-33ff-49b3-9a08-b7c8754a00001",
"reference_id": "reference_id",
"state": "failed",
"processing_errors": ["error"]
}
}