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",
batch_item: {
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"]
}
}