Update line item quantity

import { createClient } from '@spree/sdk'

const client = createClient({
  baseUrl: 'https://your-store.com',
  publishableKey: '<api-key>',
})

const cart = await client.carts.items.update('cart_abc123', 'li_abc123', {
  quantity: 5,
}, {
  bearerToken: '<token>',
})

{
  "id": "cart_UkLWZg9DAJ",
  "number": "R205272356",
  "token": "Hj1DwwY7WR3KJ9Jo6mMdDdTGmn3KFr4XBdc",
  "email": "kacie@senger.info",
  "customer_note": null,
  "currency": "USD",
  "locale": "en",
  "total_quantity": 0,
  "item_total": "0.0",
  "display_item_total": "$0.00",
  "adjustment_total": "0.0",
  "display_adjustment_total": "$0.00",
  "discount_total": "0.0",
  "display_discount_total": "$0.00",
  "tax_total": "0.0",
  "display_tax_total": "$0.00",
  "included_tax_total": "0.0",
  "display_included_tax_total": "$0.00",
  "additional_tax_total": "0.0",
  "display_additional_tax_total": "$0.00",
  "total": "0.0",
  "display_total": "$0.00",
  "gift_card_total": "0.0",
  "display_gift_card_total": "$0.00",
  "amount_due": "0.0",
  "display_amount_due": "$0.00",
  "delivery_total": "0.0",
  "display_delivery_total": "$0.00",
  "warnings": [],
  "created_at": "2026-03-28T11:44:41.729Z",
  "updated_at": "2026-03-28T11:44:41.769Z",
  "store_credit_total": "0.0",
  "display_store_credit_total": "$0.00",
  "covered_by_store_credit": false,
  "current_step": "address",
  "completed_steps": [],
  "requirements": [
    {
      "step": "address",
      "field": "ship_address",
      "message": "Shipping address is required"
    },
    {
      "step": "delivery",
      "field": "shipping_method",
      "message": "Select a shipping method for all shipments"
    }
  ],
  "shipping_eq_billing_address": false,
  "discounts": [],
  "items": [
    {
      "id": "li_UkLWZg9DAJ",
      "variant_id": "variant_UkLWZg9DAJ",
      "quantity": 1,
      "currency": "USD",
      "name": "Product 47640",
      "slug": "product-47640",
      "options_text": "",
      "price": "10.0",
      "display_price": "$10.00",
      "total": "10.0",
      "display_total": "$10.00",
      "adjustment_total": "0.0",
      "display_adjustment_total": "$0.00",
      "additional_tax_total": "0.0",
      "display_additional_tax_total": "$0.00",
      "included_tax_total": "0.0",
      "display_included_tax_total": "$0.00",
      "discount_total": "0.0",
      "display_discount_total": "$0.00",
      "pre_tax_amount": "10.0",
      "display_pre_tax_amount": "$10.00",
      "discounted_amount": "10.0",
      "display_discounted_amount": "$10.00",
      "display_compare_at_amount": "$0.00",
      "compare_at_amount": null,
      "thumbnail_url": null,
      "option_values": [],
      "digital_links": []
    }
  ],
  "fulfillments": [],
  "payments": [],
  "billing_address": {
    "id": "addr_EfhxLZ9ck8",
    "first_name": "John",
    "last_name": "Doe",
    "full_name": "John Doe",
    "address1": "178 Lovely Street",
    "address2": "Northwest",
    "postal_code": "35005",
    "city": "Herndon",
    "phone": "555-555-0199",
    "company": "Company",
    "country_name": "United States of America",
    "country_iso": "US",
    "state_text": "STATE_ABBR_185",
    "state_abbr": "STATE_ABBR_185",
    "quick_checkout": false,
    "is_default_billing": false,
    "is_default_shipping": false,
    "state_name": "STATE_NAME_185"
  },
  "shipping_address": null,
  "payment_methods": [],
  "gift_card": null
}