Updates a cart item's variant

curl --request PATCH \
  --url https://api.fluid.app/api/public/v2025-06/commerce/carts/{cart_token}/items/{item_id}/variant \
  --header 'Content-Type: application/json' \
  --data '
{
  "variant_id": 123,
  "quantity": 123
}
'

import requests

url = "https://api.fluid.app/api/public/v2025-06/commerce/carts/{cart_token}/items/{item_id}/variant"

payload = {
    "variant_id": 123,
    "quantity": 123
}
headers = {"Content-Type": "application/json"}

response = requests.patch(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'PATCH',
  headers: {'Content-Type': 'application/json'},
  body: JSON.stringify({variant_id: 123, quantity: 123})
};

fetch('https://api.fluid.app/api/public/v2025-06/commerce/carts/{cart_token}/items/{item_id}/variant', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.fluid.app/api/public/v2025-06/commerce/carts/{cart_token}/items/{item_id}/variant",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "PATCH",
  CURLOPT_POSTFIELDS => json_encode([
    'variant_id' => 123,
    'quantity' => 123
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.fluid.app/api/public/v2025-06/commerce/carts/{cart_token}/items/{item_id}/variant"

	payload := strings.NewReader("{\n  \"variant_id\": 123,\n  \"quantity\": 123\n}")

	req, _ := http.NewRequest("PATCH", url, payload)

	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.patch("https://api.fluid.app/api/public/v2025-06/commerce/carts/{cart_token}/items/{item_id}/variant")
  .header("Content-Type", "application/json")
  .body("{\n  \"variant_id\": 123,\n  \"quantity\": 123\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.fluid.app/api/public/v2025-06/commerce/carts/{cart_token}/items/{item_id}/variant")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Patch.new(url)
request["Content-Type"] = 'application/json'
request.body = "{\n  \"variant_id\": 123,\n  \"quantity\": 123\n}"

response = http.request(request)
puts response.read_body

{
  "cart": {
    "id": 123,
    "cart_token": "<string>",
    "state": "<string>",
    "state_revision": 1,
    "email": "<string>",
    "phone": "<string>",
    "language_iso": "<string>",
    "currency_code": "<string>",
    "currency_symbol": "<string>",
    "currency_decimal_places": 123,
    "type": "<string>",
    "buyer_rep_id": 123,
    "customer_id": 123,
    "enrollment_pack_id": 123,
    "email_marketing": true,
    "sms_marketing": true,
    "processed": true,
    "valid_for_checkout": true,
    "valid_for_checkout_pre_payment": true,
    "vault_without_charge": true,
    "payment_method_auto_assignable": true,
    "requires_payment_method": true,
    "requires_3ds": true,
    "immutable_items": true,
    "digital_only": true,
    "points_enabled": true,
    "messages": {},
    "metadata": {},
    "cv_total": "<string>",
    "qv_total": "<string>",
    "amount_total": 123,
    "amount_total_in_currency": "<string>",
    "sub_total": 123,
    "sub_total_in_currency": "<string>",
    "tax_total": 123,
    "tax_exempt": true,
    "tax_total_in_currency": "<string>",
    "tax_total_for_display": "<string>",
    "inclusive_shipping_tax": 123,
    "shipping_total": 123,
    "shipping_total_in_currency": "<string>",
    "shipping_total_for_display": "<string>",
    "discount_total": 123,
    "discount_total_in_currency": "<string>",
    "subtotal_after_discounts": 123,
    "subtotal_after_discounts_in_currency": "<string>",
    "price_inclusive_of_tax": true,
    "price_inclusive_tax_name": "<string>",
    "totals": {
      "gross_subtotal": "<string>",
      "gross_subtotal_in_currency": "<string>",
      "net_subtotal": "<string>",
      "net_subtotal_in_currency": "<string>",
      "item_tax": "<string>",
      "item_tax_in_currency": "<string>",
      "shipping_net": "<string>",
      "shipping_net_in_currency": "<string>",
      "shipping_tax": "<string>",
      "shipping_tax_in_currency": "<string>",
      "total_tax": "<string>",
      "total_tax_in_currency": "<string>",
      "price_inclusive_of_tax": true,
      "tax_label": "<string>"
    },
    "enrollment_fee": 123,
    "enrollment_fee_in_currency": "<string>",
    "transaction_fee": 123,
    "transaction_fee_in_currency": "<string>",
    "shipping_discount": 123,
    "discount_codes": [
      "<string>"
    ],
    "product_discount_codes": [
      "<string>"
    ],
    "shipping_discount_codes": [
      "<string>"
    ],
    "customer_total_points": 123,
    "customer_total_points_in_currency": "<string>",
    "points_applied": 123,
    "points_applied_amount_in_currency": "<string>",
    "remaining_customer_points": 123,
    "remaining_customer_points_amount_in_currency": "<string>",
    "remaining_cart_amount_after_points": 123,
    "remaining_cart_amount_after_points_in_currency": "<string>",
    "max_applicable_points": 123,
    "total_creditable_points": 123,
    "shipping_address": {},
    "billing_address": {},
    "discount_breakdown": {
      "internal_discounts": 123,
      "external_discounts": 123,
      "total_discounts": 123
    },
    "external_discount": {},
    "buyer_rep": {
      "id": 123,
      "email": "<string>",
      "full_name": "<string>",
      "image_url": "<string>",
      "external_id": "<string>"
    },
    "volume_rep": {
      "id": 123,
      "email": "<string>",
      "full_name": "<string>",
      "image_url": "<string>"
    },
    "available_shipping_methods": [
      {
        "id": "<string>",
        "title": "<string>",
        "price": 123,
        "delivery_time_estimate": "<string>",
        "price_label": "<string>"
      }
    ],
    "available_payment_methods": [
      {}
    ],
    "payment_account": {},
    "shipping_method": {
      "id": "<string>",
      "name": "<string>"
    },
    "payment_method": {},
    "items": [
      {
        "id": 123,
        "title": "<string>",
        "quantity": 123,
        "price": "<string>",
        "price_in_currency": "<string>",
        "discount_amount": "<string>",
        "discount_amount_in_currency": "<string>",
        "tax": "<string>",
        "tax_in_currency": "<string>",
        "cv": "<string>",
        "qv": "<string>",
        "cv_total": "<string>",
        "qv_total": "<string>",
        "total": "<string>",
        "total_in_currency": "<string>",
        "line_total_in_currency": "<string>",
        "total_after_discounts": "<string>",
        "total_after_discounts_in_currency": "<string>",
        "line_total_after_discounts_in_currency": "<string>",
        "unit_price_display_authoritative": true,
        "enrollment_pack_id": 123,
        "subscription": true,
        "subscription_plan_id": 123,
        "subscription_plans": [
          {}
        ],
        "subscription_only": true,
        "subscription_interval": 123,
        "subscription_interval_unit": "<string>",
        "subscription_interval_unit_identifier": "<string>",
        "subscription_price": "<string>",
        "subscription_price_in_currency": "<string>",
        "subscription_start": "<string>",
        "subscribe_and_save": "<string>",
        "subscribe_and_save_in_currency": "<string>",
        "subscribe_and_save_for_display": "<string>",
        "display_to_customer": true,
        "metadata": {},
        "image_url": "<string>",
        "free_item": true,
        "allow_subscription": true,
        "enrollment": true,
        "errors": [
          "<string>"
        ],
        "creditable_points": 123,
        "product": {},
        "variant": {
          "id": 123,
          "title": "<string>",
          "display_name": "<string>",
          "image_url": "<string>",
          "image_path": "<string>",
          "sku": "<string>",
          "primary_image": "<string>",
          "price": 123,
          "price_in_currency": "<string>",
          "currency_code": "<string>",
          "options": [
            {
              "title": "<string>",
              "value": "<string>"
            }
          ],
          "physical": true,
          "unit_of_size": "<string>",
          "height": 123,
          "width": 123,
          "length": 123,
          "unit_of_weight": "<string>",
          "weight": "<string>",
          "hs_code": "<string>"
        },
        "bundled_items": [
          {}
        ],
        "product_title": "<string>"
      }
    ],
    "ship_to": {
      "id": 123,
      "name": "<string>",
      "address1": "<string>",
      "address2": "<string>",
      "address3": "<string>",
      "city": "<string>",
      "state": "<string>",
      "subdivision_code": "<string>",
      "postal_code": "<string>",
      "country_code": "<string>",
      "phone": "<string>",
      "country_num_code": 123,
      "default": true
    },
    "bill_to": {},
    "attribution": {},
    "agreements": [
      {
        "id": 123,
        "title": "<string>",
        "show_at_checkout": true,
        "default_checked": true,
        "show_path": "<string>",
        "enrollment_pack_id": 123,
        "required": true
      }
    ],
    "country": {
      "id": 123,
      "name": "<string>",
      "iso": "<string>",
      "iso_name": "<string>",
      "iso3": "<string>",
      "currency_code": "<string>",
      "currency_symbol": "<string>",
      "province_required": true,
      "tax_enabled": true,
      "price_inclusive_of_tax": true,
      "price_inclusive_tax_name": "<string>",
      "tax_standard_rate": 123
    },
    "company": {
      "id": 123,
      "name": "<string>",
      "favicon_url": "<string>",
      "primary_domain_hostname": "<string>",
      "subdomain": "<string>",
      "logo_url": "<string>",
      "fluid_shop": "<string>",
      "collect_phone": true,
      "require_phone": true,
      "require_billing_zip": true,
      "checkout_primary_button_color": "<string>",
      "checkout_primary_text_color": "<string>",
      "checkout_secondary_button_color": "<string>",
      "checkout_secondary_text_color": "<string>",
      "order_on_behalf": true,
      "reward_points_enabled": true,
      "reward_points_apply_to_subtotal": true,
      "reward_points_label_singular": "<string>",
      "reward_points_label_plural": "<string>",
      "collect_sms_marketing": true,
      "collect_email_marketing": true,
      "bundle_subscriptions": true,
      "isolated_payment_tokens": true,
      "kount_environment": "sandbox",
      "kount_client_id": "150953359757648"
    },
    "enrollment_pack": {},
    "recurring": [
      {
        "subtotal": 123,
        "subtotal_in_currency": "<string>",
        "interval": 123,
        "interval_unit": "<string>",
        "subtotal_for_display": "<string>",
        "start_date": "<string>"
      }
    ]
  },
  "meta": {
    "request_id": "<string>",
    "timestamp": "<string>",
    "checkout_url": "<string>",
    "shop_url": "<string>"
  }
}

{
  "error_message": "<string>",
  "errors": {},
  "meta": {
    "request_id": "<string>",
    "timestamp": "<string>"
  }
}

{
  "error_message": "<string>",
  "errors": "<string>",
  "meta": {
    "request_id": "<string>",
    "timestamp": "2023-11-07T05:31:56Z",
    "shop_url": "<string>",
    "cart": {
      "id": 123,
      "cart_token": "<string>",
      "state": "<string>",
      "state_revision": 1,
      "email": "<string>",
      "phone": "<string>",
      "language_iso": "<string>",
      "currency_code": "<string>",
      "currency_symbol": "<string>",
      "currency_decimal_places": 123,
      "type": "<string>",
      "buyer_rep_id": 123,
      "customer_id": 123,
      "enrollment_pack_id": 123,
      "email_marketing": true,
      "sms_marketing": true,
      "processed": true,
      "valid_for_checkout": true,
      "valid_for_checkout_pre_payment": true,
      "vault_without_charge": true,
      "payment_method_auto_assignable": true,
      "requires_payment_method": true,
      "requires_3ds": true,
      "immutable_items": true,
      "digital_only": true,
      "points_enabled": true,
      "messages": {},
      "metadata": {},
      "cv_total": "<string>",
      "qv_total": "<string>",
      "amount_total": 123,
      "amount_total_in_currency": "<string>",
      "sub_total": 123,
      "sub_total_in_currency": "<string>",
      "tax_total": 123,
      "tax_exempt": true,
      "tax_total_in_currency": "<string>",
      "tax_total_for_display": "<string>",
      "inclusive_shipping_tax": 123,
      "shipping_total": 123,
      "shipping_total_in_currency": "<string>",
      "shipping_total_for_display": "<string>",
      "discount_total": 123,
      "discount_total_in_currency": "<string>",
      "subtotal_after_discounts": 123,
      "subtotal_after_discounts_in_currency": "<string>",
      "price_inclusive_of_tax": true,
      "price_inclusive_tax_name": "<string>",
      "totals": {
        "gross_subtotal": "<string>",
        "gross_subtotal_in_currency": "<string>",
        "net_subtotal": "<string>",
        "net_subtotal_in_currency": "<string>",
        "item_tax": "<string>",
        "item_tax_in_currency": "<string>",
        "shipping_net": "<string>",
        "shipping_net_in_currency": "<string>",
        "shipping_tax": "<string>",
        "shipping_tax_in_currency": "<string>",
        "total_tax": "<string>",
        "total_tax_in_currency": "<string>",
        "price_inclusive_of_tax": true,
        "tax_label": "<string>"
      },
      "enrollment_fee": 123,
      "enrollment_fee_in_currency": "<string>",
      "transaction_fee": 123,
      "transaction_fee_in_currency": "<string>",
      "shipping_discount": 123,
      "discount_codes": [
        "<string>"
      ],
      "product_discount_codes": [
        "<string>"
      ],
      "shipping_discount_codes": [
        "<string>"
      ],
      "customer_total_points": 123,
      "customer_total_points_in_currency": "<string>",
      "points_applied": 123,
      "points_applied_amount_in_currency": "<string>",
      "remaining_customer_points": 123,
      "remaining_customer_points_amount_in_currency": "<string>",
      "remaining_cart_amount_after_points": 123,
      "remaining_cart_amount_after_points_in_currency": "<string>",
      "max_applicable_points": 123,
      "total_creditable_points": 123,
      "shipping_address": {},
      "billing_address": {},
      "discount_breakdown": {
        "internal_discounts": 123,
        "external_discounts": 123,
        "total_discounts": 123
      },
      "external_discount": {},
      "buyer_rep": {
        "id": 123,
        "email": "<string>",
        "full_name": "<string>",
        "image_url": "<string>",
        "external_id": "<string>"
      },
      "volume_rep": {
        "id": 123,
        "email": "<string>",
        "full_name": "<string>",
        "image_url": "<string>"
      },
      "available_shipping_methods": [
        {
          "id": "<string>",
          "title": "<string>",
          "price": 123,
          "delivery_time_estimate": "<string>",
          "price_label": "<string>"
        }
      ],
      "available_payment_methods": [
        {}
      ],
      "payment_account": {},
      "shipping_method": {
        "id": "<string>",
        "name": "<string>"
      },
      "payment_method": {},
      "items": [
        {
          "id": 123,
          "title": "<string>",
          "quantity": 123,
          "price": "<string>",
          "price_in_currency": "<string>",
          "discount_amount": "<string>",
          "discount_amount_in_currency": "<string>",
          "tax": "<string>",
          "tax_in_currency": "<string>",
          "cv": "<string>",
          "qv": "<string>",
          "cv_total": "<string>",
          "qv_total": "<string>",
          "total": "<string>",
          "total_in_currency": "<string>",
          "line_total_in_currency": "<string>",
          "total_after_discounts": "<string>",
          "total_after_discounts_in_currency": "<string>",
          "line_total_after_discounts_in_currency": "<string>",
          "unit_price_display_authoritative": true,
          "enrollment_pack_id": 123,
          "subscription": true,
          "subscription_plan_id": 123,
          "subscription_plans": [
            {}
          ],
          "subscription_only": true,
          "subscription_interval": 123,
          "subscription_interval_unit": "<string>",
          "subscription_interval_unit_identifier": "<string>",
          "subscription_price": "<string>",
          "subscription_price_in_currency": "<string>",
          "subscription_start": "<string>",
          "subscribe_and_save": "<string>",
          "subscribe_and_save_in_currency": "<string>",
          "subscribe_and_save_for_display": "<string>",
          "display_to_customer": true,
          "metadata": {},
          "image_url": "<string>",
          "free_item": true,
          "allow_subscription": true,
          "enrollment": true,
          "errors": [
            "<string>"
          ],
          "creditable_points": 123,
          "product": {},
          "variant": {
            "id": 123,
            "title": "<string>",
            "display_name": "<string>",
            "image_url": "<string>",
            "image_path": "<string>",
            "sku": "<string>",
            "primary_image": "<string>",
            "price": 123,
            "price_in_currency": "<string>",
            "currency_code": "<string>",
            "options": [
              {
                "title": "<string>",
                "value": "<string>"
              }
            ],
            "physical": true,
            "unit_of_size": "<string>",
            "height": 123,
            "width": 123,
            "length": 123,
            "unit_of_weight": "<string>",
            "weight": "<string>",
            "hs_code": "<string>"
          },
          "bundled_items": [
            {}
          ],
          "product_title": "<string>"
        }
      ],
      "ship_to": {
        "id": 123,
        "name": "<string>",
        "address1": "<string>",
        "address2": "<string>",
        "address3": "<string>",
        "city": "<string>",
        "state": "<string>",
        "subdivision_code": "<string>",
        "postal_code": "<string>",
        "country_code": "<string>",
        "phone": "<string>",
        "country_num_code": 123,
        "default": true
      },
      "bill_to": {},
      "attribution": {},
      "agreements": [
        {
          "id": 123,
          "title": "<string>",
          "show_at_checkout": true,
          "default_checked": true,
          "show_path": "<string>",
          "enrollment_pack_id": 123,
          "required": true
        }
      ],
      "country": {
        "id": 123,
        "name": "<string>",
        "iso": "<string>",
        "iso_name": "<string>",
        "iso3": "<string>",
        "currency_code": "<string>",
        "currency_symbol": "<string>",
        "province_required": true,
        "tax_enabled": true,
        "price_inclusive_of_tax": true,
        "price_inclusive_tax_name": "<string>",
        "tax_standard_rate": 123
      },
      "company": {
        "id": 123,
        "name": "<string>",
        "favicon_url": "<string>",
        "primary_domain_hostname": "<string>",
        "subdomain": "<string>",
        "logo_url": "<string>",
        "fluid_shop": "<string>",
        "collect_phone": true,
        "require_phone": true,
        "require_billing_zip": true,
        "checkout_primary_button_color": "<string>",
        "checkout_primary_text_color": "<string>",
        "checkout_secondary_button_color": "<string>",
        "checkout_secondary_text_color": "<string>",
        "order_on_behalf": true,
        "reward_points_enabled": true,
        "reward_points_apply_to_subtotal": true,
        "reward_points_label_singular": "<string>",
        "reward_points_label_plural": "<string>",
        "collect_sms_marketing": true,
        "collect_email_marketing": true,
        "bundle_subscriptions": true,
        "isolated_payment_tokens": true,
        "kount_environment": "sandbox",
        "kount_client_id": "150953359757648"
      },
      "enrollment_pack": {},
      "recurring": [
        {
          "subtotal": 123,
          "subtotal_in_currency": "<string>",
          "interval": 123,
          "interval_unit": "<string>",
          "subtotal_for_display": "<string>",
          "start_date": "<string>"
        }
      ]
    }
  }
}