Item price use cases

This page describes how to modify quote item prices in an Adobe Commerce cart using the magento/module-out-of-process-totals-collector module.

For discount use cases, see Totals collector use cases. For custom fees, see Custom fees use cases.

How it works

The out-of-process totals collector exposes a dedicated webhook for item price modifications:

plugin.magento.out_of_process_totals_collector.api.get_total_modifications.item_prices

This webhook fires during cart totals collection, immediately after the subtotal is computed. Your App Builder application receives the quote and current totals and returns a JSON Patch response with target base prices for specific items. Commerce applies each price override, recomputes the affected row totals, and rolls the changes into the cart subtotal. The updated prices are then available to downstream collectors such as the discount and tax collectors.

Item prices webhook

To modify item prices from an external service, register a webhook for the method plugin.magento.out_of_process_totals_collector.api.get_total_modifications.item_prices (type after).

PaaS Only To register the webhook, modify the webhooks.xml file (in your module or in app/etc):

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_AdobeCommerceWebhooks:etc/webhooks.xsd">
    <method name="plugin.magento.out_of_process_totals_collector.api.get_total_modifications.item_prices" type="after">
        <hooks>
            <batch name="totals_collector_item_prices">
                <hook name="totals_collector_item_prices"
                      url="https://<your_app_builder>.adobeioruntime.net/api/v1/web/commerce-checkout-starter-kit/totals-collector-item-prices"
                      method="POST"
                      timeout="30000"
                      softTimeout="1000"
                      fallbackErrorMessage="We encountered an issue while calculating your item prices. Please contact the store owner for further assistance.">
                    <fields>
                        <field name="total" />
                        <field name="quote" />
                        <field name="shippingAssignment" />
                    </fields>
                </hook>
            </batch>
        </hooks>
    </method>
</config>

SaaS Only For Adobe Commerce as a Cloud Service, create the webhook in the Admin. Use method name plugin.magento.out_of_process_totals_collector.api.get_total_modifications.item_prices, type after, and configure the same fields as above.

To improve security, enable webhook signature verification.

Payload

The request body includes the quote, shipping assignment, and current subtotal totals. The webhook is only triggered when there are items in the cart. Example structure:

{
  "total": {
    "subtotal": 1000,
    "base_subtotal": 1000,
    ...
  },
  "quote": {
    "entity_id": "1",
    "store_id": 1,
    "items": [ ... ],
    ...
  },
  "shippingAssignment": {
    "items": [
      {
        "item_id": "491",
        "quote_id": "1",
        "sku": "simple-product-1",
        "price": 500,
        "base_price": 500,
        "qty": 2,
        "row_total": 1000,
        "base_row_total": 1000,
        ...
      }
    ],
    "shipping": {
      "method": "flatrate_flatrate",
      "address": { ... }
    }
  }
}

Your endpoint can use information such as item data and quote attributes to determine which prices to override.

Response format

The webhook endpoint must return a JSON Patch response. To override item prices, use a replace operation on the result/price_updates path.

Price update object fields

Example: override prices for specific items

{
  "op": "replace",
  "path": "result/price_updates",
  "value": [
      { "item_id": 491, "base_price": 19.99 },
      { "item_id": 492, "base_price": 9.99 }
    ]
}

Adjust item_id values to match the items in the quote. Items not included in price_updates are left unchanged.

For implementation guidance and development considerations, see Development considerations.