Change the inventory items behind an offer

Run batchOfferInventoryItemsWorkflow when an existing offer needs different stock behind it, for example to turn it into a kit or to swap a component. The workflow changes the offer ↔ inventory_item links and their required_quantity in one run.

Before you begin

You need these records in place:

An offer: the offer_id whose stock you change
Existing inventory items: the workflow links items that already exist and doesn’t create new ones

Change the links

Add a route that runs the batch

Pass the offer and the three optional lists: create, update, and delete.

src/api/admin/custom/offers/[id]/inventory/route.ts

import type { MedusaRequest, MedusaResponse } from "@medusajs/framework/http"
import { batchOfferInventoryItemsWorkflow } from "@mercurjs/core/workflows"

export async function POST(req: MedusaRequest, res: MedusaResponse) {
  const { result } = await batchOfferInventoryItemsWorkflow(req.scope).run({
    input: {
      offer_id: req.params.id,
      create: [
        { inventory_item_id: "iitem_01JD8Q1234567", required_quantity: 2 },
      ],
      update: [
        { inventory_item_id: "iitem_01JD8Q1234568", required_quantity: 1 },
      ],
      delete: ["iitem_01JD8Q1234569"],
    },
  })

  res.json(result)
}

create links a new item, update changes the required_quantity of a linked item, and delete unlinks an item. The inventory item itself stays in place after an unlink.

Read the result

The workflow returns what changed:

created: the link definitions it added
updated: the link definitions it rewrote
deleted: the inventory item ids it unlinked

It also emits offer.updated with { id } for the offer.

Rules the batch enforces

The workflow checks the whole payload before it writes anything. Any broken rule fails the run:

Unknown offer: Offer with id: … was not found
Unknown item in create: the inventory item must exist
Item not linked, in delete: fails with not found instead of a silent no-op
Same id twice: an id can appear once per list and in only one of the three lists

required_quantity defaults to 1 in create and is required in update.

The workflow doesn’t check that an item in create is already linked or that an item in update is linked, and it doesn’t check which store owns an item. Read the offer’s inventory_item_link and the item’s store first when your input comes from a seller.

Run code after the batch

The workflow exposes an offerInventoryItemsBatched hook. It receives the offer_id, the result, and any additional_data you passed.

src/workflows/hooks/offer-inventory-batched.ts

import { batchOfferInventoryItemsWorkflow } from "@mercurjs/core/workflows"

batchOfferInventoryItemsWorkflow.hooks.offerInventoryItemsBatched(
  async ({ offer_id, result }, { container }) => {
    const logger = container.resolve("logger")
    logger.info(`${offer_id}: ${result.deleted.length} items unlinked`)
  }
)

A validate hook runs first with the raw input, so you can reject a batch with your own rules before any link changes.

Store

Catalog

Offer

Attribute

Product Edit

Order Group

Commission

Payout

Review

Change the inventory items behind an offer

Before you begin

Change the links

Rules the batch enforces

Run code after the batch

Next steps

​Before you begin

​Change the links

​Rules the batch enforces

​Run code after the batch

​Next steps

Before you begin

Change the links

Rules the batch enforces

Run code after the batch

Next steps