> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mercurjs.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Manage offer inventory

> Attach, update, and detach inventory items on an existing offer.

In this guide, you'll learn how to change the inventory items linked to an
existing offer from your own server code.

Because inventory links to the **offer** (not the variant), the set of inventory
items backing an offer is managed through the `offer ↔ inventory_item` link.
`batchOfferInventoryItemsWorkflow` applies creates, updates, and deletes to that
link in a single run.

## Run the batch workflow

```ts title="src/api/custom/offer-inventory/route.ts" theme={null}
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: "offer_123",
      create: [{ inventory_item_id: "iitem_new", required_quantity: 2 }],
      update: [{ inventory_item_id: "iitem_existing", required_quantity: 5 }],
      delete: ["iitem_stale"],
    },
  })

  res.json(result)
}
```

The result reports the links that were `created`, `updated`, and `deleted`.

## Rules the workflow enforces

* Items in `create` must **not** already be linked to the offer; items in `update` and `delete` **must** already be linked.
* An `inventory_item_id` can't appear in more than one section, and can't be duplicated within a section.
* `create` items must reference existing `InventoryItem` records; `required_quantity` defaults to `1`.
* Deleting an item that isn't linked to the offer surfaces a 404 rather than silently no-op'ing.

<Note>
  This workflow manages the **links** between an offer and existing inventory
  items and their `required_quantity`. To create brand-new inventory items with
  starting stock as part of listing an offer, pass `inventory_items` to
  [`createOffersWorkflow`](/platform/offer/guides/create-an-offer) instead.
</Note>

The workflow emits `offer.updated` and exposes an `offerInventoryItemsBatched`
hook carrying the `offer_id`, the batch result, and any `additional_data` you
passed in.