> ## 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.

# Links to other modules

> How the Offer domain links to other modules across the marketplace.

Modules in Mercur never reference each other directly. They connect through
**module links**. The offer sits at the center of the marketplace, so it links
out to the store, the master catalog, pricing, inventory, fulfillment, and the
cart and order line items that reference it. Once a link is defined, you retrieve
related records with `query.graph` using the link alias.

```ts theme={null}
const { data: offers } = await query.graph({
  entity: "offer",
  fields: ["id", "sku", "prices.*", "inventory_items.*", "seller.name"],
})
```

## Catalog & store

| Linked module       | Relationship                                                           |
| ------------------- | ---------------------------------------------------------------------- |
| **Product**         | An offer points at one master product (`offer.product_id`, read-only). |
| **Product variant** | An offer points at one master variant (`offer.variant_id`, read-only). |
| **Seller**          | An offer belongs to one store (`offer.seller_id`, read-only).          |

## Pricing & inventory

| Linked module      | Relationship                                                                                                                       |
| ------------------ | ---------------------------------------------------------------------------------------------------------------------------------- |
| **Price**          | An offer has many prices: a writable list-link to the offer-owned rows on the master variant's shared price set.                   |
| **Inventory item** | An offer has many inventory items: a writable list-link (`offer_inventory_item`) whose pivot carries a `required_quantity` column. |

## Fulfillment

| Linked module        | Relationship                                                                       |
| -------------------- | ---------------------------------------------------------------------------------- |
| **Shipping profile** | An offer ships with one shipping profile (`offer.shipping_profile_id`, read-only). |

## Cart & order

| Linked module       | Relationship                                                                                                                                     |
| ------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------ |
| **Cart line item**  | A cart line item links to the offer it added; one offer can back many cart line items (list-link on the line-item side).                         |
| **Order line item** | An order line item links to the purchased offer; one offer can back many order line items across child orders (list-link on the line-item side). |

<Note>
  Read-only links (Product, Variant, Seller, Shipping profile) resolve from a
  field on the `offer` row and can't be written through the link itself. The
  Price and Inventory-item links are writable and are managed by the offer
  workflows.
</Note>

<Tip>
  The cart- and order-line-item links are list-links **on the line-item side** so
  the same offer can be added to many carts and placed on many orders. Without
  that, Medusa would enforce a 1:1 line-item ↔ offer relationship and block
  re-use.
</Tip>