# Sync exploding bundle availability to Shopify
URL: https://support.starshipit.com/articles/14700000000048-sync-exploding-bundle-availability-to-shopify
Canonical: https://support.starshipit.com/articles/14700000000048-sync-exploding-bundle-availability-to-shopify
Markdown: https://support.starshipit.com/articles/14700000000048-sync-exploding-bundle-availability-to-shopify.md
Updated: 2026-07-21

> For the complete documentation index, see [llms.txt](https://support.starshipit.com/llms.txt).

> Keep each exploding bundle's Shopify availability aligned with sellable component stock and open WMS order demand.

Turn on **Exploding bundles** to make WMS manage each bundle parent's Shopify available quantity. This setting is off by default and works independently of **Auto Writeback**, including when orders remain pending.

## Before you begin

Make sure:

* You have imported products from the Shopify store into WMS.
* The bundle parent is linked to a Shopify inventory item.
* The product is configured as an **exploding bundle** with valid components in WMS.
* You know which Shopify location WMS should update.

:::important
When you enable this setting, WMS becomes the source of truth for each linked exploding bundle parent's available quantity at the selected Shopify location. WMS will overwrite changes made directly to that quantity in Shopify when the next update runs.
:::

## How WMS calculates bundle availability

WMS calculates how many complete bundles you can sell from the component stock in sellable WMS locations. It also subtracts component demand from orders with a **Pending** or **Released** status.

For each bundle, WMS:

1. Finds the sellable quantity of each component.
2. Subtracts demand from pending and released orders, including direct component sales and other exploding bundles.
3. Divides each remaining component quantity by the number required for one bundle.
4. Uses the lowest whole-number result as the bundle's available quantity.
5. Sets the bundle parent's Shopify available quantity to that result.

For example, a bundle requires two units of Component A and one unit of Component B:

| Component | Sellable stock | Pending and released demand | Stock remaining | Complete bundles |
| --- | ---: | ---: | ---: | ---: |
| Component A | 20 | 4 | 16 | 8 |
| Component B | 8 | 3 | 5 | 5 |

WMS writes an available quantity of **5** to the Shopify bundle because Component B is the limiting component.

:::note
Pending orders reduce bundle availability because they already claim component stock in WMS. You do not need to enable automatic order release for this setting to work.
:::

## Enable exploding bundle availability sync

1. Go to **System > Settings**.
2. Open **Inventory Writeback** under **Products & Inventory**.
3. Find the Shopify store you want to configure.
4. Select the Shopify **Writeback Location** that WMS should update.
5. Turn on **Exploding bundles** for that store.

WMS queues an initial calculation when you enable the setting. It recalculates bundle availability after relevant stock, order demand, stock count, and bundle configuration changes.

## Understand Auto Writeback

**Exploding bundles** and **Auto Writeback** are separate settings:

| Setting | What WMS updates |
| --- | --- |
| **Exploding bundles** | Sets each linked exploding bundle parent's Shopify available quantity from WMS component stock and open order demand. |
| **Auto Writeback** | Sends normal WMS stock movements for linked products to Shopify. |

You can enable **Exploding bundles** while leaving **Auto Writeback** off. This lets Shopify continue managing normal item inventory while WMS manages the derived availability of exploding bundle parents.

## Verify the setting

1. Open an exploding bundle product in Shopify and note its available quantity at the selected location.
2. Create or update a pending WMS order that uses one of the bundle's components.
3. Wait a few seconds for the background update to run.
4. Refresh Shopify and confirm the bundle parent's available quantity reflects the remaining component stock.

If the quantity does not update, go to **System > Process Logs** and search for Shopify inventory sync errors.

## Troubleshooting

| Problem | What to check |
| --- | --- |
| The **Exploding bundles** switch is unavailable | Select a **Writeback Location** first. Make sure products have been imported from the Shopify store. |
| A bundle does not update | Confirm it is an exploding bundle, the parent is linked to Shopify, and Shopify writeback is not disabled on the product. |
| Availability is lower than expected | Check pending and released orders. Direct sales of a shared component also reduce every bundle that needs that component. |
| Availability is zero | Check that every required component has enough sellable stock after open order demand. Also check the bundle component quantities. |
| Component products are not updating in Shopify | Enable **Auto Writeback** if you also want WMS to send normal component stock movements. |

## Related articles

* [Sync WMS inventory to your sales channels](/articles/14700000000018-shopify-inventory-sync)
* [Configure products, bundles and inventory](/articles/14700000000006-starshipit-wms-products-and-inventory-configuration)
* [Manage orders and allocation in WMS](/articles/14700000000010-starshipit-wms-orders-and-allocation)