Shopify Flow not triggering “Product Variant Inventory Quantity Changed” when inventory updates come from Accumula/Mortar (Lightspeed sync)

Shopify Flow
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1

Hi everyone,

I’m running into an issue with a Shopify Flow that uses the “Product Variant Inventory Quantity Changed” trigger. I’m hoping someone can clarify whether this is a known limitation, an expected behavior, or a bug.

Context

  • The merchant uses Lightspeed Retail as their POS.

  • Inventory is synced to Shopify using Mortar (formerly Accumula).

  • The Shopify app is installed and working correctly.

  • When the merchant performs an Inventory Transfer in Lightspeed from one location to another, Mortar pushes inventory adjustments to Shopify as expected.

  • In Shopify, I can clearly see:

    • The Inventory History shows Mortar as the actor.

    • The correct locations are being adjusted.

The problem

Even though the inventory levels do change in Shopify, Shopify Flow does NOT trigger the “Product Variant Inventory Quantity Changed” workflow.

This breaks a Flow we use to update a metafield used for displaying per-location inventory quantities.

Key observations

  • Manual inventory changes in Shopify do trigger the Flow.

  • API-driven inventory changes from other apps usually also trigger this Flow.

  • But inventory transfers coming from Mortar/Accumula do NOT trigger the Flow, even though they appear in the Inventory History

Questions

  1. Is this a known limitation of the “Product Variant Inventory Quantity Changed” trigger?
    (e.g., does the trigger only fire when the inventory_quantity field changes directly, and not when only inventory_levels per location change?)

  2. Is there anything Mortar/Accumula should do differently to ensure that their inventory updates emit the proper event for Flow?

  3. Are there recommended workarounds, such as using a different Flow trigger?

Why this matters

The store relies on a metafield that must stay in sync with per-location inventory.
When Flow does not trigger, the inventory display becomes inaccurate.

Any insights, known behaviors, or technical details about how this Flow trigger works under the hood would be extremely helpful.

Thanks in advance!

2

Probably faster than Shopify figuring out if they can help you: Ask Mortar to create a flow trigger for you to use.

3

I’m not aware of why this particular app would not cause the trigger to fire, but it’s possible the type of inventory adjustment they are doing does not cause the event to be sent. It would help to get more details about the adjustments that you see are missing, like which quantity is adjusted and if the “net” of the adjustment is 0.

4

Hi Paul,

Thanks for taking the time.

Look at this example. Type = “Inventory correction” :thinking:

Capture d’écran, le 2025-11-18 à 09.24.11
Capture d’écran, le 2025-11-18 à 09.24.112426×352 18.7 KB

Here’s our flow trigger:

Capture d’écran, le 2025-11-18 à 09.26.05
Capture d’écran, le 2025-11-18 à 09.26.051286×190 13 KB

Thank you

5

I don’t see anything that would suggest this is a special case, so I’d expect it to work. Are you sure the trigger didn’t fire?

6

You are 100% correct Paul. I’ve revisited my test transfer from 10 days ago and looked at Flow history again. It took 20 minutes between the change in lightspeed and the trigger so I’ve missed it (I’ve waited 15). The next transfer took 3 minutes before it triggered…

The problem resides that the flow data contains the first inventory change at location A (-1), but still sees location B at 0 (not +1). I’m trying something: adding a wait step + get product variant data to get the right data before Run code step.

I agree that the bug made no sense, hence the reason why I’ve shared it here.

Have a nice day and thanks for your help

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