Single variant, 2 line items, Fulfillment Constraints Function limitation

Functions
1

I am using Fulfillment Constrains function to specify the fulfillment warehouses (locations) at Checkout. And I faced an issue when trying to split single variant between 2 locations.

Let me describe the business case I am trying to solve:

There are 2 locations, both in US. The inventory of product A are 3 and 3 in respective locations. When customer orders 5 items, I want to specifically define that 3 items should be fulfilled from Location B, and 2 items from Location A.

Note: I cannot use global order routing rules to prioritise Location B, since it will affect all orders., while I need priority to be determined by custom logic. I also need fulfillment to be defined at checkout because it affects shipping calculation.

So, if I specify 2 location, Shopify prioratise location 82538496228 by default, but I need 87490003172:

[
  "deliverableLinesMustFulfillFromAdd": {
    "deliverableLineIds": [
      "gid://shopify/DeliverableCartLine/1",
    ],
    "locationIds": ["gid://shopify/Location/87490003172", "gid://shopify/Location/82538496228"]
   }
]

I know that a Fulfillment Constrains function defines the fulfillment location on deliverableLines level which is more or less same as cart line item level. So i split the line item into 2 line items (by adding attribute).

Now I can specify separate locations for each line item:

[
  {
    "deliverableLinesMustFulfillFromAdd": {
        "deliverableLineIds": [
            "gid://shopify/DeliverableCartLine/0"
        ],
        "locationIds": [
            "gid://shopify/Location/82538496228"
        ]
      }
  },
  {
    "deliverableLinesMustFulfillFromAdd": {
        "deliverableLineIds": [
            "gid://shopify/DeliverableCartLine/1"
        ],
        "locationIds": [
            "gid://shopify/Location/87490003172"
        ]
      }
  }
]

But at checkout, I get No Delivery Available error, and 1 line item is removed:

image
image1026×442 35 KB

I have noticed that it happens because I specified different locations for the save product variant. Meaning, the Fulfillment Constrains function operated on product variant level rather than deliverableLine level.

Can you please verify it it’s a bug in Fulfillment Constrains function?
Maybe there is a different way to achieve my goal? Thank you!