To achieve the behaviour you want, you will need to adjust the Buy route configuration so that Odoo purchases stock directly for Warehouse SB, not for DC.

1. Update the Buy Route

Right now, the “Buy” rule of Warehouse DC is pointing to DC Receipt as its operation type.

Because of this, whenever DC faces a shortage, even an artificial one created by the pull rules, Odoo triggers a purchase for DC, not SB.

To correct this:

Change the operation type of the Buy rule for DC to SB’s Receipt operation type.

This ensures that any shortage created while fulfilling SB’s demand results in a Purchase Order for SB, not DC.

If you want to avoid confusion, you can archive the DC Receipt operation type.

This makes sure Odoo does not try to purchase for DC at all.

2. Adjust the Resupply Route From DC → SB

In your route “Resupply from DC”, for the third rule (Inter-warehouse Transit → SB/Stock):

Make sure the rule is configured as:

Take from stock ,if unavailable, trigger another rule

This ensures proper flow:

If SB does not have enough stock, Odoo first checks DC.

DC sends whatever is available (100 units in your example).

The remaining shortage (100 units) triggers the Buy rule—but now for SB, not DC.

3. What Happens After Fixing the Rules

With the corrected routing:

SO of 300 units creates demand at SB.

SB supplies its 100 units.

Odoo pulls 100 units available in DC and moves them to SB.

The remaining 100-unit shortage now triggers a Purchase Order for SB, because the Buy route is configured to replenish SB.

You may still see a backorder request in DC because the system originally generated demand for 200 from DC, but DC only had 100 available. This is normal behaviour based on pull rules and can be safely managed or ignored depending on the process.

If you have any follow-up questions or want me to check your exact routing configuration, feel free to ask!