Split a cart by supplier

Use one Select attribute as the supplier owner for every product. Products with the same option become one order unless source routing creates additional groups.

Set missing vendor behavior to Block Checkout while catalog coverage is being introduced. Once every sellable product has a valid assignment, decide whether an empty group or a single-order fallback is appropriate for exceptional items.

Related-order links make the results easier to find, but permissions, exports and supplier notifications still follow your Magento or integration setup.