Thank you for your detailed explanation.

I’m familiar with the inter-company rules and the sales/purchase flow approach, and I’ve used them successfully in a different Odoo 18 database before. However, in this current case, I intentionally do not want to use the inter-company sales/purchase rules, as I’m not "selling" the product to my other company due to taxation and regulatory constraints.

What’s puzzling is that in the other Odoo 18 DB, the inter-company transit route (without PO/SO flow) still recorded the valuation correctly on both sides. But in this setup, Company A’s cost is reduced correctly, while Company B receives the product at zero cost, even though:

• The product is shared across both companies,
• The product category is configured with automated inventory valuation (FIFO),
• The accounts are properly set,
• And multi-step routes are used through an inter-company transit location.

Is there any workaround or technical configuration that can make the valuation work properly without using the sales/purchase flow? Perhaps by modifying routes or automating landed cost generation?

Thanks again for your help!

With the standard approach in Odoo, the only way to update the cost or Stock Valuation Layer (SVL) is through the Sales Order - Purchase Order (SO-PO) flow. Any other requirement would require customization. Since the cost is variable, using automated actions will not capture the dynamic cost values accurately.