Inventory

A bundle doesn't track its own inventory (inventoryTracked is always off). Instead, stock comes from its component variants, and is decremented against them.

Availability

Bundle::getIsAvailable() returns false if any component product has no purchasable, in-stock variant. A component with an untracked variant is always treated as available.

So a bundle goes unavailable automatically when a component sells out; no manual disabling needed.

Decrement on order completion

When an order completes, the bundle's afterOrderComplete() reads the line item's frozen snapshot and, for each chosen inventory-tracked variant, brings its available stock down by:

component quantity × line item quantity

…using Commerce's Inventory::updatePurchasableInventoryLevel(…, ADJUST), with a note recording the bundle SKU. Untracked variants are skipped.