How Bundle (BOM) Products Work

Source: product.rb:270-282, bom_items_controller.rb:62-167

BOM (Bill of Materials) parent product cost is auto-calculated by summing all child item costs (both ex-tax and inc-tax) -- you cannot manually set the cost of a bundle parent
If a child product in the bundle is invalid or deleted, the parent product raises "Bundle contains an invalid or deleted product" on save
A BOM item cannot reference its own parent product -- this prevents infinite loops; the error message includes a link to the support KB article
BOM item line_total = quantity * price for each child item
Updating a bundle recalculates the parent product's retail_price, cost, and cost_including_tax from the sum of all child items
The "update_pricing" action recalculates without saving to the database -- it only returns the calculated values as JSON for preview
BOM item destroy flag uses "1" to delete and "0" to keep; new items submitted with destroy "1" are silently skipped
BOM item product group name falls back from child product to parent product if the child has no group

"Why did my bundle product's cost change automatically?" → Bundle costs are always recalculated from child items on every save
"Why can't I add this product to its own bundle?" → Self-referencing BOM items are blocked to prevent infinite loops
"Why didn't my bundle price changes save when I clicked update pricing?" → The update_pricing action only previews calculations; you must save separately
"Bundle contains an invalid or deleted product" → One of the child products in the bundle has been deleted or is invalid; check each child item