Quick answer
KitForge widgets use Shopify's cart APIs to add FBT and quantity break lines with correct properties. Theme ajax cart drawers that re-fetch or merge cart JSON must preserve KitForge private properties or discounts and analytics break.
- KitForge widget adds include private line properties required at checkout.
- Ajax cart drawers are a common failure point for FBT/QB pricing.
- Test mobile drawer flow on every theme change.
- Checkout subtotal is the final arbiter of discount application.
Theme developer guidance
When customizing cart.js handlers, preserve all line properties from /cart/add.js responses. Do not reconstruct lines from variant ID alone after KitForge widget adds.
Final recommendation
Shopify Ajax Cart API and KitForge FBT widgets work together when themes preserve line properties. Test drawer behavior after any cart customization.
If you want this kind of offer to feel native to the buying journey, Kitforge Bundles is built around that exact problem: turning related Shopify products into clearer bundle offers before the shopper reaches checkout.
FAQ
Does KitForge replace my cart drawer?
No — KitForge adds lines via Shopify cart APIs. Your theme drawer remains responsible for display.
Fixed kits in ajax cart?
Fixed kits use Cart Transform — drawer may show expanded or parent lines depending on theme. Verify fulfillment view in order admin.