Developer Reference

How Llama Upsells renders on your storefront, and how to customize it in your theme.

This reference is for developers and agencies integrating or customizing Llama Upsell & Cross-Sell in a Shopify theme. If you just want to set up campaigns, see the Guides instead.

How the app integrates with your theme

Llama Upsells renders on the storefront through a Theme App Extension — a set of app blocks you place in the theme editor plus a global app embed that loads the runtime. For standard setups, no theme code changes are required.

App blocks & app embed — the widgets (recommendations, slider, list, unlock, gift with purchase) are Shopify app blocks. The app embed injects the shared runtime and the Llama Cart. See App blocks.
App proxy — dynamic data (campaigns, products, discounts, settings) is fetched at runtime through Shopify's App Proxy, so widgets always reflect what's configured in the admin.
Shopify Functions & checkout extensions — discounts (product, volume/tier, shipping), cart/checkout validation, and post-purchase offers are all separate extensions, so they hold through Shop Pay and checkout.
Storefront events — the widgets dispatch JavaScript events you can listen to, and expose a few global functions for advanced integrations.
Metafields — data your theme can read is stored under the lc_upsell metafield namespace.
Webhooks — the app handles Shopify's mandatory GDPR compliance webhooks, and order webhooks drive Analytics attribution.