shopify-functions

name	shopify-functions
description	Build Shopify Functions for custom discount, payment, and delivery logic in a WASM sandbox. Use when creating custom discount rules, payment customizations, delivery options, or cart transformations that run server-side at checkout. Trigger with phrases like "shopify functions", "shopify discounts", "shopify wasm", "custom discount function", "shopify checkout customization".
allowed-tools	Read, Write, Edit, Bash(npm:*), Grep
version	2.7.0
license	MIT
author	Jeremy Longshore <[e-mail]>
tags	["saas","ecommerce","shopify"]
compatibility	Designed for Claude Code

Shopify Functions

Overview

Shopify Functions execute custom business logic in a WebAssembly sandbox at checkout: discounts, payment filtering, delivery customization, and cart transforms. They run server-side with strict constraints (11ms execution, 1MB memory, no network access) and replace Shopify Scripts.

Prerequisites

• Shopify CLI 3.x+ installed (npm install -g @shopify/cli)
• Shopify Partners account with a development store
• App configured for the target function API type

Instructions

Step 1: Configure the Function Extension

# extensions/product-discount/shopify.extension.toml
api_version = "2025-01"
type = "product_discounts"

[[targeting]]
target = "purchase.product-discount.run"
input_query = "extensions/product-discount/input.graphql"
export = "run"

Step 2: Define the Input Query

The input query declares what data your function receives at runtime:

# extensions/product-discount/input.graphql
query Input {
  cart {
    lines {
      quantity
      merchandise {
        ... on ProductVariant {
          id
          product { hasAnyTag(tags: ["VIP-DISCOUNT"]) }
        }
      }
    }
  }
  discountNode 
    metafield ,    value