Shopify Winter '26 Edition: Complete Developer Guide

The Shopify Winter '26 Edition (January 2026) is the largest platform update in Shopify's history, with 150+ new features and improvements. This guide breaks down everything that matters for developers, organized by impact area.

Why This Edition Is Different

Winter '26 marks Shopify's full pivot to agentic commerce -- the idea that AI agents (not just humans) will browse, negotiate, and purchase on behalf of consumers. Every major feature in this edition either enables AI agents or is built with AI assistance. As a developer, understanding this shift is essential for building relevant apps in 2026 and beyond.

AI & Agentic Commerce

The centerpiece of Winter '26. Shopify is betting that the next wave of e-commerce growth comes from AI-powered shopping agents.

Shopify Sidekick (Major Upgrade)

Sidekick, Shopify's built-in AI assistant for merchants, received its most significant upgrade since launch.

What's new:

Sidekick Extensions API -- Third-party apps can now extend Sidekick with custom capabilities. When a merchant asks Sidekick to "optimize my email campaign," your app can handle it.
Sidekick Actions -- Sidekick can now execute multi-step workflows: create a product, set up a discount, and schedule a marketing campaign in a single conversation.
Context awareness -- Sidekick now reads store analytics, recent orders, and customer data to provide contextual recommendations.
Merchant approval flows -- Sidekick proposes actions and waits for merchant confirmation before executing. Critical for trust.

Developer impact:

New Sidekick Extension Points for app developers
sidekick.action.propose and sidekick.action.execute API endpoints
Custom tool registration through the Partner Dashboard

# Register a Sidekick Extension
mutation sidekickExtensionCreate {
  sidekickExtensionCreate(input: {
    title: "Email Campaign Optimizer"
    description: "Analyzes store data and optimizes email campaigns"
    actionDefinitions: [
      {
        name: "optimize_campaign"
        description: "Optimize an email campaign based on store analytics"
        inputSchema: "{ ... }"
      }
    ]
  }) {
    sidekickExtension { id }
    userErrors { field message }
  }
}

Sidekick Extensions are in Developer Preview

As of Winter '26, Sidekick Extensions are available to approved partners. Apply through the Partner Dashboard under "Beta Programs."

Catalog API (New)

The Catalog API enables AI agents and external systems to interact with a store's product catalog in a structured, machine-readable format.

Key capabilities:

Structured product data optimized for AI consumption
Semantic search across product attributes
Price and availability queries with real-time accuracy
Product comparison and recommendation support
Multi-language and multi-currency support

Why it matters: Traditional product APIs return data designed for human-built frontends. The Catalog API returns data structured for AI agents to understand and reason about.

# Catalog API: semantic product search
query {
  catalog {
    productSearch(
      query: "comfortable running shoes for flat feet under $150"
      semanticMatch: true
      limit: 10
    ) {
      results {
        product {
          id
          title
          semanticDescription
          priceRange { minVariantPrice { amount currencyCode } }
          attributes { key value confidence }
        }
        relevanceScore
      }
    }
  }
}

Checkout Kit for AI Agents

A new SDK that enables AI shopping agents to complete purchases on behalf of consumers.

Components:

Agent Authentication -- Secure identity verification for AI agents acting on behalf of users
Cart Assembly -- Programmatic cart creation with agent-optimized validation
Payment Delegation -- Tokenized payment methods that agents can use without seeing card details
Consent Framework -- User approval flows before agent-initiated purchases

Developer impact: If you are building AI shopping assistants, chatbots, or voice commerce, this is your primary integration point.

SimGym

A simulation environment for testing AI agent interactions with Shopify stores without affecting real data or triggering real payments.

Features:

Sandboxed store replicas for agent testing
Simulated payment processing
Configurable inventory, pricing, and shipping scenarios
Performance benchmarking for agent decision-making
A/B testing of agent strategies

Use cases:

Test your AI shopping agent before connecting it to real stores
Benchmark agent performance across different store configurations
Train custom models on simulated e-commerce interactions

Tinker App

A new Shopify app for prototyping and experimenting with AI-powered store features directly in the admin.

Capabilities:

Visual prompt builder for Sidekick extensions
Test AI agent interactions with your store's live data
Preview how AI-generated product descriptions look on your theme
Experiment with dynamic pricing algorithms
Prototype custom recommendation engines

Developer Platform

Shopify Dev MCP Server

The official MCP server for AI-assisted Shopify development. See our detailed guide.

Winter '26 additions:

Full API 2026-01 schema support
Shopify Functions scaffolding for JavaScript and Rust
Checkout extension documentation and examples
Improved search relevance and response quality
New validate_graphql tool for query validation

Shopify Functions (General Availability)

Shopify Functions moved from developer preview to general availability with Winter '26.

Supported function APIs:

Function Type	Purpose	Status
Delivery Customization	Custom shipping rates and options	GA
Payment Customization	Custom payment method filtering	GA
Discount	Custom discount logic	GA
Cart Transform	Modify cart contents (bundles, gifts)	GA
Fulfillment Constraints	Restrict fulfillment options	GA
Order Routing Location Rule	Custom fulfillment routing	GA
Validation	Custom checkout validation	GA
Gate	Tokengated commerce	GA

New in Winter '26:

JavaScript support alongside Rust (Javy runtime)
Increased execution limits -- 5MB memory, 10ms execution time
Network access (limited) for external API calls
Persistent storage via metafield read access in function input
Testing framework with shopify app function test

// Example: Delivery Customization Function (JavaScript)
// @ts-check
import { DeliveryCustomization } from "@shopify/shopify-functions";

export default function deliveryCustomization(input) {
  const operations = [];

  // Block express shipping for oversized items
  for (const delivery of input.cart.deliveryGroups) {
    for (const option of delivery.deliveryOptions) {
      const hasOversizedItem = input.cart.lines.some(line =>
        line.merchandise?.product?.hasTag("oversized")
      );

      if (hasOversizedItem && option.title.includes("Express")) {
        operations.push({
          hide: { deliveryOptionHandle: option.handle }
        });
      }
    }
  }

  return { operations };
}

Theme Editor Overhaul

The Online Store editor received a major redesign:

Real-time collaborative editing -- Multiple team members can edit a theme simultaneously
Version history -- Full change history with diff view and rollback
AI-assisted content -- Generate section content, alt text, and copy from the editor
Component library -- Drag-and-drop pre-built components (hero sections, product grids, etc.)
Performance budget -- Real-time performance scoring as you edit

Developer Dashboard

A new centralized dashboard for Shopify app developers:

API usage analytics -- Real-time monitoring of API call volumes, error rates, and latency
Webhook reliability -- Track webhook delivery success rates per topic
App performance -- Load time, error rate, and merchant satisfaction metrics
Revenue analytics -- MRR, churn, install/uninstall trends
Compliance status -- GDPR, data access, and security requirement tracking

Tangle (Internal Framework, Now Documented)

Shopify publicly documented Tangle, their internal framework for building complex, type-safe GraphQL APIs. While not directly usable by external developers, understanding Tangle helps you work more effectively with Shopify's APIs.

Key concepts:

Every Shopify GraphQL type is backed by a Tangle model
Mutations follow a consistent pattern: input → model → output + userErrors
Connections (pagination) are standardized across all types
Access scopes map directly to Tangle authorization rules

OAuth Credentials Upgrade

Shopify's OAuth system received significant improvements:

Proof Key for Code Exchange (PKCE) -- Required for all new apps
Rotating refresh tokens -- Automatic token rotation for enhanced security
Scoped access tokens -- Request only the scopes you need per session
Token introspection endpoint -- Verify token validity without a store round-trip
Offline/Online token clarity -- Better documentation and tooling for token types

API Version 2026-01

The first API version of 2026 brings:

New types and fields:

CatalogProduct -- Product representation optimized for AI agents
SidekickExtension -- Register and manage Sidekick extensions
FunctionRunResult -- Improved function execution result types
CheckoutBranding -- Expanded checkout customization options

Breaking changes from 2025-10:

Product.images deprecated in favor of Product.media
Order.shippingLine moved to Order.shippingLines (plural)
Webhook payload format changes for orders/create and orders/update
InventoryLevel.available deprecated in favor of InventoryLevel.quantities

Deprecations:

REST Admin API product image endpoints (use GraphQL productMedia mutations)
ScriptTag resource (replaced by WebPixel)
Legacy checkout customization (use Checkout UI Extensions)

API Migration Timeline

2026-01 released January 2026
2025-04 will be sunset April 2026
2025-07 will be sunset July 2026

Start migrating now if you are on 2025-04 or earlier.

Store & Theme

Rollouts

A new deployment feature for theme changes:

Staged rollouts -- Push theme changes to a percentage of traffic first
Automatic rollback -- If error rates spike, changes are automatically reverted
A/B testing integration -- Compare theme versions against conversion metrics
Scheduled deployment -- Queue theme changes for specific dates/times

2,048 Variants per Product

The variant limit increased from 100 to 2,048 per product.

Developer impact:

Product forms and variant selectors need to handle larger option matrices
Inventory management UIs need pagination for variant lists
GraphQL queries for variants should use connections with cursor pagination
Metafield management per variant requires bulk operation patterns

# Paginating through variants of a high-variant-count product
query {
  product(id: "gid://shopify/Product/123") {
    variants(first: 50, after: "cursor") {
      edges {
        node {
          id
          title
          price
          inventoryQuantity
        }
      }
      pageInfo {
        hasNextPage
        endCursor
      }
    }
  }
}

Unlisted Products

Products can now be marked as unlisted -- available via direct link but not shown in search, collections, or sitemaps.

Use cases:

Exclusive products for specific customer segments
Pre-launch pages shared with influencers
B2B products only accessible through custom portals
Event-specific merchandise with limited distribution

API:

mutation {
  productUpdate(input: {
    id: "gid://shopify/Product/123"
    status: ACTIVE
    publishedScope: UNLISTED
  }) {
    product { id status }
    userErrors { field message }
  }
}

Mobile Theme Generator

An AI-powered tool that generates mobile-optimized theme variations from your existing desktop theme:

Automatic layout adjustments for small screens
Touch-target size optimization
Image resizing and art direction
Navigation simplification
Performance optimization for mobile networks

Commerce & Payments

Product Network

A new B2B feature allowing stores to share product catalogs across a network of Shopify merchants:

Suppliers publish products to the network
Retailers can browse and add products to their store
Inventory synced in real-time across the network
Pricing and margin rules set by the supplier
Fulfillment handled by the supplier (dropship model)

Developer impact: New API endpoints for network management, catalog sharing, and inter-store operations.

ACH Payments

ACH (Automated Clearing House) payments now supported through Shopify Payments:

Lower transaction fees than credit cards (0.5% vs 2.9%)
B2B merchants can accept bank-to-bank payments
Recurring payment support for subscriptions
Settlement in 3-5 business days

POS Overhaul

Shopify POS received a major update:

Unified APIs -- POS and online store use the same APIs for inventory, orders, and customers
POS UI Extensions -- Build custom POS experiences using the same extension framework as online checkout
Tap to Pay -- NFC payments via iPhone and Android devices
Staff permissions API -- Programmatic management of POS staff roles and permissions

Uber Direct Integration

Native integration with Uber Direct for same-day local delivery:

Real-time delivery quotes at checkout
Automatic driver dispatch on order fulfillment
Live tracking for merchants and customers
API for custom delivery workflow integration

Infrastructure

Oxygen V2

Shopify's hosting platform for Hydrogen storefronts received a major upgrade:

Edge compute -- Server-side rendering at 300+ global edge locations
Streaming SSR -- React Server Components with streaming for faster TTFB
Auto-scaling -- Automatic scaling from 0 to millions of requests
Environment branches -- Preview deployments for every Git branch
Log streaming -- Real-time log output to your monitoring platform

Webhook Reliability Improvements

Guaranteed delivery with configurable retry policies (up to 72 hours)
Dead letter queue -- Failed webhooks stored for manual inspection
Delivery metrics in the Developer Dashboard
Webhook versioning -- Payload format locked to your API version
Bulk webhook management via GraphQL

GraphQL Cost Improvements

Reduced costs for common queries (products, orders, customers)
Parallel query execution -- Multiple independent queries in a single request
Query complexity estimator -- New API endpoint to check cost before execution
Burst rate increases -- Higher burst limits for Shopify Plus stores

Migration Checklist

For developers updating their apps for Winter '26:

High Priority

Update to API version 2026-01
Migrate from Product.images to Product.media
Update Order.shippingLine to Order.shippingLines
Implement PKCE for OAuth flows
Handle 2,048-variant products in your UI

Medium Priority

Explore Sidekick Extensions for your app category
Test against the Catalog API for AI agent compatibility
Update webhook handling for new payload format
Migrate ScriptTag to WebPixel if applicable

Low Priority (But Worth Exploring)

Evaluate Shopify Functions for custom logic currently in your app server
Test your app in SimGym for agent compatibility
Set up the Developer Dashboard for monitoring
Experiment with the Mobile Theme Generator

Timeline

Date	Event
January 15, 2026	Winter '26 Edition announced
January 15, 2026	API 2026-01 released
February 1, 2026	Sidekick Extensions developer preview opens
March 1, 2026	Catalog API public beta
April 1, 2026	API 2025-04 sunset
April 15, 2026	Functions JavaScript runtime GA
June 2026	Summer '26 Edition (expected)

Resources

Shopify Editions Winter '26 -- Official announcement page
API 2026-01 Changelog -- Detailed API changes
Developer Changelog -- All platform changes
Migration Guide -- API version migration docs
Functions Documentation -- Shopify Functions reference
Sidekick Extensions Guide -- Building Sidekick integrations

AI & Agentic Commerce​

Shopify Sidekick (Major Upgrade)​

Catalog API (New)​

Checkout Kit for AI Agents​

SimGym​

Tinker App​

Developer Platform​

Shopify Dev MCP Server​

Shopify Functions (General Availability)​

Theme Editor Overhaul​

Developer Dashboard​

Tangle (Internal Framework, Now Documented)​

OAuth Credentials Upgrade​

API Version 2026-01​

Store & Theme​

Rollouts​

2,048 Variants per Product​

Unlisted Products​

Mobile Theme Generator​

Commerce & Payments​

Product Network​

ACH Payments​

POS Overhaul​

Uber Direct Integration​

Infrastructure​

Oxygen V2​

Webhook Reliability Improvements​

GraphQL Cost Improvements​

Migration Checklist​

High Priority​

Medium Priority​

Low Priority (But Worth Exploring)​

Timeline​

Resources​