Hydrogen 2026.1: What You Need to Know About the API Update

Shopify released Hydrogen 2026.1.0, aligning with their quarterly API release cycle. Most changes are additive, but there's one breaking change that requires immediate attention if you have custom cart discount logic.

The Breaking Change

The cartDiscountCodesUpdate mutation now requires the discountCodes argument.

Before (Implicit)

cartDiscountCodesUpdate(cartId: $cartId)

After (Explicit)

cartDiscountCodesUpdate(
  cartId: $cartId
  discountCodes: []  # Required field
)

What Else Changed

Hydrogen 2026.1.0 updates both:

• Storefront API → 2026-01
• Customer Account API → 2026-01

This is a quarterly version update aligned with Shopify's API release schedule.

Action Items

1. Update packages to Hydrogen 2026.1.0
2. Search codebase for cartDiscountCodesUpdate mutations
3. Add explicit discountCodes argument to all calls
4. Test cart discount functionality

Official Changelogs

For complete details, review:

• Storefront API 2026-01 Changelog
• Customer Account API 2026-01 Changelog

Bottom Line

10-minute fix if you have custom discount code logic. Otherwise, smooth upgrade.

The migration is straightforward but critical if your store uses programmatic discount code management. Don't skip testing cart functionality after the upgrade.

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