# Shopify’s 2026-10 API release candidate opens a two-week migration window for breaking app changes Shopify’s 2026-10 API is now available as a release candidate ahead of October 1 stable, giving app developers a short test window for changes that can alter taxes, draft-order queries, carrier-service behavior, customer-account fields and tax-app webhook payloads. This is more than a routine quarterly version bump. Several 2026-10 changes require code updates or can change order economics and checkout behavior, so Shopify apps need to test against the release candidate before production traffic begins moving to the new stable version. - Status: Active - Published: 2026-09-16T06:28:36+12:00 - Updated: 2026-09-16T06:28:36+12:00 - Categories: Web Development, Marketing & Distribution, Developer Tools, Marketplaces & Platforms - Tags: Admin GraphQL API, API migration, breaking changes, Shopify, Shopify API - Canonical HTML: https://beyondthe.news/dossiers/shopify-2026-10-release-candidate-breaking-api-migration-october ## What changed On September 15, 2026, Shopify made API version 2026-10 available as a release candidate for development testing; it becomes stable October 1. The release notes consolidate several action-required or behavior-changing migrations. Updating an unfulfilled order’s shipping address now recalculates taxes for the new destination. Deprecated `priceRule` data is removed from draft-order discount warnings and legacy `PriceRule` types are removed from the public schema. Customer Account API removes `Customer.lastIncompleteCheckout` and its unreachable `Checkout` subtree. Creating a carrier service no longer adds rates to the General shipping profile automatically. Tax-app webhook payloads also move to newer identifier semantics. Shopify recommends reviewing and adjusting affected integrations before adopting 2026-10. ## Why it matters Quarterly API versions can look like housekeeping, but this RC contains changes that affect money movement, checkout visibility and schema compatibility. An app that edits order addresses may now create payment/refund differences after tax recalculation; a shipping integration can successfully register a carrier service without making its rates visible at checkout; and stale GraphQL queries can fail when removed fields disappear. The release-candidate period is therefore the practical migration window, not merely an announcement before October. ## Order-address edits can now change the financial state of an order When an app updates the shipping address of an unfulfilled order, Shopify recalculates taxes for the new destination. Integrations that previously treated the address update as a mostly logistical mutation need to fetch updated tax lines and totals and handle any resulting amount due or refund balance. ## Removed draft-order fields create a hard GraphQL compatibility boundary Queries that still select `priceRule` from `DraftOrderDiscountNotAppliedWarning` or depend on the legacy `PriceRule` types need to migrate to newer discount title/code fields. Because the fields are removed from the public 2026-10 schema, this is not merely a deprecation warning once the app adopts the version. ## Carrier service creation no longer implies checkout visibility Registering a carrier service through GraphQL or REST now creates the service without automatically adding its rates to the General shipping profile. Apps and setup workflows must explicitly configure carrier-calculated rates in the appropriate profile. ## Customer-account integrations need to remove dead checkout queries The Customer Account API drops `Customer.lastIncompleteCheckout` and its nested `Checkout` types. Shopify says there is no Customer Account API replacement, so affected apps need to remove that dependency rather than simply rename a field. ## The RC is the safest place to find these failures Shopify marks release candidates for development rather than production. Testing now lets apps catch schema errors and behavioral differences before October 1, while supported stable versions remain available during the migration. ## Key details - The 2026-10 release candidate became available September 15, 2026. - It becomes stable October 1, 2026 and is scheduled to remain accessible until October 16, 2027. - Changing the shipping address of an unfulfilled order now recalculates taxes for the new destination. - Apps should re-query tax lines, totals and balances after an address update to detect payment or refund differences. - The deprecated `priceRule` field is removed from `DraftOrderDiscountNotAppliedWarning`, and legacy `PriceRule` schema types are removed. - Customer Account API removes `Customer.lastIncompleteCheckout` and the associated unreachable `Checkout` subtree with no direct replacement. - Creating a carrier service now registers only the service; rates must be configured in a shipping profile to appear at checkout. - The release also changes tax-app payload identifiers and includes a new `SubscriptionContractCalculation` workflow as the successor to `SubscriptionDraft` for contract edits. ## Builder takeaways - Run automated integration tests against `2026-10` now, especially order-edit, draft-order, shipping-profile, tax-app and customer-account paths. - After `orderUpdate` changes an unfulfilled order address, explicitly query taxes, order totals and balances before assuming the mutation is financially neutral. - Search GraphQL documents and generated types for `priceRule`, legacy `PriceRule` objects and `lastIncompleteCheckout` before upgrading. - If your app creates carrier services, verify that the expected shipping profile actually contains the carrier-calculated rate after setup. - Log the `X-Shopify-API-Version` response header so you can detect accidental fall-forward to a different stable version. - Keep the production API pinned to a supported stable version until your 2026-10 test suite and merchant-facing workflows pass. ## What to watch - Final 2026-10 stable notes on October 1 and any RC corrections before then. - Merchant or app-developer reports of unexpected tax-balance changes after address edits. - Migration guidance for subscription apps moving from `SubscriptionDraft` toward `SubscriptionContractCalculation`. - Any further schema removals or behavior changes added to 2026-10 before stable. - Whether Shopify updates API health reports or emergency contacts for the highest-risk migrations. ## Uncertainties - Release-candidate behavior can still change before October 1, so developers should re-read final stable release notes before production rollout. - Not every 2026-10 change affects every Shopify app; the practical migration depends on which APIs and workflows the app uses. - Some individual changes were announced earlier in the developer changelog; September 15 is the point at which they are available together in the release-candidate version. ## Sources - [2026-10: Release notes](https://shopify.dev/release-notes/2026-10) — Shopify Developer · primary release notes · 2026-09-15T00:00:00+12:00. Primary source for release-candidate status and the combined action-required/behavior-changing 2026-10 changes. - [About Shopify API versioning](https://shopify.dev/docs/api/usage/versioning) — Shopify Developer · primary documentation. Primary source for RC/stable lifecycle, October 1 stable date, support window and version fall-forward behavior.