Cart and Checkout Validation docs: localized field error target shown in three different forms (plural example silently blocks checkout)

Functions
1

API and version: Cart and Checkout Validation Function API, 2026-07 (same content on the 2026-10 page)

Summary

The documentation shows three different paths for a localized field error target:

Location Target shown
Validation Function API, “Supported checkout field targets” table $.cart.localizedfield.key
Validation Function API, JavaScript and Rust examples for required localized fields $.cart.localizedFields.${field.key}
Checkout UI extensions, Localized Fields API $.cart.localizedField.${taxIdField.key}

Only $.cart.localizedField.<KEY> (singular, camelCase, uppercase key) renders. With the plural path used in the Function examples, checkout is blocked and no message is shown anywhere.

Observed (29 July 2026, development store, API 2026-07)

  • $.cart.localizedFields.TAX_CREDENTIAL_IT: order blocked, no message. Same result with one-page and three-page checkout, with the order confirmation step on and off, and with a plain ASCII message.
  • $.cart.localizedField.TAX_CREDENTIAL_IT: message rendered under the field.

On 30 July 2026 Shopify Developer Support confirmed the singular form, called the silent drop a platform bug and said they were raising a docs correction. As of 13 September 2026 the table and both examples still show these forms.

Expected

Copying the official example renders the error under the field.

Requests

  1. Use $.cart.localizedField.<KEY> in the table and in every example, ideally with a real key such as TAX_CREDENTIAL_IT.
  2. Report an unrecognized target during development (CLI, function replay or run log) instead of discarding the error silently.

Impact

An app that follows the official example ships a validation that blocks checkout without telling the buyer what to fix.