Fix Customer.id JSDoc: clarify shop-scoping (2025-10)

[rennyG]

Summary

Clarifies that customer.id on the checkout UI extensions Customer interface is unique per shop, not globally unique.

Why

The previous JSDoc described customer.id as "A globally-unique identifier for the customer," which misled developers building multi-shop apps to assume they could key records on customer.id alone.

Change

In packages/ui-extensions/src/surfaces/checkout/api/standard/standard.ts, updates the JSDoc for Customer.id.

Before

A globally-unique identifier for the customer in the format gid://shopify/Customer/<id>.

After

An identifier for the customer in the format gid://shopify/Customer/<id>. This value is unique per shop.

Context

Feedback from Simon Bolduc during a checkout UI extensions docs review. See shop/issues-learn#1857.

A companion shopify-dev PR updates the Best practices section of the Buyer Identity API docs to prescribe keying records on shop and customer.id together for multi-shop apps.

Sibling PRs cover the same change on the 2026-07-rc, 2026-04, and 2026-01 branches.

[github-actions]

🚨🚨🚨 Docs migration in progress 🚨🚨🚨

We are actively migrating UI extension reference docs to MDX in the areas/platforms/shopify-dev zone of the monorepo. This impacts docs for the following surfaces:

• Admin UI extensions
• App Home
• Checkout UI extensions
• Customer account UI extensions
• POS UI extensions

During this migration, please be aware of the following:

.doc.ts files are being deprecated. Changes to .doc.ts files in this repo will not be reflected in the new MDX-based docs. If you need to update docs for a reference that has already been migrated, make your changes directly in the areas/platforms/shopify-dev zone of the monorepo instead.

Doc comments in .ts source files (the comment blocks above types and functions) are also affected. Generating docs from these comments currently requires a newer version of the @shopify/generate-docs library that isn't yet available. Updates to doc comments may not produce the expected output until the migration is complete.

Examples that previously lived in this repo are being moved to the areas/platforms/shopify-dev zone of the monorepo and should be authored there going forward.

What should I do?

• If your PR includes changes to .doc.ts files, doc comments, or examples, please reach out to us in #devtools-proj-templated-refs so we can help ensure your updates are captured correctly.
• If your PR is limited to source code changes (non-docs), you can ignore this notice.

Thanks for your patience while we complete the migration! 🙏

[github-actions]

We detected some changes in packages/*/package.json or packages/*/src, and there are no updates in the .changeset directory. If the changes are user-facing and should cause a version bump, run yarn changeset to track your changes and include them in the next release CHANGELOG. If you are making simple updates to repo configuration, examples, or documentation, you do not need to add a changeset.