Fix uid placement for single-entry [[extensions]] TOMLs

[nickwesselman]

WHY are these changes introduced?

addUidToToml branched on extensionsArray.length > 1 to decide between regex-based positional insertion (inside the matching [[extensions]] block) and a top-level WASM patch. A single-entry [[extensions]] array fell into the top-level branch, so uid was written outside the [[extensions]] block — the wrong location.

This is the shape produced by current shopify app init templates (e.g. ui_extension app-home), so every newly-init'd app from those templates ended up with a top-level uid after the first linkedAppContext run.

Requested by Nick Wesselman nick.wesselman@shopify.com. Investigated and authored by River.

WHAT is this pull request doing?

• Branches on whether extensionsArray exists at all. Any array shape (length 1 or many) gets the regex insertion path.
• Legacy single-extension TOMLs with top-level type/handle fields still get the top-level file.patch path.
• Adds a regression test using the exact app init template TOML shape (single-entry [[extensions]] array).
• Adds a @shopify/app patch changeset.

How to test your changes?

1. shopify app init (using a template that produces a single [[extensions]] entry, e.g. ui_extension app-home).
2. Run any flow that triggers linkedAppContext (e.g. shopify app dev).
3. Confirm uid is written inside the [[extensions]] block, after handle, rather than at the top level of the TOML.

Or run the focused unit tests:

pnpm vitest run packages/app/src/cli/services/app/add-uid-to-extension-toml.test.ts

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add

[nickwesselman]

/snapit

[nickwesselman]

/snapit

[github-actions]

🫰✨ Thanks @nickwesselman! Your snapshot has been published to npm.

Test the snapshot by installing your package globally:

pnpm i -g --@shopify:registry=https://registry.npmjs.org @shopify/cli@0.0.0-snapshot-20260506171759

Caution

After installing, validate the version by running shopify version in your terminal.
If the versions don't match, you might have multiple global instances installed.
Use which shopify to find out which one you are running and uninstall it.

[github-actions]

🫰✨ Thanks @nickwesselman! Your snapshot has been published to npm.

Test the snapshot by installing your package globally:

pnpm i -g --@shopify:registry=https://registry.npmjs.org @shopify/cli@0.0.0-snapshot-20260506171941

Caution

After installing, validate the version by running shopify version in your terminal.
If the versions don't match, you might have multiple global instances installed.
Use which shopify to find out which one you are running and uninstall it.