ENG-3443: Fix selectUser selector memoization

[gilluminate]

Ticket ENG-3443

Description Of Changes

The selectUser Redux selector in auth.slice.ts was a plain function that created a new object ({ ...user, isRootUser }) on every call. Since the returned object was referentially different each time, Redux flagged it as an unstable selector, logging a console warning and causing unnecessary rerenders in every component that consumes it (ProtectedRoute, AccountDropdownMenu, ManualTasks, MonitorList, etc.).

This PR wraps selectUser with createSelector from @reduxjs/toolkit so the result is memoized and only recomputes when state.auth changes.

Code Changes

• Memoized selectUser selector using createSelector with selectAuth as its input selector
• Added createSelector to the @reduxjs/toolkit import

Steps to Confirm

1. Run the admin UI dev server (npm run dev in clients/admin-ui/)
2. Open the browser console
3. Confirm the "Selector selectUser returned a different result when called with the same parameters" warning no longer appears on page load

Pre-Merge Checklist

• Issue requirements met
• All CI pipelines succeeded
• CHANGELOG.md updated
  • Updates unreleased work already in Changelog, no new entry necessary
• UX feedback:
  • No UX review needed
• Followup issues:
  • No followup issues
• Database migrations:
  • No migrations
• Documentation:
  • No documentation updates required

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Project	Deployment	Actions	Updated (UTC)
fides-plus-nightly	Ready	Preview, Comment	Apr 14, 2026 11:14pm

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
fides-privacy-center	Ignored		Apr 14, 2026 11:14pm

[github-actions]

Title	Lines	Statements	Branches	Functions
admin-ui		6.1% (2663/43633)	5.22% (1293/24734)	4.19% (542/12916)
fides-js		78.98% (1962/2484)	65.55% (1214/1852)	72.57% (336/463)
privacy-center		85.97% (331/385)	81.36% (179/220)	78.87% (56/71)

[claude]

Code Review

Clean, well-scoped PR. Two targeted fixes with no production risk.

auth.slice.ts — selectUser memoization

The root cause diagnosis is correct: spreading { ...user, isRootUser } in a plain selector always produces a new object reference, which RTK's selector stability check rightfully flags. Wrapping with createSelector is the right fix — the memoized result is returned unchanged as long as state.auth hasn't changed.

One minor note on the input selector granularity (see inline comment): using selectAuth means the selector recomputes on any auth change (including token), not just user changes. Not a functional issue given login/logout change both atomically, but worth knowing.

DeleteUserModal.tsx — Form.useWatch targeting

Both changes are improvements:

1. Watching only "usernameConfirmation" instead of all fields ([]) is more targeted.
2. The disabled condition change from !form.isFieldsTouched(true) → !usernameConfirmation is more semantically accurate for this UX (enable the button when text is present, not merely when the field has been touched).

One observation about form.getFieldsError() in the disabled expression (see inline comment) — benign for the current single-field form, but worth keeping in mind if the form grows.

Changelog

Changelog entry is present and accurate. ✅

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[speaker-ender]

LGTM!