[wp-trac] [WordPress Trac] #64723: Admin Reskin: Admin notices cause UI flicker and layout shift (CLS) across wp-admin

[WordPress Trac]

#64723: Admin Reskin: Admin notices cause UI flicker and layout shift (CLS) across
wp-admin
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 Reporter:  huzaifaalmesbah  |      Owner:  (none)
     Type:  defect (bug)     |     Status:  new
 Priority:  normal           |  Milestone:  Awaiting Review
Component:  Administration   |    Version:
 Severity:  normal           |   Keywords:
  Focuses:                   |
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 On certain wp-admin screens, admin notices briefly render in an incorrect
 position at the very top of the page before settling into their expected
 location below the page heading.

 This causes a visible layout shift during page load, resulting in UI
 flicker and visual instability.

 The issue is consistently reproducible when triggering admin notices on
 specific screens such as Plugins, Settings → General, and Users.

 === Environment
 - WordPress: 7.0-beta1-61709-src
 - PHP: 8.2.29
 - Server: nginx/1.29.5
 - Database: mysqli (Server: 8.4.8 / Client: mysqlnd 8.2.29)
 - Browser: Chrome 145.0.0.0
 - OS: macOS
 - Theme: Twenty Seventeen 4.0
 - MU Plugins: None activated
 - Plugins:
   * Hello Dolly 1.7.2
   * Test Reports 1.2.1

 === Steps taken
 1. Navigated to **Plugins → Installed Plugins**.
 2. Activated or deactivated a plugin.
 3. Observed the page during reload.
 4. Repeated the test on:
    - Settings → General (clicked “Save Changes”)
    - Users → Added new user and deleted a user
 5. Carefully watched the notice placement during page load.

 6. 🐞 Bug occurs

 === Expected behavior
 Admin notices should render directly below the page heading in their final
 position without any visible movement during page load.

 There should be no layout shift or UI flicker.

 === Actual behavior
 The admin notice briefly renders at the very top of the page (above the
 main heading).
 After a short moment, it shifts downward into its correct position below
 the heading, causing a visible layout jump.

 === Additional Notes
 - Issue reproducible consistently on:
   * Plugins (activate/deactivate)
   * Settings → General (save changes)
   * Users (create/delete user)

 - Issue not found on:
   * Posts (delete post)
   * Pages (delete page)

 === Screenshots/Screencast with results
 - Screencast showing the notice layout shift:
 https://files.catbox.moe/rubnd5.mp4

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Ticket URL: <https://core.trac.wordpress.org/ticket/64723>
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