[wp-trac] [WordPress Trac] #63589: Unable to live preview changes to Additional CSS in the Customizer when using a Block Theme

[WordPress Trac]

#63589: Unable to live preview changes to Additional CSS in the Customizer when
using a Block Theme
--------------------------+--------------------------
 Reporter:  westonruter   |       Owner:  westonruter
     Type:  defect (bug)  |      Status:  accepted
 Priority:  normal        |   Milestone:  6.8.2
Component:  Customize     |     Version:  6.2
 Severity:  normal        |  Resolution:
 Keywords:  has-patch     |     Focuses:
--------------------------+--------------------------
Changes (by rollybueno):

 * keywords:  has-patch needs-testing => has-patch


Comment:

 == Test Report
 === Description
 This report validates whether the indicated patch works as expected.

 Patch tested: https://github.com/WordPress/wordpress-develop/pull/9000

 === Environment
 - WordPress: 6.9-alpha-60093-src
 - PHP: 8.2.28
 - Server: nginx/1.27.5
 - Database: mysqli (Server: 8.4.5 / Client: mysqlnd 8.2.28)
 - Browser: Chrome 137.0.0.0
 - OS: Linux
 - Theme: Twenty Twenty-Five 1.2
 - MU Plugins: None activated
 - Plugins:
   * Query Monitor 3.18.0
   * Test Reports 1.2.0

 === Steps to Reproduce
 1. Activate the **Twenty Twenty-Five** theme.
 2. Navigate directly to the Customizer:`/wp-admin/customize.php`
 3. Go to the **Additional CSS** section.
 4. Add a CSS:`p { color: red; }`
 5. Observe the preview panel.

 === Steps to Apply Patch
 1. Fetch the patch:
 {{{
 git fetch upstream pull/9000/head:pr-9000
 git checkout pr-9000
 }}}
 2. Build the environment:
 {{{
 npm install
 npm run build
 }}}
 3. Repeat the reproduction steps above.

 === Actual Results
 - ✅ Live preview of Additional CSS works correctly.
 - Changes reflect immediately in the preview pane.
 - Issue is no longer reproducible with the patch applied.

 === Additional Notes
 - Issue was specific to block themes.
 - Patch tested successfully with multiple block themes.
 - No regressions observed in the Customizer.
 - ℹ️ Check the video link below for a better view of the live preview
 behavior.

 === Supplemental Artifacts
 **Applying the CSS** live without hitting the Publish to page refresh
 [[Image(https://i.imgur.com/udeLRik.png)]]

 👋👇📹 **Video screencast** – This is a better way to check and confirm
 that it works, as you can clearly see the CSS being applied in the preview
 without needing to publish.

 https://www.awesomescreenshot.com/video/41470898?key=c06faa5ddb791e636699a42f36f458a5

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/63589#comment:7>
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