WP Build Polyfills: continue the admin menu color behind the boot frame by retrofox · Pull Request #51619 · Automattic/jetpack

retrofox · 2026-08-26T17:33:09Z

Proposed changes

On trunk, every admin page generated by @wordpress/build (Forms, Premium Analytics, Newsletter, Backup, Scan, SEO, Social, VideoPress, Podcast, Activity Log, site setup in jetpack-mu-wpcom) renders inside the @wordpress/boot single-page layout: a white stage with rounded corners over a backdrop that is meant to continue the wp-admin menu. @wordpress/admin-ui maps nine core color schemes to theme seeds and falls back to modern for anything else, so on every WordPress.com scheme (nightfall, aquatic, classic-blue, classic-bright, classic-dark, contrast, powder-snow, sakura, sunset) and on any third-party scheme registered with wp_admin_css_color() the backdrop is near-black (#1e1e1e) next to a menu of another color: a black notch under the admin bar and black bands in the bottom and right margins of the frame.

With this PR the backdrop follows the menu on every scheme, with no changes in the consuming packages:

WP_Build_Polyfills::register() also arms a new WP_Build_Admin_Frame class in packages/wp-build-polyfills, the one runtime every wp-build page already loads.
On admin_head it prints a stylesheet that paints .boot-layout--single-page and the body with --wp-build-admin-menu-background, falling back to boot's own colors when the property is not set.
On in_admin_header, right after #adminmenuback is printed and before the layout mounts, it prints an inline script that samples that element's computed background into the custom property on the root element.

How it works

The layout rule boot injects at runtime is .boot-layout { background: var(--wpds-color-background-surface-neutral-weak) }, specificity (0,1,0), appended to <head> after the page stylesheets. #wpcontent .boot-layout--single-page is (1,1,0), so the override wins on specificity rather than order. The second selector covers boot 0.21 (WordPress/gutenberg#81756, Gutenberg 23.9), where the layout styles are CSS Modules and the root class is _<hash>__layout-single-page: wp-build keeps the local name in production builds (checked on @wordpress/boot@0.21.0), so [class*="__layout-single-page"] matches whatever the hash is, at the same specificity. body:has(.boot-layout--single-page) keeps the elastic-scroll area consistent without relying on boot's body sync; it is a separate rule so browsers without :has() still apply the layout rule.

Sampling the rendered menu instead of mapping schemes is the point: one mechanism covers core schemes on older cores, WordPress.com schemes and third-party schemes, and the property is only set when the sample is a real color. Pages without a boot layout are unaffected by construction: the selectors match nothing.

The fix lives in PHP because on WordPress 7.0+ the boot module that runs is core's bundled copy. WP_Script_Modules::register() ignores an id that is already registered, so bumping @wordpress/boot in a package changes nothing on WordPress.com. Core already made its nine schemes' menu color equal the ramp output (r62454), which is why only unknown schemes break.

Notes for reviewers

The class is self-contained (src/class-wp-build-admin-frame.php) so it can be removed in one commit once wp-build or boot ship the same behavior. The upstream direction is structured per-scheme seeds in wp_admin_css_color(), see Allow third-party color schemes to apply to Site Editor screens WordPress/gutenberg#80766 and Centralize WordPress admin color scheme settings WordPress/gutenberg#81980.
The accent color inside the app (--wp-admin-theme-color, primary buttons) still comes from the modern seed on unknown schemes. Same upstream problem, out of scope here.
Plugin changelog entries are in a separate commit: the change is visible to the users of every plugin that ships a wp-build page.
Which boot runs where: the Gutenberg plugin overrides core's @wordpress/boot module through the wp-build module registration (deregister, then register), so WordPress.com runs boot 0.21 once it moves from Gutenberg 23.8 to 23.9. Jetpack's own builds register only their @jetpack-* modules and keep core's boot. Both class forms were checked on a live page by renaming the layout root to the 0.21 class names: layout and body keep the menu color, and any other local name does not match.

Related product discussion/links

WOOA7S-1990, split from WOOA7S-1982
Allow third-party color schemes to apply to Site Editor screens WordPress/gutenberg#80766 and Centralize WordPress admin color scheme settings WordPress/gutenberg#81980 for the upstream fix

Does this pull request change what data or activity we track or use?

No.

Testing instructions

Register a throwaway third-party scheme in a mu-plugin, then pick Navy in Users → Profile → Admin Color Scheme:

add_action( 'admin_init', function () {
	wp_admin_css_color(
		'navy',
		'Navy',
		plugin_dir_url( __FILE__ ) . 'navy/colors.css',
		array( '#02395c', '#043959', '#2271b1', '#9ec2e6' ),
		array( 'base' => '#9ec2e6', 'focus' => '#fff', 'current' => '#fff' )
	);
} );

with navy/colors.css containing #adminmenu, #adminmenuback, #adminmenuwrap { background: #02395c; }. Any Masterbar scheme on a WordPress.com site behaves the same way.

Unknown scheme

Open Jetpack → Forms (admin.php?page=jetpack-forms-responses-wp-admin), Jetpack → Stats (admin.php?page=jetpack-premium-analytics-wp-admin) and Jetpack → Activity Log. The corner under the admin bar and the bottom and right margins around the frame must be #02395c, on load and after scrolling. On trunk they are near-black.
In DevTools, getComputedStyle( document.documentElement ).getPropertyValue( '--wp-build-admin-menu-background' ) returns rgb(2, 57, 92) and document.querySelectorAll( '#wp-build-admin-frame-css, #wp-build-admin-frame-js' ).length returns 2.

Boot 0.21

With Gutenberg 23.9 (RC1 or later) active, repeat the Navy checks: the layout root now carries _<hash>__layout-single-page and the frame must still be #02395c.

Core schemes

Switch to Blue, then Light: the frame continues the menu in both (rgb(36, 82, 120) and rgb(229, 229, 229)), so nothing regresses on the schemes that already worked.

Pages without a boot layout

Open Dashboard and Posts: nothing changes, and neither id is in the DOM (the querySelectorAll above returns 0).

Narrow viewport

Below 782px the layout goes full-screen; nothing of this is visible or broken.

Tests

jp test php packages/wp-build-polyfills

sample the wp-admin menu color behind the boot single-page layout

github-actions · 2026-08-26T17:35:15Z

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack or WordPress.com Site Helper), and enable the fix/wp-build-admin-frame-backdrop branch.
To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack fix/wp-build-admin-frame-backdrop

bin/jetpack-downloader test jetpack-mu-wpcom-plugin fix/wp-build-admin-frame-backdrop

Interested in more tips and information?

In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
Read more about our development workflow here: PCYsg-eg0-p2
Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

github-actions · 2026-08-26T17:35:17Z

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

✅ Include a description of your PR changes.
✅ Add a "[Status]" label (In Progress, Needs Review, ...).
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If you have questions about anything, reach out in #jetpack-developers for guidance!

Jetpack plugin:

The Jetpack plugin has different release cadences depending on the platform:

WordPress.com Simple releases happen as soon as you deploy your changes after merging this PR (PCYsg-Jjm-p2).
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- Scheduled release: September 7, 2026