From a89aab7296f761a03876677e271394a42dac1a80 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Thu, 26 Feb 2026 20:10:51 -0300
Subject: [PATCH 01/40] create wp-build-polyfills package

---
 .../packages/wp-build-polyfills/.gitignore    |   3 +
 .../bin/build-polyfills.mjs                   | 424 ++++++++++++++++++
 .../wp-build-polyfills/changelog/.gitkeep     |   0
 .../packages/wp-build-polyfills/composer.json |  39 ++
 .../packages/wp-build-polyfills/package.json  |  29 ++
 .../src/class-wp-build-polyfills.php          | 134 ++++++
 6 files changed, 629 insertions(+)
 create mode 100644 projects/packages/wp-build-polyfills/.gitignore
 create mode 100755 projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
 create mode 100644 projects/packages/wp-build-polyfills/changelog/.gitkeep
 create mode 100644 projects/packages/wp-build-polyfills/composer.json
 create mode 100644 projects/packages/wp-build-polyfills/package.json
 create mode 100644 projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php

diff --git a/projects/packages/wp-build-polyfills/.gitignore b/projects/packages/wp-build-polyfills/.gitignore
new file mode 100644
index 000000000000..65f08b37e4fe
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/.gitignore
@@ -0,0 +1,3 @@
+.cache/
+/node_modules
+build/
diff --git a/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs b/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
new file mode 100755
index 000000000000..17baad90405b
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
@@ -0,0 +1,424 @@
+#!/usr/bin/env node
+
+/**
+ * Build script for Core package polyfills.
+ *
+ * Bundles `@wordpress` packages that are not available in WordPress Core < 7.0
+ * (private-apis, theme, boot, route, a11y) so that plugins using
+ * wp-build can conditionally register them when Core/Gutenberg doesn't provide them.
+ *
+ * Uses the same externals strategy as wp-build's wordpress-externals-plugin:
+ * - Classic scripts (IIFE): `@wordpress/*` → window.wp.{camelCase}, vendor → globals
+ * - Script modules (ESM): `@wordpress/*` script modules → external (import map),
+ * `@wordpress/*` classic-only → window.wp.{camelCase}, vendor → globals
+ */
+
+import { createHash } from 'crypto';
+import { readFileSync, writeFileSync, mkdirSync } from 'fs';
+import { createRequire } from 'module';
+import path from 'path';
+import { fileURLToPath } from 'url';
+import { parseArgs } from 'util';
+import { build } from 'esbuild';
+
+// Resolve packages from this package's own node_modules, not the consumer's.
+const __dirname = path.dirname( fileURLToPath( import.meta.url ) );
+const packageRoot = path.resolve( __dirname, '..' );
+const require = createRequire( path.join( packageRoot, 'package.json' ) );
+
+// Parse CLI arguments.
+const { values: args } = parseArgs( {
+	options: {
+		'output-dir': { type: 'string', default: 'build/polyfills' },
+	},
+	strict: false,
+} );
+
+const outputBase = path.resolve( args[ 'output-dir' ] );
+
+// ── Vendor externals (same as wp-build) ──────────────────────────────────────
+
+const vendorExternals = {
+	react: { global: 'React', handle: 'react' },
+	'react-dom': { global: 'ReactDOM', handle: 'react-dom' },
+	'react/jsx-runtime': {
+		global: 'ReactJSXRuntime',
+		handle: 'react-jsx-runtime',
+	},
+	'react/jsx-dev-runtime': {
+		global: 'ReactJSXRuntime',
+		handle: 'react-jsx-runtime',
+	},
+	moment: { global: 'moment', handle: 'moment' },
+	lodash: { global: 'lodash', handle: 'lodash' },
+	'lodash-es': { global: 'lodash', handle: 'lodash' },
+	jquery: { global: 'jQuery', handle: 'jquery' },
+};
+
+// ── Package info cache ───────────────────────────────────────────────────────
+
+const packageJsonCache = new Map();
+
+/**
+ * Get the package JSON for a package.
+ * @param {string} packageName - The package name.
+ * @param {string} resolveDir  - The directory to resolve the package from.
+ * @return {object} The package JSON.
+ */
+function getPackageJson( packageName, resolveDir = null ) {
+	const contextDir = resolveDir || packageRoot;
+	const cacheKey = `${ packageName }@${ contextDir }`;
+
+	if ( packageJsonCache.has( cacheKey ) ) {
+		return packageJsonCache.get( cacheKey );
+	}
+
+	try {
+		const contextRequire = createRequire( path.join( contextDir, 'package.json' ) );
+
+		const pkgPath = contextRequire.resolve( `${ packageName }/package.json` );
+
+		const pkg = JSON.parse( readFileSync( pkgPath, 'utf8' ) );
+		packageJsonCache.set( cacheKey, pkg );
+
+		return pkg;
+	} catch {
+		packageJsonCache.set( cacheKey, null );
+
+		return null;
+	}
+}
+
+// ── Helpers ──────────────────────────────────────────────────────────────────
+
+/**
+ * Convert a string to camel case.
+ *
+ * @param {string} str - The string to convert.
+ * @return {string} The camel case string.
+ */
+function camelCase( str ) {
+	return str.replace( /-([a-z])/g, ( _, c ) => c.toUpperCase() );
+}
+
+/**
+ * Check if a subpath is a script module import.
+ * @param {object} packageJson - The package JSON object.
+ * @param {string} subpath     - The subpath to check.
+ * @return {boolean} Whether the subpath is a script module import.
+ */
+function isScriptModuleImport( packageJson, subpath ) {
+	const { wpScriptModuleExports } = packageJson;
+
+	if ( ! wpScriptModuleExports ) {
+		return false;
+	}
+
+	if ( ! subpath ) {
+		if ( typeof wpScriptModuleExports === 'string' ) {
+			return true;
+		}
+
+		if ( typeof wpScriptModuleExports === 'object' && wpScriptModuleExports[ '.' ] ) {
+			return true;
+		}
+
+		return false;
+	}
+
+	if ( typeof wpScriptModuleExports === 'object' && wpScriptModuleExports[ `./${ subpath }` ] ) {
+		return true;
+	}
+
+	return false;
+}
+
+/**
+ * Generate a SHA-256 hash of the content.
+ * @param {string} content - The content to hash.
+ * @return {string} The SHA-256 hash.
+ */
+function generateContentHash( content ) {
+	return createHash( 'sha256' ).update( content ).digest( 'hex' ).slice( 0, 20 );
+}
+
+// ── Externals plugin ─────────────────────────────────────────────────────────
+
+/**
+ * Create an externals plugin for the polyfills.
+ * @param {string} buildFormat - The build format.
+ * @param {string} skipPackage - The package to skip.
+ * @return {object} The externals plugin.
+ */
+function polyfillExternalsPlugin( buildFormat, skipPackage = null ) {
+	const dependencies = new Set();
+	const moduleDependencies = new Map();
+
+	return {
+		name: 'polyfill-externals',
+		setup( esb ) {
+			// Vendor externals
+			for ( const [ packageName, config ] of Object.entries( vendorExternals ) ) {
+				esb.onResolve( { filter: new RegExp( `^${ packageName }$` ) }, onResolveArgs => {
+					dependencies.add( config.handle );
+
+					return {
+						path: onResolveArgs.path,
+						namespace: 'vendor-external',
+						pluginData: { global: config.global },
+					};
+				} );
+			}
+
+			// @wordpress/* externals
+			esb.onResolve( { filter: /^@wordpress\// }, onResolveArgs => {
+				const parts = onResolveArgs.path.split( '/' );
+				const packageName = parts.slice( 0, 2 ).join( '/' );
+				const subpath = parts.length > 2 ? parts.slice( 2 ).join( '/' ) : null;
+				const shortName = parts[ 1 ];
+				const handle = `wp-${ shortName }`;
+
+				// Don't externalize the package we're building
+				if ( skipPackage && packageName === skipPackage ) {
+					return undefined;
+				}
+
+				const packageJson = getPackageJson( packageName, onResolveArgs.resolveDir );
+
+				if ( ! packageJson ) {
+					return undefined;
+				}
+
+				let isScriptModule = isScriptModuleImport( packageJson, subpath );
+				let isScript = !! packageJson.wpScript;
+
+				// Dual packages: use the format being built
+				if ( isScriptModule && isScript ) {
+					isScript = buildFormat === 'iife';
+					isScriptModule = buildFormat === 'esm';
+				}
+
+				const kind = onResolveArgs.kind === 'dynamic-import' ? 'dynamic' : 'static';
+
+				if ( isScriptModule ) {
+					if ( kind === 'static' ) {
+						moduleDependencies.set( onResolveArgs.path, 'static' );
+					} else if ( ! moduleDependencies.has( onResolveArgs.path ) ) {
+						moduleDependencies.set( onResolveArgs.path, 'dynamic' );
+					}
+
+					return {
+						path: onResolveArgs.path,
+						external: true,
+						sideEffects: !! packageJson.sideEffects,
+					};
+				}
+
+				if ( isScript ) {
+					dependencies.add( handle );
+
+					return {
+						path: onResolveArgs.path,
+						namespace: 'package-external',
+						pluginData: { globalName: 'wp' },
+					};
+				}
+
+				// Not a registered script or module — let esbuild bundle it
+				return undefined;
+			} );
+
+			esb.onLoad( { filter: /.*/, namespace: 'vendor-external' }, onLoadArgs => ( {
+				contents: `module.exports = window.${ onLoadArgs.pluginData.global };`,
+				loader: 'js',
+			} ) );
+
+			esb.onLoad( { filter: /.*/, namespace: 'package-external' }, onLoadArgs => {
+				const packagePath = onLoadArgs.path.split( '/' ).slice( 1 ).join( '/' );
+				const name = camelCase( packagePath );
+
+				return {
+					contents: `module.exports = window.${ onLoadArgs.pluginData.globalName }.${ name };`,
+					loader: 'js',
+				};
+			} );
+
+			// Generate asset file on build end
+			esb.onEnd( result => {
+				if ( result.errors.length > 0 ) {
+					return;
+				}
+
+				const outfile = esb.initialOptions.outfile;
+				const outputDir = path.dirname( outfile );
+				const baseName = path.basename( outfile, '.js' );
+
+				// Read the output to hash it
+				const outputContent = readFileSync( outfile );
+				const version = generateContentHash( outputContent );
+
+				const sortedDeps = Array.from( dependencies ).sort();
+				const depsString = sortedDeps.map( d => `'${ d }'` ).join( ', ' );
+
+				const assetParts = [ `'dependencies' => array(${ depsString })` ];
+
+				if ( moduleDependencies.size > 0 ) {
+					const modDeps = Array.from( moduleDependencies.entries() )
+						.sort( ( [ a ], [ b ] ) => a.localeCompare( b ) )
+						.map( ( [ dep, impKind ] ) => `array('id' => '${ dep }', 'import' => '${ impKind }')` )
+						.join( ', ' );
+
+					assetParts.push( `'module_dependencies' => array(${ modDeps })` );
+				}
+
+				assetParts.push( `'version' => '${ version }'` );
+
+				const assetContent = `<?php return array(${ assetParts.join( ', ' ) });`;
+
+				const assetPath = path.join( outputDir, `${ baseName }.asset.php` );
+
+				mkdirSync( outputDir, { recursive: true } );
+				writeFileSync( assetPath, assetContent );
+			} );
+		},
+	};
+}
+
+// ── Polyfill definitions ─────────────────────────────────────────────────────
+
+// Some packages (e.g. @wordpress/boot) only export ESM — no `require` or `default`
+// condition — so CJS require.resolve() fails. Resolve via /package.json (universally
+// exported) and read the `module` or `main` field instead.
+/**
+ * Resolve the entry point for a package.
+ * @param {string} packageName - The package name.
+ * @param {string} subEntry    - The subentry to resolve.
+ * @return {string} The entry point.
+ */
+function resolvePackageEntry( packageName, subEntry = null ) {
+	const pkgJsonPath = require.resolve( `${ packageName }/package.json` );
+	const pkgDir = path.dirname( pkgJsonPath );
+
+	if ( subEntry ) {
+		return path.join( pkgDir, subEntry );
+	}
+
+	const pkg = JSON.parse( readFileSync( pkgJsonPath, 'utf8' ) );
+
+	return path.join( pkgDir, pkg.module || pkg.main );
+}
+
+const classicScriptPolyfills = [
+	{
+		name: 'private-apis',
+		packageName: '@wordpress/private-apis',
+		globalName: 'wp.privateApis',
+		entry: resolvePackageEntry( '@wordpress/private-apis' ),
+	},
+	{
+		name: 'theme',
+		packageName: '@wordpress/theme',
+		globalName: 'wp.theme',
+		entry: resolvePackageEntry( '@wordpress/theme' ),
+	},
+];
+
+const scriptModulePolyfills = [
+	{
+		name: 'boot',
+		packageName: '@wordpress/boot',
+		entry: resolvePackageEntry( '@wordpress/boot' ),
+	},
+	{
+		name: 'route',
+		packageName: '@wordpress/route',
+		entry: resolvePackageEntry( '@wordpress/route' ),
+	},
+	{
+		name: 'a11y',
+		packageName: '@wordpress/a11y',
+		// a11y's wpScriptModuleExports points to a separate module entry.
+		entry: resolvePackageEntry( '@wordpress/a11y', 'build-module/module/index.mjs' ),
+	},
+];
+
+// ── Build ────────────────────────────────────────────────────────────────────
+
+const target = [ 'es2020' ];
+const builds = [];
+
+for ( const polyfill of classicScriptPolyfills ) {
+	const outputDir = path.join( outputBase, 'scripts', polyfill.name );
+
+	// Minified
+	builds.push(
+		build( {
+			entryPoints: [ polyfill.entry ],
+			outfile: path.join( outputDir, 'index.min.js' ),
+			bundle: true,
+			format: 'iife',
+			globalName: polyfill.globalName,
+			target,
+			platform: 'browser',
+			minify: true,
+			sourcemap: true,
+			plugins: [ polyfillExternalsPlugin( 'iife', polyfill.packageName ) ],
+		} )
+	);
+
+	// Non-minified
+	builds.push(
+		build( {
+			entryPoints: [ polyfill.entry ],
+			outfile: path.join( outputDir, 'index.js' ),
+			bundle: true,
+			format: 'iife',
+			globalName: polyfill.globalName,
+			target,
+			platform: 'browser',
+			minify: false,
+			sourcemap: true,
+			plugins: [ polyfillExternalsPlugin( 'iife', polyfill.packageName ) ],
+		} )
+	);
+}
+
+for ( const polyfill of scriptModulePolyfills ) {
+	const outputDir = path.join( outputBase, 'modules', polyfill.name );
+
+	const entryPoint = polyfill.entry;
+
+	// Minified
+	builds.push(
+		build( {
+			entryPoints: [ entryPoint ],
+			outfile: path.join( outputDir, 'index.min.js' ),
+			bundle: true,
+			format: 'esm',
+			target,
+			platform: 'browser',
+			minify: true,
+			sourcemap: true,
+			plugins: [ polyfillExternalsPlugin( 'esm', polyfill.packageName ) ],
+		} )
+	);
+
+	// Non-minified
+	builds.push(
+		build( {
+			entryPoints: [ entryPoint ],
+			outfile: path.join( outputDir, 'index.js' ),
+			bundle: true,
+			format: 'esm',
+			target,
+			platform: 'browser',
+			minify: false,
+			sourcemap: true,
+			plugins: [ polyfillExternalsPlugin( 'esm', polyfill.packageName ) ],
+		} )
+	);
+}
+
+await Promise.all( builds );
+// eslint-disable-next-line no-console
+console.log( 'WP Build Polyfills: Polyfill builds complete.' );
diff --git a/projects/packages/wp-build-polyfills/changelog/.gitkeep b/projects/packages/wp-build-polyfills/changelog/.gitkeep
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/projects/packages/wp-build-polyfills/composer.json b/projects/packages/wp-build-polyfills/composer.json
new file mode 100644
index 000000000000..2efe5a3a0d8c
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/composer.json
@@ -0,0 +1,39 @@
+{
+	"name": "automattic/jetpack-wp-build-polyfills",
+	"description": "Polyfills for WordPress Core packages not available in WP < 7.0",
+	"type": "jetpack-library",
+	"license": "GPL-2.0-or-later",
+	"require": {
+		"php": ">=7.2"
+	},
+	"require-dev": {
+		"automattic/jetpack-changelogger": "@dev"
+	},
+	"autoload": {
+		"classmap": [
+			"src/"
+		]
+	},
+	"repositories": [
+		{
+			"type": "path",
+			"url": "../../packages/*",
+			"options": {
+				"monorepo": true
+			}
+		}
+	],
+	"minimum-stability": "dev",
+	"prefer-stable": true,
+	"extra": {
+		"autotagger": true,
+		"mirror-repo": "Automattic/jetpack-wp-build-polyfills",
+		"textdomain": "jetpack-wp-build-polyfills",
+		"changelogger": {
+			"link-template": "https://github.com/Automattic/jetpack-wp-build-polyfills/compare/v${old}...v${new}"
+		},
+		"branch-alias": {
+			"dev-trunk": "0.1.x-dev"
+		}
+	}
+}
diff --git a/projects/packages/wp-build-polyfills/package.json b/projects/packages/wp-build-polyfills/package.json
new file mode 100644
index 000000000000..0383fd3cb5de
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/package.json
@@ -0,0 +1,29 @@
+{
+	"name": "@automattic/jetpack-wp-build-polyfills",
+	"version": "0.1.0",
+	"private": true,
+	"description": "Polyfills for WordPress Core packages not available in WP < 7.0",
+	"homepage": "https://github.com/Automattic/jetpack/tree/HEAD/projects/packages/wp-build-polyfills/#readme",
+	"repository": {
+		"type": "git",
+		"url": "https://github.com/Automattic/jetpack.git",
+		"directory": "projects/packages/wp-build-polyfills"
+	},
+	"license": "GPL-2.0-or-later",
+	"author": "Automattic",
+	"bin": {
+		"build-polyfills": "bin/build-polyfills.mjs"
+	},
+	"devDependencies": {
+		"@wordpress/a11y": "^4.40.0",
+		"@wordpress/boot": "^0.7.1",
+		"@wordpress/private-apis": "^1.40.0",
+		"@wordpress/route": "^0.6.0",
+		"@wordpress/theme": "^0.7.0",
+		"esbuild": "^0.27.0"
+	},
+	"optionalDependencies": {
+		"react": "18.3.1",
+		"react-dom": "18.3.1"
+	}
+}
diff --git a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
new file mode 100644
index 000000000000..720715ae208a
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
@@ -0,0 +1,134 @@
+<?php
+/**
+ * Polyfill registration for Core packages not available in WordPress < 7.0.
+ *
+ * Conditionally registers wp-private-apis, wp-theme (classic scripts) and
+ * `@wordpress/boot`, `@wordpress/route`, `@wordpress/a11y` (script modules)
+ * ONLY when they are not already provided by Core or Gutenberg.
+ *
+ * @package automattic/jetpack-wp-build-polyfills
+ */
+
+namespace Automattic\Jetpack\WP_Build_Polyfills;
+
+/**
+ * Registers polyfill scripts and modules for WordPress Core packages.
+ */
+class WP_Build_Polyfills {
+
+	/**
+	 * Register polyfill scripts and modules.
+	 *
+	 * Call this early (e.g. during plugin load) — it hooks into wp_default_scripts
+	 * at priority 20 so Core (default) and Gutenberg (priority 10) register first.
+	 *
+	 * @param string $base_dir  Absolute path to directory containing build/polyfills/.
+	 * @param string $base_file File path for plugins_url() computation.
+	 */
+	public static function register( $base_dir, $base_file ) {
+		$polyfills_dir = $base_dir . '/build/polyfills';
+
+		add_action(
+			'wp_default_scripts',
+			function ( $scripts ) use ( $polyfills_dir, $base_file ) {
+				self::register_scripts( $scripts, $polyfills_dir, $base_file );
+			},
+			20
+		);
+
+		add_action(
+			'wp_default_scripts',
+			function () use ( $polyfills_dir, $base_file ) {
+				self::register_modules( $polyfills_dir, $base_file );
+			},
+			20
+		);
+	}
+
+	/**
+	 * Register polyfill classic scripts.
+	 *
+	 * @param \WP_Scripts $scripts       The WP_Scripts instance.
+	 * @param string      $polyfills_dir Absolute path to the polyfills build directory.
+	 * @param string      $base_file     File path for plugins_url() computation.
+	 */
+	private static function register_scripts( $scripts, $polyfills_dir, $base_file ) {
+		$polyfills = array(
+			'wp-private-apis' => array(
+				'path'  => 'private-apis',
+				'deps'  => array(),
+				// Always replace: older Core versions ship private-apis with an
+				// incomplete allowlist that rejects @wordpress/theme and @wordpress/route.
+				// Our version is a strict superset (same API, larger allowlist).
+				'force' => true,
+			),
+			'wp-theme'        => array(
+				'path' => 'theme',
+				'deps' => array( 'wp-element', 'wp-private-apis' ),
+			),
+		);
+
+		foreach ( $polyfills as $handle => $data ) {
+			$asset_file = $polyfills_dir . '/scripts/' . $data['path'] . '/index.min.asset.php';
+
+			if ( ! file_exists( $asset_file ) ) {
+				continue;
+			}
+
+			$force = ! empty( $data['force'] );
+
+			if ( ! $force && $scripts->query( $handle, 'registered' ) ) {
+				continue;
+			}
+
+			// Deregister first when forcing replacement of an existing registration.
+			if ( $force && $scripts->query( $handle, 'registered' ) ) {
+				$scripts->remove( $handle );
+			}
+
+			$asset = require $asset_file;
+
+			$scripts->add(
+				$handle,
+				plugins_url( 'build/polyfills/scripts/' . $data['path'] . '/index.min.js', $base_file ),
+				$asset['dependencies'] ?? $data['deps'],
+				$asset['version'] ?? false
+			);
+		}
+	}
+
+	/**
+	 * Register polyfill script modules.
+	 *
+	 * Call to wp_register_script_module() silently ignores duplicate registrations (first wins),
+	 * so no explicit is_registered check is needed.
+	 *
+	 * @param string $polyfills_dir Absolute path to the polyfills build directory.
+	 * @param string $base_file     File path for plugins_url() computation.
+	 */
+	private static function register_modules( $polyfills_dir, $base_file ) {
+		if ( ! function_exists( 'wp_register_script_module' ) ) {
+			return;
+		}
+
+		$modules = array( 'boot', 'route', 'a11y' );
+
+		foreach ( $modules as $name ) {
+			$module_id  = '@wordpress/' . $name;
+			$asset_file = $polyfills_dir . '/modules/' . $name . '/index.min.asset.php';
+
+			if ( ! file_exists( $asset_file ) ) {
+				continue;
+			}
+
+			$asset = require $asset_file;
+
+			wp_register_script_module(
+				$module_id,
+				plugins_url( 'build/polyfills/modules/' . $name . '/index.min.js', $base_file ),
+				$asset['module_dependencies'] ?? array(),
+				$asset['version'] ?? false
+			);
+		}
+	}
+}

From cc7a0de2bc50dce308ce29e95cbb6746a954e502 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Thu, 26 Feb 2026 20:14:11 -0300
Subject: [PATCH 02/40] add wp-build-polyfills package as dependency of forms
 package

---
 pnpm-lock.yaml                                        |  3 +++
 projects/packages/forms/composer.json                 |  1 +
 projects/packages/forms/package.json                  |  6 ++++--
 .../packages/forms/src/dashboard/class-dashboard.php  | 11 +++++++++++
 4 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 69fb21298bc3..fd5afc622d6d 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -2558,6 +2558,9 @@ importers:
       '@automattic/jetpack-webpack-config':
         specifier: workspace:*
         version: link:../../js-packages/webpack-config
+      '@automattic/jetpack-wp-build-polyfills':
+        specifier: workspace:*
+        version: link:../wp-build-polyfills
       '@automattic/remove-asset-webpack-plugin':
         specifier: workspace:*
         version: link:../../js-packages/remove-asset-webpack-plugin
diff --git a/projects/packages/forms/composer.json b/projects/packages/forms/composer.json
index 65f86152c7fc..8520b2b828e9 100644
--- a/projects/packages/forms/composer.json
+++ b/projects/packages/forms/composer.json
@@ -7,6 +7,7 @@
 		"php": ">=7.2",
 		"automattic/jetpack-blocks": "@dev",
 		"automattic/jetpack-assets": "@dev",
+		"automattic/jetpack-wp-build-polyfills": "@dev",
 		"automattic/jetpack-connection": "@dev",
 		"automattic/jetpack-device-detection": "@dev",
 		"automattic/jetpack-external-connections": "@dev",
diff --git a/projects/packages/forms/package.json b/projects/packages/forms/package.json
index c562b692d7ec..3e7302a4261c 100644
--- a/projects/packages/forms/package.json
+++ b/projects/packages/forms/package.json
@@ -21,7 +21,8 @@
 		"build:contact-form": "webpack --config ./tools/webpack.config.contact-form.js",
 		"build:dashboard": "webpack --config ./tools/webpack.config.dashboard.js",
 		"build:form-editor": "webpack --config ./tools/webpack.config.form-editor.js",
-		"build:wp-build": "wp-build",
+		"build:polyfills": "build-polyfills",
+		"build:wp-build": "pnpm run build:polyfills && wp-build",
 		"build-production": "NODE_ENV=production BABEL_ENV=production pnpm run build && pnpm run validate",
 		"clean": "rm -rf dist/ build/ .cache/",
 		"extract-icons": "node tools/extract-icons.mjs",
@@ -35,7 +36,7 @@
 		"validate": "pnpm exec validate-es --no-error-on-unmatched-pattern dist/",
 		"watch": "concurrently 'pnpm:build:blocks --watch' 'pnpm:build:contact-form --watch' 'pnpm:build:dashboard --watch' 'pnpm:module:watch' 'pnpm:build:form-editor --watch' 'pnpm:watch:wp-build' 'pnpm:watch:icons'",
 		"watch:icons": "node tools/watch-icons.mjs",
-		"watch:wp-build": "wp-build --watch"
+		"watch:wp-build": "pnpm run build:polyfills && wp-build --watch"
 	},
 	"browserslist": [
 		"extends @wordpress/browserslist-config"
@@ -99,6 +100,7 @@
 		"@automattic/color-studio": "4.1.0",
 		"@automattic/jetpack-base-styles": "workspace:*",
 		"@automattic/jetpack-webpack-config": "workspace:*",
+		"@automattic/jetpack-wp-build-polyfills": "workspace:*",
 		"@automattic/remove-asset-webpack-plugin": "workspace:*",
 		"@babel/core": "7.29.0",
 		"@babel/runtime": "7.28.6",
diff --git a/projects/packages/forms/src/dashboard/class-dashboard.php b/projects/packages/forms/src/dashboard/class-dashboard.php
index 1200ca620141..b80fd10112ba 100644
--- a/projects/packages/forms/src/dashboard/class-dashboard.php
+++ b/projects/packages/forms/src/dashboard/class-dashboard.php
@@ -36,9 +36,20 @@ public static function load_wp_build() {
 					: 'inbox';
 
 				wp_safe_redirect( self::get_forms_admin_url( $default_tab ) );
+
 				exit;
 			}
 
+			// Register polyfills for WP < 7.0 (must run before build.php).
+			if ( class_exists( \Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::class ) ) {
+				$forms_root = dirname( __DIR__, 2 );
+
+				\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::register(
+					$forms_root,
+					$forms_root . '/build/polyfills/modules/boot/index.min.js'
+				);
+			}
+
 			$wp_build_index = dirname( __DIR__, 2 ) . '/build/build.php';
 
 			if ( file_exists( $wp_build_index ) ) {

From 7150aa0ffd159f54fac0f8079021b9eb902537db Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Thu, 26 Feb 2026 20:17:00 -0300
Subject: [PATCH 03/40] Add changelog entries.

---
 .../forms/changelog/fix-polyfill-wp-build-dependencies        | 4 ++++
 .../changelog/fix-polyfill-wp-build-dependencies              | 4 ++++
 2 files changed, 8 insertions(+)
 create mode 100644 projects/packages/forms/changelog/fix-polyfill-wp-build-dependencies
 create mode 100644 projects/packages/wp-build-polyfills/changelog/fix-polyfill-wp-build-dependencies

diff --git a/projects/packages/forms/changelog/fix-polyfill-wp-build-dependencies b/projects/packages/forms/changelog/fix-polyfill-wp-build-dependencies
new file mode 100644
index 000000000000..47f642d23ac9
--- /dev/null
+++ b/projects/packages/forms/changelog/fix-polyfill-wp-build-dependencies
@@ -0,0 +1,4 @@
+Significance: minor
+Type: fixed
+
+Add polyfills for wp-build unbundled dependencies
diff --git a/projects/packages/wp-build-polyfills/changelog/fix-polyfill-wp-build-dependencies b/projects/packages/wp-build-polyfills/changelog/fix-polyfill-wp-build-dependencies
new file mode 100644
index 000000000000..383847a6e973
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/changelog/fix-polyfill-wp-build-dependencies
@@ -0,0 +1,4 @@
+Significance: minor
+Type: added
+
+Created wp-build polyfills package

From 4d56c4f6f63b861ec781d8b373db2f930f55a495 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Thu, 26 Feb 2026 20:25:32 -0300
Subject: [PATCH 04/40] fix changelog

---
 projects/packages/wp-build-polyfills/CHANGELOG.md           | 6 ++++++
 projects/packages/wp-build-polyfills/package.json           | 2 +-
 .../jetpack/changelog/fix-polyfill-wp-build-dependencies    | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
 create mode 100644 projects/packages/wp-build-polyfills/CHANGELOG.md
 create mode 100644 projects/plugins/jetpack/changelog/fix-polyfill-wp-build-dependencies

diff --git a/projects/packages/wp-build-polyfills/CHANGELOG.md b/projects/packages/wp-build-polyfills/CHANGELOG.md
new file mode 100644
index 000000000000..03a962f457f6
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/CHANGELOG.md
@@ -0,0 +1,6 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
diff --git a/projects/packages/wp-build-polyfills/package.json b/projects/packages/wp-build-polyfills/package.json
index 0383fd3cb5de..7b88a3414b9a 100644
--- a/projects/packages/wp-build-polyfills/package.json
+++ b/projects/packages/wp-build-polyfills/package.json
@@ -1,6 +1,6 @@
 {
 	"name": "@automattic/jetpack-wp-build-polyfills",
-	"version": "0.1.0",
+	"version": "0.1.0-alpha",
 	"private": true,
 	"description": "Polyfills for WordPress Core packages not available in WP < 7.0",
 	"homepage": "https://github.com/Automattic/jetpack/tree/HEAD/projects/packages/wp-build-polyfills/#readme",
diff --git a/projects/plugins/jetpack/changelog/fix-polyfill-wp-build-dependencies b/projects/plugins/jetpack/changelog/fix-polyfill-wp-build-dependencies
new file mode 100644
index 000000000000..e93330c1de2e
--- /dev/null
+++ b/projects/plugins/jetpack/changelog/fix-polyfill-wp-build-dependencies
@@ -0,0 +1,3 @@
+Significance: patch
+Type: other
+Comment: Update composer.lock.

From c58c48a4a205249e93380792cb849b6ed1d622fb Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Thu, 26 Feb 2026 20:29:12 -0300
Subject: [PATCH 05/40] add .gitattributes

---
 .../packages/wp-build-polyfills/.gitattributes  | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 projects/packages/wp-build-polyfills/.gitattributes

diff --git a/projects/packages/wp-build-polyfills/.gitattributes b/projects/packages/wp-build-polyfills/.gitattributes
new file mode 100644
index 000000000000..b0b228d4ad6a
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/.gitattributes
@@ -0,0 +1,17 @@
+# Files not needed to be distributed in the package.
+.gitattributes    export-ignore
+.github/          export-ignore
+package.json      export-ignore
+
+# Files to include in the mirror repo, but excluded via gitignore
+# Remember to end all directories with `/**` to properly tag every file.
+# /src/js/example.min.js  production-include
+
+# Files to exclude from the mirror repo, but included in the monorepo.
+# Remember to end all directories with `/**` to properly tag every file.
+.gitignore        production-exclude
+changelog/**      production-exclude
+phpunit.xml.dist  production-exclude
+.phpcs.dir.xml    production-exclude
+tests/**          production-exclude
+.phpcsignore      production-exclude

From 4d377a95d8431c2f0e813671335a479a99fbcc93 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Thu, 26 Feb 2026 21:16:31 -0300
Subject: [PATCH 06/40] Add Phan static analysis config for wp-build-polyfills
 package

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../packages/wp-build-polyfills/.phan/config.php    | 13 +++++++++++++
 1 file changed, 13 insertions(+)
 create mode 100644 projects/packages/wp-build-polyfills/.phan/config.php

diff --git a/projects/packages/wp-build-polyfills/.phan/config.php b/projects/packages/wp-build-polyfills/.phan/config.php
new file mode 100644
index 000000000000..a0a9c626191e
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/.phan/config.php
@@ -0,0 +1,13 @@
+<?php
+/**
+ * This configuration will be read and overlaid on top of the
+ * default configuration. Command-line arguments will be applied
+ * after this file is read.
+ *
+ * @package automattic/jetpack-wp-build-polyfills
+ */
+
+// Require base config.
+require __DIR__ . '/../../../../.phan/config.base.php';
+
+return make_phan_config( dirname( __DIR__ ) );

From b313068f981c57cfec0cb69ee031a2f4313d43d7 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Thu, 26 Feb 2026 21:17:23 -0300
Subject: [PATCH 07/40] fix base_file

---
 projects/packages/forms/src/dashboard/class-dashboard.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/projects/packages/forms/src/dashboard/class-dashboard.php b/projects/packages/forms/src/dashboard/class-dashboard.php
index b80fd10112ba..6410782756b6 100644
--- a/projects/packages/forms/src/dashboard/class-dashboard.php
+++ b/projects/packages/forms/src/dashboard/class-dashboard.php
@@ -46,7 +46,7 @@ public static function load_wp_build() {
 
 				\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::register(
 					$forms_root,
-					$forms_root . '/build/polyfills/modules/boot/index.min.js'
+					$forms_root . '/composer.json' // Used only for plugins_url() computation, as it is a known file.
 				);
 			}
 

From 139cc0c7201bf940eb3941cdbe11ea1ebbaa9b8f Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Thu, 26 Feb 2026 21:57:43 -0300
Subject: [PATCH 08/40] Remove executable bit from build-polyfills.mjs
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The bin entry in package.json handles execution permissions via
npm/pnpm — no need for the git executable bit.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 projects/packages/wp-build-polyfills/bin/build-polyfills.mjs | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 mode change 100755 => 100644 projects/packages/wp-build-polyfills/bin/build-polyfills.mjs

diff --git a/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs b/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
old mode 100755
new mode 100644

From d0b45e578e2029ed994dce2f34d749cf539e1707 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Thu, 26 Feb 2026 22:35:45 -0300
Subject: [PATCH 09/40] Exclude bin/ from wp-build-polyfills production mirror

The bin/build-polyfills.mjs script is a Node.js dev build tool and
should not be shipped in the jetpack_vendor directory.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 projects/packages/wp-build-polyfills/.gitattributes | 1 +
 1 file changed, 1 insertion(+)

diff --git a/projects/packages/wp-build-polyfills/.gitattributes b/projects/packages/wp-build-polyfills/.gitattributes
index b0b228d4ad6a..00f042d8399d 100644
--- a/projects/packages/wp-build-polyfills/.gitattributes
+++ b/projects/packages/wp-build-polyfills/.gitattributes
@@ -10,6 +10,7 @@ package.json      export-ignore
 # Files to exclude from the mirror repo, but included in the monorepo.
 # Remember to end all directories with `/**` to properly tag every file.
 .gitignore        production-exclude
+bin/**            production-exclude
 changelog/**      production-exclude
 phpunit.xml.dist  production-exclude
 .phpcs.dir.xml    production-exclude

From d38be0c009571b9d51f4bdb6da1f40fedc07bb52 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 2 Mar 2026 20:56:55 -0300
Subject: [PATCH 10/40] Add @wordpress/notices polyfill and fix autoloader
 resolution

The Forms wp-build dashboard failed with "Element type is invalid" when
Gutenberg was disabled because @wordpress/boot imports SnackbarNotices
from @wordpress/notices, which is not exported by WordPress core < 7.0.

- Add @wordpress/notices as a classic script polyfill that force-replaces
  core's registration on WP < 7.0
- Move polyfill builds into wp-build-polyfills package itself (self-contained
  build with own scripts, .gitignore, .gitattributes)
- Remove forms package dependency on wp-build-polyfills npm workspace (now
  only a composer dependency for the PHP autoloader)
- Update Jetpack plugin composer.lock to resolve wp-build-polyfills as a
  transitive dependency through forms, fixing class_exists() returning false
- Clean up debug error_log statements

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 projects/packages/forms/package.json          |  6 +-
 .../forms/src/dashboard/class-dashboard.php   |  7 +-
 .../wp-build-polyfills/.gitattributes         |  1 +
 .../packages/wp-build-polyfills/.gitignore    |  2 +-
 .../bin/build-polyfills.mjs                   | 39 +++++-----
 .../packages/wp-build-polyfills/composer.json |  8 +++
 .../packages/wp-build-polyfills/package.json  |  7 +-
 .../src/class-wp-build-polyfills.php          | 72 ++++++++++---------
 projects/plugins/jetpack/composer.lock        | 50 ++++++++++++-
 9 files changed, 125 insertions(+), 67 deletions(-)

diff --git a/projects/packages/forms/package.json b/projects/packages/forms/package.json
index 3e7302a4261c..c562b692d7ec 100644
--- a/projects/packages/forms/package.json
+++ b/projects/packages/forms/package.json
@@ -21,8 +21,7 @@
 		"build:contact-form": "webpack --config ./tools/webpack.config.contact-form.js",
 		"build:dashboard": "webpack --config ./tools/webpack.config.dashboard.js",
 		"build:form-editor": "webpack --config ./tools/webpack.config.form-editor.js",
-		"build:polyfills": "build-polyfills",
-		"build:wp-build": "pnpm run build:polyfills && wp-build",
+		"build:wp-build": "wp-build",
 		"build-production": "NODE_ENV=production BABEL_ENV=production pnpm run build && pnpm run validate",
 		"clean": "rm -rf dist/ build/ .cache/",
 		"extract-icons": "node tools/extract-icons.mjs",
@@ -36,7 +35,7 @@
 		"validate": "pnpm exec validate-es --no-error-on-unmatched-pattern dist/",
 		"watch": "concurrently 'pnpm:build:blocks --watch' 'pnpm:build:contact-form --watch' 'pnpm:build:dashboard --watch' 'pnpm:module:watch' 'pnpm:build:form-editor --watch' 'pnpm:watch:wp-build' 'pnpm:watch:icons'",
 		"watch:icons": "node tools/watch-icons.mjs",
-		"watch:wp-build": "pnpm run build:polyfills && wp-build --watch"
+		"watch:wp-build": "wp-build --watch"
 	},
 	"browserslist": [
 		"extends @wordpress/browserslist-config"
@@ -100,7 +99,6 @@
 		"@automattic/color-studio": "4.1.0",
 		"@automattic/jetpack-base-styles": "workspace:*",
 		"@automattic/jetpack-webpack-config": "workspace:*",
-		"@automattic/jetpack-wp-build-polyfills": "workspace:*",
 		"@automattic/remove-asset-webpack-plugin": "workspace:*",
 		"@babel/core": "7.29.0",
 		"@babel/runtime": "7.28.6",
diff --git a/projects/packages/forms/src/dashboard/class-dashboard.php b/projects/packages/forms/src/dashboard/class-dashboard.php
index 6410782756b6..4d9d9248f0bd 100644
--- a/projects/packages/forms/src/dashboard/class-dashboard.php
+++ b/projects/packages/forms/src/dashboard/class-dashboard.php
@@ -42,12 +42,7 @@ public static function load_wp_build() {
 
 			// Register polyfills for WP < 7.0 (must run before build.php).
 			if ( class_exists( \Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::class ) ) {
-				$forms_root = dirname( __DIR__, 2 );
-
-				\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::register(
-					$forms_root,
-					$forms_root . '/composer.json' // Used only for plugins_url() computation, as it is a known file.
-				);
+				\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::register();
 			}
 
 			$wp_build_index = dirname( __DIR__, 2 ) . '/build/build.php';
diff --git a/projects/packages/wp-build-polyfills/.gitattributes b/projects/packages/wp-build-polyfills/.gitattributes
index 00f042d8399d..9b74a0e6fee5 100644
--- a/projects/packages/wp-build-polyfills/.gitattributes
+++ b/projects/packages/wp-build-polyfills/.gitattributes
@@ -6,6 +6,7 @@ package.json      export-ignore
 # Files to include in the mirror repo, but excluded via gitignore
 # Remember to end all directories with `/**` to properly tag every file.
 # /src/js/example.min.js  production-include
+build/**          production-include
 
 # Files to exclude from the mirror repo, but included in the monorepo.
 # Remember to end all directories with `/**` to properly tag every file.
diff --git a/projects/packages/wp-build-polyfills/.gitignore b/projects/packages/wp-build-polyfills/.gitignore
index 65f08b37e4fe..48368aef75da 100644
--- a/projects/packages/wp-build-polyfills/.gitignore
+++ b/projects/packages/wp-build-polyfills/.gitignore
@@ -1,3 +1,3 @@
 .cache/
 /node_modules
-build/
+/build
diff --git a/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs b/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
index 17baad90405b..82f0ee4c9fb6 100644
--- a/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
+++ b/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
@@ -1,5 +1,3 @@
-#!/usr/bin/env node
-
 /**
  * Build script for Core package polyfills.
  *
@@ -7,6 +5,11 @@
  * (private-apis, theme, boot, route, a11y) so that plugins using
  * wp-build can conditionally register them when Core/Gutenberg doesn't provide them.
  *
+ * Uses esbuild rather than webpack because these are infrastructure packages
+ * without translatable strings, so i18n / translate.wordpress.org support is not
+ * needed. The `.asset.php` metadata generation is minimal and handled directly
+ * here — there is no equivalent outside webpack's dependency-extraction plugin.
+ *
  * Uses the same externals strategy as wp-build's wordpress-externals-plugin:
  * - Classic scripts (IIFE): `@wordpress/*` → window.wp.{camelCase}, vendor → globals
  * - Script modules (ESM): `@wordpress/*` script modules → external (import map),
@@ -17,24 +20,16 @@ import { createHash } from 'crypto';
 import { readFileSync, writeFileSync, mkdirSync } from 'fs';
 import { createRequire } from 'module';
 import path from 'path';
-import { fileURLToPath } from 'url';
-import { parseArgs } from 'util';
+import process from 'process';
 import { build } from 'esbuild';
 
 // Resolve packages from this package's own node_modules, not the consumer's.
-const __dirname = path.dirname( fileURLToPath( import.meta.url ) );
-const packageRoot = path.resolve( __dirname, '..' );
+const __dirname = import.meta.dirname;
+const packageRoot = path.dirname( __dirname );
 const require = createRequire( path.join( packageRoot, 'package.json' ) );
 
-// Parse CLI arguments.
-const { values: args } = parseArgs( {
-	options: {
-		'output-dir': { type: 'string', default: 'build/polyfills' },
-	},
-	strict: false,
-} );
-
-const outputBase = path.resolve( args[ 'output-dir' ] );
+const isProduction = process.env.NODE_ENV === 'production';
+const outputBase = path.join( packageRoot, 'build' );
 
 // ── Vendor externals (same as wp-build) ──────────────────────────────────────
 
@@ -309,6 +304,12 @@ function resolvePackageEntry( packageName, subEntry = null ) {
 }
 
 const classicScriptPolyfills = [
+	{
+		name: 'notices',
+		packageName: '@wordpress/notices',
+		globalName: 'wp.notices',
+		entry: resolvePackageEntry( '@wordpress/notices' ),
+	},
 	{
 		name: 'private-apis',
 		packageName: '@wordpress/private-apis',
@@ -361,7 +362,7 @@ for ( const polyfill of classicScriptPolyfills ) {
 			target,
 			platform: 'browser',
 			minify: true,
-			sourcemap: true,
+			sourcemap: isProduction,
 			plugins: [ polyfillExternalsPlugin( 'iife', polyfill.packageName ) ],
 		} )
 	);
@@ -377,7 +378,7 @@ for ( const polyfill of classicScriptPolyfills ) {
 			target,
 			platform: 'browser',
 			minify: false,
-			sourcemap: true,
+			sourcemap: ! isProduction,
 			plugins: [ polyfillExternalsPlugin( 'iife', polyfill.packageName ) ],
 		} )
 	);
@@ -398,7 +399,7 @@ for ( const polyfill of scriptModulePolyfills ) {
 			target,
 			platform: 'browser',
 			minify: true,
-			sourcemap: true,
+			sourcemap: isProduction,
 			plugins: [ polyfillExternalsPlugin( 'esm', polyfill.packageName ) ],
 		} )
 	);
@@ -413,7 +414,7 @@ for ( const polyfill of scriptModulePolyfills ) {
 			target,
 			platform: 'browser',
 			minify: false,
-			sourcemap: true,
+			sourcemap: ! isProduction,
 			plugins: [ polyfillExternalsPlugin( 'esm', polyfill.packageName ) ],
 		} )
 	);
diff --git a/projects/packages/wp-build-polyfills/composer.json b/projects/packages/wp-build-polyfills/composer.json
index 2efe5a3a0d8c..ee2ce03d6951 100644
--- a/projects/packages/wp-build-polyfills/composer.json
+++ b/projects/packages/wp-build-polyfills/composer.json
@@ -23,6 +23,14 @@
 			}
 		}
 	],
+	"scripts": {
+		"build-production": [
+			"pnpm run build-production"
+		],
+		"build-development": [
+			"pnpm run build"
+		]
+	},
 	"minimum-stability": "dev",
 	"prefer-stable": true,
 	"extra": {
diff --git a/projects/packages/wp-build-polyfills/package.json b/projects/packages/wp-build-polyfills/package.json
index 7b88a3414b9a..590c03798804 100644
--- a/projects/packages/wp-build-polyfills/package.json
+++ b/projects/packages/wp-build-polyfills/package.json
@@ -11,12 +11,15 @@
 	},
 	"license": "GPL-2.0-or-later",
 	"author": "Automattic",
-	"bin": {
-		"build-polyfills": "bin/build-polyfills.mjs"
+	"scripts": {
+		"build": "pnpm run clean && node bin/build-polyfills.mjs",
+		"build-production": "NODE_ENV=production BABEL_ENV=production pnpm run build",
+		"clean": "rm -rf build/"
 	},
 	"devDependencies": {
 		"@wordpress/a11y": "^4.40.0",
 		"@wordpress/boot": "^0.7.1",
+		"@wordpress/notices": "^5.40.0",
 		"@wordpress/private-apis": "^1.40.0",
 		"@wordpress/route": "^0.6.0",
 		"@wordpress/theme": "^0.7.0",
diff --git a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
index 720715ae208a..e625bf031bd9 100644
--- a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
+++ b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
@@ -21,25 +21,17 @@ class WP_Build_Polyfills {
 	 *
 	 * Call this early (e.g. during plugin load) — it hooks into wp_default_scripts
 	 * at priority 20 so Core (default) and Gutenberg (priority 10) register first.
-	 *
-	 * @param string $base_dir  Absolute path to directory containing build/polyfills/.
-	 * @param string $base_file File path for plugins_url() computation.
 	 */
-	public static function register( $base_dir, $base_file ) {
-		$polyfills_dir = $base_dir . '/build/polyfills';
-
-		add_action(
-			'wp_default_scripts',
-			function ( $scripts ) use ( $polyfills_dir, $base_file ) {
-				self::register_scripts( $scripts, $polyfills_dir, $base_file );
-			},
-			20
-		);
+	public static function register() {
+		$package_root = dirname( __DIR__ );
+		$build_dir    = $package_root . '/build';
+		$base_file    = $package_root . '/composer.json';
 
 		add_action(
 			'wp_default_scripts',
-			function () use ( $polyfills_dir, $base_file ) {
-				self::register_modules( $polyfills_dir, $base_file );
+			function ( $scripts ) use ( $build_dir, $base_file ) {
+				self::register_scripts( $scripts, $build_dir, $base_file );
+				self::register_modules( $build_dir, $base_file );
 			},
 			20
 		);
@@ -48,28 +40,37 @@ function () use ( $polyfills_dir, $base_file ) {
 	/**
 	 * Register polyfill classic scripts.
 	 *
-	 * @param \WP_Scripts $scripts       The WP_Scripts instance.
-	 * @param string      $polyfills_dir Absolute path to the polyfills build directory.
-	 * @param string      $base_file     File path for plugins_url() computation.
+	 * @param \WP_Scripts $scripts   The WP_Scripts instance.
+	 * @param string      $build_dir Absolute path to the build directory.
+	 * @param string      $base_file File path for plugins_url() computation.
 	 */
-	private static function register_scripts( $scripts, $polyfills_dir, $base_file ) {
+	private static function register_scripts( $scripts, $build_dir, $base_file ) {
 		$polyfills = array(
+			'wp-notices'      => array(
+				'path'  => 'notices',
+				// Only force-replace on WP < 7.0: older Core versions ship
+				// notices without SnackbarNotices and InlineNotices component
+				// exports that @wordpress/boot depends on.
+				'force' => version_compare( $GLOBALS['wp_version'] ?? '0', '7.0-dev', '<' ),
+			),
 			'wp-private-apis' => array(
 				'path'  => 'private-apis',
-				'deps'  => array(),
-				// Always replace: older Core versions ship private-apis with an
-				// incomplete allowlist that rejects @wordpress/theme and @wordpress/route.
+				// Only force-replace on WP < 7.0: older Core versions ship
+				// private-apis with an incomplete allowlist that rejects
+				// @wordpress/theme and @wordpress/route.
 				// Our version is a strict superset (same API, larger allowlist).
-				'force' => true,
+				'force' => version_compare( $GLOBALS['wp_version'] ?? '0', '7.0-dev', '<' ),
 			),
 			'wp-theme'        => array(
 				'path' => 'theme',
-				'deps' => array( 'wp-element', 'wp-private-apis' ),
 			),
 		);
 
+		$use_minified = defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ? false : true;
+		$file_name    = $use_minified ? 'index.min' : 'index';
+
 		foreach ( $polyfills as $handle => $data ) {
-			$asset_file = $polyfills_dir . '/scripts/' . $data['path'] . '/index.min.asset.php';
+			$asset_file = $build_dir . '/scripts/' . $data['path'] . '/' . $file_name . '.asset.php';
 
 			if ( ! file_exists( $asset_file ) ) {
 				continue;
@@ -90,9 +91,9 @@ private static function register_scripts( $scripts, $polyfills_dir, $base_file )
 
 			$scripts->add(
 				$handle,
-				plugins_url( 'build/polyfills/scripts/' . $data['path'] . '/index.min.js', $base_file ),
-				$asset['dependencies'] ?? $data['deps'],
-				$asset['version'] ?? false
+				plugins_url( 'build/scripts/' . $data['path'] . '/' . $file_name . '.js', $base_file ),
+				$asset['dependencies'],
+				$asset['version']
 			);
 		}
 	}
@@ -103,19 +104,22 @@ private static function register_scripts( $scripts, $polyfills_dir, $base_file )
 	 * Call to wp_register_script_module() silently ignores duplicate registrations (first wins),
 	 * so no explicit is_registered check is needed.
 	 *
-	 * @param string $polyfills_dir Absolute path to the polyfills build directory.
-	 * @param string $base_file     File path for plugins_url() computation.
+	 * @param string $build_dir Absolute path to the build directory.
+	 * @param string $base_file File path for plugins_url() computation.
 	 */
-	private static function register_modules( $polyfills_dir, $base_file ) {
+	private static function register_modules( $build_dir, $base_file ) {
 		if ( ! function_exists( 'wp_register_script_module' ) ) {
 			return;
 		}
 
 		$modules = array( 'boot', 'route', 'a11y' );
 
+		$use_minified = defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ? false : true;
+		$file_name    = $use_minified ? 'index.min' : 'index';
+
 		foreach ( $modules as $name ) {
 			$module_id  = '@wordpress/' . $name;
-			$asset_file = $polyfills_dir . '/modules/' . $name . '/index.min.asset.php';
+			$asset_file = $build_dir . '/modules/' . $name . '/' . $file_name . '.asset.php';
 
 			if ( ! file_exists( $asset_file ) ) {
 				continue;
@@ -125,9 +129,9 @@ private static function register_modules( $polyfills_dir, $base_file ) {
 
 			wp_register_script_module(
 				$module_id,
-				plugins_url( 'build/polyfills/modules/' . $name . '/index.min.js', $base_file ),
+				plugins_url( 'build/modules/' . $name . '/' . $file_name . '.js', $base_file ),
 				$asset['module_dependencies'] ?? array(),
-				$asset['version'] ?? false
+				$asset['version']
 			);
 		}
 	}
diff --git a/projects/plugins/jetpack/composer.lock b/projects/plugins/jetpack/composer.lock
index 3c7b6c365888..2f5c9d6c3842 100644
--- a/projects/plugins/jetpack/composer.lock
+++ b/projects/plugins/jetpack/composer.lock
@@ -1493,7 +1493,7 @@
             "dist": {
                 "type": "path",
                 "url": "../../packages/forms",
-                "reference": "50f87f787265e2f589b8ecd51407ffe4013e607f"
+                "reference": "1dd808dbc752ca6926a692969c704fb12fc233bc"
             },
             "require": {
                 "automattic/jetpack-admin-ui": "@dev",
@@ -1507,6 +1507,7 @@
                 "automattic/jetpack-plans": "@dev",
                 "automattic/jetpack-status": "@dev",
                 "automattic/jetpack-sync": "@dev",
+                "automattic/jetpack-wp-build-polyfills": "@dev",
                 "php": ">=7.2"
             },
             "require-dev": {
@@ -3580,6 +3581,53 @@
                 "relative": true
             }
         },
+        {
+            "name": "automattic/jetpack-wp-build-polyfills",
+            "version": "dev-trunk",
+            "dist": {
+                "type": "path",
+                "url": "../../packages/wp-build-polyfills",
+                "reference": "e0245feb632318f808a68138bdc18b09dd39ce2e"
+            },
+            "require": {
+                "php": ">=7.2"
+            },
+            "require-dev": {
+                "automattic/jetpack-changelogger": "@dev"
+            },
+            "type": "jetpack-library",
+            "extra": {
+                "autotagger": true,
+                "mirror-repo": "Automattic/jetpack-wp-build-polyfills",
+                "textdomain": "jetpack-wp-build-polyfills",
+                "changelogger": {
+                    "link-template": "https://github.com/Automattic/jetpack-wp-build-polyfills/compare/v${old}...v${new}"
+                },
+                "branch-alias": {
+                    "dev-trunk": "0.1.x-dev"
+                }
+            },
+            "autoload": {
+                "classmap": [
+                    "src/"
+                ]
+            },
+            "scripts": {
+                "build-production": [
+                    "pnpm run build-production"
+                ],
+                "build-development": [
+                    "pnpm run build"
+                ]
+            },
+            "license": [
+                "GPL-2.0-or-later"
+            ],
+            "description": "Polyfills for WordPress Core packages not available in WP < 7.0",
+            "transport-options": {
+                "relative": true
+            }
+        },
         {
             "name": "automattic/woocommerce-analytics",
             "version": "dev-trunk",

From 7c0cf3535e148864737bdd348949c8752e6b3a39 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 2 Mar 2026 21:03:58 -0300
Subject: [PATCH 11/40] Build only one variant per mode in wp-build-polyfills

Production builds produce minified files (index.min.js), development
builds produce unminified files (index.js). This matches the Jetpack
monorepo convention and avoids the waste of building both variants.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../bin/build-polyfills.mjs                   | 55 +++++--------------
 1 file changed, 13 insertions(+), 42 deletions(-)

diff --git a/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs b/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
index 82f0ee4c9fb6..ce392249d8a2 100644
--- a/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
+++ b/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
@@ -348,37 +348,26 @@ const scriptModulePolyfills = [
 const target = [ 'es2020' ];
 const builds = [];
 
+// Production builds produce minified files (index.min.js);
+// development builds produce unminified files (index.js).
+// The PHP registration class selects the appropriate file at runtime
+// via SCRIPT_DEBUG, and skips registration if the file doesn't exist.
+const outFileName = isProduction ? 'index.min.js' : 'index.js';
+
 for ( const polyfill of classicScriptPolyfills ) {
 	const outputDir = path.join( outputBase, 'scripts', polyfill.name );
 
-	// Minified
-	builds.push(
-		build( {
-			entryPoints: [ polyfill.entry ],
-			outfile: path.join( outputDir, 'index.min.js' ),
-			bundle: true,
-			format: 'iife',
-			globalName: polyfill.globalName,
-			target,
-			platform: 'browser',
-			minify: true,
-			sourcemap: isProduction,
-			plugins: [ polyfillExternalsPlugin( 'iife', polyfill.packageName ) ],
-		} )
-	);
-
-	// Non-minified
 	builds.push(
 		build( {
 			entryPoints: [ polyfill.entry ],
-			outfile: path.join( outputDir, 'index.js' ),
+			outfile: path.join( outputDir, outFileName ),
 			bundle: true,
 			format: 'iife',
 			globalName: polyfill.globalName,
 			target,
 			platform: 'browser',
-			minify: false,
-			sourcemap: ! isProduction,
+			minify: isProduction,
+			sourcemap: true,
 			plugins: [ polyfillExternalsPlugin( 'iife', polyfill.packageName ) ],
 		} )
 	);
@@ -387,34 +376,16 @@ for ( const polyfill of classicScriptPolyfills ) {
 for ( const polyfill of scriptModulePolyfills ) {
 	const outputDir = path.join( outputBase, 'modules', polyfill.name );
 
-	const entryPoint = polyfill.entry;
-
-	// Minified
-	builds.push(
-		build( {
-			entryPoints: [ entryPoint ],
-			outfile: path.join( outputDir, 'index.min.js' ),
-			bundle: true,
-			format: 'esm',
-			target,
-			platform: 'browser',
-			minify: true,
-			sourcemap: isProduction,
-			plugins: [ polyfillExternalsPlugin( 'esm', polyfill.packageName ) ],
-		} )
-	);
-
-	// Non-minified
 	builds.push(
 		build( {
-			entryPoints: [ entryPoint ],
-			outfile: path.join( outputDir, 'index.js' ),
+			entryPoints: [ polyfill.entry ],
+			outfile: path.join( outputDir, outFileName ),
 			bundle: true,
 			format: 'esm',
 			target,
 			platform: 'browser',
-			minify: false,
-			sourcemap: ! isProduction,
+			minify: isProduction,
+			sourcemap: true,
 			plugins: [ polyfillExternalsPlugin( 'esm', polyfill.packageName ) ],
 		} )
 	);

From 461fc92f4f46f99a3489bff0f7c1ee0518a373aa Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 2 Mar 2026 22:20:34 -0300
Subject: [PATCH 12/40] Replace esbuild with webpack for wp-build-polyfills
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Switch the wp-build-polyfills build from a custom esbuild script to a
standard webpack configuration using @automattic/jetpack-webpack-config.

IIFE builds (classic scripts) use the dependency-extraction-webpack-plugin
via StandardPlugins for externals handling and .asset.php generation.

ESM builds (script modules) use a custom PolyfillModulePlugin that handles
hybrid externals — script module deps become `import @wordpress/route`,
classic-only deps become `var wp.notices` window globals — and generates
the combined dependencies/module_dependencies asset files.

This addresses the review feedback about reinventing webpack with esbuild,
and aligns with the monorepo's standard build tooling.

Also simplifies the PHP class to always use `index.js` (no min/non-min
variants), matching the Jetpack convention where minification is controlled
by the build mode (jetpack build vs jetpack build --production).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 pnpm-lock.yaml                                | 141 ++++++-
 .../wp-build-polyfills/.gitattributes         |   5 +-
 .../packages/wp-build-polyfills/.gitignore    |   2 +-
 .../bin/build-polyfills.mjs                   | 396 ------------------
 .../packages/wp-build-polyfills/package.json  |   6 +-
 .../src/class-wp-build-polyfills.php          |  14 +-
 .../wp-build-polyfills/webpack.config.js      | 338 +++++++++++++++
 7 files changed, 488 insertions(+), 414 deletions(-)
 delete mode 100644 projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
 create mode 100644 projects/packages/wp-build-polyfills/webpack.config.js

diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index fd5afc622d6d..0d12133943b0 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -2558,9 +2558,6 @@ importers:
       '@automattic/jetpack-webpack-config':
         specifier: workspace:*
         version: link:../../js-packages/webpack-config
-      '@automattic/jetpack-wp-build-polyfills':
-        specifier: workspace:*
-        version: link:../wp-build-polyfills
       '@automattic/remove-asset-webpack-plugin':
         specifier: workspace:*
         version: link:../../js-packages/remove-asset-webpack-plugin
@@ -4169,6 +4166,43 @@ importers:
         specifier: 6.0.1
         version: 6.0.1(webpack@5.105.2)
 
+  projects/packages/wp-build-polyfills:
+    devDependencies:
+      '@automattic/jetpack-webpack-config':
+        specifier: workspace:*
+        version: link:../../js-packages/webpack-config
+      '@wordpress/a11y':
+        specifier: ^4.40.0
+        version: 4.41.0
+      '@wordpress/boot':
+        specifier: ^0.7.1
+        version: 0.7.1(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)
+      '@wordpress/notices':
+        specifier: ^5.40.0
+        version: 5.41.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      '@wordpress/private-apis':
+        specifier: ^1.40.0
+        version: 1.41.0
+      '@wordpress/route':
+        specifier: ^0.6.0
+        version: 0.6.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      '@wordpress/theme':
+        specifier: ^0.7.0
+        version: 0.7.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)
+      webpack:
+        specifier: ^5.104.1
+        version: 5.105.2(webpack-cli@6.0.1)
+      webpack-cli:
+        specifier: ^6.0.1
+        version: 6.0.1(webpack@5.105.2)
+    optionalDependencies:
+      react:
+        specifier: 18.3.1
+        version: 18.3.1
+      react-dom:
+        specifier: 18.3.1
+        version: 18.3.1(react@18.3.1)
+
   projects/packages/wp-js-data-sync: {}
 
   projects/packages/yoast-promo:
@@ -10486,6 +10520,13 @@ packages:
     peerDependencies:
       react: ^18.0.0
 
+  '@wordpress/boot@0.7.1':
+    resolution: {integrity: sha512-rfoPJiDYCt4odZBmc3CL2C8wL+uH6L9Jfg+udTBk6sLx81MSgRJlhAmcH6T8LO1vemrdsChk8Z84VBO428glAA==}
+    engines: {node: '>=18.12.0', npm: '>=8.19.2'}
+    peerDependencies:
+      react: ^18.0.0
+      react-dom: ^18.0.0
+
   '@wordpress/boot@0.8.0':
     resolution: {integrity: sha512-vyjmPZXWC0FgoU27JO/8KVZVNLwELKgiSB6FO/DATy22zQBmOuqIBbGKhsf2MazPYpkwe+l5ozBp2hGgIX/ofg==}
     engines: {node: '>=18.12.0', npm: '>=8.19.2'}
@@ -10840,6 +10881,12 @@ packages:
     peerDependencies:
       react: ^18.0.0
 
+  '@wordpress/route@0.6.0':
+    resolution: {integrity: sha512-NL0JZx/KoV0rHQhua8Py+rj/Z/KfyQusRw72yCk0Ei9sna1cYywAqzZNJfKxRr+Ua2YwJSy7ybueL0/OPZ0izw==}
+    engines: {node: '>=18.12.0', npm: '>=8.19.2'}
+    peerDependencies:
+      react: ^18.0.0
+
   '@wordpress/route@0.7.0':
     resolution: {integrity: sha512-6gv0hXb+bhGNK7bLAdcbMoDOdrXFRfsJfSN1P8hm429myZESmhYrh0mEV4at4y44C06zGPTqyzSKH0sR0eCMkg==}
     engines: {node: '>=18.12.0', npm: '>=8.19.2'}
@@ -10889,6 +10936,17 @@ packages:
       stylelint:
         optional: true
 
+  '@wordpress/theme@0.7.0':
+    resolution: {integrity: sha512-ULwLCSKYraIsv83bVH+Hm5pGFen6/0/8xOXQwxMdxeU+8kSm0cTKlpQPNvJGCmAeQb2OgFcowB/8wrUdyqW8UQ==}
+    engines: {node: '>=18.12.0', npm: '>=8.19.2'}
+    peerDependencies:
+      react: ^18.0.0
+      react-dom: ^18.0.0
+      stylelint: '>=16.8.2'
+    peerDependenciesMeta:
+      stylelint:
+        optional: true
+
   '@wordpress/theme@0.8.0':
     resolution: {integrity: sha512-xXGjWNFHICBuMNfjCjTui5ChkiKmmPTJtsF5tPXnUBXJaw43xxGlL0y7lpCNPJQxz+NPMJ01KlGfxhRsHXjKrQ==}
     engines: {node: '>=18.12.0', npm: '>=8.19.2'}
@@ -24027,6 +24085,40 @@ snapshots:
       simple-html-tokenizer: 0.5.11
       uuid: 9.0.1(patch_hash=87a713b75995ed86c0ecd0cadfd1b9f85092ca16fdff7132ff98b62fc3cf2db0)
 
+  '@wordpress/boot@0.7.1(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)':
+    dependencies:
+      '@wordpress/a11y': 4.41.0
+      '@wordpress/admin-ui': 1.9.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      '@wordpress/base-styles': 6.17.0
+      '@wordpress/commands': 1.41.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      '@wordpress/components': 32.3.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      '@wordpress/compose': 7.41.0(react@18.3.1)
+      '@wordpress/core-data': 7.41.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)
+      '@wordpress/data': 10.41.0(react@18.3.1)
+      '@wordpress/editor': 14.41.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)
+      '@wordpress/element': 6.41.0
+      '@wordpress/html-entities': 4.41.0
+      '@wordpress/i18n': 6.14.0
+      '@wordpress/icons': 11.8.0(react@18.3.1)
+      '@wordpress/keyboard-shortcuts': 5.41.0(react@18.3.1)
+      '@wordpress/keycodes': 4.41.0
+      '@wordpress/lazy-editor': 1.7.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)
+      '@wordpress/notices': 5.41.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      '@wordpress/primitives': 4.41.0(react@18.3.1)
+      '@wordpress/private-apis': 1.41.0
+      '@wordpress/route': 0.6.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      '@wordpress/theme': 0.7.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)
+      '@wordpress/url': 4.41.0
+      clsx: 2.1.1
+      react: 18.3.1
+      react-dom: 18.3.1(react@18.3.1)
+    transitivePeerDependencies:
+      - '@emotion/is-prop-valid'
+      - '@types/react'
+      - '@types/react-dom'
+      - stylelint
+      - supports-color
+
   '@wordpress/boot@0.8.0(@types/react-dom@18.3.7(@types/react@18.3.28))(@types/react@18.3.28)(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)':
     dependencies:
       '@wordpress/a11y': 4.41.0
@@ -25325,6 +25417,29 @@ snapshots:
       - stylelint
       - supports-color
 
+  '@wordpress/lazy-editor@1.7.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)':
+    dependencies:
+      '@wordpress/asset-loader': 1.7.0
+      '@wordpress/base-styles': 6.17.0
+      '@wordpress/block-editor': 15.14.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)
+      '@wordpress/blocks': 15.14.0(react@18.3.1)
+      '@wordpress/components': 32.3.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      '@wordpress/core-data': 7.41.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)
+      '@wordpress/data': 10.41.0(react@18.3.1)
+      '@wordpress/editor': 14.41.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)
+      '@wordpress/element': 6.41.0
+      '@wordpress/global-styles-engine': 1.8.0(react@18.3.1)
+      '@wordpress/i18n': 6.14.0
+      '@wordpress/private-apis': 1.41.0
+    transitivePeerDependencies:
+      - '@emotion/is-prop-valid'
+      - '@types/react'
+      - '@types/react-dom'
+      - react
+      - react-dom
+      - stylelint
+      - supports-color
+
   '@wordpress/media-editor@0.4.0(@types/react@18.3.28)(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)':
     dependencies:
       '@babel/runtime': 7.28.6
@@ -25745,6 +25860,15 @@ snapshots:
       memize: 2.1.1
       react: 18.3.1
 
+  '@wordpress/route@0.6.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)':
+    dependencies:
+      '@tanstack/history': 1.161.4
+      '@tanstack/react-router': 1.166.2(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
+      '@wordpress/private-apis': 1.41.0
+      react: 18.3.1
+    transitivePeerDependencies:
+      - react-dom
+
   '@wordpress/route@0.7.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)':
     dependencies:
       '@tanstack/history': 1.161.4
@@ -25825,6 +25949,17 @@ snapshots:
     optionalDependencies:
       stylelint: 16.26.1
 
+  '@wordpress/theme@0.7.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)':
+    dependencies:
+      '@wordpress/element': 6.41.0
+      '@wordpress/private-apis': 1.41.0
+      colorjs.io: 0.6.1
+      memize: 2.1.1
+      react: 18.3.1
+      react-dom: 18.3.1(react@18.3.1)
+    optionalDependencies:
+      stylelint: 16.26.1
+
   '@wordpress/theme@0.8.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1(typescript@5.9.3))':
     dependencies:
       '@wordpress/element': 6.41.0
diff --git a/projects/packages/wp-build-polyfills/.gitattributes b/projects/packages/wp-build-polyfills/.gitattributes
index 9b74a0e6fee5..e520e59fbc62 100644
--- a/projects/packages/wp-build-polyfills/.gitattributes
+++ b/projects/packages/wp-build-polyfills/.gitattributes
@@ -10,8 +10,9 @@ build/**          production-include
 
 # Files to exclude from the mirror repo, but included in the monorepo.
 # Remember to end all directories with `/**` to properly tag every file.
-.gitignore        production-exclude
-bin/**            production-exclude
+.gitignore           production-exclude
+bin/**               production-exclude
+webpack.config.js    production-exclude
 changelog/**      production-exclude
 phpunit.xml.dist  production-exclude
 .phpcs.dir.xml    production-exclude
diff --git a/projects/packages/wp-build-polyfills/.gitignore b/projects/packages/wp-build-polyfills/.gitignore
index 48368aef75da..83a5ab2f4c63 100644
--- a/projects/packages/wp-build-polyfills/.gitignore
+++ b/projects/packages/wp-build-polyfills/.gitignore
@@ -1,3 +1,3 @@
-.cache/
 /node_modules
 /build
+/.cache
diff --git a/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs b/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
deleted file mode 100644
index ce392249d8a2..000000000000
--- a/projects/packages/wp-build-polyfills/bin/build-polyfills.mjs
+++ /dev/null
@@ -1,396 +0,0 @@
-/**
- * Build script for Core package polyfills.
- *
- * Bundles `@wordpress` packages that are not available in WordPress Core < 7.0
- * (private-apis, theme, boot, route, a11y) so that plugins using
- * wp-build can conditionally register them when Core/Gutenberg doesn't provide them.
- *
- * Uses esbuild rather than webpack because these are infrastructure packages
- * without translatable strings, so i18n / translate.wordpress.org support is not
- * needed. The `.asset.php` metadata generation is minimal and handled directly
- * here — there is no equivalent outside webpack's dependency-extraction plugin.
- *
- * Uses the same externals strategy as wp-build's wordpress-externals-plugin:
- * - Classic scripts (IIFE): `@wordpress/*` → window.wp.{camelCase}, vendor → globals
- * - Script modules (ESM): `@wordpress/*` script modules → external (import map),
- * `@wordpress/*` classic-only → window.wp.{camelCase}, vendor → globals
- */
-
-import { createHash } from 'crypto';
-import { readFileSync, writeFileSync, mkdirSync } from 'fs';
-import { createRequire } from 'module';
-import path from 'path';
-import process from 'process';
-import { build } from 'esbuild';
-
-// Resolve packages from this package's own node_modules, not the consumer's.
-const __dirname = import.meta.dirname;
-const packageRoot = path.dirname( __dirname );
-const require = createRequire( path.join( packageRoot, 'package.json' ) );
-
-const isProduction = process.env.NODE_ENV === 'production';
-const outputBase = path.join( packageRoot, 'build' );
-
-// ── Vendor externals (same as wp-build) ──────────────────────────────────────
-
-const vendorExternals = {
-	react: { global: 'React', handle: 'react' },
-	'react-dom': { global: 'ReactDOM', handle: 'react-dom' },
-	'react/jsx-runtime': {
-		global: 'ReactJSXRuntime',
-		handle: 'react-jsx-runtime',
-	},
-	'react/jsx-dev-runtime': {
-		global: 'ReactJSXRuntime',
-		handle: 'react-jsx-runtime',
-	},
-	moment: { global: 'moment', handle: 'moment' },
-	lodash: { global: 'lodash', handle: 'lodash' },
-	'lodash-es': { global: 'lodash', handle: 'lodash' },
-	jquery: { global: 'jQuery', handle: 'jquery' },
-};
-
-// ── Package info cache ───────────────────────────────────────────────────────
-
-const packageJsonCache = new Map();
-
-/**
- * Get the package JSON for a package.
- * @param {string} packageName - The package name.
- * @param {string} resolveDir  - The directory to resolve the package from.
- * @return {object} The package JSON.
- */
-function getPackageJson( packageName, resolveDir = null ) {
-	const contextDir = resolveDir || packageRoot;
-	const cacheKey = `${ packageName }@${ contextDir }`;
-
-	if ( packageJsonCache.has( cacheKey ) ) {
-		return packageJsonCache.get( cacheKey );
-	}
-
-	try {
-		const contextRequire = createRequire( path.join( contextDir, 'package.json' ) );
-
-		const pkgPath = contextRequire.resolve( `${ packageName }/package.json` );
-
-		const pkg = JSON.parse( readFileSync( pkgPath, 'utf8' ) );
-		packageJsonCache.set( cacheKey, pkg );
-
-		return pkg;
-	} catch {
-		packageJsonCache.set( cacheKey, null );
-
-		return null;
-	}
-}
-
-// ── Helpers ──────────────────────────────────────────────────────────────────
-
-/**
- * Convert a string to camel case.
- *
- * @param {string} str - The string to convert.
- * @return {string} The camel case string.
- */
-function camelCase( str ) {
-	return str.replace( /-([a-z])/g, ( _, c ) => c.toUpperCase() );
-}
-
-/**
- * Check if a subpath is a script module import.
- * @param {object} packageJson - The package JSON object.
- * @param {string} subpath     - The subpath to check.
- * @return {boolean} Whether the subpath is a script module import.
- */
-function isScriptModuleImport( packageJson, subpath ) {
-	const { wpScriptModuleExports } = packageJson;
-
-	if ( ! wpScriptModuleExports ) {
-		return false;
-	}
-
-	if ( ! subpath ) {
-		if ( typeof wpScriptModuleExports === 'string' ) {
-			return true;
-		}
-
-		if ( typeof wpScriptModuleExports === 'object' && wpScriptModuleExports[ '.' ] ) {
-			return true;
-		}
-
-		return false;
-	}
-
-	if ( typeof wpScriptModuleExports === 'object' && wpScriptModuleExports[ `./${ subpath }` ] ) {
-		return true;
-	}
-
-	return false;
-}
-
-/**
- * Generate a SHA-256 hash of the content.
- * @param {string} content - The content to hash.
- * @return {string} The SHA-256 hash.
- */
-function generateContentHash( content ) {
-	return createHash( 'sha256' ).update( content ).digest( 'hex' ).slice( 0, 20 );
-}
-
-// ── Externals plugin ─────────────────────────────────────────────────────────
-
-/**
- * Create an externals plugin for the polyfills.
- * @param {string} buildFormat - The build format.
- * @param {string} skipPackage - The package to skip.
- * @return {object} The externals plugin.
- */
-function polyfillExternalsPlugin( buildFormat, skipPackage = null ) {
-	const dependencies = new Set();
-	const moduleDependencies = new Map();
-
-	return {
-		name: 'polyfill-externals',
-		setup( esb ) {
-			// Vendor externals
-			for ( const [ packageName, config ] of Object.entries( vendorExternals ) ) {
-				esb.onResolve( { filter: new RegExp( `^${ packageName }$` ) }, onResolveArgs => {
-					dependencies.add( config.handle );
-
-					return {
-						path: onResolveArgs.path,
-						namespace: 'vendor-external',
-						pluginData: { global: config.global },
-					};
-				} );
-			}
-
-			// @wordpress/* externals
-			esb.onResolve( { filter: /^@wordpress\// }, onResolveArgs => {
-				const parts = onResolveArgs.path.split( '/' );
-				const packageName = parts.slice( 0, 2 ).join( '/' );
-				const subpath = parts.length > 2 ? parts.slice( 2 ).join( '/' ) : null;
-				const shortName = parts[ 1 ];
-				const handle = `wp-${ shortName }`;
-
-				// Don't externalize the package we're building
-				if ( skipPackage && packageName === skipPackage ) {
-					return undefined;
-				}
-
-				const packageJson = getPackageJson( packageName, onResolveArgs.resolveDir );
-
-				if ( ! packageJson ) {
-					return undefined;
-				}
-
-				let isScriptModule = isScriptModuleImport( packageJson, subpath );
-				let isScript = !! packageJson.wpScript;
-
-				// Dual packages: use the format being built
-				if ( isScriptModule && isScript ) {
-					isScript = buildFormat === 'iife';
-					isScriptModule = buildFormat === 'esm';
-				}
-
-				const kind = onResolveArgs.kind === 'dynamic-import' ? 'dynamic' : 'static';
-
-				if ( isScriptModule ) {
-					if ( kind === 'static' ) {
-						moduleDependencies.set( onResolveArgs.path, 'static' );
-					} else if ( ! moduleDependencies.has( onResolveArgs.path ) ) {
-						moduleDependencies.set( onResolveArgs.path, 'dynamic' );
-					}
-
-					return {
-						path: onResolveArgs.path,
-						external: true,
-						sideEffects: !! packageJson.sideEffects,
-					};
-				}
-
-				if ( isScript ) {
-					dependencies.add( handle );
-
-					return {
-						path: onResolveArgs.path,
-						namespace: 'package-external',
-						pluginData: { globalName: 'wp' },
-					};
-				}
-
-				// Not a registered script or module — let esbuild bundle it
-				return undefined;
-			} );
-
-			esb.onLoad( { filter: /.*/, namespace: 'vendor-external' }, onLoadArgs => ( {
-				contents: `module.exports = window.${ onLoadArgs.pluginData.global };`,
-				loader: 'js',
-			} ) );
-
-			esb.onLoad( { filter: /.*/, namespace: 'package-external' }, onLoadArgs => {
-				const packagePath = onLoadArgs.path.split( '/' ).slice( 1 ).join( '/' );
-				const name = camelCase( packagePath );
-
-				return {
-					contents: `module.exports = window.${ onLoadArgs.pluginData.globalName }.${ name };`,
-					loader: 'js',
-				};
-			} );
-
-			// Generate asset file on build end
-			esb.onEnd( result => {
-				if ( result.errors.length > 0 ) {
-					return;
-				}
-
-				const outfile = esb.initialOptions.outfile;
-				const outputDir = path.dirname( outfile );
-				const baseName = path.basename( outfile, '.js' );
-
-				// Read the output to hash it
-				const outputContent = readFileSync( outfile );
-				const version = generateContentHash( outputContent );
-
-				const sortedDeps = Array.from( dependencies ).sort();
-				const depsString = sortedDeps.map( d => `'${ d }'` ).join( ', ' );
-
-				const assetParts = [ `'dependencies' => array(${ depsString })` ];
-
-				if ( moduleDependencies.size > 0 ) {
-					const modDeps = Array.from( moduleDependencies.entries() )
-						.sort( ( [ a ], [ b ] ) => a.localeCompare( b ) )
-						.map( ( [ dep, impKind ] ) => `array('id' => '${ dep }', 'import' => '${ impKind }')` )
-						.join( ', ' );
-
-					assetParts.push( `'module_dependencies' => array(${ modDeps })` );
-				}
-
-				assetParts.push( `'version' => '${ version }'` );
-
-				const assetContent = `<?php return array(${ assetParts.join( ', ' ) });`;
-
-				const assetPath = path.join( outputDir, `${ baseName }.asset.php` );
-
-				mkdirSync( outputDir, { recursive: true } );
-				writeFileSync( assetPath, assetContent );
-			} );
-		},
-	};
-}
-
-// ── Polyfill definitions ─────────────────────────────────────────────────────
-
-// Some packages (e.g. @wordpress/boot) only export ESM — no `require` or `default`
-// condition — so CJS require.resolve() fails. Resolve via /package.json (universally
-// exported) and read the `module` or `main` field instead.
-/**
- * Resolve the entry point for a package.
- * @param {string} packageName - The package name.
- * @param {string} subEntry    - The subentry to resolve.
- * @return {string} The entry point.
- */
-function resolvePackageEntry( packageName, subEntry = null ) {
-	const pkgJsonPath = require.resolve( `${ packageName }/package.json` );
-	const pkgDir = path.dirname( pkgJsonPath );
-
-	if ( subEntry ) {
-		return path.join( pkgDir, subEntry );
-	}
-
-	const pkg = JSON.parse( readFileSync( pkgJsonPath, 'utf8' ) );
-
-	return path.join( pkgDir, pkg.module || pkg.main );
-}
-
-const classicScriptPolyfills = [
-	{
-		name: 'notices',
-		packageName: '@wordpress/notices',
-		globalName: 'wp.notices',
-		entry: resolvePackageEntry( '@wordpress/notices' ),
-	},
-	{
-		name: 'private-apis',
-		packageName: '@wordpress/private-apis',
-		globalName: 'wp.privateApis',
-		entry: resolvePackageEntry( '@wordpress/private-apis' ),
-	},
-	{
-		name: 'theme',
-		packageName: '@wordpress/theme',
-		globalName: 'wp.theme',
-		entry: resolvePackageEntry( '@wordpress/theme' ),
-	},
-];
-
-const scriptModulePolyfills = [
-	{
-		name: 'boot',
-		packageName: '@wordpress/boot',
-		entry: resolvePackageEntry( '@wordpress/boot' ),
-	},
-	{
-		name: 'route',
-		packageName: '@wordpress/route',
-		entry: resolvePackageEntry( '@wordpress/route' ),
-	},
-	{
-		name: 'a11y',
-		packageName: '@wordpress/a11y',
-		// a11y's wpScriptModuleExports points to a separate module entry.
-		entry: resolvePackageEntry( '@wordpress/a11y', 'build-module/module/index.mjs' ),
-	},
-];
-
-// ── Build ────────────────────────────────────────────────────────────────────
-
-const target = [ 'es2020' ];
-const builds = [];
-
-// Production builds produce minified files (index.min.js);
-// development builds produce unminified files (index.js).
-// The PHP registration class selects the appropriate file at runtime
-// via SCRIPT_DEBUG, and skips registration if the file doesn't exist.
-const outFileName = isProduction ? 'index.min.js' : 'index.js';
-
-for ( const polyfill of classicScriptPolyfills ) {
-	const outputDir = path.join( outputBase, 'scripts', polyfill.name );
-
-	builds.push(
-		build( {
-			entryPoints: [ polyfill.entry ],
-			outfile: path.join( outputDir, outFileName ),
-			bundle: true,
-			format: 'iife',
-			globalName: polyfill.globalName,
-			target,
-			platform: 'browser',
-			minify: isProduction,
-			sourcemap: true,
-			plugins: [ polyfillExternalsPlugin( 'iife', polyfill.packageName ) ],
-		} )
-	);
-}
-
-for ( const polyfill of scriptModulePolyfills ) {
-	const outputDir = path.join( outputBase, 'modules', polyfill.name );
-
-	builds.push(
-		build( {
-			entryPoints: [ polyfill.entry ],
-			outfile: path.join( outputDir, outFileName ),
-			bundle: true,
-			format: 'esm',
-			target,
-			platform: 'browser',
-			minify: isProduction,
-			sourcemap: true,
-			plugins: [ polyfillExternalsPlugin( 'esm', polyfill.packageName ) ],
-		} )
-	);
-}
-
-await Promise.all( builds );
-// eslint-disable-next-line no-console
-console.log( 'WP Build Polyfills: Polyfill builds complete.' );
diff --git a/projects/packages/wp-build-polyfills/package.json b/projects/packages/wp-build-polyfills/package.json
index 590c03798804..aac1e9c783f5 100644
--- a/projects/packages/wp-build-polyfills/package.json
+++ b/projects/packages/wp-build-polyfills/package.json
@@ -12,18 +12,20 @@
 	"license": "GPL-2.0-or-later",
 	"author": "Automattic",
 	"scripts": {
-		"build": "pnpm run clean && node bin/build-polyfills.mjs",
+		"build": "pnpm run clean && webpack",
 		"build-production": "NODE_ENV=production BABEL_ENV=production pnpm run build",
 		"clean": "rm -rf build/"
 	},
 	"devDependencies": {
+		"@automattic/jetpack-webpack-config": "workspace:*",
 		"@wordpress/a11y": "^4.40.0",
 		"@wordpress/boot": "^0.7.1",
 		"@wordpress/notices": "^5.40.0",
 		"@wordpress/private-apis": "^1.40.0",
 		"@wordpress/route": "^0.6.0",
 		"@wordpress/theme": "^0.7.0",
-		"esbuild": "^0.27.0"
+		"webpack": "^5.104.1",
+		"webpack-cli": "^6.0.1"
 	},
 	"optionalDependencies": {
 		"react": "18.3.1",
diff --git a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
index e625bf031bd9..9c4ee7c5fed1 100644
--- a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
+++ b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
@@ -66,11 +66,8 @@ private static function register_scripts( $scripts, $build_dir, $base_file ) {
 			),
 		);
 
-		$use_minified = defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ? false : true;
-		$file_name    = $use_minified ? 'index.min' : 'index';
-
 		foreach ( $polyfills as $handle => $data ) {
-			$asset_file = $build_dir . '/scripts/' . $data['path'] . '/' . $file_name . '.asset.php';
+			$asset_file = $build_dir . '/scripts/' . $data['path'] . '/index.asset.php';
 
 			if ( ! file_exists( $asset_file ) ) {
 				continue;
@@ -91,7 +88,7 @@ private static function register_scripts( $scripts, $build_dir, $base_file ) {
 
 			$scripts->add(
 				$handle,
-				plugins_url( 'build/scripts/' . $data['path'] . '/' . $file_name . '.js', $base_file ),
+				plugins_url( 'build/scripts/' . $data['path'] . '/index.js', $base_file ),
 				$asset['dependencies'],
 				$asset['version']
 			);
@@ -114,12 +111,9 @@ private static function register_modules( $build_dir, $base_file ) {
 
 		$modules = array( 'boot', 'route', 'a11y' );
 
-		$use_minified = defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ? false : true;
-		$file_name    = $use_minified ? 'index.min' : 'index';
-
 		foreach ( $modules as $name ) {
 			$module_id  = '@wordpress/' . $name;
-			$asset_file = $build_dir . '/modules/' . $name . '/' . $file_name . '.asset.php';
+			$asset_file = $build_dir . '/modules/' . $name . '/index.asset.php';
 
 			if ( ! file_exists( $asset_file ) ) {
 				continue;
@@ -129,7 +123,7 @@ private static function register_modules( $build_dir, $base_file ) {
 
 			wp_register_script_module(
 				$module_id,
-				plugins_url( 'build/modules/' . $name . '/' . $file_name . '.js', $base_file ),
+				plugins_url( 'build/modules/' . $name . '/index.js', $base_file ),
 				$asset['module_dependencies'] ?? array(),
 				$asset['version']
 			);
diff --git a/projects/packages/wp-build-polyfills/webpack.config.js b/projects/packages/wp-build-polyfills/webpack.config.js
new file mode 100644
index 000000000000..a30ac969e51c
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/webpack.config.js
@@ -0,0 +1,338 @@
+/**
+ * Webpack configuration for wp-build-polyfills.
+ *
+ * Bundles `@wordpress` packages not available in WordPress Core < 7.0
+ * as both classic scripts (IIFE) and script modules (ESM).
+ *
+ * IIFE builds use `@wordpress/dependency-extraction-webpack-plugin` (via
+ * jetpack-webpack-config's StandardPlugins) for externals and .asset.php.
+ *
+ * ESM builds use a custom PolyfillModulePlugin because the dep extraction
+ * plugin doesn't support hybrid externals — ESM modules that import both
+ * script modules (externalized as `import \@wordpress/route`) and classic
+ * scripts (externalized as `var wp.notices` window globals).
+ */
+
+const { readFileSync } = require( 'fs' );
+const path = require( 'path' );
+const jetpackWebpackConfig = require( '@automattic/jetpack-webpack-config/webpack' );
+
+const packageRoot = __dirname;
+const localRequire = require;
+
+const outputBase = path.join( packageRoot, 'build' );
+
+// ── Helpers ──────────────────────────────────────────────────────────────────
+
+/**
+ * Convert a dash-separated string to camelCase.
+ *
+ * @param {string} str - Input string.
+ * @return {string} camelCased string.
+ */
+function camelCaseDash( str ) {
+	return str.replace( /-([a-z])/g, ( _, c ) => c.toUpperCase() );
+}
+
+const pkgJsonCache = new Map();
+
+/**
+ * Read and cache a package's package.json.
+ *
+ * @param {string} packageName - npm package name.
+ * @return {object|null} Parsed package.json or null.
+ */
+function readPackageJson( packageName ) {
+	if ( pkgJsonCache.has( packageName ) ) {
+		return pkgJsonCache.get( packageName );
+	}
+	try {
+		const pkgPath = localRequire.resolve( `${ packageName }/package.json` );
+		const pkg = JSON.parse( readFileSync( pkgPath, 'utf8' ) );
+		pkgJsonCache.set( packageName, pkg );
+		return pkg;
+	} catch {
+		pkgJsonCache.set( packageName, null );
+		return null;
+	}
+}
+
+/**
+ * Check if a package exports a WordPress script module (default export).
+ *
+ * @param {object} pkg - Parsed package.json.
+ * @return {boolean} True if the package has wpScriptModuleExports for '.'.
+ */
+function hasScriptModuleExport( pkg ) {
+	if ( ! pkg?.wpScriptModuleExports ) {
+		return false;
+	}
+	const exports = pkg.wpScriptModuleExports;
+	return typeof exports === 'string' || ( typeof exports === 'object' && exports[ '.' ] );
+}
+
+/**
+ * Resolve the entry point for a package.
+ *
+ * Some packages (e.g. `@wordpress/boot`) only export ESM, so CJS
+ * require.resolve() fails. We resolve via package.json instead and
+ * read the `module` or `main` field.
+ *
+ * @param {string}      packageName - npm package name.
+ * @param {string|null} subEntry    - Optional sub-entry relative to package root.
+ * @return {string} Absolute path to the entry file.
+ */
+function resolveEntry( packageName, subEntry = null ) {
+	const pkgPath = localRequire.resolve( `${ packageName }/package.json` );
+	const pkgDir = path.dirname( pkgPath );
+	if ( subEntry ) {
+		return path.join( pkgDir, subEntry );
+	}
+	const pkg = JSON.parse( readFileSync( pkgPath, 'utf8' ) );
+	return path.join( pkgDir, pkg.module || pkg.main );
+}
+
+// ── Shared config ───────────────────────────────────────────────────────────
+
+const sharedConfig = {
+	mode: jetpackWebpackConfig.mode,
+	devtool: jetpackWebpackConfig.devtool,
+	optimization: {
+		...jetpackWebpackConfig.optimization,
+	},
+	resolve: {
+		...jetpackWebpackConfig.resolve,
+		modules: [ path.join( packageRoot, 'node_modules' ), 'node_modules' ],
+	},
+	module: {
+		rules: [
+			// Transpile @wordpress/* packages from node_modules.
+			jetpackWebpackConfig.TranspileRule( {
+				includeNodeModules: [ '@wordpress/' ],
+			} ),
+		],
+	},
+};
+
+// Plugins disabled for all polyfill builds: no CSS is bundled, and i18n is
+// handled by core's textdomain since @wordpress/i18n remains external.
+const disabledPlugins = {
+	MiniCssExtractPlugin: false,
+	MiniCssWithRtlPlugin: false,
+	WebpackRtlPlugin: false,
+	I18nLoaderPlugin: false,
+	I18nCheckPlugin: false,
+};
+
+// ── Polyfill definitions ────────────────────────────────────────────────────
+
+const classicPolyfills = [
+	{
+		name: 'notices',
+		packageName: '@wordpress/notices',
+		library: [ 'wp', 'notices' ],
+	},
+	{
+		name: 'private-apis',
+		packageName: '@wordpress/private-apis',
+		library: [ 'wp', 'privateApis' ],
+	},
+	{
+		name: 'theme',
+		packageName: '@wordpress/theme',
+		library: [ 'wp', 'theme' ],
+	},
+];
+
+const modulePolyfills = [
+	{ name: 'boot', packageName: '@wordpress/boot' },
+	{ name: 'route', packageName: '@wordpress/route' },
+	{
+		name: 'a11y',
+		packageName: '@wordpress/a11y',
+		// a11y's wpScriptModuleExports points to a separate module entry.
+		subEntry: 'build-module/module/index.mjs',
+	},
+];
+
+// ── IIFE configs (classic scripts) ──────────────────────────────────────────
+//
+// Uses @wordpress/dependency-extraction-webpack-plugin (via StandardPlugins)
+// for externals handling and .asset.php generation. The requestMap prevents
+// externalization of the package being polyfilled so webpack bundles it.
+
+const iifeConfigs = classicPolyfills.map( polyfill => ( {
+	name: `script-${ polyfill.name }`,
+	...sharedConfig,
+	entry: {
+		index: resolveEntry( polyfill.packageName ),
+	},
+	output: {
+		...jetpackWebpackConfig.output,
+		path: path.join( outputBase, 'scripts', polyfill.name ),
+		library: {
+			name: polyfill.library,
+			type: 'window',
+		},
+	},
+	plugins: [
+		...jetpackWebpackConfig.StandardPlugins( {
+			DependencyExtractionPlugin: {
+				requestMap: {
+					[ polyfill.packageName ]: { external: false },
+				},
+			},
+			...disabledPlugins,
+		} ),
+	],
+} ) );
+
+// ── PolyfillModulePlugin ────────────────────────────────────────────────────
+//
+// Custom webpack plugin for ESM polyfill builds. Handles:
+//   1. Externals via webpack.ExternalsPlugin — script module deps become
+//      `import @wordpress/xxx`, classic-only deps become `var wp.xxx`.
+//   2. Dependency tracking — separates classic script handles (dependencies)
+//      from module IDs (module_dependencies).
+//   3. Asset generation — writes .asset.php in the same format as
+//      @wordpress/dependency-extraction-webpack-plugin.
+
+// Vendor externals (same mapping as @wordpress/dependency-extraction-webpack-plugin).
+const VENDOR_EXTERNALS = {
+	react: { global: 'React', handle: 'react' },
+	'react-dom': { global: 'ReactDOM', handle: 'react-dom' },
+	'react/jsx-runtime': { global: 'ReactJSXRuntime', handle: 'react-jsx-runtime' },
+	'react/jsx-dev-runtime': { global: 'ReactJSXRuntime', handle: 'react-jsx-runtime' },
+	moment: { global: 'moment', handle: 'moment' },
+	lodash: { global: 'lodash', handle: 'lodash' },
+	'lodash-es': { global: 'lodash', handle: 'lodash' },
+	jquery: { global: 'jQuery', handle: 'jquery' },
+};
+
+class PolyfillModulePlugin {
+	constructor( { skipPackage } ) {
+		this.skipPackage = skipPackage;
+	}
+
+	apply( compiler ) {
+		const { webpack } = compiler;
+		const { RawSource } = webpack.sources;
+
+		const scriptDeps = new Set();
+		const moduleDeps = new Map();
+
+		// Register externals.
+		new webpack.ExternalsPlugin( 'import', ( { request }, callback ) => {
+			// Don't externalize the package being polyfilled.
+			if ( request === this.skipPackage || request.startsWith( this.skipPackage + '/' ) ) {
+				return callback();
+			}
+
+			// @wordpress/* packages.
+			if ( request.startsWith( '@wordpress/' ) ) {
+				const pkgName = request.split( '/' ).slice( 0, 2 ).join( '/' );
+				const shortName = request.split( '/' )[ 1 ];
+				const pkg = readPackageJson( pkgName );
+
+				// Prefer script module for ESM builds.
+				if ( pkg && hasScriptModuleExport( pkg ) ) {
+					moduleDeps.set( request, 'static' );
+					return callback( null, `import ${ request }` );
+				}
+
+				// Classic script (or unresolvable — default to classic since
+				// most @wordpress/* packages are classic scripts).
+				scriptDeps.add( `wp-${ shortName }` );
+				return callback( null, `var wp.${ camelCaseDash( shortName ) }` );
+			}
+
+			// Vendor externals.
+			const vendor = VENDOR_EXTERNALS[ request ];
+			if ( vendor ) {
+				scriptDeps.add( vendor.handle );
+				return callback( null, `var ${ vendor.global }` );
+			}
+
+			// Unknown — let webpack bundle it.
+			return callback();
+		} ).apply( compiler );
+
+		// Generate .asset.php files.
+		compiler.hooks.thisCompilation.tap( 'PolyfillModulePlugin', compilation => {
+			compilation.hooks.processAssets.tap(
+				{
+					name: 'PolyfillModulePlugin',
+					stage: webpack.Compilation.PROCESS_ASSETS_STAGE_ANALYSE,
+				},
+				() => {
+					for ( const [ , entrypoint ] of compilation.entrypoints ) {
+						for ( const chunk of entrypoint.chunks ) {
+							const jsFile = Array.from( chunk.files ).find( f => /\.m?js$/i.test( f ) );
+							if ( ! jsFile ) {
+								continue;
+							}
+
+							const content = compilation.getAsset( jsFile ).source.buffer();
+							const hash = webpack.util
+								.createHash( 'xxhash64' )
+								.update( content )
+								.digest( 'hex' )
+								.slice( 0, 16 );
+
+							const depsPhp = Array.from( scriptDeps )
+								.sort()
+								.map( d => `'${ d }'` )
+								.join( ', ' );
+							const modDepsPhp = Array.from( moduleDeps.entries() )
+								.sort( ( [ a ], [ b ] ) => a.localeCompare( b ) )
+								.map( ( [ id, imp ] ) => `array('id' => '${ id }', 'import' => '${ imp }')` )
+								.join( ', ' );
+
+							const parts = [ `'dependencies' => array(${ depsPhp })` ];
+							if ( moduleDeps.size > 0 ) {
+								parts.push( `'module_dependencies' => array(${ modDepsPhp })` );
+							}
+							parts.push( `'version' => '${ hash }'` );
+
+							const assetContent = `<?php return array(${ parts.join( ', ' ) });\n`;
+							const assetFilename = jsFile.replace( /\.m?js$/i, '.asset.php' );
+
+							compilation.emitAsset( assetFilename, new RawSource( assetContent ) );
+							chunk.files.add( assetFilename );
+						}
+					}
+				}
+			);
+		} );
+	}
+}
+
+// ── ESM configs (script modules) ────────────────────────────────────────────
+
+const esmConfigs = modulePolyfills.map( polyfill => ( {
+	name: `module-${ polyfill.name }`,
+	...sharedConfig,
+	entry: {
+		index: resolveEntry( polyfill.packageName, polyfill.subEntry ),
+	},
+	output: {
+		...jetpackWebpackConfig.output,
+		path: path.join( outputBase, 'modules', polyfill.name ),
+		module: true,
+		chunkFormat: 'module',
+		environment: { module: true },
+		library: { type: 'module' },
+	},
+	experiments: {
+		outputModule: true,
+	},
+	plugins: [
+		...jetpackWebpackConfig.StandardPlugins( {
+			DependencyExtractionPlugin: false,
+			...disabledPlugins,
+		} ),
+		new PolyfillModulePlugin( { skipPackage: polyfill.packageName } ),
+	],
+} ) );
+
+module.exports = [ ...iifeConfigs, ...esmConfigs ];

From a771285da1183f1d3f4c4cf42718cc9a83f22e0e Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 2 Mar 2026 23:32:39 -0300
Subject: [PATCH 13/40] Add PHP tests for wp-build-polyfills

Integration tests verifying that polyfills register when Core doesn't
provide them, force-replace on WP < 7.0, and skip when Core already
has them. Uses WorDBless via jetpack-test-environment.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../wp-build-polyfills/.gitattributes         |   2 +-
 .../packages/wp-build-polyfills/composer.json |  19 +-
 .../wp-build-polyfills/phpunit.11.xml.dist    |  36 ++
 .../wp-build-polyfills/phpunit.12.xml.dist    |  36 ++
 .../wp-build-polyfills/phpunit.9.xml.dist     |  17 +
 .../tests/php/WP_Build_Polyfills_Test.php     | 425 ++++++++++++++++++
 .../tests/php/bootstrap.php                   |  12 +
 7 files changed, 545 insertions(+), 2 deletions(-)
 create mode 100644 projects/packages/wp-build-polyfills/phpunit.11.xml.dist
 create mode 100644 projects/packages/wp-build-polyfills/phpunit.12.xml.dist
 create mode 100644 projects/packages/wp-build-polyfills/phpunit.9.xml.dist
 create mode 100644 projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
 create mode 100644 projects/packages/wp-build-polyfills/tests/php/bootstrap.php

diff --git a/projects/packages/wp-build-polyfills/.gitattributes b/projects/packages/wp-build-polyfills/.gitattributes
index e520e59fbc62..725ae946a59d 100644
--- a/projects/packages/wp-build-polyfills/.gitattributes
+++ b/projects/packages/wp-build-polyfills/.gitattributes
@@ -14,7 +14,7 @@ build/**          production-include
 bin/**               production-exclude
 webpack.config.js    production-exclude
 changelog/**      production-exclude
-phpunit.xml.dist  production-exclude
+phpunit.*.xml.dist  production-exclude
 .phpcs.dir.xml    production-exclude
 tests/**          production-exclude
 .phpcsignore      production-exclude
diff --git a/projects/packages/wp-build-polyfills/composer.json b/projects/packages/wp-build-polyfills/composer.json
index ee2ce03d6951..651ed25e6326 100644
--- a/projects/packages/wp-build-polyfills/composer.json
+++ b/projects/packages/wp-build-polyfills/composer.json
@@ -7,7 +7,10 @@
 		"php": ">=7.2"
 	},
 	"require-dev": {
-		"automattic/jetpack-changelogger": "@dev"
+		"automattic/jetpack-changelogger": "@dev",
+		"automattic/jetpack-test-environment": "@dev",
+		"automattic/phpunit-select-config": "@dev",
+		"yoast/phpunit-polyfills": "^4.0.0"
 	},
 	"autoload": {
 		"classmap": [
@@ -29,8 +32,22 @@
 		],
 		"build-development": [
 			"pnpm run build"
+		],
+		"phpunit": [
+			"phpunit-select-config phpunit.#.xml.dist --colors=always"
+		],
+		"test-coverage": [
+			"php -dpcov.directory=. ./vendor/bin/phpunit-select-config phpunit.#.xml.dist --coverage-php \"$COVERAGE_DIR/php.cov\""
+		],
+		"test-php": [
+			"@composer phpunit"
 		]
 	},
+	"config": {
+		"allow-plugins": {
+			"roots/wordpress-core-installer": true
+		}
+	},
 	"minimum-stability": "dev",
 	"prefer-stable": true,
 	"extra": {
diff --git a/projects/packages/wp-build-polyfills/phpunit.11.xml.dist b/projects/packages/wp-build-polyfills/phpunit.11.xml.dist
new file mode 100644
index 000000000000..f7418373829b
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/phpunit.11.xml.dist
@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+	bootstrap="tests/php/bootstrap.php"
+	cacheDirectory=".phpunit.cache"
+	colors="true"
+	executionOrder="depends"
+	beStrictAboutOutputDuringTests="true"
+	displayDetailsOnPhpunitDeprecations="true"
+	displayDetailsOnTestsThatTriggerDeprecations="true"
+	displayDetailsOnTestsThatTriggerErrors="true"
+	displayDetailsOnTestsThatTriggerNotices="true"
+	displayDetailsOnTestsThatTriggerWarnings="true"
+	failOnDeprecation="true"
+	failOnEmptyTestSuite="true"
+	failOnPhpunitDeprecation="true"
+	failOnNotice="true"
+	failOnRisky="true"
+	failOnWarning="true"
+>
+	<testsuites>
+		<testsuite name="main">
+			<directory suffix="Test.php">tests/php</directory>
+		</testsuite>
+	</testsuites>
+
+	<source>
+		<include>
+			<!-- Better to only include "src" than to add "." and then exclude "tests", "vendor", and so on, as PHPUnit still scans the excluded directories. -->
+			<!-- Add additional lines for any files or directories outside of src/ that need coverage. -->
+			<directory suffix=".php">src</directory>
+		</include>
+	</source>
+	<coverage ignoreDeprecatedCodeUnits="true">
+	</coverage>
+</phpunit>
diff --git a/projects/packages/wp-build-polyfills/phpunit.12.xml.dist b/projects/packages/wp-build-polyfills/phpunit.12.xml.dist
new file mode 100644
index 000000000000..f7418373829b
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/phpunit.12.xml.dist
@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+	bootstrap="tests/php/bootstrap.php"
+	cacheDirectory=".phpunit.cache"
+	colors="true"
+	executionOrder="depends"
+	beStrictAboutOutputDuringTests="true"
+	displayDetailsOnPhpunitDeprecations="true"
+	displayDetailsOnTestsThatTriggerDeprecations="true"
+	displayDetailsOnTestsThatTriggerErrors="true"
+	displayDetailsOnTestsThatTriggerNotices="true"
+	displayDetailsOnTestsThatTriggerWarnings="true"
+	failOnDeprecation="true"
+	failOnEmptyTestSuite="true"
+	failOnPhpunitDeprecation="true"
+	failOnNotice="true"
+	failOnRisky="true"
+	failOnWarning="true"
+>
+	<testsuites>
+		<testsuite name="main">
+			<directory suffix="Test.php">tests/php</directory>
+		</testsuite>
+	</testsuites>
+
+	<source>
+		<include>
+			<!-- Better to only include "src" than to add "." and then exclude "tests", "vendor", and so on, as PHPUnit still scans the excluded directories. -->
+			<!-- Add additional lines for any files or directories outside of src/ that need coverage. -->
+			<directory suffix=".php">src</directory>
+		</include>
+	</source>
+	<coverage ignoreDeprecatedCodeUnits="true">
+	</coverage>
+</phpunit>
diff --git a/projects/packages/wp-build-polyfills/phpunit.9.xml.dist b/projects/packages/wp-build-polyfills/phpunit.9.xml.dist
new file mode 100644
index 000000000000..3965963c485e
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/phpunit.9.xml.dist
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.6/phpunit.xsd"
+	bootstrap="tests/php/bootstrap.php"
+	cacheResultFile=".phpunit.cache/test-results"
+	colors="true"
+	executionOrder="depends"
+	beStrictAboutOutputDuringTests="true"
+	failOnRisky="true"
+	failOnWarning="true"
+>
+	<testsuites>
+		<testsuite name="main">
+			<directory suffix="Test.php">tests/php</directory>
+		</testsuite>
+	</testsuites>
+</phpunit>
diff --git a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
new file mode 100644
index 000000000000..81e33788c6de
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
@@ -0,0 +1,425 @@
+<?php // phpcs:ignore WordPress.Files.FileName.InvalidClassFileName
+/**
+ * Tests for WP_Build_Polyfills.
+ *
+ * @package automattic/jetpack-wp-build-polyfills
+ */
+
+namespace Automattic\Jetpack\WP_Build_Polyfills\Tests;
+
+use Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills;
+use PHPUnit\Framework\Attributes\After;
+use PHPUnit\Framework\Attributes\Before;
+use WorDBless\BaseTestCase;
+
+/**
+ * Tests for the WP_Build_Polyfills class.
+ */
+class WP_Build_Polyfills_Test extends BaseTestCase {
+
+	/**
+	 * Temporary build directory for fake asset files.
+	 *
+	 * @var string
+	 */
+	private $build_dir;
+
+	/**
+	 * Original wp_version value.
+	 *
+	 * @var string
+	 */
+	private $original_wp_version;
+
+	/**
+	 * Original wp_script_modules global.
+	 *
+	 * @var mixed
+	 */
+	private $original_wp_script_modules;
+
+	/**
+	 * Set up test fixtures.
+	 *
+	 * @before
+	 */
+	#[Before]
+	public function set_up() {
+		parent::set_up();
+
+		$this->build_dir = sys_get_temp_dir() . '/wp-build-polyfills-test-' . uniqid();
+		mkdir( $this->build_dir . '/scripts/notices', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
+		mkdir( $this->build_dir . '/scripts/private-apis', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
+		mkdir( $this->build_dir . '/scripts/theme', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
+		mkdir( $this->build_dir . '/modules/boot', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
+		mkdir( $this->build_dir . '/modules/route', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
+		mkdir( $this->build_dir . '/modules/a11y', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
+
+		$this->original_wp_version        = $GLOBALS['wp_version'];
+		$this->original_wp_script_modules = $GLOBALS['wp_script_modules'] ?? null;
+	}
+
+	/**
+	 * Tear down test fixtures.
+	 *
+	 * @after
+	 */
+	#[After]
+	public function tear_down() {
+		$GLOBALS['wp_version'] = $this->original_wp_version; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+
+		if ( null === $this->original_wp_script_modules ) {
+			unset( $GLOBALS['wp_script_modules'] );
+		} else {
+			$GLOBALS['wp_script_modules'] = $this->original_wp_script_modules; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+		}
+
+		$this->recursive_rmdir( $this->build_dir );
+
+		parent::tear_down();
+	}
+
+	/**
+	 * Create a fake asset file.
+	 *
+	 * @param string $path    Relative path within the build dir (e.g. "scripts/notices/index.asset.php").
+	 * @param array  $deps    Dependencies array.
+	 * @param string $version Version string.
+	 * @param array  $extra   Extra keys to merge into the asset array.
+	 */
+	private function create_asset_file( $path, $deps = array(), $version = '1.0.0', $extra = array() ) {
+		$data     = array_merge(
+			array(
+				'dependencies' => $deps,
+				'version'      => $version,
+			),
+			$extra
+		);
+		$contents = '<?php return ' . var_export( $data, true ) . ";\n"; // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_var_export
+		file_put_contents( $this->build_dir . '/' . $path, $contents ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_file_put_contents
+	}
+
+	/**
+	 * Create a WP_Scripts instance with polyfill handles removed.
+	 *
+	 * WP_Scripts::__construct() fires wp_default_scripts which registers core
+	 * scripts. We remove the three handles under test so tests start clean.
+	 *
+	 * @return \WP_Scripts
+	 */
+	private function create_clean_scripts() {
+		$scripts = new \WP_Scripts();
+		$scripts->remove( 'wp-notices' );
+		$scripts->remove( 'wp-private-apis' );
+		$scripts->remove( 'wp-theme' );
+		return $scripts;
+	}
+
+	/**
+	 * Invoke the private register_scripts method.
+	 *
+	 * @param \WP_Scripts $scripts WP_Scripts instance.
+	 */
+	private function invoke_register_scripts( $scripts ) {
+		$method = new \ReflectionMethod( WP_Build_Polyfills::class, 'register_scripts' );
+		$method->setAccessible( true );
+		$method->invoke( null, $scripts, $this->build_dir, __FILE__ );
+	}
+
+	/**
+	 * Invoke the private register_modules method.
+	 */
+	private function invoke_register_modules() {
+		$method = new \ReflectionMethod( WP_Build_Polyfills::class, 'register_modules' );
+		$method->setAccessible( true );
+		$method->invoke( null, $this->build_dir, __FILE__ );
+	}
+
+	/**
+	 * Check if a script module is registered.
+	 *
+	 * @param string $id Module ID.
+	 * @return bool
+	 */
+	private function is_module_registered( $id ) {
+		$registered = $this->get_registered_modules();
+		return isset( $registered[ $id ] );
+	}
+
+	/**
+	 * Get data for a registered module.
+	 *
+	 * @param string $id Module ID.
+	 * @return array|null
+	 */
+	private function get_module_data( $id ) {
+		$registered = $this->get_registered_modules();
+		return $registered[ $id ] ?? null;
+	}
+
+	/**
+	 * Get the private $registered property from WP_Script_Modules.
+	 *
+	 * @return array
+	 */
+	private function get_registered_modules() {
+		$instance = wp_script_modules();
+		$prop     = new \ReflectionProperty( $instance, 'registered' );
+		$prop->setAccessible( true );
+		return $prop->getValue( $instance );
+	}
+
+	/**
+	 * Recursively remove a directory.
+	 *
+	 * @param string $dir Directory path.
+	 */
+	private function recursive_rmdir( $dir ) {
+		if ( ! is_dir( $dir ) ) {
+			return;
+		}
+		$items = new \RecursiveIteratorIterator(
+			new \RecursiveDirectoryIterator( $dir, \RecursiveDirectoryIterator::SKIP_DOTS ),
+			\RecursiveIteratorIterator::CHILD_FIRST
+		);
+		foreach ( $items as $item ) {
+			if ( $item->isDir() ) {
+				rmdir( $item->getRealPath() ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_rmdir
+			} else {
+				unlink( $item->getRealPath() ); // phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink
+			}
+		}
+		rmdir( $dir ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_rmdir
+	}
+
+	/**
+	 * Test that all scripts are registered when all asset files exist.
+	 */
+	public function test_register_scripts_registers_all_when_asset_files_exist() {
+		$this->create_asset_file( 'scripts/notices/index.asset.php' );
+		$this->create_asset_file( 'scripts/private-apis/index.asset.php' );
+		$this->create_asset_file( 'scripts/theme/index.asset.php' );
+
+		$scripts = $this->create_clean_scripts();
+		$this->invoke_register_scripts( $scripts );
+
+		$this->assertNotFalse( $scripts->query( 'wp-notices', 'registered' ) );
+		$this->assertNotFalse( $scripts->query( 'wp-private-apis', 'registered' ) );
+		$this->assertNotFalse( $scripts->query( 'wp-theme', 'registered' ) );
+	}
+
+	/**
+	 * Test that no scripts are registered when asset files are missing.
+	 */
+	public function test_register_scripts_skips_when_asset_files_missing() {
+		$scripts = $this->create_clean_scripts();
+		$this->invoke_register_scripts( $scripts );
+
+		$this->assertFalse( $scripts->query( 'wp-notices', 'registered' ) );
+		$this->assertFalse( $scripts->query( 'wp-private-apis', 'registered' ) );
+		$this->assertFalse( $scripts->query( 'wp-theme', 'registered' ) );
+	}
+
+	/**
+	 * Test that only scripts with asset files are registered.
+	 */
+	public function test_register_scripts_registers_only_scripts_with_asset_files() {
+		$this->create_asset_file( 'scripts/notices/index.asset.php' );
+		// No asset file for private-apis or theme.
+
+		$scripts = $this->create_clean_scripts();
+		$this->invoke_register_scripts( $scripts );
+
+		$this->assertNotFalse( $scripts->query( 'wp-notices', 'registered' ) );
+		$this->assertFalse( $scripts->query( 'wp-private-apis', 'registered' ) );
+		$this->assertFalse( $scripts->query( 'wp-theme', 'registered' ) );
+	}
+
+	/**
+	 * Test that wp-theme (non-force) keeps existing registration.
+	 */
+	public function test_register_scripts_skips_wp_theme_when_already_registered() {
+		$this->create_asset_file( 'scripts/theme/index.asset.php', array(), '2.0.0' );
+
+		$scripts = $this->create_clean_scripts();
+		$scripts->add( 'wp-theme', 'https://example.com/original-theme.js', array(), '1.0.0-original' );
+
+		$this->invoke_register_scripts( $scripts );
+
+		$registered = $scripts->query( 'wp-theme', 'registered' );
+		$this->assertNotFalse( $registered );
+		$this->assertSame( '1.0.0-original', $registered->ver );
+	}
+
+	/**
+	 * Test that wp-notices is force-replaced on WP < 7.0.
+	 */
+	public function test_register_scripts_force_replaces_wp_notices_on_old_wp() {
+		$GLOBALS['wp_version'] = '6.8'; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+		$this->create_asset_file( 'scripts/notices/index.asset.php', array(), '9.9.9' );
+
+		$scripts = $this->create_clean_scripts();
+		$scripts->add( 'wp-notices', 'https://example.com/old-notices.js', array(), '1.0.0-old' );
+
+		$this->invoke_register_scripts( $scripts );
+
+		$registered = $scripts->query( 'wp-notices', 'registered' );
+		$this->assertNotFalse( $registered );
+		$this->assertSame( '9.9.9', $registered->ver );
+	}
+
+	/**
+	 * Test that wp-private-apis is force-replaced on WP < 7.0.
+	 */
+	public function test_register_scripts_force_replaces_wp_private_apis_on_old_wp() {
+		$GLOBALS['wp_version'] = '6.8'; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+		$this->create_asset_file( 'scripts/private-apis/index.asset.php', array(), '9.9.9' );
+
+		$scripts = $this->create_clean_scripts();
+		$scripts->add( 'wp-private-apis', 'https://example.com/old-private-apis.js', array(), '1.0.0-old' );
+
+		$this->invoke_register_scripts( $scripts );
+
+		$registered = $scripts->query( 'wp-private-apis', 'registered' );
+		$this->assertNotFalse( $registered );
+		$this->assertSame( '9.9.9', $registered->ver );
+	}
+
+	/**
+	 * Test that neither wp-notices nor wp-private-apis is force-replaced on WP >= 7.0.
+	 */
+	public function test_register_scripts_does_not_force_replace_on_wp_7() {
+		$GLOBALS['wp_version'] = '7.0'; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+		$this->create_asset_file( 'scripts/notices/index.asset.php', array(), '9.9.9' );
+		$this->create_asset_file( 'scripts/private-apis/index.asset.php', array(), '9.9.9' );
+
+		$scripts = $this->create_clean_scripts();
+		$scripts->add( 'wp-notices', 'https://example.com/core-notices.js', array(), '1.0.0-core' );
+		$scripts->add( 'wp-private-apis', 'https://example.com/core-private-apis.js', array(), '1.0.0-core' );
+
+		$this->invoke_register_scripts( $scripts );
+
+		$notices = $scripts->query( 'wp-notices', 'registered' );
+		$this->assertSame( '1.0.0-core', $notices->ver );
+
+		$private_apis = $scripts->query( 'wp-private-apis', 'registered' );
+		$this->assertSame( '1.0.0-core', $private_apis->ver );
+	}
+
+	/**
+	 * Test that force scripts register fine even when not pre-existing.
+	 */
+	public function test_register_scripts_force_registers_fresh_on_old_wp() {
+		$GLOBALS['wp_version'] = '6.8'; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+		$this->create_asset_file( 'scripts/notices/index.asset.php', array(), '9.9.9' );
+		$this->create_asset_file( 'scripts/private-apis/index.asset.php', array(), '8.8.8' );
+
+		$scripts = $this->create_clean_scripts();
+		$this->invoke_register_scripts( $scripts );
+
+		$notices = $scripts->query( 'wp-notices', 'registered' );
+		$this->assertNotFalse( $notices );
+		$this->assertSame( '9.9.9', $notices->ver );
+
+		$private_apis = $scripts->query( 'wp-private-apis', 'registered' );
+		$this->assertNotFalse( $private_apis );
+		$this->assertSame( '8.8.8', $private_apis->ver );
+	}
+
+	/**
+	 * Test that dependencies from asset files are passed through correctly.
+	 */
+	public function test_register_scripts_has_correct_dependencies() {
+		$this->create_asset_file( 'scripts/notices/index.asset.php', array( 'wp-element', 'wp-data' ) );
+
+		$scripts = $this->create_clean_scripts();
+		$this->invoke_register_scripts( $scripts );
+
+		$registered = $scripts->query( 'wp-notices', 'registered' );
+		$this->assertNotFalse( $registered );
+		$this->assertSame( array( 'wp-element', 'wp-data' ), $registered->deps );
+	}
+
+	/**
+	 * Test that all modules are registered when asset files exist.
+	 */
+	public function test_register_modules_registers_all_when_asset_files_exist() {
+		// Reset the script modules global so we start fresh.
+		$GLOBALS['wp_script_modules'] = new \WP_Script_Modules(); // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+
+		$this->create_asset_file(
+			'modules/boot/index.asset.php',
+			array(),
+			'1.0.0',
+			array( 'module_dependencies' => array() )
+		);
+		$this->create_asset_file(
+			'modules/route/index.asset.php',
+			array(),
+			'1.0.0',
+			array( 'module_dependencies' => array() )
+		);
+		$this->create_asset_file(
+			'modules/a11y/index.asset.php',
+			array(),
+			'1.0.0',
+			array( 'module_dependencies' => array() )
+		);
+
+		$this->invoke_register_modules();
+
+		$this->assertTrue( $this->is_module_registered( '@wordpress/boot' ) );
+		$this->assertTrue( $this->is_module_registered( '@wordpress/route' ) );
+		$this->assertTrue( $this->is_module_registered( '@wordpress/a11y' ) );
+	}
+
+	/**
+	 * Test that no modules are registered when asset files are missing.
+	 */
+	public function test_register_modules_skips_when_asset_files_missing() {
+		$GLOBALS['wp_script_modules'] = new \WP_Script_Modules(); // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+
+		$this->invoke_register_modules();
+
+		$this->assertFalse( $this->is_module_registered( '@wordpress/boot' ) );
+		$this->assertFalse( $this->is_module_registered( '@wordpress/route' ) );
+		$this->assertFalse( $this->is_module_registered( '@wordpress/a11y' ) );
+	}
+
+	/**
+	 * Test that pre-registered modules are not replaced (first-wins semantics).
+	 */
+	public function test_register_modules_does_not_replace_existing() {
+		$GLOBALS['wp_script_modules'] = new \WP_Script_Modules(); // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+
+		// Pre-register @wordpress/boot.
+		wp_register_script_module( '@wordpress/boot', 'https://example.com/core-boot.js', array(), '1.0.0-core' );
+
+		$this->create_asset_file(
+			'modules/boot/index.asset.php',
+			array(),
+			'9.9.9',
+			array( 'module_dependencies' => array() )
+		);
+
+		$this->invoke_register_modules();
+
+		$module = $this->get_module_data( '@wordpress/boot' );
+		$this->assertNotNull( $module );
+		$this->assertSame( '1.0.0-core', $module['version'] );
+	}
+
+	/**
+	 * Test that register() hooks into wp_default_scripts at priority 20.
+	 */
+	public function test_register_hooks_into_wp_default_scripts() {
+		// Remove any existing hooks so we can verify the exact priority.
+		remove_all_filters( 'wp_default_scripts' );
+
+		WP_Build_Polyfills::register();
+
+		global $wp_filter;
+		$this->assertArrayHasKey( 'wp_default_scripts', $wp_filter );
+		$this->assertArrayHasKey( 20, $wp_filter['wp_default_scripts']->callbacks );
+	}
+}
diff --git a/projects/packages/wp-build-polyfills/tests/php/bootstrap.php b/projects/packages/wp-build-polyfills/tests/php/bootstrap.php
new file mode 100644
index 000000000000..f87e4fe524e4
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/tests/php/bootstrap.php
@@ -0,0 +1,12 @@
+<?php
+/**
+ * Bootstrap.
+ *
+ * @package automattic/jetpack-wp-build-polyfills
+ */
+
+/**
+ * Include the composer autoloader.
+ */
+require_once __DIR__ . '/../../vendor/autoload.php';
+\Automattic\Jetpack\Test_Environment::init();

From b8686ddeb21d4189cda90fa24595479cb8a9b953 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 2 Mar 2026 23:46:25 -0300
Subject: [PATCH 14/40] Add phpunit.8.xml.dist for CI and update jetpack
 composer.lock

CI runs PHPUnit 8 on older PHP versions, so the config is needed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../wp-build-polyfills/phpunit.8.xml.dist       | 17 +++++++++++++++++
 projects/plugins/jetpack/composer.lock          | 16 ++++++++++++++--
 2 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 projects/packages/wp-build-polyfills/phpunit.8.xml.dist

diff --git a/projects/packages/wp-build-polyfills/phpunit.8.xml.dist b/projects/packages/wp-build-polyfills/phpunit.8.xml.dist
new file mode 100644
index 000000000000..3965963c485e
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/phpunit.8.xml.dist
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.6/phpunit.xsd"
+	bootstrap="tests/php/bootstrap.php"
+	cacheResultFile=".phpunit.cache/test-results"
+	colors="true"
+	executionOrder="depends"
+	beStrictAboutOutputDuringTests="true"
+	failOnRisky="true"
+	failOnWarning="true"
+>
+	<testsuites>
+		<testsuite name="main">
+			<directory suffix="Test.php">tests/php</directory>
+		</testsuite>
+	</testsuites>
+</phpunit>
diff --git a/projects/plugins/jetpack/composer.lock b/projects/plugins/jetpack/composer.lock
index 2f5c9d6c3842..b13b6b550ac0 100644
--- a/projects/plugins/jetpack/composer.lock
+++ b/projects/plugins/jetpack/composer.lock
@@ -3587,13 +3587,16 @@
             "dist": {
                 "type": "path",
                 "url": "../../packages/wp-build-polyfills",
-                "reference": "e0245feb632318f808a68138bdc18b09dd39ce2e"
+                "reference": "e8095b10b4cb4eac8b26dce82529f158aa5346e0"
             },
             "require": {
                 "php": ">=7.2"
             },
             "require-dev": {
-                "automattic/jetpack-changelogger": "@dev"
+                "automattic/jetpack-changelogger": "@dev",
+                "automattic/jetpack-test-environment": "@dev",
+                "automattic/phpunit-select-config": "@dev",
+                "yoast/phpunit-polyfills": "^4.0.0"
             },
             "type": "jetpack-library",
             "extra": {
@@ -3618,6 +3621,15 @@
                 ],
                 "build-development": [
                     "pnpm run build"
+                ],
+                "phpunit": [
+                    "phpunit-select-config phpunit.#.xml.dist --colors=always"
+                ],
+                "test-coverage": [
+                    "php -dpcov.directory=. ./vendor/bin/phpunit-select-config phpunit.#.xml.dist --coverage-php \"$COVERAGE_DIR/php.cov\""
+                ],
+                "test-php": [
+                    "@composer phpunit"
                 ]
             },
             "license": [

From 7bdc39120fada789451653b6fccc7eea648217d7 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 2 Mar 2026 23:58:53 -0300
Subject: [PATCH 15/40] Skip setAccessible() on PHP >= 8.1 to avoid 8.5
 deprecation

Since PHP 8.1, private methods/properties are accessible via
reflection without calling setAccessible(). PHP 8.5 deprecates
the method, causing CI failures with failOnDeprecation enabled.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../tests/php/WP_Build_Polyfills_Test.php            | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
index 81e33788c6de..98da719115f5 100644
--- a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
+++ b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
@@ -122,7 +122,9 @@ private function create_clean_scripts() {
 	 */
 	private function invoke_register_scripts( $scripts ) {
 		$method = new \ReflectionMethod( WP_Build_Polyfills::class, 'register_scripts' );
-		$method->setAccessible( true );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$method->setAccessible( true );
+		}
 		$method->invoke( null, $scripts, $this->build_dir, __FILE__ );
 	}
 
@@ -131,7 +133,9 @@ private function invoke_register_scripts( $scripts ) {
 	 */
 	private function invoke_register_modules() {
 		$method = new \ReflectionMethod( WP_Build_Polyfills::class, 'register_modules' );
-		$method->setAccessible( true );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$method->setAccessible( true );
+		}
 		$method->invoke( null, $this->build_dir, __FILE__ );
 	}
 
@@ -165,7 +169,9 @@ private function get_module_data( $id ) {
 	private function get_registered_modules() {
 		$instance = wp_script_modules();
 		$prop     = new \ReflectionProperty( $instance, 'registered' );
-		$prop->setAccessible( true );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$prop->setAccessible( true );
+		}
 		return $prop->getValue( $instance );
 	}
 

From 33535836400fcc3b24af44d343f221e058addf21 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Tue, 3 Mar 2026 19:32:21 -0300
Subject: [PATCH 16/40] Preserve native dynamic imports in boot polyfill

When webpack bundles @wordpress/boot, it converts dynamic `import(variable)`
calls into context-module stubs that always throw "Cannot find module".
This breaks route loading because boot uses `import(route.route_module)`
to load route modules via the browser's import map at runtime.

Add a webpack loader that injects `/* webpackIgnore: true */` into
dynamic import() calls with non-string-literal arguments, telling
webpack to preserve them as native browser imports.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../preserve-dynamic-imports-loader.js        | 22 +++++++++++++++++++
 .../wp-build-polyfills/webpack.config.js      | 14 ++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js

diff --git a/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js b/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js
new file mode 100644
index 000000000000..0b5472b17346
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js
@@ -0,0 +1,22 @@
+/**
+ * Webpack loader that preserves dynamic import() calls as native browser imports.
+ *
+ * When webpack encounters `import(variable)` (a dynamic import with a non-string
+ * argument), it creates a "context module" stub that always throws
+ * "Cannot find module". This is because webpack can't statically determine what
+ * module will be loaded at runtime.
+ *
+ * For packages like `@wordpress`/boot that rely on the browser's import map to
+ * resolve module IDs at runtime, these dynamic imports must be preserved as
+ * native `import()` calls. This loader adds `webpackIgnore: true` magic comments
+ * to such imports, telling webpack to leave them as-is.
+ *
+ * Only import() calls with variable arguments are affected. String-literal
+ * imports like `import("`@wordpress`/a11y")` are left untouched so that webpack's
+ * externals plugin can handle them normally.
+ * @param {string} source - The source code to process.
+ * @return {string} - The processed source code.
+ */
+module.exports = function preserveDynamicImports( source ) {
+	return source.replace( /\bimport\(\s*(?!['"`/])/g, 'import(/* webpackIgnore: true */ ' );
+};
diff --git a/projects/packages/wp-build-polyfills/webpack.config.js b/projects/packages/wp-build-polyfills/webpack.config.js
index a30ac969e51c..14e3724245bc 100644
--- a/projects/packages/wp-build-polyfills/webpack.config.js
+++ b/projects/packages/wp-build-polyfills/webpack.config.js
@@ -312,6 +312,20 @@ class PolyfillModulePlugin {
 const esmConfigs = modulePolyfills.map( polyfill => ( {
 	name: `module-${ polyfill.name }`,
 	...sharedConfig,
+	module: {
+		rules: [
+			...sharedConfig.module.rules,
+			// Preserve native dynamic imports in @wordpress/boot so the
+			// browser can resolve route module IDs via the import map.
+			// Without this, webpack replaces `import(variable)` calls with
+			// context-module stubs that always throw "Cannot find module".
+			{
+				test: /[\\/]@wordpress[\\/]boot[\\/]/,
+				enforce: 'post',
+				loader: path.resolve( packageRoot, 'preserve-dynamic-imports-loader.js' ),
+			},
+		],
+	},
 	entry: {
 		index: resolveEntry( polyfill.packageName, polyfill.subEntry ),
 	},

From 1eb5bbb979b9ef26cacc0c0f187b0489611dee75 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Wed, 4 Mar 2026 20:26:40 -0300
Subject: [PATCH 17/40] Make WP version threshold configurable and fix version
 comparison

- Add $wp_version_threshold parameter to register() (defaults to '7.0')
- Change version comparison from '7.0-dev' to '7.0' so polyfills also
  apply on pre-release builds
- Deduplicate version_compare calls into a single $force_replace variable

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../src/class-wp-build-polyfills.php          | 28 +++++++++++--------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
index 9c4ee7c5fed1..a58694114d4a 100644
--- a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
+++ b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
@@ -21,16 +21,19 @@ class WP_Build_Polyfills {
 	 *
 	 * Call this early (e.g. during plugin load) — it hooks into wp_default_scripts
 	 * at priority 20 so Core (default) and Gutenberg (priority 10) register first.
+	 *
+	 * @param string $wp_version_threshold The WordPress version below which force-replacements
+	 *                                     are applied. Defaults to '7.0'.
 	 */
-	public static function register() {
+	public static function register( $wp_version_threshold = '7.0' ) {
 		$package_root = dirname( __DIR__ );
 		$build_dir    = $package_root . '/build';
 		$base_file    = $package_root . '/composer.json';
 
 		add_action(
 			'wp_default_scripts',
-			function ( $scripts ) use ( $build_dir, $base_file ) {
-				self::register_scripts( $scripts, $build_dir, $base_file );
+			function ( $scripts ) use ( $build_dir, $base_file, $wp_version_threshold ) {
+				self::register_scripts( $scripts, $build_dir, $base_file, $wp_version_threshold );
 				self::register_modules( $build_dir, $base_file );
 			},
 			20
@@ -40,26 +43,29 @@ function ( $scripts ) use ( $build_dir, $base_file ) {
 	/**
 	 * Register polyfill classic scripts.
 	 *
-	 * @param \WP_Scripts $scripts   The WP_Scripts instance.
-	 * @param string      $build_dir Absolute path to the build directory.
-	 * @param string      $base_file File path for plugins_url() computation.
+	 * @param \WP_Scripts $scripts               The WP_Scripts instance.
+	 * @param string      $build_dir             Absolute path to the build directory.
+	 * @param string      $base_file             File path for plugins_url() computation.
+	 * @param string      $wp_version_threshold  WP version below which force-replacements apply.
 	 */
-	private static function register_scripts( $scripts, $build_dir, $base_file ) {
+	private static function register_scripts( $scripts, $build_dir, $base_file, $wp_version_threshold ) {
+		$force_replace = version_compare( $GLOBALS['wp_version'] ?? '0', $wp_version_threshold, '<' );
+
 		$polyfills = array(
 			'wp-notices'      => array(
 				'path'  => 'notices',
-				// Only force-replace on WP < 7.0: older Core versions ship
+				// Only force-replace on older WP: older Core versions ship
 				// notices without SnackbarNotices and InlineNotices component
 				// exports that @wordpress/boot depends on.
-				'force' => version_compare( $GLOBALS['wp_version'] ?? '0', '7.0-dev', '<' ),
+				'force' => $force_replace,
 			),
 			'wp-private-apis' => array(
 				'path'  => 'private-apis',
-				// Only force-replace on WP < 7.0: older Core versions ship
+				// Only force-replace on older WP: older Core versions ship
 				// private-apis with an incomplete allowlist that rejects
 				// @wordpress/theme and @wordpress/route.
 				// Our version is a strict superset (same API, larger allowlist).
-				'force' => version_compare( $GLOBALS['wp_version'] ?? '0', '7.0-dev', '<' ),
+				'force' => $force_replace,
 			),
 			'wp-theme'        => array(
 				'path' => 'theme',

From 0a487936e400821efe2128973fa538cecd226495 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Wed, 4 Mar 2026 20:37:38 -0300
Subject: [PATCH 18/40] Fix test to pass wp_version_threshold to
 register_scripts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
index 98da719115f5..02fe1bac8a9e 100644
--- a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
+++ b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
@@ -125,7 +125,7 @@ private function invoke_register_scripts( $scripts ) {
 		if ( PHP_VERSION_ID < 80100 ) {
 			$method->setAccessible( true );
 		}
-		$method->invoke( null, $scripts, $this->build_dir, __FILE__ );
+		$method->invoke( null, $scripts, $this->build_dir, __FILE__, '7.0' );
 	}
 
 	/**

From 20474541a5c2590bffeeac6eeeb47d237b7dcf66 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Wed, 4 Mar 2026 20:48:02 -0300
Subject: [PATCH 19/40] Add README for wp-build-polyfills package

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../packages/wp-build-polyfills/README.md     | 66 +++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 projects/packages/wp-build-polyfills/README.md

diff --git a/projects/packages/wp-build-polyfills/README.md b/projects/packages/wp-build-polyfills/README.md
new file mode 100644
index 000000000000..c5668a051915
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/README.md
@@ -0,0 +1,66 @@
+# Jetpack WP Build Polyfills
+
+Polyfills for WordPress Core packages not yet available in WordPress < 7.0.
+
+This package conditionally registers `@wordpress/*` packages as both classic scripts (IIFE) and script modules (ESM) when they are not already provided by Core or Gutenberg.
+It is intended to be used until WordPress 7.1 is released, at which point versions of WordPress < 7.0 will no longer be supported and this package will no longer be needed.
+
+## Problem
+
+WordPress 7.0 introduces several new packages (`@wordpress/boot`, `@wordpress/route`, `@wordpress/theme`, etc.) that plugins built with [`@wordpress/build`](https://github.com/WordPress/gutenberg/tree/trunk/packages/wp-build) depend on. On older WordPress versions, these packages are missing or ship incomplete implementations — for example, `wp-private-apis` has an allowlist that rejects `@wordpress/theme` and `@wordpress/route`, and `wp-notices` lacks component exports that `@wordpress/boot` requires.
+
+This package provides those missing packages so that plugins using `@wordpress/build` can work on WordPress versions before 7.0.
+
+## What it polyfills
+
+### Classic scripts (IIFE)
+
+| Handle            | Source package          | Force-replaced on WP < 7.0? |
+|-------------------|------------------------|------------------------------|
+| `wp-notices`      | `@wordpress/notices`    | Yes — missing component exports |
+| `wp-private-apis` | `@wordpress/private-apis` | Yes — incomplete allowlist |
+| `wp-theme`        | `@wordpress/theme`      | No — only registered if absent |
+
+### Script modules (ESM)
+
+| Module ID          | Source package       |
+|--------------------|----------------------|
+| `@wordpress/boot`  | `@wordpress/boot`    |
+| `@wordpress/route` | `@wordpress/route`   |
+| `@wordpress/a11y`  | `@wordpress/a11y`    |
+
+Script modules use "first-wins" semantics — if Core or Gutenberg already registered the module, the polyfill is silently ignored.
+
+## How it works
+
+1. `WP_Build_Polyfills::register()` hooks into `wp_default_scripts` at **priority 20**, after Core (priority 0) and Gutenberg (priority 10) have registered their scripts.
+2. For each polyfill, it checks whether a built asset file exists (`build/scripts/*/index.asset.php` or `build/modules/*/index.asset.php`).
+3. For classic scripts, it checks whether the handle is already registered. Scripts marked as `force` are deregistered and re-registered with the polyfill version. Non-force scripts are skipped if already registered.
+4. For script modules, it calls `wp_register_script_module()`, which silently ignores duplicates.
+
+## Usage
+
+Call `register()` early in your plugin — for example, during the main plugin file load:
+
+```php
+\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::register();
+```
+
+The version threshold for force-replacements can be overridden:
+
+```php
+\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::register( '7.1' );
+```
+
+## Development
+
+```bash
+# Build polyfills (development)
+pnpm run build
+
+# Build polyfills (production)
+pnpm run build-production
+
+# Run PHP tests
+composer run test-php
+```

From 4d9e74edcdb4480f44279ade344529274066eaf8 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Wed, 4 Mar 2026 21:07:32 -0300
Subject: [PATCH 20/40] Add per-handle dependency registration to
 wp-build-polyfills

Consumers now pass a name and a list of polyfill handles they need,
enabling tracking of which plugin uses which polyfill for easier
future deprecation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../forms/src/dashboard/class-dashboard.php   |  8 +-
 .../packages/wp-build-polyfills/README.md     | 19 +++-
 .../src/class-wp-build-polyfills.php          | 72 ++++++++++++++-
 .../tests/php/WP_Build_Polyfills_Test.php     | 87 ++++++++++++++++++-
 4 files changed, 176 insertions(+), 10 deletions(-)

diff --git a/projects/packages/forms/src/dashboard/class-dashboard.php b/projects/packages/forms/src/dashboard/class-dashboard.php
index 4d9d9248f0bd..46d68d454f42 100644
--- a/projects/packages/forms/src/dashboard/class-dashboard.php
+++ b/projects/packages/forms/src/dashboard/class-dashboard.php
@@ -42,7 +42,13 @@ public static function load_wp_build() {
 
 			// Register polyfills for WP < 7.0 (must run before build.php).
 			if ( class_exists( \Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::class ) ) {
-				\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::register();
+				\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::register(
+					'jetpack-forms',
+					array_merge(
+						\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::SCRIPT_HANDLES,
+						\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::MODULE_IDS
+					)
+				);
 			}
 
 			$wp_build_index = dirname( __DIR__, 2 ) . '/build/build.php';
diff --git a/projects/packages/wp-build-polyfills/README.md b/projects/packages/wp-build-polyfills/README.md
index c5668a051915..c99d0f9e7992 100644
--- a/projects/packages/wp-build-polyfills/README.md
+++ b/projects/packages/wp-build-polyfills/README.md
@@ -40,16 +40,27 @@ Script modules use "first-wins" semantics — if Core or Gutenberg already regis
 
 ## Usage
 
-Call `register()` early in your plugin — for example, during the main plugin file load:
+Call `register()` early in your plugin, specifying a consumer name and the polyfills you need:
 
 ```php
-\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::register();
+use Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills;
+
+WP_Build_Polyfills::register( 'my-plugin', array(
+    'wp-notices',
+    'wp-private-apis',
+    '@wordpress/boot',
+    '@wordpress/route',
+) );
 ```
 
-The version threshold for force-replacements can be overridden:
+Available handles are listed in `WP_Build_Polyfills::SCRIPT_HANDLES` and `WP_Build_Polyfills::MODULE_IDS`.
+
+Multiple plugins can call `register()` — the hook is only added once, and all requested polyfills are merged. You can inspect which consumers requested which polyfills via `WP_Build_Polyfills::get_consumers()`.
+
+The version threshold for force-replacements can be overridden with a third parameter:
 
 ```php
-\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::register( '7.1' );
+WP_Build_Polyfills::register( 'my-plugin', array( 'wp-notices' ), '7.1' );
 ```
 
 ## Development
diff --git a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
index a58694114d4a..3e0e7fff607d 100644
--- a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
+++ b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
@@ -16,16 +16,62 @@
  */
 class WP_Build_Polyfills {
 
+	/**
+	 * Available polyfill handles for classic scripts.
+	 */
+	const SCRIPT_HANDLES = array( 'wp-notices', 'wp-private-apis', 'wp-theme' );
+
+	/**
+	 * Available polyfill module IDs.
+	 */
+	const MODULE_IDS = array( '@wordpress/boot', '@wordpress/route', '@wordpress/a11y' );
+
+	/**
+	 * Tracks which polyfills have been requested and by which consumers.
+	 *
+	 * Keys are polyfill handles/module IDs, values are arrays of consumer names.
+	 *
+	 * @var array<string, string[]>
+	 */
+	private static $requested = array();
+
+	/**
+	 * Whether the wp_default_scripts hook has already been added.
+	 *
+	 * @var bool
+	 */
+	private static $hooked = false;
+
 	/**
 	 * Register polyfill scripts and modules.
 	 *
 	 * Call this early (e.g. during plugin load) — it hooks into wp_default_scripts
 	 * at priority 20 so Core (default) and Gutenberg (priority 10) register first.
 	 *
-	 * @param string $wp_version_threshold The WordPress version below which force-replacements
-	 *                                     are applied. Defaults to '7.0'.
+	 * @param string   $consumer             A unique identifier for the consumer (e.g. plugin slug).
+	 * @param string[] $polyfills             List of polyfill handles/module IDs to register.
+	 *                                        Use class constants SCRIPT_HANDLES and MODULE_IDS for reference.
+	 * @param string   $wp_version_threshold  The WordPress version below which force-replacements
+	 *                                        are applied. Defaults to '7.0'.
 	 */
-	public static function register( $wp_version_threshold = '7.0' ) {
+	public static function register( $consumer, $polyfills, $wp_version_threshold = '7.0' ) {
+		foreach ( $polyfills as $handle ) {
+			if ( ! in_array( $handle, self::SCRIPT_HANDLES, true ) && ! in_array( $handle, self::MODULE_IDS, true ) ) {
+				continue;
+			}
+			if ( ! isset( self::$requested[ $handle ] ) ) {
+				self::$requested[ $handle ] = array();
+			}
+			if ( ! in_array( $consumer, self::$requested[ $handle ], true ) ) {
+				self::$requested[ $handle ][] = $consumer;
+			}
+		}
+
+		if ( self::$hooked ) {
+			return;
+		}
+		self::$hooked = true;
+
 		$package_root = dirname( __DIR__ );
 		$build_dir    = $package_root . '/build';
 		$base_file    = $package_root . '/composer.json';
@@ -40,6 +86,15 @@ function ( $scripts ) use ( $build_dir, $base_file, $wp_version_threshold ) {
 		);
 	}
 
+	/**
+	 * Get the map of requested polyfills and their consumers.
+	 *
+	 * @return array<string, string[]> Keys are polyfill handles/module IDs, values are consumer names.
+	 */
+	public static function get_consumers() {
+		return self::$requested;
+	}
+
 	/**
 	 * Register polyfill classic scripts.
 	 *
@@ -73,6 +128,10 @@ private static function register_scripts( $scripts, $build_dir, $base_file, $wp_
 		);
 
 		foreach ( $polyfills as $handle => $data ) {
+			if ( ! isset( self::$requested[ $handle ] ) ) {
+				continue;
+			}
+
 			$asset_file = $build_dir . '/scripts/' . $data['path'] . '/index.asset.php';
 
 			if ( ! file_exists( $asset_file ) ) {
@@ -118,7 +177,12 @@ private static function register_modules( $build_dir, $base_file ) {
 		$modules = array( 'boot', 'route', 'a11y' );
 
 		foreach ( $modules as $name ) {
-			$module_id  = '@wordpress/' . $name;
+			$module_id = '@wordpress/' . $name;
+
+			if ( ! isset( self::$requested[ $module_id ] ) ) {
+				continue;
+			}
+
 			$asset_file = $build_dir . '/modules/' . $name . '/index.asset.php';
 
 			if ( ! file_exists( $asset_file ) ) {
diff --git a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
index 02fe1bac8a9e..23869b7898ca 100644
--- a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
+++ b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
@@ -74,6 +74,19 @@ public function tear_down() {
 			$GLOBALS['wp_script_modules'] = $this->original_wp_script_modules; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
 		}
 
+		// Reset static state.
+		$requested = new \ReflectionProperty( WP_Build_Polyfills::class, 'requested' );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$requested->setAccessible( true );
+		}
+		$requested->setValue( null, array() );
+
+		$hooked = new \ReflectionProperty( WP_Build_Polyfills::class, 'hooked' );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$hooked->setAccessible( true );
+		}
+		$hooked->setValue( null, false );
+
 		$this->recursive_rmdir( $this->build_dir );
 
 		parent::tear_down();
@@ -115,12 +128,43 @@ private function create_clean_scripts() {
 		return $scripts;
 	}
 
+	/**
+	 * Request all available polyfills for a test consumer.
+	 *
+	 * Populates the static $requested property so register_scripts/register_modules
+	 * will process all handles. Uses register() but prevents the hook from firing
+	 * by resetting $hooked afterwards.
+	 *
+	 * @param string[] $polyfills Optional specific polyfills to request. Defaults to all.
+	 */
+	private function request_polyfills( $polyfills = null ) {
+		if ( null === $polyfills ) {
+			$polyfills = array_merge( WP_Build_Polyfills::SCRIPT_HANDLES, WP_Build_Polyfills::MODULE_IDS );
+		}
+
+		// Directly set the $requested static property via reflection.
+		$requested = new \ReflectionProperty( WP_Build_Polyfills::class, 'requested' );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$requested->setAccessible( true );
+		}
+		$current = $requested->getValue( null );
+		foreach ( $polyfills as $handle ) {
+			if ( ! isset( $current[ $handle ] ) ) {
+				$current[ $handle ] = array();
+			}
+			$current[ $handle ][] = 'test';
+		}
+		$requested->setValue( null, $current );
+	}
+
 	/**
 	 * Invoke the private register_scripts method.
 	 *
 	 * @param \WP_Scripts $scripts WP_Scripts instance.
 	 */
 	private function invoke_register_scripts( $scripts ) {
+		$this->request_polyfills( WP_Build_Polyfills::SCRIPT_HANDLES );
+
 		$method = new \ReflectionMethod( WP_Build_Polyfills::class, 'register_scripts' );
 		if ( PHP_VERSION_ID < 80100 ) {
 			$method->setAccessible( true );
@@ -132,6 +176,8 @@ private function invoke_register_scripts( $scripts ) {
 	 * Invoke the private register_modules method.
 	 */
 	private function invoke_register_modules() {
+		$this->request_polyfills( WP_Build_Polyfills::MODULE_IDS );
+
 		$method = new \ReflectionMethod( WP_Build_Polyfills::class, 'register_modules' );
 		if ( PHP_VERSION_ID < 80100 ) {
 			$method->setAccessible( true );
@@ -422,10 +468,49 @@ public function test_register_hooks_into_wp_default_scripts() {
 		// Remove any existing hooks so we can verify the exact priority.
 		remove_all_filters( 'wp_default_scripts' );
 
-		WP_Build_Polyfills::register();
+		WP_Build_Polyfills::register( 'test-plugin', array( 'wp-notices' ) );
 
 		global $wp_filter;
 		$this->assertArrayHasKey( 'wp_default_scripts', $wp_filter );
 		$this->assertArrayHasKey( 20, $wp_filter['wp_default_scripts']->callbacks );
 	}
+
+	/**
+	 * Test that get_consumers returns the correct consumer map.
+	 */
+	public function test_get_consumers_tracks_polyfill_consumers() {
+		WP_Build_Polyfills::register( 'plugin-a', array( 'wp-notices', '@wordpress/boot' ) );
+		WP_Build_Polyfills::register( 'plugin-b', array( 'wp-notices', 'wp-theme' ) );
+
+		$consumers = WP_Build_Polyfills::get_consumers();
+
+		$this->assertSame( array( 'plugin-a', 'plugin-b' ), $consumers['wp-notices'] );
+		$this->assertSame( array( 'plugin-a' ), $consumers['@wordpress/boot'] );
+		$this->assertSame( array( 'plugin-b' ), $consumers['wp-theme'] );
+		$this->assertArrayNotHasKey( 'wp-private-apis', $consumers );
+	}
+
+	/**
+	 * Test that only requested polyfills are registered.
+	 */
+	public function test_register_scripts_only_registers_requested_handles() {
+		$this->create_asset_file( 'scripts/notices/index.asset.php' );
+		$this->create_asset_file( 'scripts/private-apis/index.asset.php' );
+		$this->create_asset_file( 'scripts/theme/index.asset.php' );
+
+		// Only request wp-notices.
+		$this->request_polyfills( array( 'wp-notices' ) );
+
+		$scripts = $this->create_clean_scripts();
+
+		$method = new \ReflectionMethod( WP_Build_Polyfills::class, 'register_scripts' );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$method->setAccessible( true );
+		}
+		$method->invoke( null, $scripts, $this->build_dir, __FILE__, '7.0' );
+
+		$this->assertNotFalse( $scripts->query( 'wp-notices', 'registered' ) );
+		$this->assertFalse( $scripts->query( 'wp-private-apis', 'registered' ) );
+		$this->assertFalse( $scripts->query( 'wp-theme', 'registered' ) );
+	}
 }

From e9ca4f4b2b49e589c0639e48c08d02dd5d5f40da Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Wed, 4 Mar 2026 21:16:36 -0300
Subject: [PATCH 21/40] Fix phan issue: omit null arg for static
 ReflectionProperty::getValue

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
index 23869b7898ca..6d4454bdda8c 100644
--- a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
+++ b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
@@ -147,7 +147,7 @@ private function request_polyfills( $polyfills = null ) {
 		if ( PHP_VERSION_ID < 80100 ) {
 			$requested->setAccessible( true );
 		}
-		$current = $requested->getValue( null );
+		$current = $requested->getValue();
 		foreach ( $polyfills as $handle ) {
 			if ( ! isset( $current[ $handle ] ) ) {
 				$current[ $handle ] = array();

From 8c2906bcb6a6dd39f5b6408b74ae88aea605e671 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Fri, 6 Mar 2026 20:27:38 -0300
Subject: [PATCH 22/40] Add tests for polyfill registration in
 Dashboard::load_wp_build

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../tests/php/dashboard/Dashboard_Test.php    | 72 +++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php b/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
index d1d740927164..6e6fddf7e67b 100644
--- a/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
+++ b/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
@@ -7,6 +7,7 @@
 
 namespace Automattic\Jetpack\Forms\Dashboard;
 
+use Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills;
 use PHPUnit\Framework\Attributes\CoversClass;
 use WorDBless\BaseTestCase;
 
@@ -122,6 +123,77 @@ public function test_get_forms_admin_url_wp_build_with_tab() {
 		remove_filter( 'jetpack_forms_alpha', '__return_true' );
 	}
 
+	/**
+	 * Reset WP_Build_Polyfills static state between tests.
+	 */
+	private function reset_wp_build_polyfills() {
+		$ref = new \ReflectionClass( WP_Build_Polyfills::class );
+
+		$requested = $ref->getProperty( 'requested' );
+		$requested->setValue( null, array() );
+
+		$hooked = $ref->getProperty( 'hooked' );
+		$hooked->setValue( null, false );
+	}
+
+	/**
+	 * Test load_wp_build registers polyfills when on the wp-build admin page.
+	 */
+	public function test_load_wp_build_registers_polyfills_on_wpbuild_page() {
+		$_GET['page'] = Dashboard::FORMS_WPBUILD_ADMIN_SLUG;
+
+		Dashboard::load_wp_build();
+
+		$ref       = new \ReflectionClass( WP_Build_Polyfills::class );
+		$requested = $ref->getProperty( 'requested' );
+		$value     = $requested->getValue();
+
+		$expected_handles = array_merge( WP_Build_Polyfills::SCRIPT_HANDLES, WP_Build_Polyfills::MODULE_IDS );
+
+		foreach ( $expected_handles as $handle ) {
+			$this->assertArrayHasKey( $handle, $value, "Polyfill handle '$handle' should be registered." );
+			$this->assertContains( 'jetpack-forms', $value[ $handle ], "Consumer 'jetpack-forms' should be registered for '$handle'." );
+		}
+
+		$this->reset_wp_build_polyfills();
+		unset( $_GET['page'] );
+	}
+
+	/**
+	 * Test load_wp_build does not register polyfills when on a different admin page.
+	 */
+	public function test_load_wp_build_does_not_register_polyfills_on_other_page() {
+		$_GET['page'] = 'some-other-page';
+
+		Dashboard::load_wp_build();
+
+		$ref       = new \ReflectionClass( WP_Build_Polyfills::class );
+		$requested = $ref->getProperty( 'requested' );
+		$value     = $requested->getValue();
+
+		$this->assertEmpty( $value, 'No polyfills should be registered when on a different page.' );
+
+		$this->reset_wp_build_polyfills();
+		unset( $_GET['page'] );
+	}
+
+	/**
+	 * Test load_wp_build does not register polyfills when no page is set.
+	 */
+	public function test_load_wp_build_does_not_register_polyfills_without_page() {
+		unset( $_GET['page'] );
+
+		Dashboard::load_wp_build();
+
+		$ref       = new \ReflectionClass( WP_Build_Polyfills::class );
+		$requested = $ref->getProperty( 'requested' );
+		$value     = $requested->getValue();
+
+		$this->assertEmpty( $value, 'No polyfills should be registered when no page is set.' );
+
+		$this->reset_wp_build_polyfills();
+	}
+
 	/**
 	 * Test is_jetpack_forms_admin_page when get_current_screen is not available
 	 */

From a93581d04ad6f5e58a64b1ab1aca946b236f7d33 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Fri, 6 Mar 2026 20:57:26 -0300
Subject: [PATCH 23/40] Fix reflection setAccessible for PHP < 8.1 and store
 version threshold in static property

Add setAccessible(true) guards for PHP < 8.1 when accessing private
static properties via reflection in tests. Store wp_version_threshold
as a static property so multiple register() callers can raise it,
with the highest threshold winning.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../tests/php/dashboard/Dashboard_Test.php    | 27 ++++++++++++++++---
 .../src/class-wp-build-polyfills.php          | 20 ++++++++++++--
 .../tests/php/WP_Build_Polyfills_Test.php     |  6 +++++
 3 files changed, 48 insertions(+), 5 deletions(-)

diff --git a/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php b/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
index 6e6fddf7e67b..9fcb313438cb 100644
--- a/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
+++ b/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
@@ -130,10 +130,22 @@ private function reset_wp_build_polyfills() {
 		$ref = new \ReflectionClass( WP_Build_Polyfills::class );
 
 		$requested = $ref->getProperty( 'requested' );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$requested->setAccessible( true );
+		}
 		$requested->setValue( null, array() );
 
 		$hooked = $ref->getProperty( 'hooked' );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$hooked->setAccessible( true );
+		}
 		$hooked->setValue( null, false );
+
+		$threshold = $ref->getProperty( 'wp_version_threshold' );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$threshold->setAccessible( true );
+		}
+		$threshold->setValue( null, '7.0' );
 	}
 
 	/**
@@ -146,7 +158,10 @@ public function test_load_wp_build_registers_polyfills_on_wpbuild_page() {
 
 		$ref       = new \ReflectionClass( WP_Build_Polyfills::class );
 		$requested = $ref->getProperty( 'requested' );
-		$value     = $requested->getValue();
+		if ( PHP_VERSION_ID < 80100 ) {
+			$requested->setAccessible( true );
+		}
+		$value = $requested->getValue();
 
 		$expected_handles = array_merge( WP_Build_Polyfills::SCRIPT_HANDLES, WP_Build_Polyfills::MODULE_IDS );
 
@@ -169,7 +184,10 @@ public function test_load_wp_build_does_not_register_polyfills_on_other_page() {
 
 		$ref       = new \ReflectionClass( WP_Build_Polyfills::class );
 		$requested = $ref->getProperty( 'requested' );
-		$value     = $requested->getValue();
+		if ( PHP_VERSION_ID < 80100 ) {
+			$requested->setAccessible( true );
+		}
+		$value = $requested->getValue();
 
 		$this->assertEmpty( $value, 'No polyfills should be registered when on a different page.' );
 
@@ -187,7 +205,10 @@ public function test_load_wp_build_does_not_register_polyfills_without_page() {
 
 		$ref       = new \ReflectionClass( WP_Build_Polyfills::class );
 		$requested = $ref->getProperty( 'requested' );
-		$value     = $requested->getValue();
+		if ( PHP_VERSION_ID < 80100 ) {
+			$requested->setAccessible( true );
+		}
+		$value = $requested->getValue();
 
 		$this->assertEmpty( $value, 'No polyfills should be registered when no page is set.' );
 
diff --git a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
index 3e0e7fff607d..1d9e4149359e 100644
--- a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
+++ b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
@@ -42,12 +42,24 @@ class WP_Build_Polyfills {
 	 */
 	private static $hooked = false;
 
+	/**
+	 * The WordPress version below which force-replacements are applied.
+	 * When multiple consumers call register() with different thresholds,
+	 * the highest threshold wins (most conservative approach).
+	 *
+	 * @var string
+	 */
+	private static $wp_version_threshold = '7.0';
+
 	/**
 	 * Register polyfill scripts and modules.
 	 *
 	 * Call this early (e.g. during plugin load) — it hooks into wp_default_scripts
 	 * at priority 20 so Core (default) and Gutenberg (priority 10) register first.
 	 *
+	 * When multiple consumers call this method with different thresholds, the
+	 * highest threshold wins (most conservative — polyfills active on more versions).
+	 *
 	 * @param string   $consumer             A unique identifier for the consumer (e.g. plugin slug).
 	 * @param string[] $polyfills             List of polyfill handles/module IDs to register.
 	 *                                        Use class constants SCRIPT_HANDLES and MODULE_IDS for reference.
@@ -67,6 +79,10 @@ public static function register( $consumer, $polyfills, $wp_version_threshold =
 			}
 		}
 
+		if ( version_compare( $wp_version_threshold, self::$wp_version_threshold, '>' ) ) {
+			self::$wp_version_threshold = $wp_version_threshold;
+		}
+
 		if ( self::$hooked ) {
 			return;
 		}
@@ -78,8 +94,8 @@ public static function register( $consumer, $polyfills, $wp_version_threshold =
 
 		add_action(
 			'wp_default_scripts',
-			function ( $scripts ) use ( $build_dir, $base_file, $wp_version_threshold ) {
-				self::register_scripts( $scripts, $build_dir, $base_file, $wp_version_threshold );
+			function ( $scripts ) use ( $build_dir, $base_file ) {
+				self::register_scripts( $scripts, $build_dir, $base_file, self::$wp_version_threshold );
 				self::register_modules( $build_dir, $base_file );
 			},
 			20
diff --git a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
index 6d4454bdda8c..7636b5cb4956 100644
--- a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
+++ b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
@@ -87,6 +87,12 @@ public function tear_down() {
 		}
 		$hooked->setValue( null, false );
 
+		$threshold = new \ReflectionProperty( WP_Build_Polyfills::class, 'wp_version_threshold' );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$threshold->setAccessible( true );
+		}
+		$threshold->setValue( null, '7.0' );
+
 		$this->recursive_rmdir( $this->build_dir );
 
 		parent::tear_down();

From 03509a525cb560839bb2e285280c9bd33e99b43f Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Fri, 6 Mar 2026 21:14:42 -0300
Subject: [PATCH 24/40] Fix dynamic import regex to handle leading comments and
 add additionalAssets flag

Update preserve-dynamic-imports-loader regex to correctly handle
dynamic imports with leading block/line comments. Add additionalAssets
flag to processAssets tap for proper webpack 5 asset emission.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../preserve-dynamic-imports-loader.js                   | 9 +++++++--
 projects/packages/wp-build-polyfills/webpack.config.js   | 1 +
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js b/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js
index 0b5472b17346..93f3c9e8bcd5 100644
--- a/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js
+++ b/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js
@@ -13,10 +13,15 @@
  *
  * Only import() calls with variable arguments are affected. String-literal
  * imports like `import("`@wordpress`/a11y")` are left untouched so that webpack's
- * externals plugin can handle them normally.
+ * externals plugin can handle them normally. Dynamic imports with leading
+ * comments (e.g. `import(/* webpackChunkName: ... *\/ variable)`) are also
+ * handled correctly.
  * @param {string} source - The source code to process.
  * @return {string} - The processed source code.
  */
 module.exports = function preserveDynamicImports( source ) {
-	return source.replace( /\bimport\(\s*(?!['"`/])/g, 'import(/* webpackIgnore: true */ ' );
+	return source.replace(
+		/\bimport\(\s*(?!(?:\/\/[^\n]*\n|\/\*[\s\S]*?\*\/|\s)*['"`])/g,
+		'import(/* webpackIgnore: true */ '
+	);
 };
diff --git a/projects/packages/wp-build-polyfills/webpack.config.js b/projects/packages/wp-build-polyfills/webpack.config.js
index 14e3724245bc..e514291a663b 100644
--- a/projects/packages/wp-build-polyfills/webpack.config.js
+++ b/projects/packages/wp-build-polyfills/webpack.config.js
@@ -263,6 +263,7 @@ class PolyfillModulePlugin {
 				{
 					name: 'PolyfillModulePlugin',
 					stage: webpack.Compilation.PROCESS_ASSETS_STAGE_ANALYSE,
+					additionalAssets: true,
 				},
 				() => {
 					for ( const [ , entrypoint ] of compilation.entrypoints ) {

From c1ba42b4e1cd3ad7a32e5e5d1518124789a8be6a Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Fri, 6 Mar 2026 21:35:04 -0300
Subject: [PATCH 25/40] Fix ReDoS vulnerability in dynamic import regex

Replace the regex with exponential backtracking risk with a
callback-based approach that linearly scans past comments and
whitespace to find the first meaningful character.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../preserve-dynamic-imports-loader.js        | 30 +++++++++++++++----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js b/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js
index 93f3c9e8bcd5..13a9b36b8598 100644
--- a/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js
+++ b/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js
@@ -12,7 +12,7 @@
  * to such imports, telling webpack to leave them as-is.
  *
  * Only import() calls with variable arguments are affected. String-literal
- * imports like `import("`@wordpress`/a11y")` are left untouched so that webpack's
+ * imports like `import("@wordpress/a11y")` are left untouched so that webpack's
  * externals plugin can handle them normally. Dynamic imports with leading
  * comments (e.g. `import(/* webpackChunkName: ... *\/ variable)`) are also
  * handled correctly.
@@ -20,8 +20,28 @@
  * @return {string} - The processed source code.
  */
 module.exports = function preserveDynamicImports( source ) {
-	return source.replace(
-		/\bimport\(\s*(?!(?:\/\/[^\n]*\n|\/\*[\s\S]*?\*\/|\s)*['"`])/g,
-		'import(/* webpackIgnore: true */ '
-	);
+	return source.replace( /\bimport\(/g, ( match, offset ) => {
+		// Scan past whitespace and comments to find the first meaningful character.
+		let i = offset + match.length;
+		while ( i < source.length ) {
+			if ( source[ i ] === '/' && source[ i + 1 ] === '*' ) {
+				const end = source.indexOf( '*/', i + 2 );
+				i = end === -1 ? source.length : end + 2;
+			} else if ( source[ i ] === '/' && source[ i + 1 ] === '/' ) {
+				const end = source.indexOf( '\n', i + 2 );
+				i = end === -1 ? source.length : end + 1;
+			} else if ( /\s/.test( source[ i ] ) ) {
+				i++;
+			} else {
+				break;
+			}
+		}
+
+		// String-literal imports are left for webpack's externals plugin.
+		if ( i < source.length && /['"`]/.test( source[ i ] ) ) {
+			return match;
+		}
+
+		return 'import(/* webpackIgnore: true */ ';
+	} );
 };

From da1b44461d2ed0ccdfee797e1e550e60085bd9d1 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Fri, 6 Mar 2026 21:47:14 -0300
Subject: [PATCH 26/40] Address review feedback: docs, production-exclude, and
 test cleanup

- Fix backtick-split package name in loader doc comment
- Add preserve-dynamic-imports-loader.js to production-exclude
- Add wp-notices to PHP class docblock polyfill list
- Move test cleanup to tear_down() so state resets even on failure

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../tests/php/dashboard/Dashboard_Test.php      | 17 +++++++++--------
 .../packages/wp-build-polyfills/.gitattributes  |  1 +
 .../preserve-dynamic-imports-loader.js          |  2 +-
 .../src/class-wp-build-polyfills.php            |  2 +-
 4 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php b/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
index 9fcb313438cb..1238531b1528 100644
--- a/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
+++ b/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
@@ -19,6 +19,15 @@
 #[CoversClass( Dashboard::class )]
 class Dashboard_Test extends BaseTestCase {
 
+	/**
+	 * Clean up after each test.
+	 */
+	public function tear_down() {
+		$this->reset_wp_build_polyfills();
+		unset( $_GET['page'] );
+		parent::tear_down();
+	}
+
 	/**
 	 * Test get_forms_admin_url without tab parameter
 	 */
@@ -169,9 +178,6 @@ public function test_load_wp_build_registers_polyfills_on_wpbuild_page() {
 			$this->assertArrayHasKey( $handle, $value, "Polyfill handle '$handle' should be registered." );
 			$this->assertContains( 'jetpack-forms', $value[ $handle ], "Consumer 'jetpack-forms' should be registered for '$handle'." );
 		}
-
-		$this->reset_wp_build_polyfills();
-		unset( $_GET['page'] );
 	}
 
 	/**
@@ -190,9 +196,6 @@ public function test_load_wp_build_does_not_register_polyfills_on_other_page() {
 		$value = $requested->getValue();
 
 		$this->assertEmpty( $value, 'No polyfills should be registered when on a different page.' );
-
-		$this->reset_wp_build_polyfills();
-		unset( $_GET['page'] );
 	}
 
 	/**
@@ -211,8 +214,6 @@ public function test_load_wp_build_does_not_register_polyfills_without_page() {
 		$value = $requested->getValue();
 
 		$this->assertEmpty( $value, 'No polyfills should be registered when no page is set.' );
-
-		$this->reset_wp_build_polyfills();
 	}
 
 	/**
diff --git a/projects/packages/wp-build-polyfills/.gitattributes b/projects/packages/wp-build-polyfills/.gitattributes
index 725ae946a59d..a8a09c7553b9 100644
--- a/projects/packages/wp-build-polyfills/.gitattributes
+++ b/projects/packages/wp-build-polyfills/.gitattributes
@@ -18,3 +18,4 @@ phpunit.*.xml.dist  production-exclude
 .phpcs.dir.xml    production-exclude
 tests/**          production-exclude
 .phpcsignore      production-exclude
+preserve-dynamic-imports-loader.js  production-exclude
diff --git a/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js b/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js
index 13a9b36b8598..16094da8281a 100644
--- a/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js
+++ b/projects/packages/wp-build-polyfills/preserve-dynamic-imports-loader.js
@@ -6,7 +6,7 @@
  * "Cannot find module". This is because webpack can't statically determine what
  * module will be loaded at runtime.
  *
- * For packages like `@wordpress`/boot that rely on the browser's import map to
+ * For packages like `@wordpress/boot` that rely on the browser's import map to
  * resolve module IDs at runtime, these dynamic imports must be preserved as
  * native `import()` calls. This loader adds `webpackIgnore: true` magic comments
  * to such imports, telling webpack to leave them as-is.
diff --git a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
index 1d9e4149359e..f8ac3e88a1c4 100644
--- a/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
+++ b/projects/packages/wp-build-polyfills/src/class-wp-build-polyfills.php
@@ -2,7 +2,7 @@
 /**
  * Polyfill registration for Core packages not available in WordPress < 7.0.
  *
- * Conditionally registers wp-private-apis, wp-theme (classic scripts) and
+ * Conditionally registers wp-notices, wp-private-apis, wp-theme (classic scripts) and
  * `@wordpress/boot`, `@wordpress/route`, `@wordpress/a11y` (script modules)
  * ONLY when they are not already provided by Core or Gutenberg.
  *

From 74171db8878cb8686e6bcc4769f02fb91983db99 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 9 Mar 2026 21:39:33 -0300
Subject: [PATCH 27/40] Fix PolyfillModulePlugin to match wp-build asset output

The PolyfillModulePlugin was generating incorrect dependency metadata
compared to wp-build because it couldn't resolve transitive dependencies
and lacked dynamic import detection.

- Add @wordpress/admin-ui, icons, and lazy-editor as devDependencies so
  their package.json can be read at build time
- Check wpScript field: packages with neither wpScriptModuleExports nor
  wpScript are now bundled instead of incorrectly externalized
- Use parser importCall hook to detect dynamic imports, since webpack 5's
  ExternalsPlugin reports dependencyType 'esm' for both static and
  dynamic imports

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 pnpm-lock.yaml                                |  9 ++++
 .../packages/wp-build-polyfills/package.json  |  3 ++
 .../wp-build-polyfills/webpack.config.js      | 41 +++++++++++++++++--
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 0d12133943b0..8d0c33327687 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -4174,9 +4174,18 @@ importers:
       '@wordpress/a11y':
         specifier: ^4.40.0
         version: 4.41.0
+      '@wordpress/admin-ui':
+        specifier: ^1.9.0
+        version: 1.9.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
       '@wordpress/boot':
         specifier: ^0.7.1
         version: 0.7.1(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)
+      '@wordpress/icons':
+        specifier: ^11.7.0
+        version: 11.8.0(react@18.3.1)
+      '@wordpress/lazy-editor':
+        specifier: ^1.6.1
+        version: 1.7.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1)
       '@wordpress/notices':
         specifier: ^5.40.0
         version: 5.41.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)
diff --git a/projects/packages/wp-build-polyfills/package.json b/projects/packages/wp-build-polyfills/package.json
index aac1e9c783f5..8dc8ccbc806b 100644
--- a/projects/packages/wp-build-polyfills/package.json
+++ b/projects/packages/wp-build-polyfills/package.json
@@ -19,7 +19,10 @@
 	"devDependencies": {
 		"@automattic/jetpack-webpack-config": "workspace:*",
 		"@wordpress/a11y": "^4.40.0",
+		"@wordpress/admin-ui": "^1.9.0",
 		"@wordpress/boot": "^0.7.1",
+		"@wordpress/icons": "^11.7.0",
+		"@wordpress/lazy-editor": "^1.6.1",
 		"@wordpress/notices": "^5.40.0",
 		"@wordpress/private-apis": "^1.40.0",
 		"@wordpress/route": "^0.6.0",
diff --git a/projects/packages/wp-build-polyfills/webpack.config.js b/projects/packages/wp-build-polyfills/webpack.config.js
index e514291a663b..b865ce110c27 100644
--- a/projects/packages/wp-build-polyfills/webpack.config.js
+++ b/projects/packages/wp-build-polyfills/webpack.config.js
@@ -221,6 +221,31 @@ class PolyfillModulePlugin {
 		const scriptDeps = new Set();
 		const moduleDeps = new Map();
 
+		// Track dynamic import() requests via the parser so we can
+		// distinguish them from static imports in the externals callback
+		// (webpack 5's externals API reports 'esm' for both).
+		const dynamicImportRequests = new Set();
+		compiler.hooks.compilation.tap(
+			'PolyfillModulePlugin',
+			( compilation, { normalModuleFactory } ) => {
+				const handler = parser => {
+					parser.hooks.importCall.tap( 'PolyfillModulePlugin', expr => {
+						// expr.source is the argument to import(). For string
+						// literals, extract the value.
+						if ( expr.source && expr.source.type === 'Literal' ) {
+							dynamicImportRequests.add( expr.source.value );
+						}
+					} );
+				};
+				normalModuleFactory.hooks.parser
+					.for( 'javascript/auto' )
+					.tap( 'PolyfillModulePlugin', handler );
+				normalModuleFactory.hooks.parser
+					.for( 'javascript/esm' )
+					.tap( 'PolyfillModulePlugin', handler );
+			}
+		);
+
 		// Register externals.
 		new webpack.ExternalsPlugin( 'import', ( { request }, callback ) => {
 			// Don't externalize the package being polyfilled.
@@ -236,12 +261,22 @@ class PolyfillModulePlugin {
 
 				// Prefer script module for ESM builds.
 				if ( pkg && hasScriptModuleExport( pkg ) ) {
-					moduleDeps.set( request, 'static' );
+					const kind = dynamicImportRequests.has( request ) ? 'dynamic' : 'static';
+					if ( kind === 'static' || ! moduleDeps.has( request ) ) {
+						moduleDeps.set( request, kind );
+					}
 					return callback( null, `import ${ request }` );
 				}
 
-				// Classic script (or unresolvable — default to classic since
-				// most @wordpress/* packages are classic scripts).
+				// If package is resolved and has neither wpScriptModuleExports
+				// nor wpScript, let webpack bundle it (e.g. @wordpress/admin-ui,
+				// @wordpress/icons).
+				if ( pkg && ! pkg.wpScript ) {
+					return callback();
+				}
+
+				// Classic script (includes unresolvable packages, which default
+				// to classic since most @wordpress/* packages are classic scripts).
 				scriptDeps.add( `wp-${ shortName }` );
 				return callback( null, `var wp.${ camelCaseDash( shortName ) }` );
 			}

From 2af1c6a9610cb720062cd728c7a728968d1142da Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 9 Mar 2026 21:40:33 -0300
Subject: [PATCH 28/40] Add automatic boot module asset proxy for wp-build page
 consumers

When wp-build removes the boot module bundling, page templates will
reference a missing asset file. This adds a proxy PHP file to the
polyfills package that resolves the asset data via ReflectionClass,
and auto-detection in the monorepo CLI build that copies it to the
expected location for any package with wp-build pages.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../src/boot-module-asset-proxy.php           | 35 ++++++++++++
 tools/cli/commands/build.js                   | 53 +++++++++++++++++++
 2 files changed, 88 insertions(+)
 create mode 100644 projects/packages/wp-build-polyfills/src/boot-module-asset-proxy.php

diff --git a/projects/packages/wp-build-polyfills/src/boot-module-asset-proxy.php b/projects/packages/wp-build-polyfills/src/boot-module-asset-proxy.php
new file mode 100644
index 000000000000..755c60c2d7a2
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/src/boot-module-asset-proxy.php
@@ -0,0 +1,35 @@
+<?php
+/**
+ * Boot module asset proxy for wp-build page consumers.
+ *
+ * When wp-build generates page templates, they reference a boot module asset
+ * file at a hardcoded relative path (build/modules/boot/index.min.asset.php).
+ * This proxy file is copied to that location by the monorepo build tooling,
+ * and resolves the real asset data from the wp-build-polyfills package
+ * regardless of where it is installed (vendor/ or jetpack_vendor/).
+ *
+ * @package automattic/jetpack-wp-build-polyfills
+ */
+
+// phpcs:ignore Universal.Files.SeparateFunctionsFromOO.Mixed -- This is not a class file.
+
+$class_name = 'Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills';
+
+if ( ! class_exists( $class_name ) ) {
+	return array(
+		'dependencies' => array(),
+		'version'      => '',
+	);
+}
+
+$ref        = new ReflectionClass( $class_name );
+$asset_file = dirname( $ref->getFileName(), 2 ) . '/build/modules/boot/index.asset.php';
+
+if ( ! file_exists( $asset_file ) ) {
+	return array(
+		'dependencies' => array(),
+		'version'      => '',
+	);
+}
+
+return require $asset_file;
diff --git a/tools/cli/commands/build.js b/tools/cli/commands/build.js
index b29022222851..bc1980ead595 100644
--- a/tools/cli/commands/build.js
+++ b/tools/cli/commands/build.js
@@ -595,6 +595,56 @@ async function checkCollisions( basedir ) {
 	return [ ...collisions ];
 }
 
+/**
+ * Provide the boot module asset proxy for packages using wp-build pages.
+ *
+ * When wp-build generates page templates, they reference a boot module asset
+ * file at build/modules/boot/index.min.asset.php. If the package depends on
+ * jetpack-wp-build-polyfills and has wp-build pages, this function copies the
+ * proxy file from the polyfills package to the expected location.
+ *
+ * @param {object} t - Task object.
+ */
+async function provideBootAssetProxy( t ) {
+	const pagesDir = npath.join( t.cwd, 'build', 'pages' );
+	const targetFile = npath.join( t.cwd, 'build', 'modules', 'boot', 'index.min.asset.php' );
+
+	// Only act if the package has wp-build pages and the file is missing.
+	if ( ! ( await fsExists( pagesDir ) ) || ( await fsExists( targetFile ) ) ) {
+		return;
+	}
+
+	// Look for the proxy in jetpack_vendor (production) or vendor (dev).
+	const candidates = [
+		npath.join(
+			t.cwd,
+			'jetpack_vendor',
+			'automattic',
+			'jetpack-wp-build-polyfills',
+			'src',
+			'boot-module-asset-proxy.php'
+		),
+		npath.join(
+			t.cwd,
+			'vendor',
+			'automattic',
+			'jetpack-wp-build-polyfills',
+			'src',
+			'boot-module-asset-proxy.php'
+		),
+	];
+	const proxySource = (
+		await Promise.all( candidates.map( f => fsExists( f ).then( ok => ok && f ) ) )
+	).find( Boolean );
+	if ( ! proxySource ) {
+		return;
+	}
+
+	await fs.mkdir( npath.dirname( targetFile ), { recursive: true } );
+	await fs.copyFile( proxySource, targetFile );
+	await t.output( 'Provided boot module asset proxy from wp-build-polyfills\n' );
+}
+
 /**
  * Build a project.
  *
@@ -796,6 +846,9 @@ async function buildProject( t ) {
 		} );
 	}
 
+	// Provide the boot module asset proxy for packages using wp-build pages.
+	await provideBootAssetProxy( t );
+
 	// If we're not mirroring, the build is done. Mirroring has a bunch of stuff to do yet.
 	if ( ! t.argv.forMirrors ) {
 		return;

From 1d35705616c6d130d1c66eb4af680f2ce03b5ef0 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 9 Mar 2026 22:01:02 -0300
Subject: [PATCH 29/40] Clear dependency tracking sets between compilations in
 watch mode

The PolyfillModulePlugin's scriptDeps, moduleDeps, and
dynamicImportRequests collections were never cleared between
compilations, causing stale dependencies to accumulate in watch mode.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 projects/packages/wp-build-polyfills/webpack.config.js | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/projects/packages/wp-build-polyfills/webpack.config.js b/projects/packages/wp-build-polyfills/webpack.config.js
index b865ce110c27..e53db9dff82f 100644
--- a/projects/packages/wp-build-polyfills/webpack.config.js
+++ b/projects/packages/wp-build-polyfills/webpack.config.js
@@ -228,6 +228,11 @@ class PolyfillModulePlugin {
 		compiler.hooks.compilation.tap(
 			'PolyfillModulePlugin',
 			( compilation, { normalModuleFactory } ) => {
+				// Clear stale deps from previous compilations (watch mode).
+				scriptDeps.clear();
+				moduleDeps.clear();
+				dynamicImportRequests.clear();
+
 				const handler = parser => {
 					parser.hooks.importCall.tap( 'PolyfillModulePlugin', expr => {
 						// expr.source is the argument to import(). For string

From 4933b7baf031a0b8da878b48cdd0df02289a030e Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 9 Mar 2026 22:06:32 -0300
Subject: [PATCH 30/40] Document boot module asset proxy in wp-build-polyfills
 README

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 projects/packages/wp-build-polyfills/README.md | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/projects/packages/wp-build-polyfills/README.md b/projects/packages/wp-build-polyfills/README.md
index c99d0f9e7992..f3dbdde56afc 100644
--- a/projects/packages/wp-build-polyfills/README.md
+++ b/projects/packages/wp-build-polyfills/README.md
@@ -63,6 +63,14 @@ The version threshold for force-replacements can be overridden with a third para
 WP_Build_Polyfills::register( 'my-plugin', array( 'wp-notices' ), '7.1' );
 ```
 
+## Boot module asset proxy
+
+Packages that use `@wordpress/build` to generate pages get a hardcoded reference to `build/modules/boot/index.min.asset.php` in the generated page templates. This file provides the classic script dependencies and version hash needed to bootstrap the page.
+
+When `@wordpress/build` stops bundling the boot module (as planned in upcoming Gutenberg changes), this asset file will no longer be generated. The polyfills package ships a proxy file (`src/boot-module-asset-proxy.php`) that resolves the asset data from this package's build output at runtime, using `ReflectionClass` to locate the package regardless of install path (`vendor/` or `jetpack_vendor/`).
+
+The Jetpack monorepo CLI (`jetpack build`) automatically copies this proxy to the expected location (`build/modules/boot/index.min.asset.php`) after building any package that has `build/pages/` and depends on this package. No per-consumer configuration is needed.
+
 ## Development
 
 ```bash

From 6da6394438c8ba6a81c95245f4148110398a6244 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 9 Mar 2026 22:09:12 -0300
Subject: [PATCH 31/40] Add tests for boot module asset proxy

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../tests/php/WP_Build_Polyfills_Test.php     | 60 +++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
index 7636b5cb4956..aef4678334e8 100644
--- a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
+++ b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
@@ -496,6 +496,66 @@ public function test_get_consumers_tracks_polyfill_consumers() {
 		$this->assertArrayNotHasKey( 'wp-private-apis', $consumers );
 	}
 
+	// ── Boot module asset proxy tests ─────────────────────────────────────────
+
+	/**
+	 * Test that the boot asset proxy returns the real asset data when the class
+	 * is loaded and the build asset file exists.
+	 */
+	public function test_boot_asset_proxy_returns_real_asset_data() {
+		$package_root = dirname( __DIR__, 2 );
+		$asset_file   = $package_root . '/build/modules/boot/index.asset.php';
+
+		if ( ! file_exists( $asset_file ) ) {
+			$this->markTestSkipped( 'Build asset file not present; run build first.' );
+		}
+
+		$proxy_file = $package_root . '/src/boot-module-asset-proxy.php';
+		$asset      = require $proxy_file;
+
+		$this->assertIsArray( $asset );
+		$this->assertArrayHasKey( 'dependencies', $asset );
+		$this->assertArrayHasKey( 'version', $asset );
+		$this->assertIsArray( $asset['dependencies'] );
+		$this->assertNotEmpty( $asset['version'] );
+	}
+
+	/**
+	 * Test that the boot asset proxy returns fallback data when the build
+	 * asset file does not exist.
+	 *
+	 * Temporarily renames the real asset file, requires the proxy (which uses
+	 * ReflectionClass to find the build dir), then restores the original.
+	 */
+	public function test_boot_asset_proxy_returns_fallback_when_asset_missing() {
+		$package_root = dirname( __DIR__, 2 );
+		$asset_file   = $package_root . '/build/modules/boot/index.asset.php';
+		$backup_file  = $asset_file . '.bak';
+
+		// Skip if the build hasn't run (asset file doesn't exist).
+		if ( ! file_exists( $asset_file ) ) {
+			$this->markTestSkipped( 'Build asset file not present; run build first.' );
+		}
+
+		rename( $asset_file, $backup_file ); // phpcs:ignore WordPress.WP.AlternativeFunctions.rename_rename
+
+		try {
+			// The proxy file uses `require` internally, but PHP caches the
+			// return value per file path. Use a fresh include via a wrapper
+			// to avoid the cache.
+			$proxy_file = $package_root . '/src/boot-module-asset-proxy.php';
+			$asset      = ( static function ( $file ) {
+				return require $file;
+			} )( $proxy_file );
+
+			$this->assertIsArray( $asset );
+			$this->assertSame( array(), $asset['dependencies'] );
+			$this->assertSame( '', $asset['version'] );
+		} finally {
+			rename( $backup_file, $asset_file ); // phpcs:ignore WordPress.WP.AlternativeFunctions.rename_rename
+		}
+	}
+
 	/**
 	 * Test that only requested polyfills are registered.
 	 */

From 3f71bf80518a3ce5e631ceb9b30558cee8096ee3 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 9 Mar 2026 22:43:23 -0300
Subject: [PATCH 32/40] Make boot asset proxy tests run without build artifacts
 and warn on missing proxy

- Create fixture asset files in tests instead of skipping when build
  hasn't run, ensuring deterministic execution in all environments.
- Emit a warning in provideBootAssetProxy() when build/pages exists
  but the proxy source is not found.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../tests/php/WP_Build_Polyfills_Test.php     | 47 +++++++++++++------
 tools/cli/commands/build.js                   |  6 +++
 2 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
index aef4678334e8..76b611035ab6 100644
--- a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
+++ b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
@@ -505,19 +505,36 @@ public function test_get_consumers_tracks_polyfill_consumers() {
 	public function test_boot_asset_proxy_returns_real_asset_data() {
 		$package_root = dirname( __DIR__, 2 );
 		$asset_file   = $package_root . '/build/modules/boot/index.asset.php';
+		$created      = false;
 
+		// Create a fixture asset file if the build hasn't run, so the test
+		// executes deterministically regardless of environment.
 		if ( ! file_exists( $asset_file ) ) {
-			$this->markTestSkipped( 'Build asset file not present; run build first.' );
+			$dir = dirname( $asset_file );
+			if ( ! is_dir( $dir ) ) {
+				mkdir( $dir, 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
+			}
+			file_put_contents( // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_file_put_contents
+				$asset_file,
+				"<?php\nreturn array( 'dependencies' => array( 'wp-i18n' ), 'version' => 'fixture-1.0' );\n"
+			);
+			$created = true;
 		}
 
-		$proxy_file = $package_root . '/src/boot-module-asset-proxy.php';
-		$asset      = require $proxy_file;
+		try {
+			$proxy_file = $package_root . '/src/boot-module-asset-proxy.php';
+			$asset      = require $proxy_file;
 
-		$this->assertIsArray( $asset );
-		$this->assertArrayHasKey( 'dependencies', $asset );
-		$this->assertArrayHasKey( 'version', $asset );
-		$this->assertIsArray( $asset['dependencies'] );
-		$this->assertNotEmpty( $asset['version'] );
+			$this->assertIsArray( $asset );
+			$this->assertArrayHasKey( 'dependencies', $asset );
+			$this->assertArrayHasKey( 'version', $asset );
+			$this->assertIsArray( $asset['dependencies'] );
+			$this->assertNotEmpty( $asset['version'] );
+		} finally {
+			if ( $created ) {
+				unlink( $asset_file ); // phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink
+			}
+		}
 	}
 
 	/**
@@ -531,14 +548,14 @@ public function test_boot_asset_proxy_returns_fallback_when_asset_missing() {
 		$package_root = dirname( __DIR__, 2 );
 		$asset_file   = $package_root . '/build/modules/boot/index.asset.php';
 		$backup_file  = $asset_file . '.bak';
+		$backed_up    = false;
 
-		// Skip if the build hasn't run (asset file doesn't exist).
-		if ( ! file_exists( $asset_file ) ) {
-			$this->markTestSkipped( 'Build asset file not present; run build first.' );
+		// Ensure the asset file is absent — back it up if a build has run.
+		if ( file_exists( $asset_file ) ) {
+			rename( $asset_file, $backup_file ); // phpcs:ignore WordPress.WP.AlternativeFunctions.rename_rename
+			$backed_up = true;
 		}
 
-		rename( $asset_file, $backup_file ); // phpcs:ignore WordPress.WP.AlternativeFunctions.rename_rename
-
 		try {
 			// The proxy file uses `require` internally, but PHP caches the
 			// return value per file path. Use a fresh include via a wrapper
@@ -552,7 +569,9 @@ public function test_boot_asset_proxy_returns_fallback_when_asset_missing() {
 			$this->assertSame( array(), $asset['dependencies'] );
 			$this->assertSame( '', $asset['version'] );
 		} finally {
-			rename( $backup_file, $asset_file ); // phpcs:ignore WordPress.WP.AlternativeFunctions.rename_rename
+			if ( $backed_up ) {
+				rename( $backup_file, $asset_file ); // phpcs:ignore WordPress.WP.AlternativeFunctions.rename_rename
+			}
 		}
 	}
 
diff --git a/tools/cli/commands/build.js b/tools/cli/commands/build.js
index bc1980ead595..cd7e18f7c5cf 100644
--- a/tools/cli/commands/build.js
+++ b/tools/cli/commands/build.js
@@ -637,6 +637,12 @@ async function provideBootAssetProxy( t ) {
 		await Promise.all( candidates.map( f => fsExists( f ).then( ok => ok && f ) ) )
 	).find( Boolean );
 	if ( ! proxySource ) {
+		await t.output(
+			chalk.yellow(
+				'Warning: build/pages exists but wp-build-polyfills boot module asset proxy was not found.\n'
+			) +
+				chalk.yellow( 'Ensure automattic/jetpack-wp-build-polyfills is installed via Composer.\n' )
+		);
 		return;
 	}
 

From 1c60ad6e1dd5f458ba102bca26a295e542c575ad Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Tue, 10 Mar 2026 20:10:38 -0300
Subject: [PATCH 33/40] update wp-build

---
 pnpm-lock.yaml                       | 10 +++++-----
 projects/packages/forms/package.json |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 8d0c33327687..30ca2b24dcb5 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -2598,8 +2598,8 @@ importers:
         specifier: 6.41.0
         version: 6.41.0
       '@wordpress/build':
-        specifier: 0.8.0
-        version: 0.8.0(@babel/core@7.29.0)(@wordpress/boot@0.8.0(@types/react-dom@18.3.7(@types/react@18.3.28))(@types/react@18.3.28)(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1))(@wordpress/route@0.7.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1))(@wordpress/theme@0.8.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1))(browserslist@4.28.1)
+        specifier: 0.10.1-next.v.202603102151.0
+        version: 0.10.1-next.v.202603102151.0(@babel/core@7.29.0)(@wordpress/boot@0.8.0(@types/react-dom@18.3.7(@types/react@18.3.28))(@types/react@18.3.28)(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1))(@wordpress/route@0.7.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1))(@wordpress/theme@0.8.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1))(browserslist@4.28.1)
       '@wordpress/date':
         specifier: 5.41.0
         version: 5.41.0
@@ -10547,8 +10547,8 @@ packages:
     resolution: {integrity: sha512-Cp9JcjdL6ZYVNUGgXR/XOO9Fueb3i0dzpvdpC1pB/iJldiQWYRPZ7LMCaJrwprG92/AfuU68BaR5CwTwrSN5tA==}
     engines: {node: '>=18.12.0', npm: '>=8.19.2'}
 
-  '@wordpress/build@0.8.0':
-    resolution: {integrity: sha512-703tl7VoGLNtAAEdVzLVWAVkid6jMh6tGZgD1NNH/2mWy+FXmOv/m5NxeoD+FD6Je3d93ladA+ln83ZcPH7Mzw==}
+  '@wordpress/build@0.10.1-next.v.202603102151.0':
+    resolution: {integrity: sha512-uk7LIvouTnrMTgFnvdGvS/BhVjBkkL5fwnr8JCyRud4AObAzsJRixu+ZG//T6SNLdJuiLdF5zihMBKCEqVvN8g==}
     engines: {node: '>=20.10.0', npm: '>=10.2.3'}
     hasBin: true
     peerDependencies:
@@ -24164,7 +24164,7 @@ snapshots:
 
   '@wordpress/browserslist-config@6.41.0': {}
 
-  '@wordpress/build@0.8.0(@babel/core@7.29.0)(@wordpress/boot@0.8.0(@types/react-dom@18.3.7(@types/react@18.3.28))(@types/react@18.3.28)(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1))(@wordpress/route@0.7.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1))(@wordpress/theme@0.8.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1))(browserslist@4.28.1)':
+  '@wordpress/build@0.10.1-next.v.202603102151.0(@babel/core@7.29.0)(@wordpress/boot@0.8.0(@types/react-dom@18.3.7(@types/react@18.3.28))(@types/react@18.3.28)(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1))(@wordpress/route@0.7.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1))(@wordpress/theme@0.8.0(react-dom@18.3.1(react@18.3.1))(react@18.3.1)(stylelint@16.26.1))(browserslist@4.28.1)':
     dependencies:
       '@emotion/babel-plugin': 11.13.5
       autoprefixer: 10.4.27(postcss@8.5.6)
diff --git a/projects/packages/forms/package.json b/projects/packages/forms/package.json
index c562b692d7ec..a1ec8492247c 100644
--- a/projects/packages/forms/package.json
+++ b/projects/packages/forms/package.json
@@ -112,7 +112,7 @@
 		"@typescript/native-preview": "7.0.0-dev.20260225.1",
 		"@wordpress/api-fetch": "7.41.0",
 		"@wordpress/browserslist-config": "6.41.0",
-		"@wordpress/build": "0.8.0",
+		"@wordpress/build": "0.10.1-next.v.202603102151.0",
 		"@wordpress/date": "5.41.0",
 		"autoprefixer": "10.4.20",
 		"browserslist": "^4.24.0",

From 019f1bc434d92d54fca805d05a08a3df8832e541 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Tue, 10 Mar 2026 20:17:41 -0300
Subject: [PATCH 34/40] remove unnecessary class_exists check

---
 .../forms/src/dashboard/class-dashboard.php     | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/projects/packages/forms/src/dashboard/class-dashboard.php b/projects/packages/forms/src/dashboard/class-dashboard.php
index 46d68d454f42..f4e0129a2fed 100644
--- a/projects/packages/forms/src/dashboard/class-dashboard.php
+++ b/projects/packages/forms/src/dashboard/class-dashboard.php
@@ -12,6 +12,7 @@
 use Automattic\Jetpack\Connection\Initial_State as Connection_Initial_State;
 use Automattic\Jetpack\Forms\ContactForm\Contact_Form_Plugin;
 use Automattic\Jetpack\Tracking;
+use Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills;
 
 if ( ! defined( 'ABSPATH' ) ) {
 	exit( 0 );
@@ -41,15 +42,13 @@ public static function load_wp_build() {
 			}
 
 			// Register polyfills for WP < 7.0 (must run before build.php).
-			if ( class_exists( \Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::class ) ) {
-				\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::register(
-					'jetpack-forms',
-					array_merge(
-						\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::SCRIPT_HANDLES,
-						\Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills::MODULE_IDS
-					)
-				);
-			}
+			WP_Build_Polyfills::register(
+				'jetpack-forms',
+				array_merge(
+					WP_Build_Polyfills::SCRIPT_HANDLES,
+					WP_Build_Polyfills::MODULE_IDS
+				)
+			);
 
 			$wp_build_index = dirname( __DIR__, 2 ) . '/build/build.php';
 

From 0a302ccf68dbba922b1cb4ebef44e77de139f8c0 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Fri, 13 Mar 2026 17:57:29 -0300
Subject: [PATCH 35/40] Improve wp-build-polyfills test setup and phpcs
 configuration

Add tests/.phpcs.dir.xml with Jetpack-Tests ruleset to eliminate
inline phpcs:ignore comments. Use secure atomic mkdir for temp
directory creation to prevent symlink race conditions. Fix inaccurate
docblock on request_polyfills helper.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../wp-build-polyfills/tests/.phpcs.dir.xml   |  4 +
 .../tests/php/WP_Build_Polyfills_Test.php     | 94 +++++++++----------
 2 files changed, 49 insertions(+), 49 deletions(-)
 create mode 100644 projects/packages/wp-build-polyfills/tests/.phpcs.dir.xml

diff --git a/projects/packages/wp-build-polyfills/tests/.phpcs.dir.xml b/projects/packages/wp-build-polyfills/tests/.phpcs.dir.xml
new file mode 100644
index 000000000000..46951fe77b37
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/tests/.phpcs.dir.xml
@@ -0,0 +1,4 @@
+<?xml version="1.0"?>
+<ruleset>
+	<rule ref="Jetpack-Tests" />
+</ruleset>
diff --git a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
index 76b611035ab6..f91e0895cb8a 100644
--- a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
+++ b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
@@ -1,10 +1,4 @@
-<?php // phpcs:ignore WordPress.Files.FileName.InvalidClassFileName
-/**
- * Tests for WP_Build_Polyfills.
- *
- * @package automattic/jetpack-wp-build-polyfills
- */
-
+<?php
 namespace Automattic\Jetpack\WP_Build_Polyfills\Tests;
 
 use Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills;
@@ -20,7 +14,7 @@ class WP_Build_Polyfills_Test extends BaseTestCase {
 	/**
 	 * Temporary build directory for fake asset files.
 	 *
-	 * @var string
+	 * @var ?string
 	 */
 	private $build_dir;
 
@@ -42,18 +36,32 @@ class WP_Build_Polyfills_Test extends BaseTestCase {
 	 * Set up test fixtures.
 	 *
 	 * @before
+	 * @throws \RuntimeException If a temporary directory cannot be created.
 	 */
 	#[Before]
 	public function set_up() {
 		parent::set_up();
 
-		$this->build_dir = sys_get_temp_dir() . '/wp-build-polyfills-test-' . uniqid();
-		mkdir( $this->build_dir . '/scripts/notices', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
-		mkdir( $this->build_dir . '/scripts/private-apis', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
-		mkdir( $this->build_dir . '/scripts/theme', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
-		mkdir( $this->build_dir . '/modules/boot', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
-		mkdir( $this->build_dir . '/modules/route', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
-		mkdir( $this->build_dir . '/modules/a11y', 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
+		$this->build_dir = null;
+		$base            = sys_get_temp_dir() . DIRECTORY_SEPARATOR . 'wp-build-polyfills-test-';
+		for ( $i = 0; $i < 1000; $i++ ) {
+			$tmpdir = $base . uniqid();
+			// Atomic mkdir prevents symlink race (TOCTOU).
+			if ( @mkdir( $tmpdir, 0700 ) ) { // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged
+				$this->build_dir = $tmpdir;
+				break;
+			}
+		}
+		if ( null === $this->build_dir ) {
+			throw new \RuntimeException( 'Failed to create temporary directory' );
+		}
+
+		mkdir( $this->build_dir . '/scripts/notices', 0755, true );
+		mkdir( $this->build_dir . '/scripts/private-apis', 0755, true );
+		mkdir( $this->build_dir . '/scripts/theme', 0755, true );
+		mkdir( $this->build_dir . '/modules/boot', 0755, true );
+		mkdir( $this->build_dir . '/modules/route', 0755, true );
+		mkdir( $this->build_dir . '/modules/a11y', 0755, true );
 
 		$this->original_wp_version        = $GLOBALS['wp_version'];
 		$this->original_wp_script_modules = $GLOBALS['wp_script_modules'] ?? null;
@@ -66,13 +74,11 @@ public function set_up() {
 	 */
 	#[After]
 	public function tear_down() {
-		$GLOBALS['wp_version'] = $this->original_wp_version; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
-
+		$GLOBALS['wp_version'] = $this->original_wp_version;
 		if ( null === $this->original_wp_script_modules ) {
 			unset( $GLOBALS['wp_script_modules'] );
 		} else {
-			$GLOBALS['wp_script_modules'] = $this->original_wp_script_modules; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
-		}
+			$GLOBALS['wp_script_modules'] = $this->original_wp_script_modules;      }
 
 		// Reset static state.
 		$requested = new \ReflectionProperty( WP_Build_Polyfills::class, 'requested' );
@@ -114,9 +120,8 @@ private function create_asset_file( $path, $deps = array(), $version = '1.0.0',
 			),
 			$extra
 		);
-		$contents = '<?php return ' . var_export( $data, true ) . ";\n"; // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_var_export
-		file_put_contents( $this->build_dir . '/' . $path, $contents ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_file_put_contents
-	}
+		$contents = '<?php return ' . var_export( $data, true ) . ";\n";
+		file_put_contents( $this->build_dir . '/' . $path, $contents ); }
 
 	/**
 	 * Create a WP_Scripts instance with polyfill handles removed.
@@ -137,9 +142,9 @@ private function create_clean_scripts() {
 	/**
 	 * Request all available polyfills for a test consumer.
 	 *
-	 * Populates the static $requested property so register_scripts/register_modules
-	 * will process all handles. Uses register() but prevents the hook from firing
-	 * by resetting $hooked afterwards.
+	 * Populates the static $requested property via reflection so
+	 * register_scripts/register_modules will process all handles,
+	 * without triggering the wp_default_scripts hook.
 	 *
 	 * @param string[] $polyfills Optional specific polyfills to request. Defaults to all.
 	 */
@@ -242,13 +247,10 @@ private function recursive_rmdir( $dir ) {
 		);
 		foreach ( $items as $item ) {
 			if ( $item->isDir() ) {
-				rmdir( $item->getRealPath() ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_rmdir
-			} else {
-				unlink( $item->getRealPath() ); // phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink
-			}
+				rmdir( $item->getRealPath() );          } else {
+				unlink( $item->getRealPath() );         }
 		}
-		rmdir( $dir ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_rmdir
-	}
+		rmdir( $dir );  }
 
 	/**
 	 * Test that all scripts are registered when all asset files exist.
@@ -313,7 +315,7 @@ public function test_register_scripts_skips_wp_theme_when_already_registered() {
 	 * Test that wp-notices is force-replaced on WP < 7.0.
 	 */
 	public function test_register_scripts_force_replaces_wp_notices_on_old_wp() {
-		$GLOBALS['wp_version'] = '6.8'; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+		$GLOBALS['wp_version'] = '6.8';
 		$this->create_asset_file( 'scripts/notices/index.asset.php', array(), '9.9.9' );
 
 		$scripts = $this->create_clean_scripts();
@@ -330,7 +332,7 @@ public function test_register_scripts_force_replaces_wp_notices_on_old_wp() {
 	 * Test that wp-private-apis is force-replaced on WP < 7.0.
 	 */
 	public function test_register_scripts_force_replaces_wp_private_apis_on_old_wp() {
-		$GLOBALS['wp_version'] = '6.8'; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+		$GLOBALS['wp_version'] = '6.8';
 		$this->create_asset_file( 'scripts/private-apis/index.asset.php', array(), '9.9.9' );
 
 		$scripts = $this->create_clean_scripts();
@@ -347,7 +349,7 @@ public function test_register_scripts_force_replaces_wp_private_apis_on_old_wp()
 	 * Test that neither wp-notices nor wp-private-apis is force-replaced on WP >= 7.0.
 	 */
 	public function test_register_scripts_does_not_force_replace_on_wp_7() {
-		$GLOBALS['wp_version'] = '7.0'; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+		$GLOBALS['wp_version'] = '7.0';
 		$this->create_asset_file( 'scripts/notices/index.asset.php', array(), '9.9.9' );
 		$this->create_asset_file( 'scripts/private-apis/index.asset.php', array(), '9.9.9' );
 
@@ -368,7 +370,7 @@ public function test_register_scripts_does_not_force_replace_on_wp_7() {
 	 * Test that force scripts register fine even when not pre-existing.
 	 */
 	public function test_register_scripts_force_registers_fresh_on_old_wp() {
-		$GLOBALS['wp_version'] = '6.8'; // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
+		$GLOBALS['wp_version'] = '6.8';
 		$this->create_asset_file( 'scripts/notices/index.asset.php', array(), '9.9.9' );
 		$this->create_asset_file( 'scripts/private-apis/index.asset.php', array(), '8.8.8' );
 
@@ -403,8 +405,7 @@ public function test_register_scripts_has_correct_dependencies() {
 	 */
 	public function test_register_modules_registers_all_when_asset_files_exist() {
 		// Reset the script modules global so we start fresh.
-		$GLOBALS['wp_script_modules'] = new \WP_Script_Modules(); // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
-
+		$GLOBALS['wp_script_modules'] = new \WP_Script_Modules();
 		$this->create_asset_file(
 			'modules/boot/index.asset.php',
 			array(),
@@ -435,8 +436,7 @@ public function test_register_modules_registers_all_when_asset_files_exist() {
 	 * Test that no modules are registered when asset files are missing.
 	 */
 	public function test_register_modules_skips_when_asset_files_missing() {
-		$GLOBALS['wp_script_modules'] = new \WP_Script_Modules(); // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
-
+		$GLOBALS['wp_script_modules'] = new \WP_Script_Modules();
 		$this->invoke_register_modules();
 
 		$this->assertFalse( $this->is_module_registered( '@wordpress/boot' ) );
@@ -448,8 +448,7 @@ public function test_register_modules_skips_when_asset_files_missing() {
 	 * Test that pre-registered modules are not replaced (first-wins semantics).
 	 */
 	public function test_register_modules_does_not_replace_existing() {
-		$GLOBALS['wp_script_modules'] = new \WP_Script_Modules(); // phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited
-
+		$GLOBALS['wp_script_modules'] = new \WP_Script_Modules();
 		// Pre-register @wordpress/boot.
 		wp_register_script_module( '@wordpress/boot', 'https://example.com/core-boot.js', array(), '1.0.0-core' );
 
@@ -512,9 +511,8 @@ public function test_boot_asset_proxy_returns_real_asset_data() {
 		if ( ! file_exists( $asset_file ) ) {
 			$dir = dirname( $asset_file );
 			if ( ! is_dir( $dir ) ) {
-				mkdir( $dir, 0755, true ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_mkdir
-			}
-			file_put_contents( // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_file_put_contents
+				mkdir( $dir, 0755, true );          }
+			file_put_contents(
 				$asset_file,
 				"<?php\nreturn array( 'dependencies' => array( 'wp-i18n' ), 'version' => 'fixture-1.0' );\n"
 			);
@@ -532,8 +530,7 @@ public function test_boot_asset_proxy_returns_real_asset_data() {
 			$this->assertNotEmpty( $asset['version'] );
 		} finally {
 			if ( $created ) {
-				unlink( $asset_file ); // phpcs:ignore WordPress.WP.AlternativeFunctions.unlink_unlink
-			}
+				unlink( $asset_file );          }
 		}
 	}
 
@@ -552,7 +549,7 @@ public function test_boot_asset_proxy_returns_fallback_when_asset_missing() {
 
 		// Ensure the asset file is absent — back it up if a build has run.
 		if ( file_exists( $asset_file ) ) {
-			rename( $asset_file, $backup_file ); // phpcs:ignore WordPress.WP.AlternativeFunctions.rename_rename
+			rename( $asset_file, $backup_file );
 			$backed_up = true;
 		}
 
@@ -570,8 +567,7 @@ public function test_boot_asset_proxy_returns_fallback_when_asset_missing() {
 			$this->assertSame( '', $asset['version'] );
 		} finally {
 			if ( $backed_up ) {
-				rename( $backup_file, $asset_file ); // phpcs:ignore WordPress.WP.AlternativeFunctions.rename_rename
-			}
+				rename( $backup_file, $asset_file ); }
 		}
 	}
 

From efc2852baab5353ff341bf35de2133c94eec743c Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Fri, 13 Mar 2026 17:59:25 -0300
Subject: [PATCH 36/40] Replace duplicate phpunit configs with symlinks

phpunit.12.xml.dist is identical to phpunit.11.xml.dist, and
phpunit.8.xml.dist is identical to phpunit.9.xml.dist, matching
the convention used elsewhere in the monorepo.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../wp-build-polyfills/phpunit.12.xml.dist    | 37 +------------------
 .../wp-build-polyfills/phpunit.8.xml.dist     | 18 +--------
 2 files changed, 2 insertions(+), 53 deletions(-)
 mode change 100644 => 120000 projects/packages/wp-build-polyfills/phpunit.12.xml.dist
 mode change 100644 => 120000 projects/packages/wp-build-polyfills/phpunit.8.xml.dist

diff --git a/projects/packages/wp-build-polyfills/phpunit.12.xml.dist b/projects/packages/wp-build-polyfills/phpunit.12.xml.dist
deleted file mode 100644
index f7418373829b..000000000000
--- a/projects/packages/wp-build-polyfills/phpunit.12.xml.dist
+++ /dev/null
@@ -1,36 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-	xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
-	bootstrap="tests/php/bootstrap.php"
-	cacheDirectory=".phpunit.cache"
-	colors="true"
-	executionOrder="depends"
-	beStrictAboutOutputDuringTests="true"
-	displayDetailsOnPhpunitDeprecations="true"
-	displayDetailsOnTestsThatTriggerDeprecations="true"
-	displayDetailsOnTestsThatTriggerErrors="true"
-	displayDetailsOnTestsThatTriggerNotices="true"
-	displayDetailsOnTestsThatTriggerWarnings="true"
-	failOnDeprecation="true"
-	failOnEmptyTestSuite="true"
-	failOnPhpunitDeprecation="true"
-	failOnNotice="true"
-	failOnRisky="true"
-	failOnWarning="true"
->
-	<testsuites>
-		<testsuite name="main">
-			<directory suffix="Test.php">tests/php</directory>
-		</testsuite>
-	</testsuites>
-
-	<source>
-		<include>
-			<!-- Better to only include "src" than to add "." and then exclude "tests", "vendor", and so on, as PHPUnit still scans the excluded directories. -->
-			<!-- Add additional lines for any files or directories outside of src/ that need coverage. -->
-			<directory suffix=".php">src</directory>
-		</include>
-	</source>
-	<coverage ignoreDeprecatedCodeUnits="true">
-	</coverage>
-</phpunit>
diff --git a/projects/packages/wp-build-polyfills/phpunit.12.xml.dist b/projects/packages/wp-build-polyfills/phpunit.12.xml.dist
new file mode 120000
index 000000000000..9fdb7a2c745c
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/phpunit.12.xml.dist
@@ -0,0 +1 @@
+phpunit.11.xml.dist
\ No newline at end of file
diff --git a/projects/packages/wp-build-polyfills/phpunit.8.xml.dist b/projects/packages/wp-build-polyfills/phpunit.8.xml.dist
deleted file mode 100644
index 3965963c485e..000000000000
--- a/projects/packages/wp-build-polyfills/phpunit.8.xml.dist
+++ /dev/null
@@ -1,17 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-	xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.6/phpunit.xsd"
-	bootstrap="tests/php/bootstrap.php"
-	cacheResultFile=".phpunit.cache/test-results"
-	colors="true"
-	executionOrder="depends"
-	beStrictAboutOutputDuringTests="true"
-	failOnRisky="true"
-	failOnWarning="true"
->
-	<testsuites>
-		<testsuite name="main">
-			<directory suffix="Test.php">tests/php</directory>
-		</testsuite>
-	</testsuites>
-</phpunit>
diff --git a/projects/packages/wp-build-polyfills/phpunit.8.xml.dist b/projects/packages/wp-build-polyfills/phpunit.8.xml.dist
new file mode 120000
index 000000000000..707bde67863c
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/phpunit.8.xml.dist
@@ -0,0 +1 @@
+phpunit.9.xml.dist
\ No newline at end of file

From fd38c8b19fb80003907af694958a178e0af50109 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Fri, 13 Mar 2026 18:00:52 -0300
Subject: [PATCH 37/40] Fix misleading i18n comment in wp-build-polyfills
 webpack config

The i18n plugins are disabled because Core doesn't provide
translations for these packages (they aren't shipped with Core),
not because @wordpress/i18n is external.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 projects/packages/wp-build-polyfills/webpack.config.js | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/projects/packages/wp-build-polyfills/webpack.config.js b/projects/packages/wp-build-polyfills/webpack.config.js
index e53db9dff82f..f062d9946237 100644
--- a/projects/packages/wp-build-polyfills/webpack.config.js
+++ b/projects/packages/wp-build-polyfills/webpack.config.js
@@ -114,8 +114,9 @@ const sharedConfig = {
 	},
 };
 
-// Plugins disabled for all polyfill builds: no CSS is bundled, and i18n is
-// handled by core's textdomain since @wordpress/i18n remains external.
+// Plugins disabled for all polyfill builds: no CSS is bundled, and the i18n
+// loader/checker are unnecessary since Core doesn't provide translations for
+// these packages (they aren't shipped with Core in the first place).
 const disabledPlugins = {
 	MiniCssExtractPlugin: false,
 	MiniCssWithRtlPlugin: false,

From 7e302d91a02fbbe20d7fce5800e9d3341bb23d46 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Fri, 13 Mar 2026 18:15:50 -0300
Subject: [PATCH 38/40] Move boot asset file copy from CLI to forms build
 script

Instead of a runtime proxy that resolves asset data via class
autoloading, copy the built asset file directly at build time.
Add a Node.js bin script (provide-boot-asset-file) in wp-build-polyfills
that consumers call after wp-build. Remove boot-module-asset-proxy.php
and the load_boot_module_asset_file() static method as they are no
longer needed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 pnpm-lock.yaml                                |  3 +
 projects/packages/forms/package.json          |  4 +-
 .../packages/wp-build-polyfills/README.md     | 10 ++-
 .../bin/provide-boot-asset-file.js            | 28 +++++++
 .../packages/wp-build-polyfills/package.json  |  3 +
 .../src/boot-module-asset-proxy.php           | 35 ---------
 .../tests/php/WP_Build_Polyfills_Test.php     | 76 -------------------
 tools/cli/commands/build.js                   | 59 --------------
 8 files changed, 44 insertions(+), 174 deletions(-)
 create mode 100755 projects/packages/wp-build-polyfills/bin/provide-boot-asset-file.js
 delete mode 100644 projects/packages/wp-build-polyfills/src/boot-module-asset-proxy.php

diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 30ca2b24dcb5..2e3ff0d7f2ac 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -2558,6 +2558,9 @@ importers:
       '@automattic/jetpack-webpack-config':
         specifier: workspace:*
         version: link:../../js-packages/webpack-config
+      '@automattic/jetpack-wp-build-polyfills':
+        specifier: workspace:*
+        version: link:../wp-build-polyfills
       '@automattic/remove-asset-webpack-plugin':
         specifier: workspace:*
         version: link:../../js-packages/remove-asset-webpack-plugin
diff --git a/projects/packages/forms/package.json b/projects/packages/forms/package.json
index a1ec8492247c..954c0bc20956 100644
--- a/projects/packages/forms/package.json
+++ b/projects/packages/forms/package.json
@@ -16,8 +16,9 @@
 	"author": "Automattic",
 	"type": "module",
 	"scripts": {
-		"build": "pnpm run clean && pnpm run build:blocks && pnpm run build:contact-form && pnpm run build:dashboard && pnpm run build:wp-build && pnpm run build:form-editor && pnpm run module:build",
+		"build": "pnpm run clean && pnpm run build:blocks && pnpm run build:contact-form && pnpm run build:dashboard && pnpm run build:wp-build && pnpm run build:boot-asset && pnpm run build:form-editor && pnpm run module:build",
 		"build:blocks": "webpack --config ./tools/webpack.config.blocks.js",
+		"build:boot-asset": "provide-boot-asset-file",
 		"build:contact-form": "webpack --config ./tools/webpack.config.contact-form.js",
 		"build:dashboard": "webpack --config ./tools/webpack.config.dashboard.js",
 		"build:form-editor": "webpack --config ./tools/webpack.config.form-editor.js",
@@ -99,6 +100,7 @@
 		"@automattic/color-studio": "4.1.0",
 		"@automattic/jetpack-base-styles": "workspace:*",
 		"@automattic/jetpack-webpack-config": "workspace:*",
+		"@automattic/jetpack-wp-build-polyfills": "workspace:*",
 		"@automattic/remove-asset-webpack-plugin": "workspace:*",
 		"@babel/core": "7.29.0",
 		"@babel/runtime": "7.28.6",
diff --git a/projects/packages/wp-build-polyfills/README.md b/projects/packages/wp-build-polyfills/README.md
index f3dbdde56afc..58b029ce19b2 100644
--- a/projects/packages/wp-build-polyfills/README.md
+++ b/projects/packages/wp-build-polyfills/README.md
@@ -63,13 +63,17 @@ The version threshold for force-replacements can be overridden with a third para
 WP_Build_Polyfills::register( 'my-plugin', array( 'wp-notices' ), '7.1' );
 ```
 
-## Boot module asset proxy
+## Boot module asset file
 
 Packages that use `@wordpress/build` to generate pages get a hardcoded reference to `build/modules/boot/index.min.asset.php` in the generated page templates. This file provides the classic script dependencies and version hash needed to bootstrap the page.
 
-When `@wordpress/build` stops bundling the boot module (as planned in upcoming Gutenberg changes), this asset file will no longer be generated. The polyfills package ships a proxy file (`src/boot-module-asset-proxy.php`) that resolves the asset data from this package's build output at runtime, using `ReflectionClass` to locate the package regardless of install path (`vendor/` or `jetpack_vendor/`).
+When `@wordpress/build` stops bundling the boot module (as planned in upcoming Gutenberg changes), this asset file will no longer be generated. This package builds its own boot module asset file, and ships a bin script (`provide-boot-asset-file`) that copies it to the expected location in the consumer's build directory.
 
-The Jetpack monorepo CLI (`jetpack build`) automatically copies this proxy to the expected location (`build/modules/boot/index.min.asset.php`) after building any package that has `build/pages/` and depends on this package. No per-consumer configuration is needed.
+Consuming packages should add `@automattic/jetpack-wp-build-polyfills` as a devDependency and call the script after `wp-build`:
+
+```json
+"build:boot-proxy": "provide-boot-asset-file"
+```
 
 ## Development
 
diff --git a/projects/packages/wp-build-polyfills/bin/provide-boot-asset-file.js b/projects/packages/wp-build-polyfills/bin/provide-boot-asset-file.js
new file mode 100755
index 000000000000..349b04a601a4
--- /dev/null
+++ b/projects/packages/wp-build-polyfills/bin/provide-boot-asset-file.js
@@ -0,0 +1,28 @@
+#!/usr/bin/env node
+/* global __dirname, process */
+
+/**
+ * Copy the boot module asset file into the consumer's build directory.
+ *
+ * When wp-build generates page templates, they reference a boot module asset
+ * file at build/modules/boot/index.min.asset.php. This script copies the
+ * built asset file from this package to that expected location.
+ *
+ * Run this from the consuming package's root directory after wp-build.
+ */
+
+const { cpSync, existsSync, mkdirSync } = require( 'fs' );
+const path = require( 'path' );
+
+const assetSource = path.join( __dirname, '..', 'build', 'modules', 'boot', 'index.asset.php' );
+const targetDir = path.join( process.cwd(), 'build', 'modules', 'boot' );
+const targetFile = path.join( targetDir, 'index.min.asset.php' );
+
+if ( ! existsSync( assetSource ) ) {
+	throw new Error(
+		`Boot module asset file not found at ${ assetSource }. Ensure wp-build-polyfills has been built first.`
+	);
+}
+
+mkdirSync( targetDir, { recursive: true } );
+cpSync( assetSource, targetFile );
diff --git a/projects/packages/wp-build-polyfills/package.json b/projects/packages/wp-build-polyfills/package.json
index 8dc8ccbc806b..cadcb3bdacf3 100644
--- a/projects/packages/wp-build-polyfills/package.json
+++ b/projects/packages/wp-build-polyfills/package.json
@@ -11,6 +11,9 @@
 	},
 	"license": "GPL-2.0-or-later",
 	"author": "Automattic",
+	"bin": {
+		"provide-boot-asset-file": "bin/provide-boot-asset-file.js"
+	},
 	"scripts": {
 		"build": "pnpm run clean && webpack",
 		"build-production": "NODE_ENV=production BABEL_ENV=production pnpm run build",
diff --git a/projects/packages/wp-build-polyfills/src/boot-module-asset-proxy.php b/projects/packages/wp-build-polyfills/src/boot-module-asset-proxy.php
deleted file mode 100644
index 755c60c2d7a2..000000000000
--- a/projects/packages/wp-build-polyfills/src/boot-module-asset-proxy.php
+++ /dev/null
@@ -1,35 +0,0 @@
-<?php
-/**
- * Boot module asset proxy for wp-build page consumers.
- *
- * When wp-build generates page templates, they reference a boot module asset
- * file at a hardcoded relative path (build/modules/boot/index.min.asset.php).
- * This proxy file is copied to that location by the monorepo build tooling,
- * and resolves the real asset data from the wp-build-polyfills package
- * regardless of where it is installed (vendor/ or jetpack_vendor/).
- *
- * @package automattic/jetpack-wp-build-polyfills
- */
-
-// phpcs:ignore Universal.Files.SeparateFunctionsFromOO.Mixed -- This is not a class file.
-
-$class_name = 'Automattic\Jetpack\WP_Build_Polyfills\WP_Build_Polyfills';
-
-if ( ! class_exists( $class_name ) ) {
-	return array(
-		'dependencies' => array(),
-		'version'      => '',
-	);
-}
-
-$ref        = new ReflectionClass( $class_name );
-$asset_file = dirname( $ref->getFileName(), 2 ) . '/build/modules/boot/index.asset.php';
-
-if ( ! file_exists( $asset_file ) ) {
-	return array(
-		'dependencies' => array(),
-		'version'      => '',
-	);
-}
-
-return require $asset_file;
diff --git a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
index f91e0895cb8a..1d71d6902da1 100644
--- a/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
+++ b/projects/packages/wp-build-polyfills/tests/php/WP_Build_Polyfills_Test.php
@@ -495,82 +495,6 @@ public function test_get_consumers_tracks_polyfill_consumers() {
 		$this->assertArrayNotHasKey( 'wp-private-apis', $consumers );
 	}
 
-	// ── Boot module asset proxy tests ─────────────────────────────────────────
-
-	/**
-	 * Test that the boot asset proxy returns the real asset data when the class
-	 * is loaded and the build asset file exists.
-	 */
-	public function test_boot_asset_proxy_returns_real_asset_data() {
-		$package_root = dirname( __DIR__, 2 );
-		$asset_file   = $package_root . '/build/modules/boot/index.asset.php';
-		$created      = false;
-
-		// Create a fixture asset file if the build hasn't run, so the test
-		// executes deterministically regardless of environment.
-		if ( ! file_exists( $asset_file ) ) {
-			$dir = dirname( $asset_file );
-			if ( ! is_dir( $dir ) ) {
-				mkdir( $dir, 0755, true );          }
-			file_put_contents(
-				$asset_file,
-				"<?php\nreturn array( 'dependencies' => array( 'wp-i18n' ), 'version' => 'fixture-1.0' );\n"
-			);
-			$created = true;
-		}
-
-		try {
-			$proxy_file = $package_root . '/src/boot-module-asset-proxy.php';
-			$asset      = require $proxy_file;
-
-			$this->assertIsArray( $asset );
-			$this->assertArrayHasKey( 'dependencies', $asset );
-			$this->assertArrayHasKey( 'version', $asset );
-			$this->assertIsArray( $asset['dependencies'] );
-			$this->assertNotEmpty( $asset['version'] );
-		} finally {
-			if ( $created ) {
-				unlink( $asset_file );          }
-		}
-	}
-
-	/**
-	 * Test that the boot asset proxy returns fallback data when the build
-	 * asset file does not exist.
-	 *
-	 * Temporarily renames the real asset file, requires the proxy (which uses
-	 * ReflectionClass to find the build dir), then restores the original.
-	 */
-	public function test_boot_asset_proxy_returns_fallback_when_asset_missing() {
-		$package_root = dirname( __DIR__, 2 );
-		$asset_file   = $package_root . '/build/modules/boot/index.asset.php';
-		$backup_file  = $asset_file . '.bak';
-		$backed_up    = false;
-
-		// Ensure the asset file is absent — back it up if a build has run.
-		if ( file_exists( $asset_file ) ) {
-			rename( $asset_file, $backup_file );
-			$backed_up = true;
-		}
-
-		try {
-			// The proxy file uses `require` internally, but PHP caches the
-			// return value per file path. Use a fresh include via a wrapper
-			// to avoid the cache.
-			$proxy_file = $package_root . '/src/boot-module-asset-proxy.php';
-			$asset      = ( static function ( $file ) {
-				return require $file;
-			} )( $proxy_file );
-
-			$this->assertIsArray( $asset );
-			$this->assertSame( array(), $asset['dependencies'] );
-			$this->assertSame( '', $asset['version'] );
-		} finally {
-			if ( $backed_up ) {
-				rename( $backup_file, $asset_file ); }
-		}
-	}
-
 	/**
 	 * Test that only requested polyfills are registered.
 	 */
diff --git a/tools/cli/commands/build.js b/tools/cli/commands/build.js
index cd7e18f7c5cf..b29022222851 100644
--- a/tools/cli/commands/build.js
+++ b/tools/cli/commands/build.js
@@ -595,62 +595,6 @@ async function checkCollisions( basedir ) {
 	return [ ...collisions ];
 }
 
-/**
- * Provide the boot module asset proxy for packages using wp-build pages.
- *
- * When wp-build generates page templates, they reference a boot module asset
- * file at build/modules/boot/index.min.asset.php. If the package depends on
- * jetpack-wp-build-polyfills and has wp-build pages, this function copies the
- * proxy file from the polyfills package to the expected location.
- *
- * @param {object} t - Task object.
- */
-async function provideBootAssetProxy( t ) {
-	const pagesDir = npath.join( t.cwd, 'build', 'pages' );
-	const targetFile = npath.join( t.cwd, 'build', 'modules', 'boot', 'index.min.asset.php' );
-
-	// Only act if the package has wp-build pages and the file is missing.
-	if ( ! ( await fsExists( pagesDir ) ) || ( await fsExists( targetFile ) ) ) {
-		return;
-	}
-
-	// Look for the proxy in jetpack_vendor (production) or vendor (dev).
-	const candidates = [
-		npath.join(
-			t.cwd,
-			'jetpack_vendor',
-			'automattic',
-			'jetpack-wp-build-polyfills',
-			'src',
-			'boot-module-asset-proxy.php'
-		),
-		npath.join(
-			t.cwd,
-			'vendor',
-			'automattic',
-			'jetpack-wp-build-polyfills',
-			'src',
-			'boot-module-asset-proxy.php'
-		),
-	];
-	const proxySource = (
-		await Promise.all( candidates.map( f => fsExists( f ).then( ok => ok && f ) ) )
-	).find( Boolean );
-	if ( ! proxySource ) {
-		await t.output(
-			chalk.yellow(
-				'Warning: build/pages exists but wp-build-polyfills boot module asset proxy was not found.\n'
-			) +
-				chalk.yellow( 'Ensure automattic/jetpack-wp-build-polyfills is installed via Composer.\n' )
-		);
-		return;
-	}
-
-	await fs.mkdir( npath.dirname( targetFile ), { recursive: true } );
-	await fs.copyFile( proxySource, targetFile );
-	await t.output( 'Provided boot module asset proxy from wp-build-polyfills\n' );
-}
-
 /**
  * Build a project.
  *
@@ -852,9 +796,6 @@ async function buildProject( t ) {
 		} );
 	}
 
-	// Provide the boot module asset proxy for packages using wp-build pages.
-	await provideBootAssetProxy( t );
-
 	// If we're not mirroring, the build is done. Mirroring has a bunch of stuff to do yet.
 	if ( ! t.argv.forMirrors ) {
 		return;

From 10a0ba1e0cb2adecb7d30ccf7f550f5b315ef086 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Fri, 13 Mar 2026 19:29:59 -0300
Subject: [PATCH 39/40] fix build test

---
 projects/plugins/jetpack/tests/e2e/package.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/projects/plugins/jetpack/tests/e2e/package.json b/projects/plugins/jetpack/tests/e2e/package.json
index fcef5bb28b3c..78e9b02e90d2 100644
--- a/projects/plugins/jetpack/tests/e2e/package.json
+++ b/projects/plugins/jetpack/tests/e2e/package.json
@@ -3,7 +3,7 @@
 	"type": "module",
 	"scripts": {
 		"allure-report": "allure generate --clean --output ./output/allure-report ./output/allure-results && allure open ./output/allure-report",
-		"build": "pnpm jetpack build packages/my-jetpack js-packages/social-logos js-packages/boost-score-api js-packages/components js-packages/number-formatters packages/forms packages/assets packages/connection packages/publicize packages/blaze plugins/jetpack -v --no-pnpm-install --production",
+		"build": "pnpm jetpack build packages/my-jetpack js-packages/social-logos js-packages/boost-score-api js-packages/components js-packages/number-formatters packages/wp-build-polyfills packages/forms packages/assets packages/connection packages/publicize packages/blaze plugins/jetpack -v --no-pnpm-install --production",
 		"clean": "rm -rf output",
 		"config:decrypt": "pnpm test-decrypt-default-config && pnpm test-decrypt-config",
 		"distclean": "rm -rf node_modules",

From 2d5f4c69e81b8773a33a36ed3344b9a2ed97c424 Mon Sep 17 00:00:00 2001
From: Douglas <douglas.henri@automattic.com>
Date: Mon, 16 Mar 2026 17:59:15 -0300
Subject: [PATCH 40/40] fix test

---
 projects/packages/forms/tests/php/dashboard/Dashboard_Test.php | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php b/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
index 1238531b1528..b95dfdcbdb5e 100644
--- a/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
+++ b/projects/packages/forms/tests/php/dashboard/Dashboard_Test.php
@@ -24,7 +24,7 @@ class Dashboard_Test extends BaseTestCase {
 	 */
 	public function tear_down() {
 		$this->reset_wp_build_polyfills();
-		unset( $_GET['page'] );
+		unset( $_GET['page'], $_GET['p'] );
 		parent::tear_down();
 	}
 
@@ -162,6 +162,7 @@ private function reset_wp_build_polyfills() {
 	 */
 	public function test_load_wp_build_registers_polyfills_on_wpbuild_page() {
 		$_GET['page'] = Dashboard::FORMS_WPBUILD_ADMIN_SLUG;
+		$_GET['p']    = '/responses/inbox';
 
 		Dashboard::load_wp_build();