diff -r 48c4eec2b7e6 -r 8c2e4d02f4ef wp/wp-includes/class-wp-url-pattern-prefixer.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/class-wp-url-pattern-prefixer.php	Fri Sep 05 18:52:52 2025 +0200
@@ -0,0 +1,135 @@
+<?php
+/**
+ * Class 'WP_URL_Pattern_Prefixer'.
+ *
+ * @package WordPress
+ * @subpackage Speculative Loading
+ * @since 6.8.0
+ */
+
+/**
+ * Class for prefixing URL patterns.
+ *
+ * This class is intended primarily for use as part of the speculative loading feature.
+ *
+ * @since 6.8.0
+ * @access private
+ */
+class WP_URL_Pattern_Prefixer {
+
+	/**
+	 * Map of `$context_string => $base_path` pairs.
+	 *
+	 * @since 6.8.0
+	 * @var array<string, string>
+	 */
+	private $contexts;
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 6.8.0
+	 *
+	 * @param array<string, string> $contexts Optional. Map of `$context_string => $base_path` pairs. Default is the
+	 *                                        contexts returned by the
+	 *                                        {@see WP_URL_Pattern_Prefixer::get_default_contexts()} method.
+	 */
+	public function __construct( array $contexts = array() ) {
+		if ( count( $contexts ) > 0 ) {
+			$this->contexts = array_map(
+				static function ( string $str ): string {
+					return self::escape_pattern_string( trailingslashit( $str ) );
+				},
+				$contexts
+			);
+		} else {
+			$this->contexts = self::get_default_contexts();
+		}
+	}
+
+	/**
+	 * Prefixes the given URL path pattern with the base path for the given context.
+	 *
+	 * This ensures that these path patterns work correctly on WordPress subdirectory sites, for example in a multisite
+	 * network, or when WordPress itself is installed in a subdirectory of the hostname.
+	 *
+	 * The given URL path pattern is only prefixed if it does not already include the expected prefix.
+	 *
+	 * @since 6.8.0
+	 *
+	 * @param string $path_pattern URL pattern starting with the path segment.
+	 * @param string $context      Optional. Context to use for prefixing the path pattern. Default 'home'.
+	 * @return string URL pattern, prefixed as necessary.
+	 */
+	public function prefix_path_pattern( string $path_pattern, string $context = 'home' ): string {
+		// If context path does not exist, the context is invalid.
+		if ( ! isset( $this->contexts[ $context ] ) ) {
+			_doing_it_wrong(
+				__FUNCTION__,
+				esc_html(
+					sprintf(
+						/* translators: %s: context string */
+						__( 'Invalid URL pattern context %s.' ),
+						$context
+					)
+				),
+				'6.8.0'
+			);
+			return $path_pattern;
+		}
+
+		/*
+		 * In the event that the context path contains a :, ? or # (which can cause the URL pattern parser to switch to
+		 * another state, though only the latter two should be percent encoded anyway), it additionally needs to be
+		 * enclosed in grouping braces. The final forward slash (trailingslashit ensures there is one) affects the
+		 * meaning of the * wildcard, so is left outside the braces.
+		 */
+		$context_path         = $this->contexts[ $context ];
+		$escaped_context_path = $context_path;
+		if ( strcspn( $context_path, ':?#' ) !== strlen( $context_path ) ) {
+			$escaped_context_path = '{' . substr( $context_path, 0, -1 ) . '}/';
+		}
+
+		/*
+		 * If the path already starts with the context path (including '/'), remove it first
+		 * since it is about to be added back.
+		 */
+		if ( str_starts_with( $path_pattern, $context_path ) ) {
+			$path_pattern = substr( $path_pattern, strlen( $context_path ) );
+		}
+
+		return $escaped_context_path . ltrim( $path_pattern, '/' );
+	}
+
+	/**
+	 * Returns the default contexts used by the class.
+	 *
+	 * @since 6.8.0
+	 *
+	 * @return array<string, string> Map of `$context_string => $base_path` pairs.
+	 */
+	public static function get_default_contexts(): array {
+		return array(
+			'home'       => self::escape_pattern_string( trailingslashit( (string) wp_parse_url( home_url( '/' ), PHP_URL_PATH ) ) ),
+			'site'       => self::escape_pattern_string( trailingslashit( (string) wp_parse_url( site_url( '/' ), PHP_URL_PATH ) ) ),
+			'uploads'    => self::escape_pattern_string( trailingslashit( (string) wp_parse_url( wp_upload_dir( null, false )['baseurl'], PHP_URL_PATH ) ) ),
+			'content'    => self::escape_pattern_string( trailingslashit( (string) wp_parse_url( content_url(), PHP_URL_PATH ) ) ),
+			'plugins'    => self::escape_pattern_string( trailingslashit( (string) wp_parse_url( plugins_url(), PHP_URL_PATH ) ) ),
+			'template'   => self::escape_pattern_string( trailingslashit( (string) wp_parse_url( get_stylesheet_directory_uri(), PHP_URL_PATH ) ) ),
+			'stylesheet' => self::escape_pattern_string( trailingslashit( (string) wp_parse_url( get_template_directory_uri(), PHP_URL_PATH ) ) ),
+		);
+	}
+
+	/**
+	 * Escapes a string for use in a URL pattern component.
+	 *
+	 * @since 6.8.0
+	 * @see https://urlpattern.spec.whatwg.org/#escape-a-pattern-string
+	 *
+	 * @param string $str String to be escaped.
+	 * @return string String with backslashes added where required.
+	 */
+	private static function escape_pattern_string( string $str ): string {
+		return addcslashes( $str, '+*?:{}()\\' );
+	}
+}