diff -r 7b1b88e27a20 -r 48c4eec2b7e6 wp/wp-includes/rest-api/endpoints/class-wp-rest-site-health-controller.php
--- a/wp/wp-includes/rest-api/endpoints/class-wp-rest-site-health-controller.php	Thu Sep 29 08:06:27 2022 +0200
+++ b/wp/wp-includes/rest-api/endpoints/class-wp-rest-site-health-controller.php	Fri Sep 05 18:40:08 2025 +0200
@@ -43,6 +43,7 @@
 	 * Registers API routes.
 	 *
 	 * @since 5.6.0
+	 * @since 6.1.0 Adds page-cache async test.
 	 *
 	 * @see register_rest_route()
 	 */
@@ -151,11 +152,29 @@
 			array(
 				'methods'             => 'GET',
 				'callback'            => array( $this, 'get_directory_sizes' ),
-				'permission_callback' => function() {
-					return $this->validate_request_permission( 'debug_enabled' ) && ! is_multisite();
+				'permission_callback' => function () {
+					return $this->validate_request_permission( 'directory_sizes' ) && ! is_multisite();
 				},
 			)
 		);
+
+		register_rest_route(
+			$this->namespace,
+			sprintf(
+				'/%s/%s',
+				$this->rest_base,
+				'page-cache'
+			),
+			array(
+				array(
+					'methods'             => 'GET',
+					'callback'            => array( $this, 'test_page_cache' ),
+					'permission_callback' => function () {
+						return $this->validate_request_permission( 'page_cache' );
+					},
+				),
+			)
+		);
 	}
 
 	/**
@@ -243,6 +262,18 @@
 	}
 
 	/**
+	 * Checks that full page cache is active.
+	 *
+	 * @since 6.1.0
+	 *
+	 * @return array The test result.
+	 */
+	public function test_page_cache() {
+		$this->load_admin_textdomain();
+		return $this->site_health->get_test_page_cache();
+	}
+
+	/**
 	 * Gets the current directory sizes for this install.
 	 *
 	 * @since 5.6.0
@@ -305,7 +336,7 @@
 		// Accounts for inner REST API requests in the admin.
 		if ( ! is_admin() ) {
 			$locale = determine_locale();
-			load_textdomain( 'default', WP_LANG_DIR . "/admin-$locale.mo" );
+			load_textdomain( 'default', WP_LANG_DIR . "/admin-$locale.mo", $locale );
 		}
 	}