diff --git a/.github/workflows/test-js.yml b/.github/workflows/test-js.yml
index f6d6c710e..9a713c00f 100644
--- a/.github/workflows/test-js.yml
+++ b/.github/workflows/test-js.yml
@@ -27,3 +27,7 @@ jobs:
           npm run lint
         env:
           CI: true
+      - name: Run unit tests
+        run: npm run test:unit
+        env:
+          CI: true
diff --git a/composer.json b/composer.json
index 6e11b3148..e1e5fb532 100644
--- a/composer.json
+++ b/composer.json
@@ -20,7 +20,7 @@
 		"phpunit/phpunit": "9.6.5",
 		"yoast/phpunit-polyfills": "^4.0",
 		"phpstan/phpstan": "^2.1",
-		"php-stubs/woocommerce-stubs": "^10.8",
+		"php-stubs/woocommerce-stubs": "^11.0",
 		"php-stubs/acf-pro-stubs": "^6.8",
 		"wpackagist-plugin/woocommerce": "*",
 		"automattic/vipwpcs": "^3.0",
diff --git a/composer.lock b/composer.lock
index f81925300..439b236c2 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,20 +4,20 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "556f279ce85f25f708f60329f1f7067c",
+    "content-hash": "5a247aa373965f7dae85a8a3c4b3cb01",
     "packages": [
         {
             "name": "codeinwp/themeisle-sdk",
-            "version": "3.3.58",
+            "version": "3.3.61",
             "source": {
                 "type": "git",
                 "url": "https://github.com/Codeinwp/themeisle-sdk.git",
-                "reference": "d6807c0b7308e323bd77cced667dee3f2d5e6a82"
+                "reference": "9fe698b52dec768a0dd8b500fb51efe40962ee99"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/Codeinwp/themeisle-sdk/zipball/d6807c0b7308e323bd77cced667dee3f2d5e6a82",
-                "reference": "d6807c0b7308e323bd77cced667dee3f2d5e6a82",
+                "url": "https://api.github.com/repos/Codeinwp/themeisle-sdk/zipball/9fe698b52dec768a0dd8b500fb51efe40962ee99",
+                "reference": "9fe698b52dec768a0dd8b500fb51efe40962ee99",
                 "shasum": ""
             },
             "require-dev": {
@@ -43,9 +43,9 @@
             ],
             "support": {
                 "issues": "https://github.com/Codeinwp/themeisle-sdk/issues",
-                "source": "https://github.com/Codeinwp/themeisle-sdk/tree/v3.3.58"
+                "source": "https://github.com/Codeinwp/themeisle-sdk/tree/v3.3.61"
             },
-            "time": "2026-07-29T08:38:52+00:00"
+            "time": "2026-08-24T15:59:27+00:00"
         },
         {
             "name": "enshrined/svg-sanitize",
@@ -1044,24 +1044,24 @@
         },
         {
             "name": "php-stubs/woocommerce-stubs",
-            "version": "v10.9.1",
+            "version": "v11.0.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/php-stubs/woocommerce-stubs.git",
-                "reference": "e6d583b9fa05b3f5ff67f86c939b45a0c35b8444"
+                "reference": "923dd29055713886efd7f85ea2510b9c6955a714"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/php-stubs/woocommerce-stubs/zipball/e6d583b9fa05b3f5ff67f86c939b45a0c35b8444",
-                "reference": "e6d583b9fa05b3f5ff67f86c939b45a0c35b8444",
+                "url": "https://api.github.com/repos/php-stubs/woocommerce-stubs/zipball/923dd29055713886efd7f85ea2510b9c6955a714",
+                "reference": "923dd29055713886efd7f85ea2510b9c6955a714",
                 "shasum": ""
             },
             "require": {
-                "php-stubs/wordpress-stubs": "^5.3 || ^6.0"
+                "php-stubs/wordpress-stubs": "^5.3 || ^6.0 || ^7.0"
             },
             "require-dev": {
                 "php": "~7.1 || ~8.0",
-                "php-stubs/generator": "^0.8.0"
+                "php-stubs/generator": "^0.9.0"
             },
             "suggest": {
                 "symfony/polyfill-php73": "Symfony polyfill backporting some PHP 7.3+ features to lower PHP versions",
@@ -1082,9 +1082,9 @@
             ],
             "support": {
                 "issues": "https://github.com/php-stubs/woocommerce-stubs/issues",
-                "source": "https://github.com/php-stubs/woocommerce-stubs/tree/v10.9.1"
+                "source": "https://github.com/php-stubs/woocommerce-stubs/tree/v11.0.0"
             },
-            "time": "2026-06-25T10:47:57+00:00"
+            "time": "2026-08-04T19:31:58+00:00"
         },
         {
             "name": "php-stubs/wordpress-stubs",
@@ -1202,27 +1202,27 @@
         },
         {
             "name": "phpcsstandards/phpcsextra",
-            "version": "1.4.0",
+            "version": "1.5.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/PHPCSStandards/PHPCSExtra.git",
-                "reference": "fa4b8d051e278072928e32d817456a7fdb57b6ca"
+                "reference": "39467533fdb742446d68c1d10ac33d625ee0311c"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/PHPCSStandards/PHPCSExtra/zipball/fa4b8d051e278072928e32d817456a7fdb57b6ca",
-                "reference": "fa4b8d051e278072928e32d817456a7fdb57b6ca",
+                "url": "https://api.github.com/repos/PHPCSStandards/PHPCSExtra/zipball/39467533fdb742446d68c1d10ac33d625ee0311c",
+                "reference": "39467533fdb742446d68c1d10ac33d625ee0311c",
                 "shasum": ""
             },
             "require": {
                 "php": ">=5.4",
-                "phpcsstandards/phpcsutils": "^1.1.0",
-                "squizlabs/php_codesniffer": "^3.13.0 || ^4.0"
+                "phpcsstandards/phpcsutils": "^1.2.3",
+                "squizlabs/php_codesniffer": "^3.13.5 || ^4.0.1"
             },
             "require-dev": {
                 "php-parallel-lint/php-console-highlighter": "^1.0",
                 "php-parallel-lint/php-parallel-lint": "^1.4.0",
-                "phpcsstandards/phpcsdevcs": "^1.1.6",
+                "phpcsstandards/phpcsdevcs": "^1.2.0",
                 "phpcsstandards/phpcsdevtools": "^1.2.1",
                 "phpunit/phpunit": "^4.5 || ^5.0 || ^6.0 || ^7.0 || ^8.0 || ^9.3.4"
             },
@@ -1280,32 +1280,32 @@
                     "type": "thanks_dev"
                 }
             ],
-            "time": "2025-06-14T07:40:39+00:00"
+            "time": "2026-07-27T11:13:17+00:00"
         },
         {
             "name": "phpcsstandards/phpcsutils",
-            "version": "1.1.1",
+            "version": "1.2.3",
             "source": {
                 "type": "git",
                 "url": "https://github.com/PHPCSStandards/PHPCSUtils.git",
-                "reference": "f7eb16f2fa4237d5db9e8fed8050239bee17a9bd"
+                "reference": "5f35d9408c54d7b529501f3c688b6eae562aea1f"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/PHPCSStandards/PHPCSUtils/zipball/f7eb16f2fa4237d5db9e8fed8050239bee17a9bd",
-                "reference": "f7eb16f2fa4237d5db9e8fed8050239bee17a9bd",
+                "url": "https://api.github.com/repos/PHPCSStandards/PHPCSUtils/zipball/5f35d9408c54d7b529501f3c688b6eae562aea1f",
+                "reference": "5f35d9408c54d7b529501f3c688b6eae562aea1f",
                 "shasum": ""
             },
             "require": {
                 "dealerdirect/phpcodesniffer-composer-installer": "^0.4.1 || ^0.5 || ^0.6.2 || ^0.7 || ^1.0",
                 "php": ">=5.4",
-                "squizlabs/php_codesniffer": "^3.13.0 || ^4.0"
+                "squizlabs/php_codesniffer": "^3.13.5 || ^4.0.1"
             },
             "require-dev": {
                 "ext-filter": "*",
                 "php-parallel-lint/php-console-highlighter": "^1.0",
                 "php-parallel-lint/php-parallel-lint": "^1.4.0",
-                "phpcsstandards/phpcsdevcs": "^1.1.6",
+                "phpcsstandards/phpcsdevcs": "^1.2.0",
                 "yoast/phpunit-polyfills": "^1.1.0 || ^2.0.0 || ^3.0.0"
             },
             "type": "phpcodesniffer-standard",
@@ -1373,7 +1373,7 @@
                     "type": "thanks_dev"
                 }
             ],
-            "time": "2025-08-10T01:04:45+00:00"
+            "time": "2026-07-27T10:28:41+00:00"
         },
         {
             "name": "phpstan/phpstan",
@@ -3047,16 +3047,16 @@
         },
         {
             "name": "wp-coding-standards/wpcs",
-            "version": "3.2.0",
+            "version": "3.4.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/WordPress/WordPress-Coding-Standards.git",
-                "reference": "d2421de7cec3274ae622c22c744de9a62c7925af"
+                "reference": "ec2ff942335f33683a5957a85d138753876a05cf"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/WordPress/WordPress-Coding-Standards/zipball/d2421de7cec3274ae622c22c744de9a62c7925af",
-                "reference": "d2421de7cec3274ae622c22c744de9a62c7925af",
+                "url": "https://api.github.com/repos/WordPress/WordPress-Coding-Standards/zipball/ec2ff942335f33683a5957a85d138753876a05cf",
+                "reference": "ec2ff942335f33683a5957a85d138753876a05cf",
                 "shasum": ""
             },
             "require": {
@@ -3064,17 +3064,17 @@
                 "ext-libxml": "*",
                 "ext-tokenizer": "*",
                 "ext-xmlreader": "*",
-                "php": ">=5.4",
-                "phpcsstandards/phpcsextra": "^1.4.0",
-                "phpcsstandards/phpcsutils": "^1.1.0",
-                "squizlabs/php_codesniffer": "^3.13.0"
+                "php": ">=7.2",
+                "phpcsstandards/phpcsextra": "^1.5.1",
+                "phpcsstandards/phpcsutils": "^1.2.3",
+                "squizlabs/php_codesniffer": "^3.13.5"
             },
             "require-dev": {
                 "php-parallel-lint/php-console-highlighter": "^1.0.0",
                 "php-parallel-lint/php-parallel-lint": "^1.4.0",
-                "phpcompatibility/php-compatibility": "^9.0",
+                "phpcompatibility/php-compatibility": "^10.0.0@dev",
                 "phpcsstandards/phpcsdevtools": "^1.2.0",
-                "phpunit/phpunit": "^4.0 || ^5.0 || ^6.0 || ^7.0 || ^8.0 || ^9.0"
+                "phpunit/phpunit": "^8.0 || ^9.0"
             },
             "suggest": {
                 "ext-iconv": "For improved results",
@@ -3109,7 +3109,7 @@
                     "type": "custom"
                 }
             ],
-            "time": "2025-07-24T20:08:31+00:00"
+            "time": "2026-07-27T11:53:23+00:00"
         },
         {
             "name": "wpackagist-plugin/woocommerce",
diff --git a/inc/class-base-css.php b/inc/class-base-css.php
index 0739628ba..aa16c163e 100644
--- a/inc/class-base-css.php
+++ b/inc/class-base-css.php
@@ -683,10 +683,10 @@ public function get_animation_classes( $blocks ) {
 		);
 
 		foreach ( $blocks as $block ) {
-			if ( isset( $block['attrs']['className'] ) && ! empty( $block['attrs']['className'] ) ) {
-				if ( preg_match( '/\banimated\b/', $block['attrs']['className'] ) ) {
-					$classes = array_merge( $classes, explode( ' ', trim( $block['attrs']['className'] ) ) );
-				}
+			$block_classes = Registration::get_class_name( isset( $block['attrs'] ) ? $block['attrs'] : array() );
+
+			if ( ! empty( $block_classes ) && preg_match( '/\banimated\b/', $block_classes ) ) {
+				$classes = array_merge( $classes, explode( ' ', trim( $block_classes ) ) );
 			}
 
 			if ( isset( $block['innerBlocks'] ) && ! empty( $block['innerBlocks'] ) && is_array( $block['innerBlocks'] ) ) {
diff --git a/inc/class-main.php b/inc/class-main.php
index 39d1aed7d..ca415d8a3 100644
--- a/inc/class-main.php
+++ b/inc/class-main.php
@@ -529,11 +529,29 @@ public function generate_svg_attachment_metadata( $metadata, $attachment_id ) {
 		}
 
 		$svg_path = get_attached_file( $attachment_id );
+
+		if ( empty( $svg_path ) || ! file_exists( $svg_path ) || ! is_readable( $svg_path ) ) {
+			return $metadata;
+		}
+
 		$filename = basename( $svg_path );
 
-		$svg        = simplexml_load_file( $svg_path );
+		// Keep malformed SVG errors internal instead of emitting PHP warnings.
+		$previous_state = libxml_use_internal_errors( true );
+		$svg            = simplexml_load_file( $svg_path );
+		libxml_clear_errors();
+		libxml_use_internal_errors( $previous_state );
+
+		if ( false === $svg ) {
+			return $metadata;
+		}
+
 		$attributes = $svg->attributes();
 
+		if ( ! isset( $attributes->width, $attributes->height ) ) {
+			return $metadata;
+		}
+
 		// Update metadata with SVG dimensions.
 		$metadata['width']  = intval( (string) $attributes->width );
 		$metadata['height'] = intval( (string) $attributes->height );
diff --git a/inc/class-registration.php b/inc/class-registration.php
index fff5da32a..5ae5a2b0d 100644
--- a/inc/class-registration.php
+++ b/inc/class-registration.php
@@ -97,6 +97,38 @@ public static function get_editor_global_defaults() {
 		return is_object( $defaults ) ? $defaults : new \stdClass();
 	}
 
+	/**
+	 * Get the `className` attribute of a block as a string.
+	 *
+	 * @param mixed $attributes Block attributes.
+	 * @return string
+	 */
+	public static function get_class_name( $attributes ) {
+		if ( ! is_array( $attributes ) || ! isset( $attributes['className'] ) ) {
+			return '';
+		}
+
+		$class_name = $attributes['className'];
+
+		if ( is_array( $class_name ) ) {
+			// Flatten nested arrays and drop anything that is not printable.
+			$flat = array();
+
+			array_walk_recursive(
+				$class_name,
+				function ( $value ) use ( &$flat ) {
+					if ( is_scalar( $value ) ) {
+						$flat[] = (string) $value;
+					}
+				}
+			);
+
+			return implode( ' ', $flat );
+		}
+
+		return is_scalar( $class_name ) ? (string) $class_name : '';
+	}
+
 	/**
 	 * Initialize the class
 	 */
@@ -633,6 +665,7 @@ function () {
 					'nonce'              => wp_create_nonce( 'wp_rest' ),
 					'messages'           => array(
 						'submission'           => __( 'Form submission from', 'otter-blocks' ),
+						'success'              => __( 'Success', 'otter-blocks' ),
 						'captcha-not-loaded'   => __( 'Captcha is not loaded. Please check your browser plugins to allow it.', 'otter-blocks' ),
 						'check-captcha'        => __( 'Please check the captcha.', 'otter-blocks' ),
 						'invalid-email'        => __( 'The email address is invalid!', 'otter-blocks' ),
@@ -968,26 +1001,80 @@ public function register_blocks() {
 				);
 			}
 
-			if ( isset( $dynamic_blocks[ $block ] ) && class_exists( $dynamic_blocks[ $block ] ) ) {
-				$classname = $dynamic_blocks[ $block ];
-				$renderer  = new $classname();
+			$renderer = isset( $dynamic_blocks[ $block ] ) ? self::instantiate_safely( $dynamic_blocks[ $block ] ) : null;
 
-				if ( method_exists( $renderer, 'render' ) ) {
-					register_block_type_from_metadata(
-						$metadata_file,
-						array(
-							'render_callback' => array( $renderer, 'render' ),
-						)
-					);
+			if ( null !== $renderer && method_exists( $renderer, 'render' ) ) {
+				register_block_type_from_metadata(
+					$metadata_file,
+					array(
+						'render_callback' => array( $renderer, 'render' ),
+					)
+				);
 
-					continue;
-				}
+				continue;
 			}
 
 			register_block_type_from_metadata( $metadata_file );
 		}
 	}
 
+	/**
+	 * Instantiate a class without ever fataling the request.
+	 *
+	 * @param mixed $classname Class name to instantiate.
+	 * @return object|null The instance, or null when it cannot be built.
+	 */
+	private static function instantiate_safely( $classname ) {
+		if ( ! is_string( $classname ) || '' === trim( $classname ) ) {
+			self::log_skipped_class( $classname, 'is not a class name' );
+
+			return null;
+		}
+
+		try {
+			// An autoloader can throw or fatal on its own; keep it inside the try.
+			if ( ! class_exists( $classname ) ) {
+				self::log_skipped_class( $classname, 'could not be loaded' );
+
+				return null;
+			}
+
+			$reflection = new \ReflectionClass( $classname );
+
+			if ( ! $reflection->isInstantiable() ) {
+				self::log_skipped_class( $classname, 'is not instantiable' );
+
+				return null;
+			}
+
+			$constructor = $reflection->getConstructor();
+
+			if ( null !== $constructor && $constructor->getNumberOfRequiredParameters() > 0 ) {
+				self::log_skipped_class( $classname, 'requires constructor arguments' );
+
+				return null;
+			}
+
+			return $reflection->newInstance();
+		} catch ( \Throwable $e ) {
+			// Covers Error too: a missing dependency inside the constructor.
+			self::log_skipped_class( $classname, 'threw while being instantiated: ' . $e->getMessage() );
+
+			return null;
+		}
+	}
+
+	/**
+	 * Log a class the plugin had to skip.
+	 *
+	 * @param mixed  $classname Class name, or whatever was given in its place.
+	 * @param string $reason    Why it was skipped.
+	 * @return void
+	 */
+	private static function log_skipped_class( $classname, $reason ) {
+		error_log( '[Otter Blocks] Skipped ' . ( is_string( $classname ) ? $classname : gettype( $classname ) ) . ': ' . $reason . '.' ); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
+	}
+
 	/**
 	 * Initialize AMP blocks.
 	 *
@@ -1002,10 +1089,10 @@ public function init_amp_blocks() {
 		);
 
 		foreach ( $classnames as $classname ) {
-			$classname = new $classname();
+			$instance = self::instantiate_safely( $classname );
 
-			if ( method_exists( $classname, 'instance' ) ) {
-				$classname->instance();
+			if ( null !== $instance && method_exists( $instance, 'instance' ) ) {
+				$instance->instance();
 			}
 		}
 	}
@@ -1075,7 +1162,7 @@ public function subscribe_fa( $block_content, $block ) {
 		$has_navigation_block = \WP_Block_Type_Registry::get_instance()->is_registered( 'core/navigation' );
 
 		if ( $has_navigation_block && ( 'core/navigation-link' === $block['blockName'] || 'core/navigation-submenu' === $block['blockName'] ) ) {
-			if ( isset( $block['attrs']['className'] ) && strpos( $block['attrs']['className'], 'fa-' ) !== false ) {
+			if ( strpos( self::get_class_name( isset( $block['attrs'] ) ? $block['attrs'] : array() ), 'fa-' ) !== false ) {
 				self::$is_fa_loaded = true;
 
 				// See the src/blocks/plugins/menu-icons/inline.css file for where this comes from.
@@ -1117,7 +1204,7 @@ public function load_sticky( $block_content, $block ) {
 			return $block_content;
 		}
 
-		if ( isset( $block['attrs']['className'] ) && false !== strpos( $block['attrs']['className'], 'o-sticky' ) ) {
+		if ( false !== strpos( self::get_class_name( isset( $block['attrs'] ) ? $block['attrs'] : array() ), 'o-sticky' ) ) {
 			$asset_file = include OTTER_BLOCKS_PATH . '/build/blocks/sticky.asset.php';
 			wp_enqueue_script(
 				'otter-sticky',
@@ -1196,7 +1283,7 @@ public function load_condition_hide_on_styles( $block_content, $block ) {
 	 * @access public
 	 */
 	public static function condition_hide_on_style() {
-		echo '<style id="o-condition-hide-inline-css">@media (max-width:768px){.o-hide-on-mobile{display:none!important}}@media (min-width:769px) and (max-width:1024px){.o-hide-on-tablet{display:none!important}}@media (min-width:1025px){.o-hide-on-desktop{display:none!important}}</style>';
+		echo '<style id="o-condition-hide-inline-css">@layer theme, base, components, utilities;@media (max-width:768px){@layer utilities{.o-hide-on-mobile:is(.o-hide-on-mobile,#_){display:none!important}}}@media (min-width:769px) and (max-width:1024px){@layer utilities{.o-hide-on-tablet:is(.o-hide-on-tablet,#_){display:none!important}}}@media (min-width:1025px){@layer utilities{.o-hide-on-desktop:is(.o-hide-on-desktop,#_){display:none!important}}}</style>';
 	}
 
 	/**
diff --git a/inc/css/blocks/class-posts-css.php b/inc/css/blocks/class-posts-css.php
index 19da67532..5e09dab5c 100644
--- a/inc/css/blocks/class-posts-css.php
+++ b/inc/css/blocks/class-posts-css.php
@@ -8,6 +8,7 @@
 namespace ThemeIsle\GutenbergBlocks\CSS\Blocks;
 
 use ThemeIsle\GutenbergBlocks\Base_CSS;
+use ThemeIsle\GutenbergBlocks\Registration;
 
 use ThemeIsle\GutenbergBlocks\CSS\CSS_Utility;
 
@@ -429,8 +430,7 @@ function ( $position, $css_variable ) {
 							return $value[ $position ];
 						},
 						'condition' => function ( $attrs ) {
-							// @phpstan-ignore-next-line
-							return isset( $attrs['className'] ) && strpos( $attrs['className'], 'is-style-tiled' ) !== false;
+							return strpos( Registration::get_class_name( $attrs ), 'is-style-tiled' ) !== false;
 						},
 					);
 				},
diff --git a/inc/integrations/api/form-response-data.php b/inc/integrations/api/form-response-data.php
index e696dc223..f9e678ae5 100644
--- a/inc/integrations/api/form-response-data.php
+++ b/inc/integrations/api/form-response-data.php
@@ -105,8 +105,8 @@ public function __construct() {
 		$this->response['success']       = false;
 		$this->response['reasons']       = array();
 		$this->response['code']          = self::SUCCESS_EMAIL_SEND;
-		$this->response['displayError']  = 'Error. Please try again.';
-		$this->response['submitMessage'] = 'Success';
+		$this->response['displayError']  = __( 'Error. Please try again.', 'otter-blocks' );
+		$this->response['submitMessage'] = __( 'Success', 'otter-blocks' );
 	}
 
 	/**
diff --git a/inc/plugins/class-atomic-wind-blocks.php b/inc/plugins/class-atomic-wind-blocks.php
index 1ac4cd425..db9815003 100644
--- a/inc/plugins/class-atomic-wind-blocks.php
+++ b/inc/plugins/class-atomic-wind-blocks.php
@@ -15,6 +15,13 @@
  */
 class Atomic_Wind_Blocks {
 
+	/**
+	 * CSS version for the Atomic Wind blocks.
+	 *
+	 * @var string
+	 */
+	const ATOMIC_WIND_CSS_VERSION = '1.0.0';
+
 	/**
 	 * Whether we are currently inside a query loop render.
 	 *
@@ -326,7 +333,7 @@ public function output_singular_css() {
 		$this->expected[ $queried->ID ] = substr_count( $queried->post_content, '<!-- wp:atomic-wind/' );
 		wp_enqueue_style( 'atomic-wind-base' );
 
-		$cached_css = get_post_meta( $queried->ID, '_atomic_wind_css', true );
+		$cached_css = $this->get_cached_css( $queried->ID );
 
 		if ( ! $cached_css ) {
 			$this->enqueue_generator();
@@ -353,7 +360,7 @@ public function maybe_enqueue_style_builder() {
 
 		if ( ! $queried instanceof \WP_Post
 			|| ! $this->post_has_atomic_wind_blocks( $queried )
-			|| get_post_meta( $queried->ID, '_atomic_wind_css', true )
+			|| $this->get_cached_css( $queried->ID )
 			|| ! current_user_can( 'edit_post', $queried->ID ) ) {
 			return;
 		}
@@ -435,7 +442,7 @@ public function output_late_css() {
 				if ( $post instanceof \WP_Post && $this->post_has_atomic_wind_blocks( $post ) ) {
 					$this->expected[ $id ] = substr_count( $post->post_content, '<!-- wp:atomic-wind/' );
 
-					$cached_css = get_post_meta( $id, '_atomic_wind_css', true );
+					$cached_css = $this->get_cached_css( $id );
 
 					if ( $cached_css ) {
 						$hash = md5( $cached_css );
@@ -507,10 +514,27 @@ public function rest_save_style( \WP_REST_Request $request ) {
 		$css     = $request->get_param( 'css' );
 
 		$success = update_post_meta( $post_id, '_atomic_wind_css', wp_slash( $css ) );
+		update_post_meta( $post_id, '_atomic_wind_css_version', self::ATOMIC_WIND_CSS_VERSION );
 
 		return new \WP_REST_Response( array( 'success' => $success ), 200 );
 	}
 
+	/**
+	 * Read cached CSS, ignoring stylesheets built by an older generator.
+	 *
+	 * @param int $post_id Post ID.
+	 * @return string
+	 */
+	private function get_cached_css( $post_id ) {
+		if ( self::ATOMIC_WIND_CSS_VERSION !== get_post_meta( $post_id, '_atomic_wind_css_version', true ) ) {
+			return '';
+		}
+
+		$css = get_post_meta( $post_id, '_atomic_wind_css', true );
+
+		return is_string( $css ) ? $css : '';
+	}
+
 	/**
 	 * REST permission callback for the style endpoint.
 	 *
@@ -534,6 +558,7 @@ public function rest_save_style_permissions( \WP_REST_Request $request ) {
 	 */
 	public function clear_cached_css( $post_id ) {
 		delete_post_meta( $post_id, '_atomic_wind_css' );
+		delete_post_meta( $post_id, '_atomic_wind_css_version' );
 	}
 
 	/**
diff --git a/inc/render/class-posts-grid-block.php b/inc/render/class-posts-grid-block.php
index da6b61d48..4e1afe4f1 100644
--- a/inc/render/class-posts-grid-block.php
+++ b/inc/render/class-posts-grid-block.php
@@ -7,6 +7,8 @@
 
 namespace ThemeIsle\GutenbergBlocks\Render;
 
+use ThemeIsle\GutenbergBlocks\Registration;
+
 /**
  * Class Posts_Grid_Block
  */
@@ -26,7 +28,7 @@ public function render( $attributes ) {
 		add_filter( 'wp_img_tag_add_auto_sizes', '__return_false' );
 		$has_pagination = isset( $attributes['hasPagination'] ) && $attributes['hasPagination'];
 		$page_number    = 1;
-		$is_tiled       = isset( $attributes['className'] ) && false !== strpos( $attributes['className'], 'is-style-tiled' );
+		$is_tiled       = false !== strpos( Registration::get_class_name( $attributes ), 'is-style-tiled' );
 
 		if ( $has_pagination ) {
 			if ( ! empty( get_query_var( 'page' ) ) || ! empty( get_query_var( 'paged' ) ) ) {
@@ -301,7 +303,7 @@ protected function render_featured_post( $post, $attributes ) {
 		$image_alt = get_post_meta( $thumb_id, '_wp_attachment_image_alt', true );
 		$style     = '';
 		$image_url = wp_get_attachment_image_src( $thumb_id, $size );
-		$is_tiled  = isset( $attributes['className'] ) && false !== strpos( $attributes['className'], 'is-style-tiled' );
+		$is_tiled  = false !== strpos( Registration::get_class_name( $attributes ), 'is-style-tiled' );
 
 		if ( ! $image_alt ) {
 			$image_alt = get_the_title( $id );
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 07f689482..c1ba7b1a4 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -420,12 +420,6 @@ parameters:
 			count: 1
 			path: inc/class-pro.php
 
-		-
-			rawMessage: 'Call to function method_exists() with ThemeIsle\GutenbergBlocks\Render\AMP\Circle_Counter_Block|ThemeIsle\GutenbergBlocks\Render\AMP\Lottie_Block|ThemeIsle\GutenbergBlocks\Render\AMP\Slider_Block and ''instance'' will always evaluate to true.'
-			identifier: function.alreadyNarrowedType
-			count: 1
-			path: inc/class-registration.php
-
 		-
 			rawMessage: 'Method ThemeIsle\GutenbergBlocks\Registration::block_categories() has parameter $categories with no value type specified in iterable type array.'
 			identifier: missingType.iterableValue
diff --git a/plugins/blocks-animation/composer.lock b/plugins/blocks-animation/composer.lock
index d03d95990..e4c2804b4 100644
--- a/plugins/blocks-animation/composer.lock
+++ b/plugins/blocks-animation/composer.lock
@@ -8,16 +8,16 @@
     "packages": [
         {
             "name": "codeinwp/themeisle-sdk",
-            "version": "3.3.58",
+            "version": "3.3.61",
             "source": {
                 "type": "git",
                 "url": "https://github.com/Codeinwp/themeisle-sdk.git",
-                "reference": "d6807c0b7308e323bd77cced667dee3f2d5e6a82"
+                "reference": "9fe698b52dec768a0dd8b500fb51efe40962ee99"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/Codeinwp/themeisle-sdk/zipball/d6807c0b7308e323bd77cced667dee3f2d5e6a82",
-                "reference": "d6807c0b7308e323bd77cced667dee3f2d5e6a82",
+                "url": "https://api.github.com/repos/Codeinwp/themeisle-sdk/zipball/9fe698b52dec768a0dd8b500fb51efe40962ee99",
+                "reference": "9fe698b52dec768a0dd8b500fb51efe40962ee99",
                 "shasum": ""
             },
             "require-dev": {
@@ -43,9 +43,9 @@
             ],
             "support": {
                 "issues": "https://github.com/Codeinwp/themeisle-sdk/issues",
-                "source": "https://github.com/Codeinwp/themeisle-sdk/tree/v3.3.58"
+                "source": "https://github.com/Codeinwp/themeisle-sdk/tree/v3.3.61"
             },
-            "time": "2026-07-29T08:38:52+00:00"
+            "time": "2026-08-24T15:59:27+00:00"
         }
     ],
     "packages-dev": [],
diff --git a/plugins/blocks-css/composer.lock b/plugins/blocks-css/composer.lock
index c2a3c2df6..e61f91b1d 100644
--- a/plugins/blocks-css/composer.lock
+++ b/plugins/blocks-css/composer.lock
@@ -8,16 +8,16 @@
     "packages": [
         {
             "name": "codeinwp/themeisle-sdk",
-            "version": "3.3.58",
+            "version": "3.3.61",
             "source": {
                 "type": "git",
                 "url": "https://github.com/Codeinwp/themeisle-sdk.git",
-                "reference": "d6807c0b7308e323bd77cced667dee3f2d5e6a82"
+                "reference": "9fe698b52dec768a0dd8b500fb51efe40962ee99"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/Codeinwp/themeisle-sdk/zipball/d6807c0b7308e323bd77cced667dee3f2d5e6a82",
-                "reference": "d6807c0b7308e323bd77cced667dee3f2d5e6a82",
+                "url": "https://api.github.com/repos/Codeinwp/themeisle-sdk/zipball/9fe698b52dec768a0dd8b500fb51efe40962ee99",
+                "reference": "9fe698b52dec768a0dd8b500fb51efe40962ee99",
                 "shasum": ""
             },
             "require-dev": {
@@ -43,9 +43,9 @@
             ],
             "support": {
                 "issues": "https://github.com/Codeinwp/themeisle-sdk/issues",
-                "source": "https://github.com/Codeinwp/themeisle-sdk/tree/v3.3.58"
+                "source": "https://github.com/Codeinwp/themeisle-sdk/tree/v3.3.61"
             },
-            "time": "2026-07-29T08:38:52+00:00"
+            "time": "2026-08-24T15:59:27+00:00"
         }
     ],
     "packages-dev": [],
diff --git a/plugins/otter-pro/inc/render/class-modal-block.php b/plugins/otter-pro/inc/render/class-modal-block.php
index 609337978..5fac80cf8 100644
--- a/plugins/otter-pro/inc/render/class-modal-block.php
+++ b/plugins/otter-pro/inc/render/class-modal-block.php
@@ -8,6 +8,7 @@
 namespace ThemeIsle\OtterPro\Render;
 
 use ThemeIsle\OtterPro\Plugins\License;
+use ThemeIsle\GutenbergBlocks\Registration;
 
 /**
  * Class Modal_CSS.
@@ -45,8 +46,10 @@ public function render( $attributes, $content, $block ) {
 
 		$classes = array( 'wp-block-themeisle-blocks-modal', 'is-active', 'is-front' );
 
-		if ( ! empty( $attributes['className'] ) ) {
-			$classes[] = esc_attr( $attributes['className'] );
+		$class_name = Registration::get_class_name( $attributes );
+
+		if ( ! empty( $class_name ) ) {
+			$classes[] = esc_attr( $class_name );
 		}
 
 		if ( ! empty( $attributes['closeButtonType'] ) && 'outside' === $attributes['closeButtonType'] ) {
diff --git a/plugins/otter-pro/inc/server/class-dashboard-server.php b/plugins/otter-pro/inc/server/class-dashboard-server.php
index df505f61e..e55b763ea 100644
--- a/plugins/otter-pro/inc/server/class-dashboard-server.php
+++ b/plugins/otter-pro/inc/server/class-dashboard-server.php
@@ -35,6 +35,20 @@ class Dashboard_Server {
 	 */
 	public $version = 'v1';
 
+	/**
+	 * Neve price IDs that bundle Otter Pro.
+	 *
+	 * @var int[]
+	 */
+	const VALID_NEVE_PLANS = array( 5, 6, 9, 14, 17, 20, 23, 27, 28, 29 );
+
+	/**
+	 * License statuses describing a key that does cover Otter Pro but cannot be used right now.
+	 *
+	 * @var string[]
+	 */
+	const NON_PLAN_LICENSE_STATUSES = array( 'expired', 'active_expired', 'revoked', 'site_inactive', 'no_activations_left', 'not_active' );
+
 	/**
 	 * Initialize the class
 	 */
@@ -141,11 +155,21 @@ public function toggle_license( $request ) {
 		}
 
 		$response = apply_filters( 'themeisle_sdk_license_process_otter', $fields['key'], $fields['action'] );
+		$plan     = (int) apply_filters( 'product_otter_license_plan', 0 );
 
 		if ( is_wp_error( $response ) ) {
+			$message = $response->get_error_message();
+			if (
+				'activate' === $fields['action'] &&
+				'themeisle-license-invalid' === $response->get_error_code() &&
+				$this->is_ineligible_plan( $plan )
+			) {
+				$message = __( 'Entered license key does not include Otter Pro.', 'otter-pro' );
+			}
+
 			return new \WP_REST_Response(
 				array(
-					'message' => $response->get_error_message(),
+					'message' => $message,
 					'success' => false,
 				)
 			);
@@ -164,6 +188,28 @@ public function toggle_license( $request ) {
 		);
 	}
 
+	/**
+	 * Whether the stored license data proves the key belongs to a plan without Otter Pro.
+	 *
+	 * @param int $plan Price ID reported for the stored license.
+	 * @return bool
+	 */
+	private function is_ineligible_plan( $plan ) {
+		$license_data = License::get_license_data();
+
+		if ( ! is_object( $license_data ) || ! isset( $license_data->price_id ) ) {
+			return false;
+		}
+
+		$status = isset( $license_data->license ) ? $license_data->license : '';
+
+		if ( in_array( $status, self::NON_PLAN_LICENSE_STATUSES, true ) ) {
+			return false;
+		}
+
+		return ! in_array( $plan, self::VALID_NEVE_PLANS, true );
+	}
+
 	/**
 	 * The instance method for the static class.
 	 * Defines and returns the instance of the static class.
diff --git a/src/atomic-wind/tailwind/generator-frontend.js b/src/atomic-wind/tailwind/generator-frontend.js
index 3417512af..b87065272 100644
--- a/src/atomic-wind/tailwind/generator-frontend.js
+++ b/src/atomic-wind/tailwind/generator-frontend.js
@@ -4,6 +4,7 @@ import indexCSS from 'tailwindcss/index.css';
 import preflightCSS from 'tailwindcss/preflight.css';
 import themeCSS from 'tailwindcss/theme.css';
 import utilitiesCSS from 'tailwindcss/utilities.css';
+import { scopeToAtomicWind } from './scope-css';
 
 const assets = {
 	index: indexCSS,
@@ -71,7 +72,7 @@ async function build( kind ) {
 		return;
 	}
 
-	sheet.textContent = compiler.build( Array.from( newClasses ) );
+	sheet.textContent = scopeToAtomicWind( compiler.build( Array.from( newClasses ) ) );
 }
 
 function rebuild( kind ) {
diff --git a/src/atomic-wind/tailwind/generator.js b/src/atomic-wind/tailwind/generator.js
index fdc601ec3..a044c8212 100644
--- a/src/atomic-wind/tailwind/generator.js
+++ b/src/atomic-wind/tailwind/generator.js
@@ -4,6 +4,7 @@ import indexCSS from 'tailwindcss/index.css';
 import preflightCSS from 'tailwindcss/preflight.css';
 import themeCSS from 'tailwindcss/theme.css';
 import utilitiesCSS from 'tailwindcss/utilities.css';
+import { prefixCss, scopeToAtomicWind } from './scope-css';
 
 const assets = {
 	index: indexCSS,
@@ -87,157 +88,6 @@ function resolveEditorContext() {
 	return null;
 }
 
-function splitSelectorList( selectorText ) {
-	const selectors = [];
-	let current = '';
-	let parenDepth = 0;
-	let bracketDepth = 0;
-	let braceDepth = 0;
-	let inSingleQuote = false;
-	let inDoubleQuote = false;
-	let escaped = false;
-
-	for ( const char of selectorText ) {
-		if ( escaped ) {
-			current += char;
-			escaped = false;
-			continue;
-		}
-
-		if ( '\\' === char ) {
-			current += char;
-			escaped = true;
-			continue;
-		}
-
-		if ( '\'' === char && ! inDoubleQuote ) {
-			inSingleQuote = ! inSingleQuote;
-			current += char;
-			continue;
-		}
-
-		if ( '"' === char && ! inSingleQuote ) {
-			inDoubleQuote = ! inDoubleQuote;
-			current += char;
-			continue;
-		}
-
-		if ( inSingleQuote || inDoubleQuote ) {
-			current += char;
-			continue;
-		}
-
-		if ( '(' === char ) {
-			parenDepth++;
-			current += char;
-			continue;
-		}
-		if ( ')' === char ) {
-			parenDepth = Math.max( 0, parenDepth - 1 );
-			current += char;
-			continue;
-		}
-
-		if ( '[' === char ) {
-			bracketDepth++;
-			current += char;
-			continue;
-		}
-		if ( ']' === char ) {
-			bracketDepth = Math.max( 0, bracketDepth - 1 );
-			current += char;
-			continue;
-		}
-
-		if ( '{' === char ) {
-			braceDepth++;
-			current += char;
-			continue;
-		}
-		if ( '}' === char ) {
-			braceDepth = Math.max( 0, braceDepth - 1 );
-			current += char;
-			continue;
-		}
-
-		if ( ',' === char && 0 === parenDepth && 0 === bracketDepth && 0 === braceDepth ) {
-			selectors.push( current.trim() );
-			current = '';
-			continue;
-		}
-
-		current += char;
-	}
-
-	if ( current.trim() ) {
-		selectors.push( current.trim() );
-	}
-
-	return selectors;
-}
-
-function prefixSelectorList( selectorText, scopeSelector ) {
-	return splitSelectorList( selectorText )
-		.map( ( selector ) => {
-			if ( /^(:root|:host|html|body)(\b|$|:|\.|#|\[)/.test( selector ) ) {
-				return scopeSelector;
-			}
-
-			return `${scopeSelector} ${selector}`;
-		} )
-		.join( ', ' );
-}
-
-function scopeRuleCss( rule, scopeSelector ) {
-	if ( CSSRule.STYLE_RULE === rule.type ) {
-		const open = rule.cssText.indexOf( '{' );
-		if ( -1 === open ) {
-			return rule.cssText;
-		}
-
-		const prefixedSelector = prefixSelectorList( rule.selectorText, scopeSelector );
-		const body = rule.cssText.slice( open );
-		return `${prefixedSelector}${body}`;
-	}
-
-	if (
-		CSSRule.FONT_FACE_RULE === rule.type ||
-		CSSRule.KEYFRAMES_RULE === rule.type ||
-		( 'PROPERTY_RULE' in CSSRule && CSSRule.PROPERTY_RULE === rule.type )
-	) {
-		return rule.cssText;
-	}
-
-	if ( rule.cssRules && rule.cssRules.length > 0 ) {
-		const open = rule.cssText.indexOf( '{' );
-		const close = rule.cssText.lastIndexOf( '}' );
-		if ( -1 !== open && -1 !== close ) {
-			return `${rule.cssText.slice( 0, open + 1 )}${scopeCssRules( rule.cssRules, scopeSelector )}}`;
-		}
-	}
-
-	return rule.cssText;
-}
-
-function scopeCssRules( rules, scopeSelector ) {
-	return Array.from( rules ).map( ( rule ) => scopeRuleCss( rule, scopeSelector ) ).join( '' );
-}
-
-function scopeGeneratedCss( css, scopeSelector ) {
-	if ( ! css || ! scopeSelector ) {
-		return css;
-	}
-
-	try {
-		const parsed = new CSSStyleSheet();
-		parsed.replaceSync( css );
-		return scopeCssRules( parsed.cssRules, scopeSelector );
-	} catch ( error ) {
-		console.error( error );
-		return css;
-	}
-}
-
 function attachObserver( root ) {
 	if ( observer ) {
 		observer.disconnect();
@@ -369,14 +219,14 @@ async function build( kind ) {
 		return;
 	}
 
-	const generated = compiler.build( Array.from( newClasses ) );
-	const scopedCss = activeScopeSelector ? scopeGeneratedCss( generated, activeScopeSelector ) : generated;
+	const generated = scopeToAtomicWind( compiler.build( Array.from( newClasses ) ) );
+	const scopedCss = activeScopeSelector ? prefixCss( generated, activeScopeSelector ) : generated;
 	ensureStyleTag( activeDocument );
 	sheet.textContent = scopedCss;
 }
 
 // Lets other editor features (the Design Library pattern previews) generate
-// unscoped Tailwind CSS for an arbitrary class list. Kept separate from the
+// Tailwind CSS for an arbitrary class list. Kept separate from the
 // canvas compiler: it must not pollute the canvas sheet, and canvas full
 // rebuilds reset that compiler, which would drop classes fed in here. The
 // compiler is cumulative — each call returns the full stylesheet for every
@@ -392,7 +242,7 @@ window.atomicWindGenerateCss = async ( classNames ) => {
 	}
 
 	const instance = await apiCompiler;
-	return instance.build( Array.from( new Set( classNames ) ) );
+	return scopeToAtomicWind( instance.build( Array.from( new Set( classNames ) ) ) );
 };
 
 function rebuild( kind ) {
diff --git a/src/atomic-wind/tailwind/scope-css.js b/src/atomic-wind/tailwind/scope-css.js
new file mode 100644
index 000000000..11564efbd
--- /dev/null
+++ b/src/atomic-wind/tailwind/scope-css.js
@@ -0,0 +1,385 @@
+/**
+ * Selector rewriting for the generated Tailwind stylesheet.
+ *
+ * Tailwind ships preflight, whose rules target bare HTML elements (`h1`,
+ * `button`, `img`, `*`). Injected as-is they reset the whole document and win
+ * over the theme's own element styles, so every element-anchored rule is
+ * confined to the Atomic Wind block subtree. Class-anchored rules (the
+ * utilities) stay global — they only match our generated markup anyway.
+ */
+
+const ATOMIC_ROOT = '[class*="wp-block-atomic-wind-"]';
+const ATOMIC_MATCH = `:where(${ ATOMIC_ROOT }, ${ ATOMIC_ROOT } *)`;
+// Zero specificity, so a theme rule aimed at the block wrapper still wins.
+const ATOMIC_SELF = `:where(${ ATOMIC_ROOT })`;
+
+// At-rules whose bodies are not selector lists and must be emitted verbatim.
+const OPAQUE_AT_RULE = /^@(-[a-z]+-)?(keyframes|font-face|property|counter-style|font-feature-values|font-palette-values|page|viewport|charset|import|namespace)\b/i;
+
+// Document-level subjects: they carry inherited defaults, not element resets.
+const ROOT_SELECTOR = /^(:root|:host|html|body)$/;
+
+const ROOT_PREFIX = /^(:root|:host|html|body)(?=$|[\s>+~])/;
+
+const LEGACY_PSEUDO_ELEMENT = /^:(before|after|first-line|first-letter)\b/i;
+
+const COMBINATOR = /[\s>+~]/;
+
+/**
+ * Mark every character that sits outside brackets, parentheses and strings.
+ *
+ * @param {string} text Selector or prelude text.
+ * @return {boolean[]} Per-character top-level flags.
+ */
+function topLevelMask( text ) {
+	const mask = new Array( text.length ).fill( false );
+	let depth = 0;
+	let quote = '';
+	let escaped = false;
+
+	for ( let i = 0; i < text.length; i++ ) {
+		const char = text[ i ];
+
+		if ( escaped ) {
+			escaped = false;
+			continue;
+		}
+
+		if ( '\\' === char ) {
+			escaped = true;
+			continue;
+		}
+
+		if ( quote ) {
+			if ( char === quote ) {
+				quote = '';
+			}
+			continue;
+		}
+
+		if ( '"' === char || '\'' === char ) {
+			quote = char;
+			continue;
+		}
+
+		if ( '(' === char || '[' === char || '{' === char ) {
+			mask[ i ] = 0 === depth;
+			depth++;
+			continue;
+		}
+
+		if ( ')' === char || ']' === char || '}' === char ) {
+			depth = Math.max( 0, depth - 1 );
+			mask[ i ] = 0 === depth;
+			continue;
+		}
+
+		mask[ i ] = 0 === depth;
+	}
+
+	return mask;
+}
+
+/**
+ * Split a comma-separated selector list, ignoring commas nested in `:is()` & co.
+ *
+ * @param {string} selectorText Selector list.
+ * @return {string[]} Individual selectors.
+ */
+export function splitSelectorList( selectorText ) {
+	const mask = topLevelMask( selectorText );
+	const selectors = [];
+	let start = 0;
+
+	for ( let i = 0; i < selectorText.length; i++ ) {
+		if ( ',' === selectorText[ i ] && mask[ i ] ) {
+			selectors.push( selectorText.slice( start, i ).trim() );
+			start = i + 1;
+		}
+	}
+
+	selectors.push( selectorText.slice( start ).trim() );
+
+	return selectors.filter( Boolean );
+}
+
+/**
+ * Locate the start of the subject compound (everything after the last combinator).
+ *
+ * @param {string} selector Single selector.
+ * @return {number} Index the subject compound starts at.
+ */
+function subjectStart( selector ) {
+	const mask = topLevelMask( selector );
+	let start = 0;
+
+	for ( let i = 0; i < selector.length; i++ ) {
+		if ( mask[ i ] && COMBINATOR.test( selector[ i ] ) ) {
+			start = i + 1;
+		}
+	}
+
+	return start;
+}
+
+/**
+ * Find where the subject's pseudo-element suffix begins.
+ *
+ * @param {string} subject Subject compound.
+ * @return {number} Index of the pseudo-element, or -1.
+ */
+function pseudoElementStart( subject ) {
+	const mask = topLevelMask( subject );
+
+	for ( let i = 0; i < subject.length; i++ ) {
+		if ( ! mask[ i ] || ':' !== subject[ i ] ) {
+			continue;
+		}
+
+		if ( ':' === subject[ i + 1 ] || LEGACY_PSEUDO_ELEMENT.test( subject.slice( i ) ) ) {
+			return i;
+		}
+	}
+
+	return -1;
+}
+
+/**
+ * Whether the subject is already anchored to a class or id.
+ *
+ * Those are the generated utilities; attribute-only subjects (`[hidden]`) still
+ * match theme markup, so they get scoped like bare elements do.
+ *
+ * @param {string} subject Subject compound.
+ * @return {boolean} True when the rule cannot leak onto theme markup.
+ */
+function isAnchored( subject ) {
+	const mask = topLevelMask( subject );
+
+	for ( let i = 0; i < subject.length; i++ ) {
+		if ( mask[ i ] && ( '.' === subject[ i ] || '#' === subject[ i ] ) ) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+/**
+ * Confine one selector to the Atomic Wind subtree when it targets bare elements.
+ *
+ * @param {string} selector Single selector.
+ * @return {string} Scoped selector.
+ */
+function scopeSelectorToBlocks( selector ) {
+	const start = subjectStart( selector );
+	const subject = selector.slice( start );
+
+	if ( 0 === start && ROOT_SELECTOR.test( subject ) ) {
+		return ATOMIC_SELF;
+	}
+
+	if ( isAnchored( subject ) ) {
+		return selector;
+	}
+
+	const prefix = selector.slice( 0, start );
+	const pseudo = pseudoElementStart( subject );
+	const base = -1 === pseudo ? subject : subject.slice( 0, pseudo );
+	const suffix = -1 === pseudo ? '' : subject.slice( pseudo );
+
+	return `${ prefix }${ base || '*' }${ ATOMIC_MATCH }${ suffix }`;
+}
+
+/**
+ * Index of the `}` closing the block opened at `open`.
+ *
+ * @param {string} css  Stylesheet text.
+ * @param {number} open Index of the opening brace.
+ * @return {number} Index of the matching brace, or -1 when unterminated.
+ */
+function blockEnd( css, open ) {
+	let depth = 0;
+	let quote = '';
+	let escaped = false;
+
+	for ( let i = open; i < css.length; i++ ) {
+		const char = css[ i ];
+
+		if ( escaped ) {
+			escaped = false;
+			continue;
+		}
+
+		if ( '\\' === char ) {
+			escaped = true;
+			continue;
+		}
+
+		if ( quote ) {
+			if ( char === quote ) {
+				quote = '';
+			}
+			continue;
+		}
+
+		if ( '/' === char && '*' === css[ i + 1 ] ) {
+			const end = css.indexOf( '*/', i + 2 );
+			i = -1 === end ? css.length : end + 1;
+			continue;
+		}
+
+		if ( '"' === char || '\'' === char ) {
+			quote = char;
+			continue;
+		}
+
+		if ( '{' === char ) {
+			depth++;
+			continue;
+		}
+
+		if ( '}' === char ) {
+			depth--;
+			if ( 0 === depth ) {
+				return i;
+			}
+		}
+	}
+
+	return -1;
+}
+
+/**
+ * Rewrite every style-rule selector in a stylesheet.
+ *
+ * A falsy return from `transform` drops the rule.
+ *
+ * @param {string}   css       Stylesheet text.
+ * @param {Function} transform Receives the selector list and the declaration block.
+ * @return {string} Rewritten stylesheet.
+ */
+export function transformCssSelectors( css, transform ) {
+	let out = '';
+	let prelude = '';
+	let i = 0;
+
+	while ( i < css.length ) {
+		const char = css[ i ];
+
+		if ( '/' === char && '*' === css[ i + 1 ] ) {
+			const end = css.indexOf( '*/', i + 2 );
+			i = -1 === end ? css.length : end + 2;
+			continue;
+		}
+
+		if ( '\\' === char ) {
+			prelude += css.slice( i, i + 2 );
+			i += 2;
+			continue;
+		}
+
+		if ( '"' === char || '\'' === char ) {
+			let end = i + 1;
+			while ( end < css.length ) {
+				if ( '\\' === css[ end ] ) {
+					end += 2;
+					continue;
+				}
+				if ( css[ end ] === char ) {
+					end++;
+					break;
+				}
+				end++;
+			}
+			prelude += css.slice( i, end );
+			i = end;
+			continue;
+		}
+
+		if ( '{' === char ) {
+			const end = blockEnd( css, i );
+			const close = -1 === end ? css.length : end;
+			const body = css.slice( i + 1, close );
+			const trimmed = prelude.trim();
+
+			if ( trimmed.startsWith( '@' ) ) {
+				const inner = OPAQUE_AT_RULE.test( trimmed ) ? body : transformCssSelectors( body, transform );
+				out += `${ trimmed }{${ inner }}`;
+			} else {
+				const selector = transform( trimmed, body );
+				if ( selector ) {
+					out += `${ selector }{${ body }}`;
+				}
+			}
+
+			prelude = '';
+			i = close + 1;
+			continue;
+		}
+
+		if ( ';' === char ) {
+			out += `${ prelude.trim() };`;
+			prelude = '';
+			i++;
+			continue;
+		}
+
+		if ( '}' === char ) {
+			i++;
+			continue;
+		}
+
+		prelude += char;
+		i++;
+	}
+
+	return out + prelude.trim();
+}
+
+/**
+ * Keep Tailwind's element resets and variables inside Atomic Wind blocks.
+ *
+ * @param {string} css Generated stylesheet.
+ * @return {string} Scoped stylesheet.
+ */
+export function scopeToAtomicWind( css ) {
+	if ( ! css ) {
+		return css;
+	}
+
+	return transformCssSelectors( css, ( selectorText ) => {
+		const scoped = splitSelectorList( selectorText ).map( scopeSelectorToBlocks );
+
+		return Array.from( new Set( scoped ) ).join( ', ' );
+	} );
+}
+
+/**
+ * Prefix every selector with a container scope (used for the editor canvas).
+ *
+ * @param {string} css           Generated stylesheet.
+ * @param {string} scopeSelector Container selector.
+ * @return {string} Prefixed stylesheet.
+ */
+export function prefixCss( css, scopeSelector ) {
+	if ( ! css || ! scopeSelector ) {
+		return css;
+	}
+
+	return transformCssSelectors( css, ( selectorText ) =>
+		splitSelectorList( selectorText )
+			.map( ( selector ) => {
+				// The container stands in for the document root, so substitute it
+				// for a leading root compound rather than prepending.
+				const rooted = selector.match( ROOT_PREFIX );
+
+				if ( rooted ) {
+					return `${ scopeSelector }${ selector.slice( rooted[ 0 ].length ) }`;
+				}
+
+				return `${ scopeSelector } ${ selector }`;
+			} )
+			.join( ', ' )
+	);
+}
diff --git a/src/atomic-wind/tailwind/test/scope-css.test.js b/src/atomic-wind/tailwind/test/scope-css.test.js
new file mode 100644
index 000000000..f19b7d87e
--- /dev/null
+++ b/src/atomic-wind/tailwind/test/scope-css.test.js
@@ -0,0 +1,185 @@
+import { prefixCss, scopeToAtomicWind, splitSelectorList } from '../scope-css';
+
+const MATCH = ':where([class*="wp-block-atomic-wind-"], [class*="wp-block-atomic-wind-"] *)';
+const SELF = ':where([class*="wp-block-atomic-wind-"])';
+
+describe( 'splitSelectorList', () => {
+	it( 'ignores commas nested in functional pseudo-classes and strings', () => {
+		expect( splitSelectorList( 'a:is(b, c), d[title="x, y"], e' ) ).toEqual( [
+			'a:is(b, c)',
+			'd[title="x, y"]',
+			'e',
+		] );
+	} );
+} );
+
+describe( 'scopeToAtomicWind', () => {
+	it( 'confines element resets to the block subtree', () => {
+		expect( scopeToAtomicWind( 'h1, h2 { font-size: inherit; }' ) ).toBe(
+			`h1${ MATCH }, h2${ MATCH }{ font-size: inherit; }`
+		);
+	} );
+
+	it( 'leaves utility rules global', () => {
+		const css = '.flex{display:flex}#id{color:red}';
+		expect( scopeToAtomicWind( css ) ).toBe( css );
+	} );
+
+	it( 'scopes the subject compound only, keeping ancestors intact', () => {
+		expect( scopeToAtomicWind( ':where(select:is([multiple])) optgroup{font-weight:bolder}' ) ).toBe(
+			`:where(select:is([multiple])) optgroup${ MATCH }{font-weight:bolder}`
+		);
+	} );
+
+	it( 'keeps the pseudo-element last and qualifies bare ones with a universal', () => {
+		expect( scopeToAtomicWind( '::placeholder, h1::before, p:first-line{opacity:1}' ) ).toBe(
+			`*${ MATCH }::placeholder, h1${ MATCH }::before, p${ MATCH }:first-line{opacity:1}`
+		);
+	} );
+
+	it( 'scopes attribute-anchored rules, which still match theme markup', () => {
+		expect( scopeToAtomicWind( '[hidden]{display:none !important}' ) ).toBe(
+			`[hidden]${ MATCH }{display:none !important}`
+		);
+	} );
+
+	it( 'moves document-level styling onto the block wrapper', () => {
+		expect( scopeToAtomicWind( 'html, :host{line-height:1.5;tab-size:4}' ) ).toBe(
+			`${ SELF }{line-height:1.5;tab-size:4}`
+		);
+	} );
+
+	it( 'moves theme variables onto the block wrapper so they cannot shadow theme ones', () => {
+		expect( scopeToAtomicWind( ':root, :host{--spacing:0.25rem;--text-lg:1.125rem}' ) ).toBe(
+			`${ SELF }{--spacing:0.25rem;--text-lg:1.125rem}`
+		);
+	} );
+
+	it( 'scopes the universal custom-property initializers', () => {
+		expect( scopeToAtomicWind( '*, ::before, ::backdrop{--tw-content:""}' ) ).toBe(
+			`*${ MATCH }, *${ MATCH }::before, *${ MATCH }::backdrop{--tw-content:""}`
+		);
+	} );
+
+	it( 'keeps a document root used as an ancestor, scoping its subject instead', () => {
+		// `[body_&]:text-red-500` and friends put a root in front of the real
+		// subject; collapsing the whole selector would drop that subject and
+		// apply the declarations to every block wrapper.
+		expect( scopeToAtomicWind( 'body .\\[body_\\&\\]\\:text-red-500{color:red}' ) ).toBe(
+			'body .\\[body_\\&\\]\\:text-red-500{color:red}'
+		);
+
+		expect( scopeToAtomicWind( 'html figure{margin:0}' ) ).toBe(
+			`html figure${ MATCH }{margin:0}`
+		);
+	} );
+
+	it( 'recurses into conditional at-rules', () => {
+		expect( scopeToAtomicWind( '@layer base{@media (width >= 48rem){img{display:block}}}' ) ).toBe(
+			`@layer base{@media (width >= 48rem){img${ MATCH }{display:block}}}`
+		);
+	} );
+
+	it( 'emits keyframes, @property and @import verbatim', () => {
+		const css = '@import "x.css";@property --tw-x{syntax:"*";inherits:false}@keyframes spin{from{transform:rotate(0)}to{transform:rotate(1turn)}}';
+		expect( scopeToAtomicWind( css ) ).toBe( css );
+	} );
+
+	it( 'leaves nested selectors inside a utility rule untouched', () => {
+		const css = '.space-y-4{:where(& > :not(:last-child)){margin-block-start:0}}.hover\\:underline{&:hover{text-decoration:underline}}';
+		expect( scopeToAtomicWind( css ) ).toBe( css );
+	} );
+
+	it( 'keeps escaped arbitrary-value selectors intact and keeps scoping after them', () => {
+		// Tailwind escapes the quotes in `after:content-["it's"]`, leaving a lone
+		// apostrophe. Reading it as a string opener used to swallow the rest of
+		// the stylesheet, silently leaking every element rule that followed.
+		const utility = '.after\\:content-\\[\\"it\\\'s\\"\\]';
+		const css = `${ utility }{--tw-content:"it's"}h1{font-size:inherit}`;
+
+		expect( scopeToAtomicWind( css ) ).toBe(
+			`${ utility }{--tw-content:"it's"}h1${ MATCH }{font-size:inherit}`
+		);
+	} );
+
+	it( 'does not split selectors on escaped commas', () => {
+		const utility = '.grid-cols-\\[repeat\\(2\\,minmax\\(0\\,1fr\\)\\)\\]';
+		const css = `${ utility }{grid-template-columns:repeat(2,minmax(0,1fr))}`;
+
+		expect( scopeToAtomicWind( css ) ).toBe( css );
+	} );
+
+	it( 'handles a Tailwind-shaped stylesheet layer by layer', () => {
+		const css = [
+			'@layer properties;@layer theme, base, components, utilities;',
+			'@layer theme{:root, :host{--spacing:0.25rem}}',
+			'@layer base{*, ::before{box-sizing:border-box;margin:0}',
+			'html, :host{line-height:1.5}',
+			'ul, menu{list-style:none}',
+			'input:where([type="button"])::file-selector-button{appearance:button}}',
+			'@layer utilities{.flex{display:flex !important}',
+			'.hover\\:underline{&:hover{@media (hover: hover){text-decoration:underline !important}}}}',
+			'@property --tw-content{syntax:"*";initial-value:"";inherits:false}',
+		].join( '' );
+
+		const out = scopeToAtomicWind( css );
+
+		// Layer statements, theme variables, utilities and @property pass through.
+		expect( out ).toContain( '@layer properties;@layer theme, base, components, utilities;' );
+		expect( out ).toContain( `@layer theme{${ SELF }{--spacing:0.25rem}}` );
+		expect( out ).toContain( '.flex{display:flex !important}' );
+		expect( out ).toContain( '.hover\\:underline{&:hover{@media (hover: hover){text-decoration:underline !important}}}' );
+		expect( out ).toContain( '@property --tw-content{syntax:"*";initial-value:"";inherits:false}' );
+
+		// Every base-layer rule is confined to the blocks.
+		expect( out ).toContain( `*${ MATCH }, *${ MATCH }::before{box-sizing:border-box;margin:0}` );
+		expect( out ).toContain( `${ SELF }{line-height:1.5}` );
+		expect( out ).toContain( `ul${ MATCH }, menu${ MATCH }{list-style:none}` );
+		expect( out ).toContain( `input:where([type="button"])${ MATCH }::file-selector-button{appearance:button}` );
+
+		// No bare element selector survives at the start of a rule.
+		expect( out ).not.toMatch( /(^|[{};])\s*(html|ul|menu|input)\s*[,{]/ );
+	} );
+
+	it( 'is a no-op on empty input', () => {
+		expect( scopeToAtomicWind( '' ) ).toBe( '' );
+	} );
+} );
+
+describe( 'prefixCss', () => {
+	it( 'prefixes selectors and collapses document-level ones onto the scope', () => {
+		expect( prefixCss( 'h1{color:red}html{tab-size:4}', ':where(.editor-styles-wrapper)' ) ).toBe(
+			':where(.editor-styles-wrapper) h1{color:red}:where(.editor-styles-wrapper){tab-size:4}'
+		);
+	} );
+
+	it( 'substitutes the scope for a leading document root, keeping the descendant', () => {
+		// The container is itself inside `body`, so prepending would produce
+		// `:where(.editor-styles-wrapper) body .utility` — unsatisfiable.
+		expect( prefixCss( 'body .utility{color:red}', ':where(.editor-styles-wrapper)' ) ).toBe(
+			':where(.editor-styles-wrapper) .utility{color:red}'
+		);
+
+		expect( prefixCss( 'html figure:where(x){margin:0}', ':where(.editor-styles-wrapper)' ) ).toBe(
+			':where(.editor-styles-wrapper) figure:where(x){margin:0}'
+		);
+	} );
+
+	it( 'keeps the combinator when substituting the scope', () => {
+		expect( prefixCss( 'body > .utility{color:red}', ':where(.editor-styles-wrapper)' ) ).toBe(
+			':where(.editor-styles-wrapper) > .utility{color:red}'
+		);
+	} );
+
+	it( 'prefixes an already-scoped stylesheet without touching escaped utilities', () => {
+		const utility = '.hover\\:bg-\\[\\#C65D07\\]';
+
+		expect( prefixCss( `${ utility }{background:#C65D07}`, ':where(.editor-styles-wrapper)' ) ).toBe(
+			`:where(.editor-styles-wrapper) ${ utility }{background:#C65D07}`
+		);
+	} );
+
+	it( 'returns the stylesheet untouched without a scope selector', () => {
+		expect( prefixCss( 'h1{color:red}', '' ) ).toBe( 'h1{color:red}' );
+	} );
+} );
diff --git a/src/blocks/frontend/form/index.js b/src/blocks/frontend/form/index.js
index 18dc5c5d1..930d57ce0 100644
--- a/src/blocks/frontend/form/index.js
+++ b/src/blocks/frontend/form/index.js
@@ -59,7 +59,7 @@ const extractFormFields = async( form ) => {
 
 
 	/** @type {Array.<import('./types').FormFieldData>} */
-	const formFieldsData = [{ label: window?.themeisleGutenbergForm?.messages['form-submission'] || 'Form submission from', value: window.location.href, metadata: { position: 0 }}];
+	const formFieldsData = [{ label: window?.themeisleGutenbergForm?.messages?.submission || 'Form submission from', value: window.location.href, metadata: { position: 0 }}];
 
 	/**
 	 * All input fields that belong to the current form. Fields from inner forms are removed.
@@ -488,7 +488,7 @@ const collectAndSendInputFormData = async( form, btn, displayMsg ) => {
 						return;
 					}
 
-					const msg = res?.submitMessage ? res.submitMessage :  'Success';
+					const msg = res?.submitMessage ? res.submitMessage : ( window?.themeisleGutenbergForm?.messages?.success || 'Success' );
 					displayMsg.setMsg( msg ).show();
 
 					form?.querySelector( 'form' )?.reset();
@@ -573,7 +573,7 @@ domReady( () => {
 			spinner.show();
 
 			handleAfterSubmit( confirmRecord(), displayMsg, ( res, displayMsg ) => {
-				const msg = res?.submitMessage ? res.submitMessage :  'Success';
+				const msg = res?.submitMessage ? res.submitMessage : ( window?.themeisleGutenbergForm?.messages?.success || 'Success' );
 				displayMsg.setMsg( msg ).show();
 
 				if ( 0 < res?.redirectLink?.length ) {
diff --git a/src/blocks/test/e2e/blocks/atomic-wind-css-scope.spec.js b/src/blocks/test/e2e/blocks/atomic-wind-css-scope.spec.js
new file mode 100644
index 000000000..b52887233
--- /dev/null
+++ b/src/blocks/test/e2e/blocks/atomic-wind-css-scope.spec.js
@@ -0,0 +1,89 @@
+/**
+ * Internal dependencies
+ */
+import { test, expect } from '../fixtures';
+import { setAtomicWind } from '../helpers/design-library';
+import { publishAndViewPost } from '../helpers/editor';
+
+/**
+ * The generated Tailwind stylesheet carries preflight, whose rules target bare
+ * HTML elements, and a theme layer defining variables such as `--spacing`. It
+ * is injected into the document head, so both must only reach markup inside
+ * Atomic Wind blocks — theme markup elsewhere keeps its own element styling and
+ * its own variables.
+ */
+test.describe( 'Atomic Wind Tailwind CSS scope', () => {
+	test.beforeEach( async({ otterUtils, admin }) => {
+		await setAtomicWind( otterUtils, true );
+		await admin.createNewPost();
+	});
+
+	test.afterAll( async({ otterUtils }) => {
+		await setAtomicWind( otterUtils, false );
+	});
+
+	test( 'resets elements inside the block without touching theme markup', async({ editor, page }) => {
+		await editor.insertBlock({
+			name: 'core/list',
+			attributes: { className: 'theme-list' },
+			innerBlocks: [
+				{ name: 'core/list-item', attributes: { content: 'Theme item' } }
+			]
+		});
+
+		await editor.insertBlock({
+			name: 'atomic-wind/box',
+			attributes: { className: 'flex mt-4 p-8' },
+			innerBlocks: [
+				{
+					name: 'core/list',
+					attributes: { className: 'block-list' },
+					innerBlocks: [
+						{ name: 'core/list-item', attributes: { content: 'Block item' } }
+					]
+				}
+			]
+		});
+
+		await publishAndViewPost({ editor, page });
+
+		const box = page.locator( '.wp-block-atomic-wind-box' );
+
+		// The utility landing proves the stylesheet reached the page at all,
+		// so the assertions below cannot pass on a missing stylesheet.
+		await expect( box ).toHaveCSS( 'display', 'flex' );
+
+		// `mt-4`/`p-8` resolve through `var(--spacing)`, which is defined on the
+		// block wrapper rather than at `:root`. Zero values here would mean the
+		// variables no longer reach the utilities.
+		await expect( box ).toHaveCSS( 'margin-top', '16px' );
+		await expect( box ).toHaveCSS( 'padding', '32px' );
+
+		await expect( page.locator( 'ul.block-list' ) ).toHaveCSS( 'list-style-type', 'none' );
+		await expect( page.locator( 'ul.theme-list' ) ).toHaveCSS( 'list-style-type', 'disc' );
+	});
+
+	test( 'keeps Tailwind theme variables out of the document root', async({ editor, page }) => {
+		// `mt-4` is what pulls `--spacing` into the theme layer; without a
+		// variable-consuming utility the stylesheet defines none and the
+		// assertion below would hold either way.
+		await editor.insertBlock({
+			name: 'atomic-wind/box',
+			attributes: { className: 'flex mt-4' }
+		});
+
+		await publishAndViewPost({ editor, page });
+
+		await expect( page.locator( '.wp-block-atomic-wind-box' ) ).toHaveCSS( 'display', 'flex' );
+
+		const [ rootSpacing, blockSpacing ] = await page.evaluate( () => [
+			getComputedStyle( document.documentElement ).getPropertyValue( '--spacing' ).trim(),
+			getComputedStyle( document.querySelector( '.wp-block-atomic-wind-box' ) )
+				.getPropertyValue( '--spacing' )
+				.trim()
+		] );
+
+		expect( rootSpacing ).toBe( '' );
+		expect( blockSpacing ).toBe( '0.25rem' );
+	});
+});
diff --git a/src/blocks/test/e2e/blocks/atomic-wind-hide-conditions.spec.js b/src/blocks/test/e2e/blocks/atomic-wind-hide-conditions.spec.js
new file mode 100644
index 000000000..d28873609
--- /dev/null
+++ b/src/blocks/test/e2e/blocks/atomic-wind-hide-conditions.spec.js
@@ -0,0 +1,90 @@
+/**
+ * Internal dependencies
+ */
+import { test, expect } from '../fixtures';
+import { setAtomicWind } from '../helpers/design-library';
+import { publishAndViewPost } from '../helpers/editor';
+
+/**
+ * Atomic Wind compiles Tailwind in important mode, so a `flex` utility lands as
+ * `display:flex!important`. The "Hide on" screen-size condition is also
+ * `!important`, so unless its rules outrank the utilities the block stays
+ * visible on the device it was hidden for, depending on which stylesheet the
+ * page happened to print last.
+ */
+const MOBILE = { width: 375, height: 700 };
+const TABLET = { width: 900, height: 700 };
+const DESKTOP = { width: 1280, height: 700 };
+
+const insertHiddenBox = ( editor, screenSizes ) =>
+	editor.insertBlock({
+		name: 'atomic-wind/box',
+		attributes: {
+			className: 'flex gap-4 p-8',
+			otterConditions: [
+				[
+					{
+						type: 'screenSize',
+						screen_sizes: screenSizes
+					}
+				]
+			]
+		},
+		innerBlocks: [
+			{ name: 'core/paragraph', attributes: { content: 'Boxed content' }}
+		]
+	});
+
+test.describe( 'Atomic Wind hide on screen size', () => {
+	test.beforeEach( async({ otterUtils, admin }) => {
+		await setAtomicWind( otterUtils, true );
+		await admin.createNewPost();
+	});
+
+	test.afterAll( async({ otterUtils }) => {
+		await setAtomicWind( otterUtils, false );
+	});
+
+	test( 'hiding on mobile beats the flex utility', async({ editor, page }) => {
+		await insertHiddenBox( editor, [ 'mobile' ] );
+		await publishAndViewPost({ editor, page });
+
+		const box = page.locator( '.wp-block-atomic-wind-box' );
+
+		await expect( box ).toHaveClass( /o-hide-on-mobile/ );
+
+		// Outside the hidden range the utility must still apply, so a passing
+		// hidden assertion cannot come from a stylesheet that never loaded.
+		await page.setViewportSize( TABLET );
+		await expect( box ).toHaveCSS( 'display', 'flex' );
+
+		await page.setViewportSize( MOBILE );
+		await expect( box ).toHaveCSS( 'display', 'none' );
+	});
+
+	test( 'hiding on tablet beats the flex utility', async({ editor, page }) => {
+		await insertHiddenBox( editor, [ 'tablet' ] );
+		await publishAndViewPost({ editor, page });
+		const box = page.locator( '.wp-block-atomic-wind-box' );
+		await expect( box ).toHaveClass( /o-hide-on-tablet/ );
+		await page.setViewportSize( MOBILE );
+		await expect( box ).toHaveCSS( 'display', 'flex' );
+		await page.setViewportSize( TABLET );
+		await expect( box ).toHaveCSS( 'display', 'none' );
+	});
+
+	test( 'hiding on desktop beats the flex utility', async({ editor, page }) => {
+		await insertHiddenBox( editor, [ 'desktop' ] );
+		await publishAndViewPost({ editor, page });
+
+		const box = page.locator( '.wp-block-atomic-wind-box' );
+
+		await expect( box ).toHaveClass( /o-hide-on-desktop/ );
+
+		await page.setViewportSize( MOBILE );
+		await expect( box ).toHaveCSS( 'display', 'flex' );
+
+		await page.setViewportSize( DESKTOP );
+		await expect( box ).toHaveCSS( 'display', 'none' );
+	});
+});
diff --git a/src/blocks/test/e2e/playwright.config.js b/src/blocks/test/e2e/playwright.config.js
index 04cc7bd68..1e8d3105b 100644
--- a/src/blocks/test/e2e/playwright.config.js
+++ b/src/blocks/test/e2e/playwright.config.js
@@ -58,6 +58,8 @@ const SERIAL_SPECS = [
 
 	// Flips the site-wide atomic-wind blocks option.
 	'**/blocks/atomic-wind-list-view.spec.js',
+	'**/blocks/atomic-wind-css-scope.spec.js',
+	'**/blocks/atomic-wind-hide-conditions.spec.js',
 
 	// Mutates the shared admin user's metabox order and editor preferences.
 	'**/blocks/woocommerce-builder.spec.js',
diff --git a/tests/php/foreign-sabberworm-sandbox.php b/tests/php/foreign-sabberworm-sandbox.php
index 21c32becd..a3c0dde6e 100644
--- a/tests/php/foreign-sabberworm-sandbox.php
+++ b/tests/php/foreign-sabberworm-sandbox.php
@@ -75,6 +75,8 @@ function ( $class ) {
 		}
 	);
 
+	// Base_CSS reads block class names through Registration::get_class_name().
+	require OTTER_BLOCKS_PATH . '/inc/class-registration.php';
 	require OTTER_BLOCKS_PATH . '/inc/class-base-css.php';
 
 	$base   = new \ThemeIsle\GutenbergBlocks\Base_CSS();
diff --git a/tests/test-atomic-wind-blocks.php b/tests/test-atomic-wind-blocks.php
index 0c85a50bc..024fde399 100644
--- a/tests/test-atomic-wind-blocks.php
+++ b/tests/test-atomic-wind-blocks.php
@@ -1137,6 +1137,17 @@ private function make_atomic_wind_post( $classes ) {
 		);
 	}
 
+	/**
+	 * Helper: set cached CSS for a post.
+	 *
+	 * @param int    $post_id Post ID.
+	 * @param string $css CSS string.
+	 */
+	private function set_cached_css( $post_id, $css ) {
+		update_post_meta( $post_id, '_atomic_wind_css', $css );
+		update_post_meta( $post_id, '_atomic_wind_css_version', Atomic_Wind_Blocks::ATOMIC_WIND_CSS_VERSION );
+	}
+
 	// -------------------------------------------------------
 	// Save-time CSS warm (hidden-iframe render)
 	// -------------------------------------------------------
@@ -1288,8 +1299,8 @@ public function test_output_late_css_inlines_multiple_rendered_posts() {
 
 		$a = $this->make_atomic_wind_post( 'flex' );
 		$b = $this->make_atomic_wind_post( 'grid' );
-		update_post_meta( $a, '_atomic_wind_css', '.flex{display:flex}' );
-		update_post_meta( $b, '_atomic_wind_css', '.grid{display:grid}' );
+		$this->set_cached_css( $a, '.flex{display:flex}' );
+		$this->set_cached_css( $b, '.grid{display:grid}' );
 
 		global $post;
 		$post = get_post( $a );
@@ -1316,8 +1327,8 @@ public function test_output_late_css_dedupes_identical_blobs() {
 
 		$a = $this->make_atomic_wind_post( 'flex' );
 		$b = $this->make_atomic_wind_post( 'flex' );
-		update_post_meta( $a, '_atomic_wind_css', '.flex{display:flex}' );
-		update_post_meta( $b, '_atomic_wind_css', '.flex{display:flex}' );
+		$this->set_cached_css( $a, '.flex{display:flex}' );
+		$this->set_cached_css( $b, '.flex{display:flex}' );
 
 		global $post;
 		$post = get_post( $a );
@@ -1341,7 +1352,7 @@ public function test_frontend_css_is_not_enqueued_until_a_block_renders() {
 		$this->reset_style_globals();
 
 		$post_id = $this->make_atomic_wind_post( 'flex' );
-		update_post_meta( $post_id, '_atomic_wind_css', '.flex{display:flex}' );
+		$this->set_cached_css( $post_id, '.flex{display:flex}' );
 
 		$GLOBALS['wp_query']->posts = array( get_post( $post_id ) );
 
@@ -1358,7 +1369,7 @@ public function test_output_late_css_inlines_tracked_post_and_skips_generator()
 		$this->instance->enqueue_base_css();
 
 		$late = $this->make_atomic_wind_post( 'flex' );
-		update_post_meta( $late, '_atomic_wind_css', '.late{color:blue}' );
+		$this->set_cached_css( $late, '.late{color:blue}' );
 
 		global $post;
 		$post = get_post( $late );
@@ -1384,7 +1395,7 @@ public function test_output_late_css_collects_blocks_rendered_by_normal_footer_c
 		update_option( 'themeisle_blocks_settings_atomic_wind_blocks', true );
 
 		$late = $this->make_atomic_wind_post( 'flex' );
-		update_post_meta( $late, '_atomic_wind_css', '.footer-callback{color:purple}' );
+		$this->set_cached_css( $late, '.footer-callback{color:purple}' );
 
 		global $post;
 		$post = get_post( $late );
@@ -1414,7 +1425,7 @@ public function test_output_late_css_falls_back_to_generator_when_counts_exceed(
 		$this->reset_in_query( false );
 
 		$late = $this->make_atomic_wind_post( 'flex' );
-		update_post_meta( $late, '_atomic_wind_css', '.late{color:blue}' );
+		$this->set_cached_css( $late, '.late{color:blue}' );
 
 		global $post;
 		$post = get_post( $late );
@@ -1435,7 +1446,7 @@ public function test_output_singular_css_inlines_queried_post_in_head() {
 		$this->reset_style_globals();
 
 		$singular = $this->make_atomic_wind_post( 'flex' );
-		update_post_meta( $singular, '_atomic_wind_css', '.flex{display:flex}' );
+		$this->set_cached_css( $singular, '.flex{display:flex}' );
 
 		$this->go_to( get_permalink( $singular ) );
 		$this->instance->enqueue_base_css();
@@ -1458,11 +1469,47 @@ public function test_output_singular_css_enqueues_generator_without_cache() {
 		$this->assertTrue( wp_script_is( 'atomic-wind-tailwind-generator', 'enqueued' ) );
 	}
 
+	public function test_output_singular_css_regenerates_css_from_an_older_generator() {
+		$this->reset_style_globals();
+
+		$singular = $this->make_atomic_wind_post( 'flex' );
+		// Stylesheet cached before the resets were scoped to Atomic Wind blocks.
+		update_post_meta( $singular, '_atomic_wind_css', 'h1{font-size:inherit}' );
+
+		$this->go_to( get_permalink( $singular ) );
+		$this->instance->output_singular_css();
+
+		$this->assertSame( '', $this->inline_style_for( 'atomic-wind-tailwind' ) );
+		$this->assertTrue( wp_script_is( 'atomic-wind-tailwind-generator', 'enqueued' ) );
+	}
+
+	public function test_rest_save_style_stamps_the_generator_version() {
+		$request = new WP_REST_Request( 'POST', '/otter/v1/atomic-wind/style' );
+		$request->set_param( 'postId', $this->post_id );
+		$request->set_param( 'css', '.flex{display:flex}' );
+
+		$this->instance->rest_save_style( $request );
+
+		$this->assertSame(
+			Atomic_Wind_Blocks::ATOMIC_WIND_CSS_VERSION,
+			get_post_meta( $this->post_id, '_atomic_wind_css_version', true )
+		);
+	}
+
+	public function test_clear_cached_css_drops_the_version_stamp() {
+		$post_id = $this->make_atomic_wind_post( 'flex' );
+		$this->set_cached_css( $post_id, '.flex{display:flex}' );
+
+		$this->instance->clear_cached_css( $post_id );
+
+		$this->assertSame( '', get_post_meta( $post_id, '_atomic_wind_css_version', true ) );
+	}
+
 	public function test_output_singular_css_noop_on_non_singular_views() {
 		$this->reset_style_globals();
 
 		$listed = $this->make_atomic_wind_post( 'flex' );
-		update_post_meta( $listed, '_atomic_wind_css', '.flex{display:flex}' );
+		$this->set_cached_css( $listed, '.flex{display:flex}' );
 
 		$this->go_to( home_url( '/' ) );
 		$this->instance->output_singular_css();
@@ -1476,7 +1523,7 @@ public function test_output_late_css_skips_post_already_inlined_at_head() {
 		$this->reset_in_query( false );
 
 		$singular = $this->make_atomic_wind_post( 'flex' );
-		update_post_meta( $singular, '_atomic_wind_css', '.flex{display:flex}' );
+		$this->set_cached_css( $singular, '.flex{display:flex}' );
 
 		$this->go_to( get_permalink( $singular ) );
 		$this->instance->output_singular_css();
diff --git a/tests/test-block-class-name.php b/tests/test-block-class-name.php
new file mode 100644
index 000000000..0e4333f4c
--- /dev/null
+++ b/tests/test-block-class-name.php
@@ -0,0 +1,156 @@
+<?php
+/**
+ * Class Test_Block_Class_Name
+ *
+ * @package gutenberg-blocks
+ */
+
+use ThemeIsle\GutenbergBlocks\Base_CSS;
+use ThemeIsle\GutenbergBlocks\Registration;
+use ThemeIsle\GutenbergBlocks\Render\Posts_Grid_Block;
+
+/**
+ * An array `className` attribute must not fatal the render/asset paths that
+ * search it with string functions.
+ */
+class Test_Block_Class_Name extends WP_UnitTestCase {
+
+	/**
+	 * Static asset flags mutated by the paths under test, restored in teardown.
+	 *
+	 * @var array<string, bool>
+	 */
+	private $saved_flags = array();
+
+	/**
+	 * Set up test environment.
+	 */
+	public function set_up() {
+		parent::set_up();
+
+		$this->saved_flags = array(
+			'is_fa_loaded' => Registration::$is_fa_loaded,
+			'sticky'       => Registration::$scripts_loaded['sticky'],
+		);
+	}
+
+	/**
+	 * Tear down test environment.
+	 */
+	public function tear_down() {
+		Registration::$is_fa_loaded                = $this->saved_flags['is_fa_loaded'];
+		Registration::$scripts_loaded['sticky']    = $this->saved_flags['sticky'];
+
+		wp_dequeue_script( 'otter-sticky' );
+		wp_deregister_script( 'otter-sticky' );
+
+		parent::tear_down();
+	}
+
+	/**
+	 * A string `className` is returned untouched.
+	 */
+	public function test_get_class_name_returns_string_attribute() {
+		$this->assertSame( 'is-style-tiled o-sticky', Registration::get_class_name( array( 'className' => 'is-style-tiled o-sticky' ) ) );
+	}
+
+	/**
+	 * An array `className` is flattened to a space separated list.
+	 */
+	public function test_get_class_name_flattens_array_attribute() {
+		$this->assertSame(
+			'fa-solid fa-star extra',
+			Registration::get_class_name( array( 'className' => array( 'fa-solid', array( 'fa-star' ), 'extra' ) ) )
+		);
+	}
+
+	/**
+	 * Missing, empty and non-printable values fall back to an empty string.
+	 */
+	public function test_get_class_name_returns_empty_string_for_unusable_values() {
+		$this->assertSame( '', Registration::get_class_name( array() ) );
+		$this->assertSame( '', Registration::get_class_name( 'not-an-array' ) );
+		$this->assertSame( '', Registration::get_class_name( array( 'className' => array() ) ) );
+		$this->assertSame( '', Registration::get_class_name( array( 'className' => new stdClass() ) ) );
+		$this->assertSame( '', Registration::get_class_name( array( 'className' => array( new stdClass() ) ) ) );
+	}
+
+	/**
+	 * The Font Awesome subscriber must read an array `className` without fataling.
+	 */
+	public function test_subscribe_fa_handles_array_class_name() {
+		Registration::$is_fa_loaded = false;
+
+		$block = array(
+			'blockName' => 'core/navigation-link',
+			'attrs'     => array( 'className' => array( 'fa-solid', 'fa-star' ) ),
+		);
+
+		$this->assertSame( 'content', Registration::instance()->subscribe_fa( 'content', $block ) );
+
+		if ( \WP_Block_Type_Registry::get_instance()->is_registered( 'core/navigation' ) ) {
+			$this->assertTrue( Registration::$is_fa_loaded, 'The array class list contains fa-, so FA must be flagged as needed.' );
+		}
+	}
+
+	/**
+	 * The sticky subscriber must read an array `className` without fataling.
+	 */
+	public function test_load_sticky_handles_array_class_name() {
+		Registration::$scripts_loaded['sticky'] = false;
+
+		$block = array(
+			'blockName' => 'core/group',
+			'attrs'     => array( 'className' => array( 'o-sticky', 'o-sticky-pos-top' ) ),
+		);
+
+		$this->assertSame( 'content', Registration::instance()->load_sticky( 'content', $block ) );
+		$this->assertTrue( wp_script_is( 'otter-sticky', 'enqueued' ) );
+	}
+
+	/**
+	 * Animation class collection must read an array `className` without fataling.
+	 */
+	public function test_get_animation_classes_handles_array_class_name() {
+		$base_css = new Base_CSS();
+
+		$blocks = array(
+			array(
+				'blockName' => 'core/paragraph',
+				'attrs'     => array( 'className' => array( 'animated', 'fadeIn' ) ),
+			),
+		);
+
+		$this->assertSame( array( 'animated', 'fadeIn' ), array_values( $base_css->get_animation_classes( $blocks ) ) );
+	}
+
+	/**
+	 * The posts block must render with an array `className` instead of fataling.
+	 */
+	public function test_posts_grid_block_renders_with_array_class_name() {
+		$this->factory()->post->create( array( 'post_title' => 'Otter array className' ) );
+
+		WP_Block_Supports::init();
+		WP_Block_Supports::$block_to_render = array( 'blockName' => 'themeisle-blocks/posts-grid' );
+
+		$render = new Posts_Grid_Block();
+		$output = $render->render(
+			array(
+				'id'           => 'wp-block-themeisle-blocks-posts-grid-a94bab18',
+				'className'    => array( 'is-style-tiled', 'custom' ),
+				'columns'      => 2,
+				'style'        => 'grid',
+				'postTypes'    => array(),
+				'template'     => array( 'title' ),
+				'postsToShow'  => 1,
+				'order'        => 'desc',
+				'orderBy'      => 'date',
+				'offset'       => 0,
+				'displayTitle' => true,
+				'titleTag'     => 'h5',
+			)
+		);
+
+		$this->assertStringContainsString( 'Otter array className', $output );
+	}
+}
diff --git a/tests/test-dashboard-server-license.php b/tests/test-dashboard-server-license.php
new file mode 100644
index 000000000..2507acc83
--- /dev/null
+++ b/tests/test-dashboard-server-license.php
@@ -0,0 +1,314 @@
+<?php
+/**
+ * Class Dashboard_Server_License
+ *
+ * @package gutenberg-blocks
+ */
+
+use ThemeIsle\OtterPro\Plugins\License;
+use ThemeIsle\OtterPro\Server\Dashboard_Server;
+
+/**
+ * Tests for the license error messages returned by otter/v1/toggle_license.
+ */
+class Test_Dashboard_Server_License extends WP_UnitTestCase {
+
+	/**
+	 * The message the SDK returns for a license the store rejected.
+	 */
+	const SDK_INVALID_MESSAGE = 'ERROR: Invalid license provided.';
+
+	/**
+	 * Option the SDK writes the store's answer to, derived from the plugin dir.
+	 */
+	const LICENSE_DATA_OPTION = 'otter_pro_license_data';
+
+	/**
+	 * The message the dashboard should show for a plan mismatch.
+	 */
+	const PLAN_MISMATCH_MESSAGE = 'Entered license key does not include Otter Pro.';
+
+	/**
+	 * Instance under test.
+	 *
+	 * @var Dashboard_Server
+	 */
+	private $server;
+
+	/**
+	 * Define the Otter Pro basefile the success path needs.
+	 *
+	 * The suite never boots otter-pro (development.php bails because WPINC is
+	 * not defined when Composer loads it), so the constant License reads for the
+	 * license option name is missing. Point it at the real plugin file.
+	 */
+	public static function set_up_before_class() {
+		parent::set_up_before_class();
+
+		if ( ! defined( 'OTTER_PRO_BASEFILE' ) ) {
+			define( 'OTTER_PRO_BASEFILE', dirname( __DIR__ ) . '/plugins/otter-pro/otter-pro.php' );
+		}
+	}
+
+	/**
+	 * Set up test environment.
+	 *
+	 * The server is built directly instead of through instance(): init() would
+	 * register an otter_dashboard_data filter that reads OTTER_PRO_VERSION,
+	 * which is not defined in the test suite.
+	 */
+	public function set_up() {
+		parent::set_up();
+		$this->server = new Dashboard_Server();
+		delete_option( self::LICENSE_DATA_OPTION );
+	}
+
+	/**
+	 * Make the SDK license process return the given value.
+	 *
+	 * @param mixed $result Value the filter should return.
+	 */
+	private function mock_license_process( $result ) {
+		remove_all_filters( 'themeisle_sdk_license_process_otter' );
+		add_filter(
+			'themeisle_sdk_license_process_otter',
+			function () use ( $result ) {
+				return $result;
+			}
+		);
+	}
+
+	/**
+	 * Make the stored license plan resolve to the given price ID.
+	 *
+	 * @param int|string $plan Price ID.
+	 */
+	private function mock_license_plan( $plan ) {
+		remove_all_filters( 'product_otter_license_plan' );
+		add_filter(
+			'product_otter_license_plan',
+			function () use ( $plan ) {
+				return $plan;
+			}
+		);
+	}
+
+	/**
+	 * Mirror what the SDK stores after the store answers an activation.
+	 *
+	 * do_license_process() writes the response to the license data option before
+	 * it returns the WP_Error, and the plan filter reports price_id from that
+	 * same option, falling back to -1 when the response carried none.
+	 *
+	 * @param string   $status   License status returned by the store.
+	 * @param int|null $price_id Price ID returned by the store, null if absent.
+	 */
+	private function mock_store_response( $status, $price_id = null ) {
+		$data = array(
+			'license' => $status,
+			'key'     => 'a-license-key',
+		);
+
+		if ( null !== $price_id ) {
+			$data['price_id'] = $price_id;
+		}
+
+		update_option( self::LICENSE_DATA_OPTION, (object) $data );
+		$this->mock_license_plan( null === $price_id ? -1 : $price_id );
+	}
+
+	/**
+	 * Run toggle_license and return the response payload.
+	 *
+	 * @param array $body JSON body.
+	 *
+	 * @return array
+	 */
+	private function toggle( $body ) {
+		$request = new WP_REST_Request( 'POST', '/otter/v1/toggle_license' );
+		$request->set_header( 'content-type', 'application/json' );
+		$request->set_body( wp_json_encode( $body ) );
+
+		$response = $this->server->toggle_license( $request );
+
+		$this->assertInstanceOf( 'WP_REST_Response', $response );
+
+		return $response->get_data();
+	}
+
+	/**
+	 * Activate with the given key and return the response payload.
+	 *
+	 * @param string $key License key.
+	 *
+	 * @return array
+	 */
+	private function activate( $key = 'neve-personal-license-key' ) {
+		return $this->toggle(
+			array(
+				'action' => 'activate',
+				'key'    => $key,
+			)
+		);
+	}
+
+	/**
+	 * A key the store answered for with a plan outside the allow list does not
+	 * include Otter Pro, so the generic SDK error is replaced by the reason.
+	 *
+	 * 1 and 2 are Neve Personal; 7, 12 and 30 are higher Neve tiers that still
+	 * exclude Otter Pro.
+	 */
+	public function test_activation_with_an_unsupported_plan_reports_the_plan_mismatch() {
+		$this->mock_license_process( new WP_Error( 'themeisle-license-invalid', self::SDK_INVALID_MESSAGE ) );
+
+		foreach ( array( 1, 2, 7, 12, 30 ) as $plan ) {
+			$this->assertNotContains( $plan, Dashboard_Server::VALID_NEVE_PLANS, "Plan {$plan} is a fixture for an unsupported plan" );
+
+			$this->mock_store_response( 'invalid', $plan );
+
+			$data = $this->activate();
+
+			$this->assertFalse( $data['success'], "Activation should fail for plan {$plan}" );
+			$this->assertSame( self::PLAN_MISMATCH_MESSAGE, $data['message'], "Plan {$plan} should report the plan mismatch, not the generic SDK error" );
+		}
+	}
+
+	/**
+	 * Plans that do bundle Otter Pro keep the SDK message: a rejected key on an
+	 * agency plan is not a plan problem.
+	 */
+	public function test_activation_with_a_supported_plan_keeps_the_sdk_message() {
+		$this->mock_license_process( new WP_Error( 'themeisle-license-invalid', self::SDK_INVALID_MESSAGE ) );
+
+		$this->assertNotEmpty( Dashboard_Server::VALID_NEVE_PLANS, 'The supported plan list should not be empty' );
+
+		foreach ( Dashboard_Server::VALID_NEVE_PLANS as $plan ) {
+			$this->mock_store_response( 'invalid', $plan );
+
+			$data = $this->activate( 'some-agency-license-key' );
+
+			$this->assertFalse( $data['success'] );
+			$this->assertSame( self::SDK_INVALID_MESSAGE, $data['message'], "Plan {$plan} bundles Otter Pro, so the SDK message should be kept" );
+		}
+	}
+
+	/**
+	 * A key that does cover Otter Pro but is expired, revoked or out of
+	 * activations is rejected with the same themeisle-license-invalid code. Its
+	 * plan is not the problem, so the SDK message must survive.
+	 *
+	 * Price ID 1 is deliberate: it is a standalone Otter plan per
+	 * License::$plans_map and is absent from VALID_NEVE_PLANS, so the plan check
+	 * alone would misreport every one of these as a plan mismatch.
+	 */
+	public function test_unusable_but_eligible_key_keeps_the_sdk_message() {
+		$this->mock_license_process( new WP_Error( 'themeisle-license-invalid', self::SDK_INVALID_MESSAGE ) );
+
+		foreach ( Dashboard_Server::NON_PLAN_LICENSE_STATUSES as $status ) {
+			foreach ( array_keys( License::$plans_map ) as $plan ) {
+				$this->mock_store_response( $status, $plan );
+
+				$data = $this->activate( 'an-otter-standalone-key' );
+
+				$this->assertFalse( $data['success'] );
+				$this->assertSame( self::SDK_INVALID_MESSAGE, $data['message'], "A {$status} key on Otter plan {$plan} is not a plan mismatch" );
+			}
+		}
+	}
+
+	/**
+	 * A key the store did not recognise comes back without a price ID, so the
+	 * plan filter reports -1. That is not evidence of anything and must not be
+	 * rewritten.
+	 */
+	public function test_unrecognised_key_without_a_price_id_keeps_the_sdk_message() {
+		$this->mock_license_process( new WP_Error( 'themeisle-license-invalid', self::SDK_INVALID_MESSAGE ) );
+
+		foreach ( array( 'invalid', 'missing', 'item_name_mismatch' ) as $status ) {
+			$this->mock_store_response( $status );
+
+			$data = $this->activate( 'a-made-up-key' );
+
+			$this->assertFalse( $data['success'] );
+			$this->assertSame( self::SDK_INVALID_MESSAGE, $data['message'], "A {$status} key with no price ID should keep the SDK message" );
+		}
+	}
+
+	/**
+	 * Only the store's rejection can be caused by a plan mismatch. Every other
+	 * failure is reported as the SDK worded it, even while an unsupported plan
+	 * is stored from an earlier key.
+	 */
+	public function test_only_the_invalid_license_error_is_rewritten() {
+		$this->mock_store_response( 'invalid', 1 );
+
+		$codes = array(
+			'themeisle-license-500'            => 'ERROR: Failed to connect to the license service.',
+			'themeisle-license-404'            => 'ERROR: Failed to validate license. Please try again in one minute.',
+			'themeisle-license-invalid-format' => 'Invalid license.',
+			'themeisle-license-already-active' => 'License is already active.',
+		);
+
+		foreach ( $codes as $code => $message ) {
+			$this->mock_license_process( new WP_Error( $code, $message ) );
+
+			$data = $this->activate();
+
+			$this->assertFalse( $data['success'] );
+			$this->assertSame( $message, $data['message'], "Error {$code} is not a plan mismatch and should be reported as-is" );
+		}
+	}
+
+	/**
+	 * The rewrite is gated on the activate action, so deactivation failures are
+	 * never reported as a plan mismatch.
+	 */
+	public function test_deactivation_keeps_the_sdk_message() {
+		$this->mock_store_response( 'invalid', 1 );
+
+		$errors = array(
+			'themeisle-license-already-deactivate' => 'License not active.',
+			'themeisle-license-invalid'            => self::SDK_INVALID_MESSAGE,
+		);
+
+		foreach ( $errors as $code => $message ) {
+			$this->mock_license_process( new WP_Error( $code, $message ) );
+
+			$data = $this->toggle( array( 'action' => 'deactivate' ) );
+
+			$this->assertFalse( $data['success'] );
+			$this->assertSame( $message, $data['message'], "Deactivation error {$code} should be reported as-is" );
+		}
+	}
+
+	/**
+	 * A successful toggle is unaffected by the stored plan: the rewrite is gated
+	 * on the SDK returning a WP_Error.
+	 */
+	public function test_successful_toggle_is_not_rewritten() {
+		$this->mock_license_process( true );
+		$this->mock_store_response( 'invalid', 1 );
+
+		$data = $this->activate( 'a-valid-license-key' );
+
+		$this->assertTrue( $data['success'] );
+		$this->assertSame( 'Activated.', $data['message'] );
+		$this->assertArrayHasKey( 'license', $data );
+	}
+
+	/**
+	 * A malformed payload is rejected before the SDK is called.
+	 */
+	public function test_invalid_action_payload_is_rejected() {
+		$this->mock_license_process( new WP_Error( 'themeisle-license-invalid', self::SDK_INVALID_MESSAGE ) );
+		$this->mock_store_response( 'invalid', 1 );
+
+		foreach ( array( array(), array( 'action' => 'activate' ) ) as $body ) {
+			$data = $this->toggle( $body );
+
+			$this->assertFalse( $data['success'] );
+			$this->assertSame( 'Invalid Action. Please refresh the page and try again.', $data['message'] );
+		}
+	}
+}
diff --git a/tests/test-registration.php b/tests/test-registration.php
index d12b2983c..6ba0709c6 100644
--- a/tests/test-registration.php
+++ b/tests/test-registration.php
@@ -7,6 +7,73 @@
 
 use ThemeIsle\GutenbergBlocks\Registration;
 
+/**
+ * Renderer whose constructor touches a class that is absent from the deployed
+ * artifact: `class_exists()` on the renderer passes, `new` fatals.
+ */
+class Otter_Renderer_With_Missing_Dependency {
+	/**
+	 * Constructor.
+	 */
+	public function __construct() {
+		new Otter_Dependency_That_Does_Not_Exist();
+	}
+
+	/**
+	 * Render the block.
+	 *
+	 * @param array $attributes Block attributes.
+	 * @return string
+	 */
+	public function render( $attributes ) {
+		return '';
+	}
+}
+
+/**
+ * Renderer that cannot be instantiated: a singleton with a private constructor.
+ */
+class Otter_Renderer_With_Private_Constructor {
+	/**
+	 * Constructor.
+	 */
+	private function __construct() {
+	}
+
+	/**
+	 * Render the block.
+	 *
+	 * @param array $attributes Block attributes.
+	 * @return string
+	 */
+	public function render( $attributes ) {
+		return '';
+	}
+}
+
+/**
+ * Renderer whose constructor takes a required argument.
+ */
+class Otter_Renderer_Requiring_Arguments {
+	/**
+	 * Constructor.
+	 *
+	 * @param string $required Required dependency.
+	 */
+	public function __construct( $required ) {
+	}
+
+	/**
+	 * Render the block.
+	 *
+	 * @param array $attributes Block attributes.
+	 * @return string
+	 */
+	public function render( $attributes ) {
+		return '';
+	}
+}
+
 /**
  * Editor localization tests: the global defaults handed to the editor must
  * always be an object, or every block's Edit component crashes on null.
@@ -87,7 +154,7 @@ public function test_editor_global_defaults_is_object_when_option_is_missing() {
 	 * bootstrap, so the plugin's blocks are unregistered first to keep this a
 	 * clean registration instead of "already registered" notices.
 	 *
-	 * @param string $classname                Renderer class to map form-captcha to.
+	 * @param mixed  $classname                Renderer class to map form-captcha to.
 	 * @param string $expected_include_failure Path whose failed include is expected, or empty if no include failure is expected.
 	 * @return void
 	 */
@@ -244,4 +311,59 @@ public function test_register_blocks_survives_dynamic_renderer_class_whose_file_
 		$this->assertFalse( class_exists( $class, false ), 'The renderer class must not have been defined.' );
 		$this->assertCaptchaRegisteredWithoutRenderer();
 	}
+
+	/**
+	 * The renderer class loads, but its constructor references a class that is
+	 * missing — the reported "class not found" fatal. Registration must fall back
+	 * instead of taking the request down.
+	 */
+	public function test_register_blocks_survives_renderer_whose_constructor_hits_a_missing_class() {
+		$this->register_blocks_with_captcha_renderer( 'Otter_Renderer_With_Missing_Dependency' );
+
+		$this->assertCaptchaRegisteredWithoutRenderer();
+	}
+
+	/**
+	 * A loadable but uninstantiable renderer (abstract class, or a singleton with
+	 * a private constructor) must degrade too.
+	 */
+	public function test_register_blocks_survives_uninstantiable_renderer() {
+		$this->register_blocks_with_captcha_renderer( 'Otter_Renderer_With_Private_Constructor' );
+
+		$this->assertCaptchaRegisteredWithoutRenderer();
+	}
+
+	/**
+	 * A renderer whose constructor requires arguments cannot be built with `new`.
+	 */
+	public function test_register_blocks_survives_renderer_requiring_constructor_arguments() {
+		$this->register_blocks_with_captcha_renderer( 'Otter_Renderer_Requiring_Arguments' );
+
+		$this->assertCaptchaRegisteredWithoutRenderer();
+	}
+
+	/**
+	 * A non-string entry injected through the filter must not reach
+	 * `class_exists()`, which throws a TypeError on those in PHP 8.
+	 */
+	public function test_register_blocks_survives_non_string_renderer_entry() {
+		$this->register_blocks_with_captcha_renderer( array( 'Otter_Renderer_With_Private_Constructor' ) );
+
+		$this->assertCaptchaRegisteredWithoutRenderer();
+	}
+
+	/**
+	 * The AMP list has no filter to inject through, so the guard there is covered
+	 * by running it: it must complete, and every class it ships must still be
+	 * loadable, which is what a stale classmap would break.
+	 */
+	public function test_init_amp_blocks_completes_and_ships_loadable_classes() {
+		( new Registration() )->init_amp_blocks();
+
+		foreach ( array( 'Circle_Counter_Block', 'Lottie_Block', 'Slider_Block' ) as $short ) {
+			$classname = '\\ThemeIsle\\GutenbergBlocks\\Render\\AMP\\' . $short;
+
+			$this->assertTrue( class_exists( $classname ), $classname . ' is registered as an AMP block but cannot be loaded.' );
+		}
+	}
 }
diff --git a/tests/test-svg-upload.php b/tests/test-svg-upload.php
index 4f176a747..314df2c92 100644
--- a/tests/test-svg-upload.php
+++ b/tests/test-svg-upload.php
@@ -209,4 +209,120 @@ public function test_used_css_properties_returns_default_when_input_is_not_array
 		$this->assertContains( 'border-radius', $result );
 		$this->assertContains( 'transform', $result );
 	}
+
+	/**
+	 * Create an SVG attachment post for the supplied file path.
+	 *
+	 * @param string $file Attached file path to store, may be empty.
+	 * @return int
+	 */
+	private function create_svg_attachment( $file ) {
+		$attachment_id = $this->factory()->attachment->create_object(
+			array(
+				'file'           => $file,
+				'post_mime_type' => 'image/svg+xml',
+			)
+		);
+
+		return $attachment_id;
+	}
+
+	/**
+	 * A missing SVG file must not fatal, and metadata is returned untouched.
+	 */
+	public function test_generate_svg_attachment_metadata_with_missing_file() {
+		$main          = new ThemeIsle\GutenbergBlocks\Main();
+		$attachment_id = $this->create_svg_attachment( '/does/not/exist/missing.svg' );
+		$metadata      = array( 'sizes' => array() );
+
+		$result = $main->generate_svg_attachment_metadata( $metadata, $attachment_id );
+
+		$this->assertSame( $metadata, $result );
+
+		wp_delete_attachment( $attachment_id, true );
+	}
+
+	/**
+	 * get_attached_file() returning false must not fatal.
+	 */
+	public function test_generate_svg_attachment_metadata_when_attached_file_is_false() {
+		$main          = new ThemeIsle\GutenbergBlocks\Main();
+		$attachment_id = $this->create_svg_attachment( '' );
+		$metadata      = array( 'sizes' => array() );
+
+		$force_false = '__return_false';
+		add_filter( 'get_attached_file', $force_false );
+
+		$result = $main->generate_svg_attachment_metadata( $metadata, $attachment_id );
+
+		remove_filter( 'get_attached_file', $force_false );
+
+		$this->assertSame( $metadata, $result );
+
+		wp_delete_attachment( $attachment_id, true );
+	}
+
+	/**
+	 * A file that is not valid XML must not fatal.
+	 */
+	public function test_generate_svg_attachment_metadata_with_malformed_svg() {
+		$main      = new ThemeIsle\GutenbergBlocks\Main();
+		$svg_path  = wp_tempnam( 'broken.svg' );
+		file_put_contents( $svg_path, '<svg width="10" height="10">' );
+
+		$attachment_id = $this->create_svg_attachment( $svg_path );
+		$metadata      = array( 'sizes' => array() );
+
+		$result = $main->generate_svg_attachment_metadata( $metadata, $attachment_id );
+
+		$this->assertSame( $metadata, $result );
+
+		wp_delete_attachment( $attachment_id, true );
+		if ( file_exists( $svg_path ) ) {
+			unlink( $svg_path );
+		}
+	}
+
+	/**
+	 * A valid SVG still gets its dimensions filled in.
+	 */
+	public function test_generate_svg_attachment_metadata_with_valid_svg() {
+		$main     = new ThemeIsle\GutenbergBlocks\Main();
+		$svg_path = wp_tempnam( 'valid.svg' );
+		file_put_contents( $svg_path, '<svg xmlns="http://www.w3.org/2000/svg" width="24" height="42"></svg>' );
+
+		$attachment_id = $this->create_svg_attachment( $svg_path );
+
+		$result = $main->generate_svg_attachment_metadata( array( 'sizes' => array() ), $attachment_id );
+
+		$this->assertSame( 24, $result['width'] );
+		$this->assertSame( 42, $result['height'] );
+		$this->assertSame( basename( $svg_path ), $result['file'] );
+
+		wp_delete_attachment( $attachment_id, true );
+		if ( file_exists( $svg_path ) ) {
+			unlink( $svg_path );
+		}
+	}
+
+	/**
+	 * An SVG without width/height attributes must not produce zeroed dimensions.
+	 */
+	public function test_generate_svg_attachment_metadata_without_dimension_attributes() {
+		$main     = new ThemeIsle\GutenbergBlocks\Main();
+		$svg_path = wp_tempnam( 'no-dimensions.svg' );
+		file_put_contents( $svg_path, '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 42"></svg>' );
+
+		$attachment_id = $this->create_svg_attachment( $svg_path );
+		$metadata      = array( 'sizes' => array() );
+
+		$result = $main->generate_svg_attachment_metadata( $metadata, $attachment_id );
+
+		$this->assertSame( $metadata, $result );
+
+		wp_delete_attachment( $attachment_id, true );
+		if ( file_exists( $svg_path ) ) {
+			unlink( $svg_path );
+		}
+	}
 }