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function wp_render_custom_css_support_styles( $parsed_block ) {
	$custom_css = $parsed_block['attrs']['style']['css'] ?? null;
	if ( ! is_string( $custom_css ) || '' === trim( $custom_css ) ) {
		return $parsed_block;
	}

	$block_type = WP_Block_Type_Registry::get_instance()->get_registered( $parsed_block['blockName'] );
	if ( ! block_has_support( $block_type, 'customCSS', true ) ) {
		return $parsed_block;
	}

	// Validate CSS doesn't contain HTML markup (same validation as global styles REST API).
	if ( preg_match( '#</?\w+#', $custom_css ) ) {
		return $parsed_block;
	}

	// Generate a unique class name for this block instance.
	$class_name          = wp_unique_id_from_values( $parsed_block, 'wp-custom-css-' );
	$existing_class_name = $parsed_block['attrs']['className'] ?? null;
	$updated_class_name  = is_string( $existing_class_name )
		? "$existing_class_name $class_name"
		: $class_name;

	_wp_array_set( $parsed_block, array( 'attrs', 'className' ), $updated_class_name );

	// Process the custom CSS using the same method as global styles.
	$selector      = '.' . $class_name;
	$processed_css = WP_Theme_JSON::process_blocks_custom_css( $custom_css, $selector );

	if ( ! empty( $processed_css ) ) {
		/*
		 * Register and add inline style for block custom CSS.
		 * The style depends on global-styles to ensure custom CSS loads after
		 * and can override global styles.
		 */
		wp_register_style( 'wp-block-custom-css', false, array( 'global-styles' ) );
		wp_add_inline_style( 'wp-block-custom-css', $processed_css );
	}

	return $parsed_block;
}