%s

 block for a specific MCP client.
	 *
	 * @since 0.0.6
	 * @experimental May change without notice before 1.0.0.
	 *
	 * @param array  $server      Server row data.
	 * @param string $client_slug Client slug.
	 * @param array  $config      Config array to JSON-encode.
	 * @return void
	 */
	protected function config_json_pre_block( array $server, string $client_slug, array $config ): void {
		$json = wp_json_encode( $config, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES );
		printf(
			'
%3$s
',
			esc_attr( sanitize_key( $client_slug ) ),
			esc_attr( (string) (int) $server['id'] ),
			esc_html( (string) $json )
		);
	}

	/**
	 * Renders the "Copy Configuration" JS button for a config block.
	 *
	 * @since 0.0.6
	 * @experimental May change without notice before 1.0.0.
	 *
	 * @param string $target_selector CSS selector of the 
 to copy.
	 * @return void
	 */
	protected function copy_config_button( string $target_selector ): void {
		printf(
			'%2$s',
			esc_attr( $target_selector ),
			esc_html__( 'Copy Configuration', 'acrossai-mcp-manager' )
		);
	}

	/**
	 * Renders a "server not found" notice when the server ID is invalid.
	 *
	 * @since 0.0.6
	 * @return void
	 */
	protected function render_missing_server_notice(): void {
		printf(
			'
%s
',
			esc_html__( 'MCP server not found.', 'acrossai-mcp-manager' )
		);
	}

	/**
	 * Renders the "feature currently disabled" notice with a link back to
	 * the MCP settings tab. Used by NpmClientBlock when its F012 toggle is
	 * off. (SEC-013-005)
	 *
	 * @since 0.0.6
	 * @experimental May change without notice before 1.0.0.
	 *
	 * @param string $feature_label    Feature label (e.g. 'npm / npx CLI').
	 * @param string $enable_link_text Link text (e.g. 'enable CLI Connections').
	 * @param string $explanation      Explanatory paragraph.
	 * @return void
	 */
	protected function render_feature_disabled_notice( string $feature_label, string $enable_link_text, string $explanation ): void {
		$settings_url = admin_url( 'admin.php?page=acrossai-settings&tab=mcp' );
		printf(
			'
%1$s
%2$s %4$s.
%5$s
',
			esc_html__( 'This feature is currently disabled.', 'acrossai-mcp-manager' ),
			esc_html( sprintf( /* translators: %s: feature name */ __( 'To use the %s feature, please', 'acrossai-mcp-manager' ), $feature_label ) ),
			esc_url( $settings_url ),
			esc_html( $enable_link_text ),
			esc_html( $explanation )
		);
	}

	/**
	 * Renders a section heading inside a block body.
	 *
	 * @since 0.0.6
	 * @param string $heading Heading text (already i18n'd).
	 * @return void
	 */
	protected function render_section_heading( string $heading ): void {
		printf( '
%s
', esc_html( $heading ) );
	}

	/**
	 * Shortcode entry point. Subclasses may override; default just renders
	 * with the shortcode's server attribute.
	 *
	 * @since 0.0.6
	 * @experimental May change without notice before 1.0.0.
	 *
	 * @param array|string $atts Shortcode attributes.
	 * @return string
	 */
	public static function shortcode( $atts ): string {
		$atts      = shortcode_atts(
			array(
				'server' => '0',
			),
			is_array( $atts ) ? $atts : array(),
			'acrossai_mcp_block'
		);
		$server_id = absint( $atts['server'] );
		if ( 0 === $server_id ) {
			return '';
		}
		ob_start();
		static::instance()->render( $server_id, array( 'context' => 'shortcode' ) );
		return (string) ob_get_clean();
	}

	/**
	 * Singleton instance accessor. Subclasses each maintain their own $instance.
	 *
	 * @since 0.0.6
	 * @return static
	 */
	abstract public static function instance();
}