BigPipeTestHooks.php

<?php

declare (strict_types=1);
namespace Drupal\big_pipe_test\Hook;

use Drupal\Core\Hook\Attribute\Hook;

/**
 * Hook implementations for big_pipe_test.
 */
class BigPipeTestHooks {
    
    /**
     * Implements hook_page_top().
     */
    public function pageTop(array &$page_top) {
        // Ensure this hook is invoked on every page load.
        $page_top['#cache']['max-age'] = 0;
        $request = \Drupal::request();
        if ($request->query
            ->get('trigger_session')) {
            $request->getSession()
                ->set('big_pipe_test', TRUE);
        }
    }

}