Testing at Next Major produces ``` In PluginManager.php line 798: symfony/runtime contains a Composer plugin which is blocked by your allow-plugins config. You may add it to the list if you consider it safe. You can run "composer config --no-plugins allow-plugins.symfony/runtime [true|false]" to enable it (true) or disable it explicitly and suppress this exception (false) See https://getcomposer.org/allow-plugins ``` This is due to a change on 11 May 2026 - see the [Change Record](https://www.drupal.org/node/3553275)