7 files declare their use of CommandInterface in Zircon Profile 8

EditorDialogSave.php in core/modules/editor/src/Ajax/EditorDialogSave.php

Contains \Drupal\editor\Ajax\EditorDialogSave.

HighlightCommand.php in core/modules/views/src/Ajax/HighlightCommand.php

Contains \Drupal\views\Ajax\HighlightCommand.

ReplaceTitleCommand.php in core/modules/views/src/Ajax/ReplaceTitleCommand.php

Contains \Drupal\views\Ajax\ReplaceTitleCommand.

ScrollTopCommand.php in core/modules/views/src/Ajax/ScrollTopCommand.php

Contains \Drupal\views\Ajax\ScrollTopCommand.

SetSubtreesCommand.php in core/modules/toolbar/src/Ajax/SetSubtreesCommand.php

Contains \Drupal\toolbar\Ajax\SetSubtreesCommand.

ShowButtonsCommand.php in core/modules/views/src/Ajax/ShowButtonsCommand.php

Contains \Drupal\views\Ajax\ShowButtonsCommand.

TriggerPreviewCommand.php in core/modules/views/src/Ajax/TriggerPreviewCommand.php

Contains \Drupal\views\Ajax\TriggerPreviewCommand.