McBrigadierCommandsRegisterEvent

An event fired every time the server or proxy rebuilds its command dispatcher.

Register the listener as early as possible: from PluginBootstrap on Paper, or from the constructor of your plugin or mod on other platforms.

On Paper, once any plugin registers the bootstrap command handler, the startup dispatcher is built in McBrigadierRegistry.Phase.BOOTSTRAP, before any JavaPlugin exists. A listener registered from the plugin constructor, onLoad or onEnable is then only called on /minecraft:reload.