WP CLI composer autoload bug

app.php

<?php

require_once __DIR__ . '/vendor/autoload.php';

/**
 * Load dotenv if .env file is present
 */
if ( file_exists( __DIR__ . '/.env.php' ) ) {
	Arrilot\DotEnv\DotEnv::load( __DIR__ . '/.env.php' );
}

composer.json

{
	"config": {
		"preferred-install": "dist",
		"vendor-dir": "mu-plugins/app/vendor"
	},
	"extra": {
		"installer-paths": {
			"mu-plugins/{$name}/": [
				"type:wordpress-muplugin"
			]
		}
	},
	"require": {
		"php": ">=5.5",
		"composer/installers": "~1.0.12",
		"arrilot/dotenv-php": "^1.0"
	}
}