Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires pestphp/pest ^4.0.0 -> satisfiable by pestphp/pest[v4.0.0, ..., 4.x-dev]. - pestphp/pest[v4.0.0, ..., 4.x-dev] require pestphp/pest-plugin ^4.0.0 -> satisfiable by pestphp/pest-plugin[v4.0.0, 4.x-dev] from composer repo (https://repo.packagist.org) but pestphp/pest-plugin 5.x-dev is the root package and cannot be modified. See https://getcomposer.org/dep-on-root for details and assistance.