Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires vimeo/psalm ^5.23 -> satisfiable by vimeo/psalm[5.23.0, ..., 5.26.1]. - vimeo/psalm[5.23.0, ..., 5.26.1] require php ^7.4 || ~8.0.0 || ~8.1.0 || ~8.2.0 || ~8.3.0 -> your php version (8.4.0-dev) does not satisfy that requirement.