Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires vimeo/psalm ^4.3||^5.16.0 -> satisfiable by vimeo/psalm[4.3.0, ..., 4.30.0, 5.16.0, ..., 5.26.1]. - vimeo/psalm[4.3.0, ..., 4.11.2] require symfony/console ^3.4.17 || ^4.1.6 || ^5.0 -> found symfony/console[v3.4.17, ..., v3.4.47, v4.1.6, ..., v4.4.49, v5.0.0, ..., v5.4.47] but these were not loaded, likely because it conflicts with another require. - vimeo/psalm[4.12.0, ..., 4.30.0] require symfony/console ^3.4.17 || ^4.1.6 || ^5.0 || ^6.0 -> found symfony/console[v3.4.17, ..., v3.4.47, v4.1.6, ..., v4.4.49, v5.0.0, ..., v5.4.47, v6.0.0, ..., v6.4.15] but these were not loaded, likely because it conflicts with another require. - vimeo/psalm[5.16.0, ..., 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.