Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires psalm/plugin-phpunit ^0.19.0 -> satisfiable by psalm/plugin-phpunit[0.19.0, 0.19.1, 0.19.2]. - psalm/plugin-phpunit 0.19.0 requires vimeo/psalm dev-master || ^5@beta || ^5.0 -> found vimeo/psalm[dev-master, 5.0.0-alpha1, ..., 5.x-dev, 7.x-dev (alias of dev-master)] but it conflicts with your root composer.json require (~4.30.0). - psalm/plugin-phpunit 0.19.1 requires vimeo/psalm dev-master || ^5@beta || ^5.0 || ^6.0 -> found vimeo/psalm[dev-master, 5.0.0-alpha1, ..., 5.x-dev, 6.0.0, 6.x-dev, 7.x-dev (alias of dev-master)] but it conflicts with your root composer.json require (~4.30.0). - psalm/plugin-phpunit 0.19.2 requires php >=8.1 -> your php version (8.0.30) does not satisfy that requirement.