Your requirements could not be resolved to an installable set of packages. Problem 1 - psalm/plugin-phpunit is locked to version 0.18.4 and an update of this package was not requested. - psalm/plugin-phpunit 0.18.4 requires vimeo/psalm dev-master || dev-4.x || ^4.7.1 || ^5@beta || ^5.0 -> satisfiable by vimeo/psalm[4.7.1, ..., 4.30.0, 5.0.0, ..., 5.26.1]. - 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. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.