Your requirements could not be resolved to an installable set of packages. Problem 1 - vimeo/psalm[4.5.0, ..., 4.30.0] require sebastian/diff ^3.0 || ^4.0 -> satisfiable by sebastian/diff[3.0.0, ..., 3.0.4, 4.0.0, ..., 4.0.5]. - You can only install one version of a package, so only one of these can be installed: sebastian/diff[3.0.0, ..., 3.0.4, 4.0.0, ..., 4.0.5, 6.0.0]. - phpunit/phpunit 11.0.0 requires sebastian/diff ^6.0 -> satisfiable by sebastian/diff[6.0.0]. - Root composer.json requires phpunit/phpunit ^11.0.0 -> satisfiable by phpunit/phpunit[11.0.0]. - Root composer.json requires vimeo/psalm ^4.5 -> satisfiable by vimeo/psalm[4.5.0, ..., 4.30.0]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.