Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires infection/infection ^0.29.10 -> satisfiable by infection/infection[0.29.10]. - Root composer.json requires phpunit/phpunit ^12.0.2 -> satisfiable by phpunit/phpunit[12.0.2]. - infection/infection 0.29.10 requires sebastian/diff ^3.0.2 || ^4.0 || ^5.0 || ^6.0 -> satisfiable by sebastian/diff[3.0.2, ..., 3.0.6, 4.0.0, ..., 4.0.6, 5.0.0, ..., 5.1.1, 6.0.0, 6.0.1, 6.0.2]. - phpunit/phpunit 12.0.2 requires sebastian/diff ^7.0.0 -> satisfiable by sebastian/diff[7.0.0]. - sebastian/diff 3.0.2 requires php ^7.1 -> your php version (8.3.99; overridden via config.platform, actual: 8.3.16) does not satisfy that requirement. - sebastian/diff[4.0.0, ..., 4.0.1] require php ^7.3 -> your php version (8.3.99; overridden via config.platform, actual: 8.3.16) does not satisfy that requirement. - You can only install one version of a package, so only one of these can be installed: sebastian/diff[3.0.2, ..., 3.0.6, 4.0.0, ..., 4.0.6, 5.0.0, ..., 5.1.1, 6.0.0, 6.0.1, 6.0.2, 7.0.0]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.