Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires vimeo/psalm ^4.5 -> satisfiable by vimeo/psalm[4.5.0, ..., 4.30.0]. - phpunit/phpunit[10.0.0, ..., 10.5.3] require sebastian/diff ^5.0 -> satisfiable by sebastian/diff[5.0.0, 5.0.1, 5.0.2, 5.0.3]. - Conclusion: don't install sebastian/diff 5.0.0 (conflict analysis result) - Root composer.json requires phpunit/phpunit ^10.0.0 -> satisfiable by phpunit/phpunit[10.0.0, ..., 10.5.3]. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.