Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires phpunit/phpunit ^13.0 -> satisfiable by phpunit/phpunit[13.0.0, ..., 13.3.1]. - Root composer.json requires psalm/plugin-phpunit ^0.19.0 -> satisfiable by psalm/plugin-phpunit[0.19.0, ..., 0.19.7]. - phpunit/phpunit[13.0.0, ..., 13.1.0] require sebastian/diff ^8.0.0 -> satisfiable by sebastian/diff[8.0.0, ..., 8.3.0]. - phpunit/phpunit[13.1.1, ..., 13.1.9] require sebastian/diff ^8.1.0 -> satisfiable by sebastian/diff[8.1.0, 8.2.0, 8.2.1, 8.3.0]. - phpunit/phpunit[13.1.10, ..., 13.1.14] require sebastian/diff ^8.3.0 -> satisfiable by sebastian/diff[8.3.0]. - phpunit/phpunit[13.2.0, ..., 13.3.1] require sebastian/diff ^9.0 -> satisfiable by sebastian/diff[9.0.0]. - Conclusion: don't install sebastian/diff 8.3.0 (conflict analysis result) - Conclusion: don't install sebastian/diff 9.0.0 (conflict analysis result) Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.