Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires jangregor/phpstan-prophecy dev-master as 1.1.0 -> satisfiable by jangregor/phpstan-prophecy[dev-master]. - jangregor/phpstan-prophecy dev-master requires phpstan/phpstan ^2.0.0 -> found phpstan/phpstan[2.0.0, 2.0.1, 2.0.2, 2.0.3] but it conflicts with your root composer.json require (1.12.7).