Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires lctrs/psalm-psr-container-plugin ^1.9 -> satisfiable by lctrs/psalm-psr-container-plugin[1.9.0]. - lctrs/psalm-psr-container-plugin 1.9.0 requires php >=8.0.2 <8.3.0 -> your php version (8.3.0RC3) does not satisfy that requirement.