Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires mezzio/mezzio-tooling ^2.9 -> satisfiable by mezzio/mezzio-tooling[2.9.0]. - mezzio/mezzio-tooling 2.9.0 requires php ~8.1.0 || ~8.2.0 || ~8.3.0 -> your php version (8.4.3) does not satisfy that requirement. Problem 2 - Root composer.json requires vimeo/psalm ^5.25 -> satisfiable by vimeo/psalm[5.25.0, 5.26.0, 5.26.1]. - vimeo/psalm[5.25.0, ..., 5.26.1] require php ^7.4 || ~8.0.0 || ~8.1.0 || ~8.2.0 || ~8.3.0 -> your php version (8.4.3) does not satisfy that requirement.