Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires vimeo/psalm ^5.26.1 -> satisfiable by vimeo/psalm[5.26.1]. - vimeo/psalm 5.26.1 requires php ^7.4 || ~8.0.0 || ~8.1.0 || ~8.2.0 || ~8.3.0 -> your php version (8.5.0RC1) does not satisfy that requirement. Problem 2 - Root composer.json requires psalm/plugin-phpunit ^0.19.0 -> satisfiable by psalm/plugin-phpunit[0.19.0, ..., 0.19.5]. - psalm/plugin-phpunit 0.19.0 requires vimeo/psalm dev-master || ^5@beta || ^5.0 -> satisfiable by vimeo/psalm[5.26.1]. - psalm/plugin-phpunit 0.19.2 requires vimeo/psalm dev-master || ^6 -> found vimeo/psalm[6.0.0, ..., 6.13.1] but it conflicts with your root composer.json require (^5.26.1). - psalm/plugin-phpunit 0.19.3 requires vimeo/psalm dev-master || ^6 || ^7 -> found vimeo/psalm[6.0.0, ..., 6.13.1] but it conflicts with your root composer.json require (^5.26.1). - psalm/plugin-phpunit[0.19.4, ..., 0.19.5] require vimeo/psalm dev-master || ^6.10.0 -> found vimeo/psalm[6.10.0, ..., 6.13.1] but it conflicts with your root composer.json require (^5.26.1). - vimeo/psalm 5.26.1 requires php ^7.4 || ~8.0.0 || ~8.1.0 || ~8.2.0 || ~8.3.0 -> your php version (8.5.0RC1) does not satisfy that requirement. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.