Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires lctrs/psalm-psr-container-plugin ^1.11 -> satisfiable by lctrs/psalm-psr-container-plugin[1.11.0]. - Root composer.json requires psalm/plugin-phpunit ^0.20.0 -> satisfiable by psalm/plugin-phpunit[0.20.0, 0.20.1]. - lctrs/psalm-psr-container-plugin 1.11.0 requires vimeo/psalm ^6.8.8 -> satisfiable by vimeo/psalm[6.15.1, 6.16.0, 6.16.1]. - psalm/plugin-phpunit[0.20.0, ..., 0.20.1] require psalm/psalm-plugin-api ^0.1 -> satisfiable by psalm/psalm-plugin-api[0.1.0]. - psalm/psalm-plugin-api 0.1.0 conflicts with vimeo/psalm <7.0.0. Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.