Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires tempest/core dev-main -> satisfiable by tempest/core[dev-main]. - tempest/core dev-main requires tempest/event-bus dev-main -> satisfiable by tempest/event-bus[dev-main] from composer repo (https://repo.packagist.org) but tempest/event-bus is the root package and cannot be modified. See https://getcomposer.org/dep-on-root for details and assistance.