Methods, computer program products, and systems facilitate installation of a multi-installer program. A method involves executing a custom action holding an installer mutex associated with installing a core installation via a core installer of a multi-installer program, spawning from within the custom action a spawned custom action capable of awaiting execution until the custom action no longer holds the installer mutex, and executing the spawned custom action to confirm when installation conditions are met for implementing an add-on installation associated with an add-on installer of the multi-installer program. The method may also involve confirming to a target user that the installation conditions are met. When the installation conditions are met, multiple installation actions can be implemented sequentially. The installation conditions may include the installer mutex no longer being held but available for use, completion of core installation, and an installer service being available to complete the add-on installation.