Modifications made by multiple controller devices to an environment model describing a shared automated environment can be coordinated. One of the controller devices can be designated as a coordinator, and any controller device other than the coordinator can send an update request to the coordinator. The coordinator can determine whether to accept or reject the requested modification and can report its determination to the requesting controller device. If the coordinator accepts the request, the coordinator can instigate operations to update the environment model across all controller devices of all users. If the coordinator rejects the request, the environment model is not updated. The controller device that made the request can update its local copy of the environment model and roll back the update if the request is rejected.