private ApplicationVersions loadApplication(Session session, Optional<ApplicationVersions> previousApplicationVersions) {
        log.log(Level.FINE, () -> "Loading application for " + session);
        SessionZooKeeperClient sessionZooKeeperClient = createSessionZooKeeperClient(session.getSessionId());
        ActivatedModelsBuilder builder = new ActivatedModelsBuilder(session.getTenantName(),
                                                                    session.getSessionId(),
                                                                    sessionZooKeeperClient,
                                                                    previousApplicationVersions,
                                                                    sessionPreparer.getExecutor(),
                                                                    curator,
                                                                    metrics,
                                                                    flagSource,
                                                                    hostProvisionerProvider,
                                                                    configserverConfig,
                                                                    zone,
                                                                    modelFactoryRegistry,
                                                                    configDefinitionRepo,
                                                                    onnxModelCost,
                                                                    endpointCertificateSecretStores);
        return ApplicationVersions.fromList(builder.buildModels(session.getApplicationId(),
                                                                session.getDockerImageRepository(),
                                                                session.getVespaVersion(),
                                                                session.getVersionToBuildFirst(),
                                                                sessionZooKeeperClient.loadApplicationPackage(),
                                                                new AllocatedHostsFromAllModels(),
                                                                clock.instant()));
    }
A session for which we don't have a watcher, i.e. hitherto unknown to us.

@param sessionId session id for the new session
configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionRepository.java