.withSystemProperties(invokerRequest.systemProperties())
                .withUserProperties(user)
                .withTopDirectory(invokerRequest.topDirectory())
                .withRootDirectory(invokerRequest.rootDirectory().orElse(null))
                .build();
    }

    public Logger logger;

    // this one "evolves" as process progresses (instance is immutable but instances are replaced)

        public Builder withTopDirectory(@Nonnull Path topDirectory) {
            this.topDirectory = requireNonNull(topDirectory, "topDirectory");
            return this;
        }

        public Builder withRootDirectory(@Nullable Path rootDirectory) {
            this.rootDirectory = rootDirectory;
            return this;
        }

        public ProtoSession build() {