jjs uses Javac's APIs to implement package/class tab-completion. But, javac may not be available (running in JRE) or jjs may be running under security manager (jjs disables javac uses in that case - because javac API throws SecurityException -- perhaps not meant to be run under security manager at all). So, jjs should provide fallback in such cases - perhaps jjs can directly use "jrt fs" file system to provide package/class name completion for platform classes at least.