1. Support for traditional copy/paste shortcuts is problematic, since Ctrl-C is interpreted as the SIGINT signal. Copying via the mouse menu should work. Pasting is supported via Ctrl+Shift+V.

2. We had these reported from several users and we will investigate as soon as we can: https://github.com/leaningtech/webvm/issues/102

To answer you question: filesystem chunks are cached/persisted using a local IndexedDB. It provides a fairly strong level of persistence, although the user can wipe it out of course.