And what if the computer is kidnapped by the US Army while it's copying the files?
You just can't defend against everything, but an imperfect solution can still be an improvement over the status quo.
No, but imagine doing all the work to collect up a list of files that failed only to say, pop a modal at the end of the process that coincides with the user hitting Enter because they were multitasking and it auto-accepts the dialog. Information gone, context lost, in fact your entire design has failed to change the experience at all! All because of one UI overlap that's actually very common.
We have shared workstations for example where this would be a typical use case for non-tecchnical users across multiple user logins: ensuring you can check that the big data transfer was complete a few hours later would be very useful, but if you only do a fraction of the work for completeness then again, it's of no benefit.
> kidnapped by the US Army.... You just can't defend against everything
Of course not.
The litmus test IMO should be "what would a normal intelligent human do in this situation?"
A human would copy every file it could, maintaining a list of issues. When you were available to address concerns, it'd present the options to you. The human would give up if the US Army showed up, but a human would restart a TCP connection automatically without asking for permission again (or more analogously, redial a phone call). A human would save their work automatically, and when you showed back up, would find that work for you.
(In 2026, things like "retry" should be automatic outside some very specific limitations too, because of course a human would try again if they failed).