I oversee some junior and mid-level developers. In this person's opinion, based of course on my own experience, traits I most strongly associate with someone be

I oversee some junior and mid-level developers. In this person's opinion, based of course on my own experience, traits I most strongly associate with someone becoming a mid-level developers involves identifying issues that have not been specifically brought to their attention; seeing problems coming down the pipe or seeing ways that something they're doing (or not doing) now could cause problems later; seeing opportunities in how we work or what we do that we could take advantage of now for a pay-off later. Essentially, providing useful output in both directions. It's not just being better and faster at writing code. I'd expect a mid-level not to make various of certain classes of mistakes, but not making those mistakes just makes someone a skilled junior dev; mid-level is about seeing beyond the boundaries of the ticket at hand.