@malabarba: that's what my logic tells me as well, though that is not how things appear; there is one file, and the REPL is closed when I close spacemacs. After reopening, I cannot switch to a REPL with cider-switch-to-repl-buffer ("No active repl connections"), so it would seem that nothing from the old buffer has "survived".

Of course, the problem has persisted now, but it was very weird at the time. Maybe it'll pop up again.

*ceased, not persisted! (English as a second language here : )