I am no Windows expert, but I read in Issue 18597 that Ctrl+C is treated as EOF, except that a SIGINT is also sent in the background. This would explain why you see an EOFError. The partial traceback may also be from the same EOFError. Or both cases could be truncated reports of KeyboardInterrupt chained onto EOFError.

I understand the code path for input() may bypass the usual stdin.read() and readline() methods. Issue 18597 is about readline(), so it may not be an exact duplicate.

See also Issue 17619, which hints that KeyboardInterrupt handling for input() was worked on and fixed in 3.3. So why is it broken again in 3.4? A regression test would be nice, if at all possible. Does Windows have an equivalent of pseudo terminals?

Possibly also related is Issue 13673, about functions (like input) raising an exception (like EOFError), when SIGINT has been received. It mentions the interpreter completely failing to report the entire traceback, or truncating the traceback. It might be worth trying out the patch there. It might also be interesting to check sys.last_value in the interactive case.