Seems to be behaviour that differs between OSes. (I use Windows)
It causes a new problem with the new Debug Logging option though... Maybe if the protocol-dump related data could be omitted somehow?'
Didn't you add this read timer to read output every 500 millisecond?
https://github.com/coblee/litecoin/blob/master/src/qt/miningpage.cpp#L29
That seems to work for me. Is it not working on Windows?
Can you try a few things on Windows? Instead of waiting on signal readyReadStandardOutput(), use readyReadStandardError(). Does that help? If not, how about just readyRead()
I know minerd only outputs to stderr, so stdout might not be flushed after each printout.