In Java, it defaults to 1MB on platforms other than Windows. I've seen people OOM themselves by setting the default thread stack size massively high - they had

In Java, it defaults to 1MB on platforms other than Windows. I've seen people OOM themselves by setting the default thread stack size massively high - they had likely gotten confused with the args (they'd used -Xss when I think they meant -Xms) and given their threads 1GiB of stack each. I can't speak to how Java manages stack size between itself and the OS though, I'm sure there's deep magic there.