Foreign reserves are only about 1/2 trillion and dropped about 5% last month. They aren’t in the best position, and the longer this goes on, the more the downside accelerates. Once people think you’ll run out soon, you’re screwed.
At these prices, SA can’t just turn oil into dollars (well, not many dollars anyway).
I imagine that foreign creditors will allow KSA to get much closer to 0 than they’d allow most other countries because KSA has a clearer path to repayment; bow out of the current oil production spat with Russia. But spending down 5% in one month is alarming.