The event isn't just "there was a coin flip". The event was "there is a coin flip and I have been woken up". For this event, two thirds of the time the coin f

The event isn't just "there was a coin flip". The event was "there is a coin flip and I have been woken up". For this event, two thirds of the time the coin flip will have been tails. Halfers forget that there is an extra piece of information available "I have been woken up". SB knows that one third of the time she has been woken up it is because the coin flip was heads, and two thirds of the time it was tails. Anyway, this is a stupid "paradox". It is extremely simple to build a simulation of SB being woken up and coin tosses, and if you do so, you get the clear answer - 1/3. There is no sampling issue or other trick that makes this simulation hard to write correctly...