I’m curious what’s the regulation in this scenario? In Canada I think light off means 4-way stop signs so everyone obeys that, or at least most of everyone. What’s the situation in SF?

Yes, that is the same law in California, but so many people drift through stop signs that the guidance is close to meaningless.

In addition, there are 4-way stop signs all over SF and tourists regularly comment on how they work here.

The law is clear - yield to the right, but that is a pretty slow system in congested roads.

The local custom in SF is that someone is usually obviously first, rightmost, or just most aggressive, and opposing pairs of cars go simultaneously, while being wary about left turns.

Of course pedestrians have right of way in California, so someone in a crosswalk gives implied right of way to the road parallel to the person's crosswalk.

The result is 2x or better throughput, and lots of confused tourists.

So ... with the lights out on a Saturday before Xmas, there was a mess of SF local driving protocol, irritated shoppers, people coming to SF for Xmas parties, and just normal Saturday car and foot traffic.

I thought Waymo did pretty well, but as I said, I didn't see any ones that were dead in the middle of the street..

Legally in the United States a completely dead traffic signal becomes an all way stop.