Rabobank's Michael Every has an early hot-take on the situation:

At this stage, with news hazy and facts on the ground absent, there appear two realistic scenarios.

One is that this attack is theatre to placate the large crowds who were so recently on Iran’s streets.

The alternative is that Iran has genuinely decided to test Trump by also upping the ante.

The only way to tell is if there are US casualties.

If we get images of dead and injured US soldiers, then the worst-case scenarios begin to open up. If no real damage has been done by these missiles, but Tehran gets to show the crowds it responded, then more positive possibilities are still available. We will find out shortly – but breaking news is that there are ‘only’ Iraqi casualties, according to its Ministry of Defence. It remains to be seen if that is a red line for Trump, or is the kind of collateral damage he was expecting after taking out former IRGC head Soleimani.

Given that this move from Iran appears totally out of keeping with their usual strategic acumen, either the loss of Soleimani has meant a total loss of talent, and/or self-control, or this is indeed a token level of revenge.

I will cautiously stick to that interpretation for now.