you will smoke if and only if you have the gene, and you will have the gene if and only if you smoke, and in which case you shouldn't smoke
This implicitly assumes EDT.
At the point at which the gene is a perfect predictor, if you have a genetic test and you don't have the gene, and then smoke
But that's not what CDT counterfactuals do. You cut off previous nodes. As the choice to smoke doesn't causally affect the gene, smoking doesn't counterfactually contradict the prediction. If you would actually smoke, then yes, but counterfactuals don't imply there's any chance of it happening in reality.
This implicitly assumes EDT.
No it doesn't. It assumes a "perfect predictor" is what it is. I don't give a damn about evidence - we're specifying properties of a universe here.
But that's not what CDT counterfactuals do.
CDT assumes causality makes sense in the universe. Your hypotheticals don't take place in a universe with the kind of causality causal decision theory depends upon.
You cut off previous nodes. As the choice to smoke doesn't causally affect the gene, smoking doesn't counterfactually contradict the prediction.
In the case ...
You're given the option to torture everyone in the universe, or inflict a dust speck on everyone in the universe. Either you are the only one in the universe, or there are 3^^^3 perfect copies of you (far enough apart that you will never meet.) In the latter case, all copies of you are chosen, and all make the same choice. (Edit: if they choose specks, each person gets one dust speck. This was not meant to be ambiguous.)
As it happens, a perfect and truthful predictor has declared that you will choose torture iff you are alone.
What do you do?
How does your answer change if the predictor made the copies of you conditional on their prediction?
How does your answer change if, in addition to that, you're told you are the original?