So what happens when AIXI determines that there's this large computer, call it BRAIN whose outputs tend to exactly correlate with its outputs? AIXI may then discover the hypothesis that the observed effects of AIXI's outputs on the world are really caused by BRAIN's outputs. It may attempt to test this hypothesis by making some trivial modification to BRAIN so that it's outputs differ from AIXI's at some inconsequential time (not by dropping an anvil on BRAIN, because this would be very costly if the hypothesis is true). After verifying this, AIXI may then determine that various hardware improvements to BRAIN will cause its outputs to more closely match the theoretical Solomonoff Inductor, thus improving AIXI's long term payoff.

I mean, AIXI is waaaay too complicated for me to actually properly predict, but is this scenario actually so unreasonable?