Tbf, from the way they were described it should have been fairly easy to defeat the Sophons even without any science-fiction technology; just build e.g. 10-20 particle accelerators distributed over the world and take measurements close enough in time to each other that you cannot be at multiple sites without exceeding the speed of light. Then at most 3 of them could be corrupted for any given run, and these can be thrown out as statistical noise.