So I've been playing a long and involved LotS campaign. An exo wave was announced and reached the 100% point, then it said that 2500 points were on the way to my planets. Shortly afterwards, the 2500 points warning disappeared, and about a minute later everything in the galaxy got nuked, as if a MkIII nuclear warhead had been set off. All planets were gone, there was no supply anywhere, only MkV and other nuclear-immune stuff was left.
I'd not built any nukes at all, or indeed any other warheads. I've attached a save of just after this happening. I can try to find an earlier one if that helps, but it may be about 15m before the 'incident'. Looked all over the wiki, but couldn't see any enemies that could do this sort of damage.
Is there some sort of insane, extra-nasty hunter-killer type thing that is capable of doing this? AIP is pretty high, and the game is near the 13 hour mark with >5 Spire cities built. Any ideas, please let me know!