When a unit is retrofitted on the move, it retrofits all units in its army and no cost for the retrofit is applied.



Steps I took to recreate bug:



Create two demons (lots of travel time)

Create an updated demon template that I can afford to apply to one demon but not to both

Give a move order to the demons

Quickly select one demon and hit retrofit, then agree to the dialogue to retrofit.

Viola, both demons are retrofitted, no resources are deducted.



Have not tested in multiplayer, but if it works there, I would consider this a serious bug-- not only does it give a potentially game-breaking advantage to the exploiting player, but other players have no way of seeing that the exploit was used.

Interesting... you can't give a lot of orders while the unit is on the move so being able to retrofit it on the move seems like an unintended option anyway. Did you do it while moving the unit outside of your territory? That might explain why no resources are deducted because you can't normally retrofit units outside of it. Definitely something worth looking into at any rate.

No, it has to be in your own territory, and multiple units have to be on the move. My own speculation is more along the lines of the way it reselects your entire army after every step it takes. The retrofit is aimed at one unit, but by the time the dialogue is clicked, all units have been selected, at which point the cost is applied, found to be larger than the player can pay, and some emergency code kicks in to prevent any resources going negative, Just speculation, though.



Used this in my most recent single-player game to fully upgrade both my starting units at no dust cost.