How does upgrading work?

[Caine]

It says to add units to the list so that they can turn into it. Am I reading this wrong? I was hoping this would kinda work like zerg larvae turning into zergling 'n' what not.

[Eternal Satron]

Upgrading instantaneously changes the base blueprint of the unit. All the current blocks that don't fit into the new blueprint are lost. Blocks that are a lower level then the new blueprint are deactivated until the are fully rebuilt/repaired. (as if they were only partially built to begin with.)

Upgrading is great for making higher tier versions of the same unit, or for having a base unit that can upgrade into several different variants. (For example a base unit that can be upgraded to have different weapons). Units being upgraded need to be built using repair modules, so having other units around to help with the upgrade, or having a repair module on both the new and old blueprints for the upgrading unit is a necessity. If an upgrading unit has a repair module on it, it will automatically start to repair itself after the upgrade.

[Caine]

Good to know the actual upgrade mechanic, but to rephrase it, how do I get the mechanic to work. I've attempted it, but it just won't let my units upgrade.

[Eternal Satron]

Upgrading should only fail under two circumstances. 1. The upgrade module isn't built or finished yet. 2. The new blueprint has no modules in common with the old blueprint. (Positioning within the blueprint editor matters here). Its generally best practice to load the base blueprint, edit it and save it as a new blueprint.