I'm not really sure if this is a bug or a hidden game mechanic, but I'm posting just in case.

For a number of games now, I've found that terraforming planets sometimes removes the Sterile qualifier on a planet. For example, when terraforming a Lava planet into a Desert, the description tells you that the planet will still be sterile. Sometimes this is true but I've experienced many times wherein a Desert (or Ice) planet suddenly loses its Sterile qualifier with no explanation given. As far as I can tell, this is not limited to Hot planets since I've had this happen when terraforming Barren planets into Ice and so on. Otherwise, the mechanic seems to be removing sterile qualifiers or adding fertile qualifiers as one would expect.

And did the sterile-specific bonuses stay? (Like AI labor +5 production on sterile, biophobic +20 happiness). Just to know if it's a gameplay bug, or a "tooltip" bug.

I have also encountered this bug, and there are also reports in the steam forum about terraforming being buggy. The bonusses are not applied, seems that terraforming is not well usable in the current state.

Hi guys!

This is a known issue we ahave marked on fixed on our end so it should be pushed to a public version sooner than later :)

Cheers,