Sometimes, a soulknife may qualify for a prestige class with “+1 level of existing manifesting class” as part of a normal class benefit. This increased psionic training helps those who follow the path of the mind blade as well as the path of the manifester. At each level where a manifester level would increase by one, treat the soulknife as if he had gained a level of soulknife for the purposes of Mind Blade and/or Mind Blade Enhancement where appropriate.
It’s less common, but sometimes a multiclass soulknife enters one of these prestige classes with a bit of manifesting talent. In this special case, each indicated level of the prestige class advances both the soulknife’s mind blade and mind blade enhancement as above, and his existing manifesting prowess by one level.