Bradigus has Stonebuilder:
Only construct warbeasts can be part of this model’s battlegroup. This model cannot take control of wild living warbeasts.
Druid Wilder has Attached:
Before the start of the game, attach this model to a friendly Faction Leader for the rest of the game. Each leader can only have one model/unit attached to it. The attached model is a part of its Leader’s battlegroup.
Is there some specific timing where you get to have a model that isn’t a construct warbeast in Bradigus’s battlegroup because it is attached to leader after list creation but before the start of the game?