Challah bread can be split for a few reasons:   1.     Over proofing: If the dough is left to rise for too long, it can become too puffy and cause the bread to split as it bakes. Make sure you are following the recipe's proofing instructions carefully and not leaving the dough to rise for too long.   2.     Under-kneading: If the dough is not kneaded enough, it may not develop enough gluten, which can cause the bread to split as it bakes. Make sure you are kneading the dough until it is smooth and elastic.   3.     Insufficient shaping: If the dough is not shaped properly before baking, it can cause weak spots in the bread, which can lead to splitting. Make sure you are shaping the dough tightly and evenly.   4.     Too high oven temperature: If the oven temperature is too high, it can cause the bread to rise too quickly and split. Make sure you are baking the bread at the correct temperature as stated in the recipe.   By addressing these potential issues, you can help prevent your challah bread from splitting.