You can thicken the lower half of the ledge (may need to make it slightly deeper also) and notch the pergola joists so that they sit on top. If you do this I would recommend making the joist slightly deeper also.
Chances are that your architect will select a joist deep for visual appearance that is deeper than what is required to prevent the joist from splitting at the notch.
Chances are that your architect will select a joist deep for visual appearance that is deeper than what is required to prevent the joist from splitting at the notch.