I agree that it looks nice. If you enlarge the picture, it doesn't look like the posts are imbedded at all. They are all the way to the edge of the slab, and split. No visible fasteners at the post/beam either. I'm thinking the rigidity comes from the beam mortised into the post. There must be a few screws that we can't see. I can imagine using 6" Timberloks from both sides to lock the post onto the beam. But it sure seems like it'd start to rack as the wood shrinks and changes.
The rigidity is in the upper and lower connections to make a "box." If only upper, then much more massive than if combined with lower.
There are companies that make standard brackets to rid the braces. If you have to meet permit requirements though you may have to have an engineer spec the lateral and moment loads and that your DIY connections have met them.
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