Need help reinforcing a pergola
I'd add a knee brace that matches your post size. Install (2) Simpson Strong Tie KBS1Z at the base of each brace and provide a single thru bolt at the top of the brace, centered at the mid depth of the beam. The thru bolt should be similar to those used at the top of the posts, just make sure you penetrate all 3 members and it's at least 1/4" in diameter. Make sure the brace is angled somewhere between 30 and 60 degrees and you're in the clear.


 http://embed.widencdn.net/pdf/plus/ssttoolbox/qyjicced3n/C-C-2019-p296.pdf