[arminiusreturns]

May I suggest my favorite: blockdiag (including seqdiag, nwdiag, and actdiag, and rackdiag (rackdiag super slept on!))

I've evaluated every diagrams-as-code tool in existence just about, and revisit them every year or two, and I keep coming back to blockdiag. Mermaid looked nice but had many issues I ran into.

blockdiag doesn't look as pretty out of the box, but when done right it looks really good, especially as an SVG