Disclaimer: I took over maintenance of the Cap'n Proto C bindings a couple years ago.

That makes sense. There is some opportunity though since the Cap'n Proto RPC had always lacked a JavaScript RPC implementation. For example, I had always been planning on using the Cap'n Proto OCaml implementation (which had full RPC) and using one of the two mature OCaml->JavaScript frameworks to get a JavaScript implementation. Long story short: Not now, but I'd be interested in seeing if Cap'n Web can be ported to OCaml. I suspect other language communities may be interested. Promise chaining is a killer feature and was (previously) difficult to implement. Aside: Promise chaining is quite undersold on your blog post; it is co-equal to capabilities in my estimation.

I tried using the C library recently but was turned off by the lack of bounds checking. I’m not sure how anyone could reasonably accept packets over the wire which allow arbitrary memory access. Am I misunderstanding? Any hope this can be fixed?