BRbrian_meek·Sep 30, 2025
OP here. Thanks for all the thoughtful feedback, I really appreciate it.
I mentioned in the README that I leaned heavily on Claude Opus for the port. One of the biggest challenges was tamping down its default “everything is production-ready in a week” optimism. That said, I also discovered along the way which guardrails worked and which didn’t for guiding it toward a compliant implementation. It was good learning, and honestly, fun.
I’m genuinely interested in the Cap’n Web protocol. Writing this in Rust gave me a much clearer sense of where I would and wouldn’t use it. Credit to the Cloudflare team for defining the protocol and shipping a solid reference implementation, this wouldn’t have been possible otherwise.
A good example of why a second client (even one bootstrapped with AI) is useful: in implementation I ran into a spec ambiguity
Read the rest
around array escaping (documented here: https://github.com/cloudflare/capnweb/issues/68
). My initial Rust serializer emitted unescaped arrays at lower levels, and I even patched the TS reference to accept them. In the end, escaping arrays at all levels turned out to be the cleaner and more consistent approach, so I’ve recommended that clarification in the issue.
On naming: fair point about possible confusion with Cap’n Proto. If the Cloudflare team ever wants the crate names for an official Rust impl, they’re theirs. If there’s interest in pushing this to production ready quality, I’d also be glad to put in the work.
Thanks again for the constructive input. Happy to dive into technical details if folks are curious.