We decided against io-ts because we'd still have to write the validator ourself (unless we used their type system as the source of truth, which wouldn't easily

We decided against io-ts because we'd still have to write the validator ourself (unless we used their type system as the source of truth, which wouldn't easily work for our project because we generate most of our types from an openAPI schema), which is exactly what we wanted to avoid doing. I hadn't heard of Zod before, but i really liked the "parse don't validate" blog post linked. Turns out that's exactly how we've been using typescript-is. But it still suffers from the problem of expecting to be the source of truth and thus not working well with generated types.