Those of you familiar with GQL - how are you handling errors? I see some use error union types on results. It's cool it makes things typesafe but I'm wondering if there are any downsides?

I use union types for errors - but only on mutation results not normal queries. One challenge we had with customers is that if a mutation fails, they still get back a 200 response - because an error type is a valid response. So we’ve had cases were people weren’t checking the response and assumed that a 200 OK meant the mutation worked - which I don’t think is a bad assumption. We have an item on our backlog to look into returning 400/500s based on the query result

Thats an issue even with normal errors right since gql always returns 200s

yeah, unless something goes wrong in the graphql server itself

Also aren't your customers using generated client libraries? Does that help at all?

Most are, but not everyone makes sure to exhaustively check the types, or even uses a typed language