Gleam / Lustre are fantastic, and I hope to use them in anger at some point, but it's my understanding that they don't aim to be as "total" as Elm (quotation marks because I don't think Elm was total in the formal sense). That is, while Lustre is very much following in Elm's footsteps, both it and the language have not been designed around avoiding runtime failure at all costs. (Which makes sense, given the Erlang/BEAM heritage.)