Claude reads and writes Gleam just fine. I think as long as the language syntax is well documented (with examples) and has meaningful diagnostics, LLMs can be useful. Gleam has both brilliant docs and diagnostics rivalling Rust. Gleam is also very well designed language wise, not many reserved words, very explicit APIs… also something that helps LLMs.

Contrast with the likes of Swift - been around for years but it’s so bloated and obscure that coding agents (not just humans) have problems using it fully.