I've used it for 6 months on the async branch and the master branch and master was incredibly stable. Async is less so because it's a large scale effort to try

I've used it for 6 months on the async branch and the master branch and master was incredibly stable. Async is less so because it's a large scale effort to try and convert over the entire API with minimal breakage(apart from fairings/middlewares). You can pin to a specific stable nightly if you're needing extra sanity, although CI makes this hard with the nightly docker images. There's a tracking issue for proc_macro_hygine here: https://github.com/rust-lang/rust/issues/54727 https://github.com/rust-lang/rust/issues/54727 Looks like the last feature is almost stable!