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I use paredit myself but I also think that parinfer is very interesting: https://shaunlebron.github.io/parinfer/

The repo is archived. Last commit is 2 years ago. Is the project completed, or abandoned?

The Parinfer core algorithm is mostly "complete", with the remaining work being various editor integrations (which can be quite tricky).

I maintain an up-to-date fork of Parinfer JS here: https://github.com/oakmac/parinfer

The Rust implementation is also popular and actively maintained: https://github.com/eraserhd/parinfer-rust

Both, most editors have their own implementation though, this repo is more a demonstration on the idea around the UX.