Tried Pheonix framework / Elixir in Cursor out of curiosity last weekend and it was the best experience I’ve had so far with agentic coding. I don’t know either yet — purely an experiment. My instructions doc required TDD, a feature list, had links to pheonix/elixir/tailwind/postgres doc and sonnet 4 did a great job utilizing pheonix cli which reduces a lot of boilerplate generation. Proved changes worked with tests at each iteration. The key thing was it didn’t lose its bearings as the project got more complex. Other web app frameworks I’m familiar with invariably get lost adding npm packages left and right, fiddling with config files and wrapped in an “extension cord” needing rescuing. I think there is something to so many node world version changes and approaches in framework implementation in training data that pollute the decision making. Also I realized watching sonnet construct the project was actually a really compelling way of learning a new framework/language to me. I can stop and ask “why are you doing this? how does that work?’ and inspect the code. Made me interested in learning more about elixir.
I've been using elixir / phoenix / liveview for a year now, basically since LLM coding has been a thing and it's been transformative. The usual "getting started" problems were so diminished that i feel like i hardly missed a beat. The usual "this won't compile / how do i do this in a new unknown language" issues that previously could have taken hours to resolve were basically gone. My LLM pair programmer just took care of it. Coming from python / django / cue, it's a breath of fresh air. It's so much easier as all the paradigms come built in with the stack (async workers, etc). The elixir / erlang library is surprisingly complete.
With regards to producing code, it seems to be doing very well. The most impressive thing it did for me was a PDF OCR from scratch using google cloud. All i had to do was plug in my credentials, hook up the code and it just worked. Magic.
Highly recommended.