This appears to be vibecoded but not disclosed as such. 2k commits from a single author starting from June 1st with really long commit messages and source code comments. The GitHub org has 19 additional projects that are all recently created.
edit: Yup, found a very long blog post that says it's made with LLMs near the end https://yogthos.net/posts/2026-07-02-jolt.html
I think the author has been very open about the use of LLMs. And while I am very wary of LLM slop, this is one use case where it makes complete sense to utilize them to the fullest. A Clojure implementation already exists for LLMs to reference, and tons of test cases to verify behavior. It doesn't get better than that for LLM usage.
Vibecoding means you don't pay much attention to the code, not the case here.