I have a slightly different goal from Jank because my goal is to provide a runtime that supports existing Clojure libraries. I've spent the time to map out Java standard library APIs that popular libraries use and to create shims on top of Chez that allows them to run seamlessly. You can see a list of libraries that are fully tested and officially supported here. https://jolt-lang.github.io/docs/libraries.html
On top of that, I expose the API for creating shims in user space, so people can easily add their own for the libraries they want to use that might not be covered in the core. And I leverage this functionality myself to create libraries for JDBC layer or crypto that rely on doing FFI to shared system libraries that aren't part of the core runtime.
In terms of how production ready Jolt is, it's still fairly new obviously, so there will inevitably be bugs. However, it already passes full https://github.com/jank-lang/clojure-test-suite from Jank, and has its own conformance corpus https://github.com/jolt-lang/jolt/blob/main/test/chez/corpus... which is a superset of that. On top of that, I'm now able to run original test suites for the libraries I support and compare them with JVM outputs to ensure there aren't unintended divergences.
The other side of it is the benchmark harness which I use to ensure performance stays reasonably close to the JVM, in most cases it's within 1.x, and the worst case is around 6x right now. https://github.com/jolt-lang/jolt/tree/main/bench
So, Jolt basically aims to be a drop in JVM replacement for running existing Clojure code.
What a wonderful excuse to dive back into Clojure! This looks fantastic. I wonder what neat stuff might be made in Clojure thanks to a C FFI that wasn’t doable on top of the JVM.
Oh I would definitely recommend ClojureScript or Squint for running in the browser. Using Gambit to compile to Js was really just an illustration of how Jolt has a portable layer that can be compiled to a completely different Scheme backend. I don't really intend to compete with the existing frontend solutions because you really want to keep your dialect as light as possible to minimize the size and friction with the existing Js ecosystem.
You're probably thinking of Ian Piumarta's COLA project (Combined Object Lambda Architecture), which had parts named after cola soft-drinks (Coke was a lisp-like language, Pepsi was a Smalltalk-like language, and Jolt was an early implementation of Coke):
Clojure hosted on Chez Scheme (same as Racket). So cool. I tried building a standalone executable for the Chess game in my Clojure book using "jolt build -m chess-game.cli -o chess_jolt" and it simply worked great.
I tried again with a datomic demo and it needed the source code to the open source version of datomic, so I need to do some work on that.
Curious about the executable size and performance. Mark, you started me on AI with your, "Common LISP Modules: Artificial Intelligence in the Era of Neural Networks and Chaos Theory". I have never been able to fully leave Lisp behind. I'll have to try this on my linux box. What's your take on using jolt practically for work vs. learning? Thanks!
Congrats, this is awesome! I have followed your writing and have your book, so was excited to see this was you.
I have one question, can one drop into Scheme the way one can call Java in clojure, or is one totally firewalled from the underlying Scheme implementation?
Great to see Gambit getting love to. Gambit and Chez are amazing achievements.
Awesome work, have you looked into using Racket's fork of Chez? It supports some additional extensions and architectures from base Chez that would seem to beneficial as a compiler target, at least that was the case a couple years ago.
Thanks, and I have good news on that front actually. I recently factored out a portable Scheme layer and got Jolt to compile against Gambit as a backend. And given that Racket is basically an extension of Chez, it should be trivial to build against it now.
I think the name being the same is worth bringing up. Ideally you would avoid name collisions with big projects but admittedly it does happen all the time.
How much "production ready" / "battle tested" would this be ?
(Not to start a flame war, I'm genuinely curious about the differences.)
[1] https://github.com/jank-lang/jank
On top of that, I expose the API for creating shims in user space, so people can easily add their own for the libraries they want to use that might not be covered in the core. And I leverage this functionality myself to create libraries for JDBC layer or crypto that rely on doing FFI to shared system libraries that aren't part of the core runtime.
In terms of how production ready Jolt is, it's still fairly new obviously, so there will inevitably be bugs. However, it already passes full https://github.com/jank-lang/clojure-test-suite from Jank, and has its own conformance corpus https://github.com/jolt-lang/jolt/blob/main/test/chez/corpus... which is a superset of that. On top of that, I'm now able to run original test suites for the libraries I support and compare them with JVM outputs to ensure there aren't unintended divergences.
The other side of it is the benchmark harness which I use to ensure performance stays reasonably close to the JVM, in most cases it's within 1.x, and the worst case is around 6x right now. https://github.com/jolt-lang/jolt/tree/main/bench
So, Jolt basically aims to be a drop in JVM replacement for running existing Clojure code.
Although it is rather verbose, and it is easier to have a C header and run jextract on it, instead of the manual boilerplate.
No idea how well AI tooling would manage.
For example look at this arc from sqlite4clj https://github.com/andersmurphy/sqlite4clj/blob/master/src/s... it's very elegant.
(Also can plug my own libvips wrapper using coffi https://github.com/outskirtslabs/vips)
Using FFI/FFM "vanilla" with java interop is also viable, and in my experience the SOTA models do just fine with it (with or without jextract).
https://janet-lang.org/
https://github.com/nooga/let-go
Fun fact. It also runs on plan9:
https://github.com/nooga/legmacs/issues/1
https://www.piumarta.com/software/cola/
Have to give it a try.
I tried again with a datomic demo and it needed the source code to the open source version of datomic, so I need to do some work on that.
I have one question, can one drop into Scheme the way one can call Java in clojure, or is one totally firewalled from the underlying Scheme implementation?
Great to see Gambit getting love to. Gambit and Chez are amazing achievements.
I wrote up a post on how this works here https://yogthos.net/posts/2026-08-07-portable-jolt.html
(not just JVM and JavaScript runtimes)
However to be fair, none of it came to mind when I saw the title.