fun fact: clojurescript had support for asynchronous paradigm through core.async library (CSP style) long before async/await landed in javascript itself.
edit: i'm in no way trying to diminish the value of this release, just pointing out how cool it is that you can get new language features before they are available in the host language by just adding a library to your dependencies. clojure is awesome!
True, but there are many reasons to avoid core.async, especially in 2026.
It balloons up the Js artifact, has no inherent error model, and transforms into state machine code that's hard to read/debug if something goes wrong. Plus, the `go` macro encourages overly-large functions, because it can't transform code outside its own sexpr.
As one Cognitect put it, "core.async is beautiful nonsense".
I'll pitch in here, as I've been doing a lot of thinking about this issue and ended up writing my own (tiny) tools for handling anomalies, modeled on the very well thought-out https://github.com/cognitect-labs/anomalies categorization.
This is actually a much wider problem and not specific to core.async. Handling anomalies is difficult. It used to be that you would have exceptions and errors which would be thrown, unwinding the stack. This pattern no longer works in asynchronous code, or code that needs to pass anomalies between the server and the client. In practical applications, an anomaly might need to be returned from a function, passed through a `core.async` channel, then thrown, unwinding the stack on the server side, then caught and passed to the client side over a WebSocket, and then displayed to the user there.
Solving this well is not easy. I think my toolkit, iterated and improved over the years, is close to what I need. But I'm pretty sure it wouldn't handle all the real-world use cases yet.
But again, this is not specific to core.async in any way.
At a first glance, it does much more than what I would want to.
My status toolkit just extends the Cognitect anomalies to be statuses, adding ::failed (parameters correct, but could not perform request), ::ok, ::accepted and ::in-progress. It also adds a bunch of utility functions like status/?! (throws the parameter if it's anomaly, returns the parameter otherwise) and macros like status/-?> (threads if an expression is not an anomaly). That's it.
For me it also lacks observability. It has been a few years since I last used Clojure, but I found manifold to be a much better fit for actual production code that you want to optimize.
I loved ztellman’s “everything must flow” talk on the topic.
I wish an alternative to JS for the front end would catch on and be something more than obscure... I'd love to use something like clojurescript, but I struggle to imagine doing so for anything but a personal side project :/ Maybe this is easier to adopt if you're already a clojure shop for the backend?
Don't be afraid, it's great! I certainly wouldn't call it "obscure", I've been using it for 10 years now to compile a complex app into highly-optimized client-side code. And the community is very welcoming and mature.
You're still able to do so, as we've been able to in ClojureScript land for many years already, since ultimately they're just Promises! I don't think that's going away with this new function hints.
Is that something people want to get rid of? Back when I did some clojurescript people were pretty proud of being able to have it used automatically. What's the plan to get the same benefits? Or is the argument that the benefits aren't significant 15ish years on?
I can finally use this little brain worm that has lived in my head for more than a decade now: IcedCoffeeScript has existed for ages https://maxtaco.github.io/coffee-script/ since well before ES got it.
fun fact: clojurescript had support for asynchronous paradigm through core.async library (CSP style) long before async/await landed in javascript itself.
edit: i'm in no way trying to diminish the value of this release, just pointing out how cool it is that you can get new language features before they are available in the host language by just adding a library to your dependencies. clojure is awesome!
True, but there are many reasons to avoid core.async, especially in 2026.
It balloons up the Js artifact, has no inherent error model, and transforms into state machine code that's hard to read/debug if something goes wrong. Plus, the `go` macro encourages overly-large functions, because it can't transform code outside its own sexpr.
As one Cognitect put it, "core.async is beautiful nonsense".
> has no inherent error model
I'll pitch in here, as I've been doing a lot of thinking about this issue and ended up writing my own (tiny) tools for handling anomalies, modeled on the very well thought-out https://github.com/cognitect-labs/anomalies categorization.
This is actually a much wider problem and not specific to core.async. Handling anomalies is difficult. It used to be that you would have exceptions and errors which would be thrown, unwinding the stack. This pattern no longer works in asynchronous code, or code that needs to pass anomalies between the server and the client. In practical applications, an anomaly might need to be returned from a function, passed through a `core.async` channel, then thrown, unwinding the stack on the server side, then caught and passed to the client side over a WebSocket, and then displayed to the user there.
Solving this well is not easy. I think my toolkit, iterated and improved over the years, is close to what I need. But I'm pretty sure it wouldn't handle all the real-world use cases yet.
But again, this is not specific to core.async in any way.
What is your opinion on farolero[0]?
[0]: https://github.com/IGJoshua/farolero
At a first glance, it does much more than what I would want to.
My status toolkit just extends the Cognitect anomalies to be statuses, adding ::failed (parameters correct, but could not perform request), ::ok, ::accepted and ::in-progress. It also adds a bunch of utility functions like status/?! (throws the parameter if it's anomaly, returns the parameter otherwise) and macros like status/-?> (threads if an expression is not an anomaly). That's it.
I deliberately avoid trying to do too much here.
For me it also lacks observability. It has been a few years since I last used Clojure, but I found manifold to be a much better fit for actual production code that you want to optimize.
I loved ztellman’s “everything must flow” talk on the topic.
Heh, I used to maintain manifold/aleph for a few years after Zach left the Clojure community.
And here I thought I was too dumb to grok core.async all those years ago (ps I still am)
I wish an alternative to JS for the front end would catch on and be something more than obscure... I'd love to use something like clojurescript, but I struggle to imagine doing so for anything but a personal side project :/ Maybe this is easier to adopt if you're already a clojure shop for the backend?
After reading
https://hypermedia.systems/
I came to the conclusion that the best frontend is no frontend.
Don't be afraid, it's great! I certainly wouldn't call it "obscure", I've been using it for 10 years now to compile a complex app into highly-optimized client-side code. And the community is very welcoming and mature.
You should try Gleam. I'm using it in production to great delight:
https://blisswriter.app/
https://blog.nestful.app/p/how-we-dropped-vue-for-gleam-and
https://www.scala-js.org/ is quite phenomenal.
Massive, cheers dude and congrats on the release. I’d say it’s such a good time to get into Clojure/Script but, well … it has been for a while!
Seems like wrapping async await functions with CSP was a better way to handle this . Clojure already had a nicer pattern for this
You're still able to do so, as we've been able to in ClojureScript land for many years already, since ultimately they're just Promises! I don't think that's going away with this new function hints.
https://clojurescript.org/guides/promise-interop#using-promi...
this release is about exposing the host language primitives to clojurescript
core.async isn't going anywhere, if async/await works better than promise based implementation, core.async will get an update in it's .cljs parts
This is important for JavaScript interop without having to include additional libraries very cool and was missing for a long time
Congratulations on the release :-)
Nice! Now also get rid of the elephant in the room - "Google Closure Compiler" and then we can really celebrate.
Is that something people want to get rid of? Back when I did some clojurescript people were pretty proud of being able to have it used automatically. What's the plan to get the same benefits? Or is the argument that the benefits aren't significant 15ish years on?
For the moment thought the article was about CoffeeScript... But it already supports async/await :)
I can finally use this little brain worm that has lived in my head for more than a decade now: IcedCoffeeScript has existed for ages https://maxtaco.github.io/coffee-script/ since well before ES got it.