Faster startup idea
Let me know if you're interested in this idea, and I can try to put together a PR:
I think you could possibly pre-compile a javascript file that exposes just cljs.js/eval-str
or a wrapped version as its public API, and commit this to the repo as if it were just a vendored-in javascript library.
You could then produce a separate build, without cljs.js, for the app part. The app part could be responsible for injecting a script tag with the cljs eval library file, listening for it to load, and only enabling the "Run" button once it is present.
I'm not sure that it would work, but again, I can try it out if you'd like.