mmm it was nice to depend my backend jvm on the frontend js

I think you can achieve it using custom Jar task

so without depending with: compile project("😒fn-adapters-core:frontend-core") directly?

yes, without dependency on project which doesn’t make a sense if you do not share code (if you do, better to use MPP plugin for that), so instead you just add dependency frontend-code build task and pack result of frontend build to backend’s jar using custom Jar task config (see gradle docs how to do that)