Ah, the .js files in my folders were caused by a symbolic link that I had for fixing another problem. After removing this symlink, the .js files are not created inside src anymore.
Now it runs very fast and smoothly, thank you for the great work!
However, the problem that ionic run android hangs at “build dev finished” persists (using “–dev” flag because I’m using typescript@next), whereas ionic serve works without problems. Do you have any ideas what could cause this?