Maglev Main (V3) css compile error

[ishields]

Switching over to main to try out Maglev V3 I encountered the below error

ExecJS::RuntimeError in HomeController#index
CssSyntaxError: /Users/ianshields/.rvm/gems/ruby-3.4.2/bundler/gems/maglev-core-9f3ff656d096/app/assets/stylesheets/maglev/application.css:141:12: Unknown word
139 | th {
140 | min-width: 1em;
> 141 | // border: 2px solid $color-grey;
| ^
142 | @apply border-2;
143 | @apply border-solid;

Here is the AI Analysis - that comment is almost certainly a bug in the new Maglev code. The file at maglev-core/app/assets/stylesheets/maglev/tailwind.css.erb uses // inside a block that gets processed as plain CSS—PostCSS trips over it unless you’re compiling with Sass. When you were on 2.1.0 it probably built differently (or that line wasn’t there yet). Upgrading to their main branch exposed it.

[did]

👋 @ishields! This is weird, application.css file doesn't have 141 lines. I've got some idea how/why it happened.
Could you tell me what you're using in your main app to precompile assets? Thanks!

[ishields]

@did We were using webpacker which is super legacy so I just updated it to shakapacker (long over due) which is more modern and maintained. Seems like the issue still persists though.