How do I *not* merge with app.css?

[NullVoxPopuli]

I'm wanting to control CSS order in my app's app.css.
(I have looked at the ordering doc: it's not what I want ;) )

I've tried intermediateOutputPath, which doesn't error when I import, but I see that CSS from my add-ons that specify the intermediate output path are still concat'd in the wrong order.

in my app:

@import 'a.css';
@import 'b.css';

in addon a:

options: {
  cssModules: {
     intermediateOutputPath: 'a.css',
  },
},

in addon b:

options: {
  cssModules: {
     intermediateOutputPath: 'b.css',
  },
},

however, in my vendor.css in the browser, I see:

// b.css styles
// a.css is no where to be found

and app.css in the browser does not contain the @import contents