I am using version 3.1.8 and had great trouble getting a css file to avoid getting hashed by the module code.

I have a transition.css.

My config was this:

      postcss({
        extract: true,
        modules: true,
        use: ['sass'],
      }),

I had to log this code to work it out even though I read #292 #296

      const autoModules = options.autoModules !== false && options.onlyModules !== true;   // true
      const isAutoModule = autoModules && isModuleFile(_this.id);                          // false
      const supportModules = autoModules ? isAutoModule : options.modules;      // finally false

I ended up eventually with this

      postcss({
        extract: true,
        modules: false,
        autoModules: true,
        use: ['sass'],
      }),

It never occurred to me that modules: false would be the answer or autoModules would not apply to everything.

Should there not just be 1 boolean field and that is it? { modules: boolean }

I don't know the history and apologies if this comes across rude as this is not my intent.