Hi @jaffadog
I’m in the similar scenario but in full site with a different CDN. In your experiment, did you ever test config DISCOURSE_CDN_URL with the website domain URL. For example, in full CDN mode, if your website URL is https://foo.bar.com; then the CDN URL should be https://foo.bar.com as well. If we leave DISCOURSE_CDN_URL empty then website assets url will start with relative path. For example as below snippet,
<link rel="preload" href="/extra-locales/admin?v=8f522e122c802d1ed66dfa7fecafbb35" as="script">
<script defer src="/extra-locales/admin?v=8f522e122c802d1ed66dfa7fecafbb35"></script>
This just looks not elegant in a production website, though both URL make request to https://foo.bar.com.