We just shipped support for the ugliest part of HTTP: Vary – Cloudflare Blog

Cloudflare has added configurable Vary support to Cache Rules, letting sites control how request headers influence caching. The feature lets operators normalize known negotiation headers, pass exact values when needed, or bypass caching for unpredictable variations, reducing unnecessary cache fragmentation while preventing wrong responses. This change improves cache accuracy for content that varies by language, format, or other headers.