This is quite elegant. Handling egress IP rotation at the application level via headers is much cleaner than spinning up multiple proxy containers or messing with complex iptables/routing rules. Especially useful for large IPv6 blocks where you have a huge address space but want to avoid being flagged by destination rate-limiters.

Out of curiosity, how does it handle the neighbor discovery (NDP) overhead if you're rotating through thousands of IPv6 addresses?