> Is there any way to test these changes against a simulation of real world routes? Including to ensure that traffic that shouldn’t hit Cloudflare servers, continues to resolve routes that don’t hit Cloudflare?

You can get access to view of routes from different parts of networks but you do not have access to those routers policies, so no

> I have to imagine there’s academic research on how to simulate a fork of global BGP state, no? Surely there’s a tensor representation of the BGP graph that can be simulated on GPU clusters?

Just simulating your peers and maybe layer after is most likely good enough. And you can probably do it with a bunch of cgroups and some actual routing software. There are also network sims like GNS3 that can even just run router images