Comment by jshier

No network namespaces, but the various Network Extension APIs might be able to do this, though it's difficult. RocketSim (I'm unaffiliated, just an example) recently added a simulator-specific network throttle (to replace the system-wide Network Link Conditioner Apple ships) using a content filter extension. Even though this is a system-wide API, it seems you can limit its impact to a single app. And it seemed to properly compose with Proxyman and Cloudflare's Warp VPN at the same time, so perhaps it could be a general solution.