On macOS, the proxy is best effort. Programs that ignore HTTPS_PROXY/HTTP_PROXY can connect directly. This is a platform limitation (macOS Seatbelt doesn't support forced proxy routing).
BUT, the default behaviour (no net) is fully enforced at the kernel level. Domain filtering relies on the program respecting proxy env vars.
It does but because I'm inheriting the seatbelt settings from Codex, I'm not resetting it in Zerobox (I thought it's a safer option). Let me look into this, there should be a way to take Codex' profile and safely combine/modify it.
BUT, the default behaviour (no net) is fully enforced at the kernel level. Domain filtering relies on the program respecting proxy env vars.