Internal site host
site1.localhost:3000
Rewrites /foo to /s/site1/foo and keeps /checkout local at /s/site1/checkout.
Next 16 Multisite Sandbox
Host-based site routing with shared checkout
Unknown hosts fall back to this page. Configured hosts are resolved in proxy.ts and rewritten to local site routes or an external origin depending on the host mapping.
External alias host
external.localhost:3000
Rewrites normal paths to the configured external origin, but keeps /checkout inside this app at /s/external/checkout.