Proxy Requests and Apple's Reachability Preflight
Let the intended proxied request establish its own result instead of rejecting it because a separate reachability check used a different network assumption.
A reachability preflight can reject a download before the application tries its proxy route. A direct assessment of the destination asks a different question from reaching an intermediary that connects to that destination.
Apple deprecates SCNetworkReachability preflight use and recommends attempting the connection. Conditions can change between check and operation, and positive flags never establish proxy authentication, TLS verification, or destination acceptance.
Report the operation's result
Let the HTTP client's result distinguish connection failure, proxy challenge, and application response. An appropriate URLSession connectivity-waiting configuration can defer an operation until a suitable path exists; it does not supply credentials.
Show waiting or failure states for the request the user made. Network-path observations remain useful diagnostics, but should not become a permanent offline veto based on an earlier lookup using another routing assumption.