Root cause is not the key or code — it's a network egress block. The agent proxy's status log showed four connect_rejected entries, all gateway answered 403 to CONNECT for api.reply.io:443, timestamped to match the watchdog's four retries. An unauthenticated curl to api.reply.io returned the same CONNECT tunnel failed, response 403 with no key involved, so it isn't an auth problem. The proxy README is explicit that a 403 CONNECT means the host isn't on this session's egress allowlist and must not be retried or routed around, so I did neither.