Neon's `psql -h pg.neon.tech` command lets developers connect to any Neon project without remembering credentials. Behind the scenes, a 'Link Proxy' server speaks the Postgres protocol and uses the NoticeResponse message type to display a clickable authentication URL. The control plane then feeds connection details back to the Link Proxy, which forwards all traffic between psql and the actual Postgres compute. Both the regular Neon Proxy and Link Proxy are open source.
