google.com also covers www.google.com; other
subdomains need their own entry). A redirect is followed only if its new
destination passes both gates again. The agent never holds this list; it
proposes, the gateway decides.ubag_ph_…), never the key. UBAG swaps it for the real key at the
boundary: only in the Authorization header, and only on this host. Anywhere else
(another host, the URL, another header, a redirect) the placeholder trips a block as
an exfiltration attempt. Anything the server echoes back is redacted before the agent
sees it. The real key here is a demo secret, not a credential to anything.