Proxy auth

Hey,
  
 Since we're talking about proxies....
Im curious to know what others think the right thing
according to the intent of the 1.1 spec to do is
in this situation:

If you have two chained proxy servers:

client -> proxy1 -> proxy2 -> origin server

If proxy 2 challenges for proxy-authentication (in its realm),
should the challenge go back to the client if proxy1 doesnt intend
to satisfy the challenge ?

My understanding was that the intent was that this situation was
to be covered.  By this I mean a client can auth to a proxy up the chain.
The spec is somewhat ambiguous, it says the proxy-auth headers are 
hop-by-hop, but then mentions that chained proxy-auth can work.