DHCPv6: is it possible to have a fixed prefix delegation for a host while allowing the IPv6 address assigned to be dynamic?

[Erik Andersen]

I would like to hand out static DHCPv6 prefix delegations to hosts based 
on their client-id.

I currently have a system of include files that includes on file for 
each host.

Those files have something like:

host 3c906af6703a {
         host-identifier option dhcp6.client-id 
00:03:00:01:3c:90:6a:f6:70:3c;
         fixed-prefix6 2607:f248:320:130::/60;
}

They are included in part of a pool6 in a subnet6:


         pool6 { # For normal/WAN clients, not DOCSIS
                 allow unknown-clients;
                 deny members of "docsis";

                 # Range for clients
                 range6 2607:f248:102:10::10 2607:f248:102:10::ffff;

                 # Range for clients requesting a temporary address
                 range6 2607:f248:102:10::2:0/112 temporary;

                 # Include static prefix delegations
                 include "/etc/dhcp/staticpdinclude.conf";
         }

But when a client is requesting a non-temporary address and a prefix 
(and is covered by a host definition), the response packet says there is 
no available address, and the log shows:

Unable to pick client address: no addresses available  - shared network 
2607:f248:102:10::/64: 0 total, 0 active,  0 abandoned

Why wouldn't the host directive inherit the range6 definition and use 
something from that range?

Is it possible to have a dynamically picked non-temporary address 
assigned to a client, along with a fixed delagated prefix? If so, can 
someone share an example configuration that does that?

Thanks,

Erik