The wiki documentation doesn't document all of the options that the current (as of 6.38.5) ipv6 dhcp client has, so I need to ask here. (Specifically, prefix-hint)

My router shows the prefix I've been given, it's /64. I'm trying various things to see if I can get a prefix larger (smaller mask) than /64. I've tried /60 and /48, but I'm not sure I'm doing it right. I'm sniffing all attempts and I only ever get back a /64.

There's some indication that my ISP might hand out a /60. They (ISP) won't talk to me about it, and I'm not sure I know how to properly "ask" for it with the IPv6 dhcp client.

Here is the current setup that is working with a /64:
Do I need to use prefix-hint, or maybe some other setup? Can someone help?

Thanks.

Yes, typically a 'hint', if supported by your ISP

That was it, thanks very much. I now have a /60 on my router.

Now I need to figure out how to hand out other subnets programmatically when the ISP changes the prefix every few days

You can assign static ipv6, where what change is only the prefix. Example:
Prefix: 2001:123:1:0::/60
Using the code above:
Subnet 1: 2001:123:1:0:c:b/64
Subnet 2: 2001:123:1:1::1:2:3/64

If prefix is changed, the first 4 groups change, the rest stay the same.

Thanks!

Next topic is IPv6 route filtering. I haven't been able to figure it out. This is for another topic.