All right. I'll take a stab at answering my own question. What I was hoping to do was set the base url in the response so my templates didn't need to worry about it and could just use a real generic "step_two" action. However, looking into it more (and duh! thinking about it), resolving relative urls is a pure client operation - there's nothing that I can find that will allow me to set a base url in the response header - only in the content. I've come up with the following solutions:

• simplify fixuphandler to just redirect to /step_one url when step is missing.
• inject id into params as and let the templates prepend it to generic action
• set ENV var and let the templates prepend ...
• use param or ENV not as action but for setting "<base>" tag.

I'm leaning to just redirecting ...

-derby

update

• instead of redirecting in the fixuphandler, use mod_rewrite to redirect