Isn't plan mode just a "make a plan first, don't change anything yet" addendum to your prompt? Haven't tried Pi, but given it's famous extensibility, that should not be too hard to build.

If you really want a “plan mode” you can ask Pi to add it. This is the strength of Pi. It isn’t opinionated far past excellent execution.

Anything extra you can add yourself. You just ask whatever model you’re using to query the documentation included in the pi application and then its away.

My base instructions for all harnesses say something like "when the user asks you to do something that seems like it would be complex, come up with a plan first."

Works.

I've found that OMP strikes a good balance