I also do the same. I am on the 200$ maxpro plan. I often let the plan go to pretty fine level of detail, e.g. describe exactly what test conditions to check, what exact code conditions to follow. Do you write this to a separate plan file? I find myself doing this a lot since after compaction Claude starts to have code drift.

Do you also get it to add to it's to-do list?

I also find that having the o3 model review the plan helps catch gaps. Do you do the same?