One strategy I use in the planning phase is even when I know how I'd implement the solution, I ask the Claude/Codex how they would solve the problem or implement the feature without giving them any clues - and then compare their solutions to my own. Often I am pleasantly surprised by alternative ways of doing things and ideas that we integrate into the final design.
I like this, though it does leave me feeling more nervous when I really don't know how I'd solve the problem, still requires trust.
Same. I've been creating "research" documents where I let it do a freeform survey of possible solutions/have sketch out it's own solution. I'll then sketch out a plan based on what I think is good or what I think it missed, and then I'll have it interrogate me for a final PRD document. It then implements the feature in reviewable chunks, and I'll give it feedback or tweak the PRD doc as needed.
Finally feel like I have a good workflow where I can fully benefit from these things without sacrificing my understanding of what they're doing.