I was doing the same, but recently I noticed that Claude now writes its plans to a markdown file somewhere nested in the ~/.claude/plans directory. It will carry a reference to it through compaction. Basically mimicking my own workflow!

This can be customized via a shell env variable that I cannot remember ATM.

The downside (upside?) is that the plan will not end up in your repo. Which sometimes I want. I love the native plan mode though.