Shift+Tab twice in Claude Code drops you into it. While you're in plan mode, Claude can read, search, and think, but it can't write a single file. It produces a plan. You read it. If the plan is wrong, you correct it before any code gets touched. When the plan looks right, you exit and let it execute.
How to use it: Shift+Tab twice. Ask for what you want. Read the plan carefully. Push back where it's wrong. Iterate until the plan matches the reality of your repo. Then exit plan mode and tell it to execute.
A few things I do inside plan mode that pay off: Ask it to list the exact files it intends to touch. Anything unexpected on that list is a red flag. Ask what it's assuming.
Half the time the assumption is the bug you would have shipped. Ask for the rollback. If it can't explain how to undo the change, the plan isn't done.
Stop treating Claude as a fast typist that occasionally writes code you have to fix, and start treating it like a pair you discuss the approach with first. Plans before code. Same thing I'd want from a human.