Core concept: Claude Code switches permission modes from the prompt with one key, mid-session. Plan is one of those modes, so the mode key is also the plan-mode key. The docs name it plainly.

Why A is correct:

The permission-modes page says "Enter plan mode by pressing Shift+Tab or prefixing a single prompt with /plan."
The same page says "Press Shift+Tab again to leave plan mode without approving a plan", which is the toggle the question asks about.
The interactive-mode reference lists Shift+Tab as "Cycle permission modes", running default then acceptEdits then plan.
It works during a live session. No restart and no settings change are needed.

Why the others are wrong:

B: Plain Tab does not cycle modes. At the prompt it is used for completion and for accepting a history match.
C: Ctrl+P is not a Claude Code plan-mode binding. The slash command /plan exists, but the key does not.
D: Esc interrupts Claude or closes a dialog. Double Esc clears the draft or opens the rewind menu. Neither enters plan mode.

Remember: Shift+Tab cycles permission modes, and plan mode is a stop on that cycle.

Question 268