Figure 4.2 Two ways to plan. Interleaved (left) is a tight cycle: decide one
step, act, observe, and decide again—maximally adaptive, structurally
myopic. Plan-then-execute (right) has a planner draft the whole plan and an
executor work through it. What keeps the second design honest is the replan
path in accent: when the executor meets a surprise, control returns to the
planner to revise. A plan with no replan arrow is just a blind executor.
