= Solution
Use $a,w,g,r$ for the agent, monster, gold and arrow, and abbreviate $sq_{ij}$ to $s_{ij}$. A physically safe <STRIPS> plan is
$$
\begin{aligned}
&\operatorname{Move}(a,s_{11},s_{21}),\quad \operatorname{Move}(a,s_{21},s_{22}),\\
&\operatorname{Shoot}(a,s_{22},r,w,s_{23}),\\
&\operatorname{Move}(a,s_{22},s_{23}),\quad \operatorname{Move}(a,s_{23},s_{13}),\\
&\operatorname{Take}(a,g,s_{13}),\\
&\operatorname{Move}(a,s_{13},s_{23}),\quad \operatorname{Move}(a,s_{23},s_{22}),\\
&\operatorname{Move}(a,s_{22},s_{21}),\quad \operatorname{Move}(a,s_{21},s_{11}).
\end{aligned}
$$
Every movement follows a listed adjacency <predicate>. The shot is taken from $s_{22}$ while the arrow is held, and kills the monster before entry into $s_{23}$. The pit at $s_{12}$ is never entered. The pickup establishes possession of the gold, and the last four movements restore the exit location while preserving that possession. Thus \b[ten actions achieve the formal goal and the intended safe return]; arriving at the exit is the source model’s representation of leaving.
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