Parent State ID: 16
State Depth: 5
Action Taken: stack(a, d)
Action Reasoning: To move towards the goal state, stack block 'a' on block 'd' since block 'd' is already on the table and block 'a' is clear and ready to be placed.
State Description: Block a is on top of block d. Block d is on the table and no longer clear. Blocks b and c remain clear and on the table. The hand is empty.
Action Path: ['unstack(c, b)', 'put-down(c)', 'unstack(d, a)', 'put-down(d)', 'stack(a, d)']

INACTIVE REASON: deactivated because diagram generation failed or invalid action chosen: The hand is not holding block 'a', violating the precondition for the stack action.
