Parent State ID: 24
State Depth: 9
Action Taken: stack(a, b)
Action Reasoning: To achieve the goal state, block 'a' needs to be on top of block 'b'. Since block 'a' is already on the table and clear, the next step is to stack 'a' onto 'b'.
State Description: Block 'a' is on top of block 'b' and clear. Block 'b' is on the table and supporting block 'a'. Block 'c' is on top of block 'b' and supporting block 'd'. Block 'd' is on top of block 'c' and clear. The hand is empty.
Action Path: ['unstack(d, a)', 'put-down(d)', 'unstack(a, c)', 'put-down(a)', 'pick-up(d)', 'stack(d, c)', 'unstack(d, c)', 'stack(d, c)', 'stack(a, b)']

INACTIVE REASON: deactivated because diagram generation failed or invalid action chosen: Preconditions for stack(a, b) are not satisfied; block b is not clear, and the hand is not holding block a.
