# t000__ep047__blocks

- **suite / variant:** `` / ``
- **instruction:** Stack the yellow block on the wooden block
- **success:** False
- **control steps:** 833  (16.3s at 51 Hz)
- **policy inferences:** 142  (replan_steps=6)
- **video:** `blocks/ep047/rollout.mp4`
- **features:** `142` prefix tensors (`prefix`; model=``)

## Semantic timeline

| seconds | control_step | policy_step | phrase |
|---|---|---|---|
| 0.0–3.0 | 0–152 | 0–25 | reaching toward yellow block |
| 3.0–6.0 | 153–305 | 25–50 | grasping the yellow block |
| 6.0–9.0 | 306–458 | 51–76 | lifting yellow block toward target |
| 9.0–12.0 | 459–611 | 76–101 | lowering block and slipping off |
| 12.0–15.0 | 612–764 | 102–127 | hovering gripper near tabletop |
| 15.0–16.3 | 765–832 | 127–138 | idle above table surface |

## Failure

- **yes**
- **onset type:** obvious_mistake
- **onset:** 8.784313725490197 s (00:08.8)
- **frame / control_step:** 448 (policy_step=74, chunk_index=4)
- **coarse onset:** 10.5 s (refined=True)
- **mode:** placement_or_insertion_failure
- **reason:** The robot successfully grasped the yellow block and carried it to the wooden block, but misaligned the final placement, causing the yellow block to slip off the wooden block and fall onto the table.
  Summary: misaligned placement; block slipped off target
- **recovery:** Re-grasp the fallen yellow block from the tabletop, align it carefully above the wooden block, and gently stack it on top.
  Summary: re-grasp yellow block; align and stack on wooden block
- **prevention:** Align the yellow block directly over the center of the wooden block and lower it smoothly before releasing the grip.
  Summary: center yellow block over target; release carefully
- **justification:** At around 10.5 seconds, the robot lowers the yellow block onto the edge of the wooden block rather than centering it. This poor placement causes the yellow block to tilt and slide off onto the table, leaving the task unfulfilled.