# t000__ep031__blocks

- **suite / variant:** `` / ``
- **instruction:** Stack the yellow block on the wooden block
- **success:** False
- **control steps:** 364  (7.3s at 50 Hz)
- **policy inferences:** 63  (replan_steps=6)
- **video:** `blocks/ep031/rollout.mp4`
- **features:** `63` prefix tensors (`prefix`; model=``)

## Semantic timeline

| seconds | control_step | policy_step | phrase |
|---|---|---|---|
| 0.0–3.0 | 0–149 | 0–24 | lowering arm toward yellow block |
| 3.0–6.0 | 150–299 | 25–49 | closing gripper; lifting empty |
| 6.0–7.3 | 300–363 | 50–60 | hovering empty gripper above block |

## Failure

- **yes**
- **onset type:** obvious_mistake
- **onset:** 4.06 s (00:04.1)
- **frame / control_step:** 203 (policy_step=33, chunk_index=5)
- **coarse onset:** 4.8 s (refined=True)
- **mode:** grasp_failure
- **reason:** The robot aligned with the yellow block and attempted to grasp it, but the gripper slipped during closure, failing to hold the block as the arm lifted.
  Summary: grasp failed; yellow block not acquired
- **recovery:** Lower the arm back down, reposition the gripper over the center of the yellow block, securely close the fingers around it, and resume stacking on the wooden block.
  Summary: reposition gripper; regrasp yellow block; stack on wooden block
- **prevention:** Ensure precise alignment and grasp depth over the yellow block before closing the gripper so that it is firmly held during lifting.
  Summary: center gripper over block; secure grasp before lifting
- **justification:** Around 4.8 seconds into the video, the robot closes its gripper on the yellow block, but fails to establish a stable grasp. The fingers close completely while the yellow block remains on the table, and the arm lifts up empty.