# t000__ep030__blocks

- **suite / variant:** `` / ``
- **instruction:** Stack the yellow block on the wooden block
- **success:** False
- **control steps:** 394  (7.8s at 51 Hz)
- **policy inferences:** 68  (replan_steps=6)
- **video:** `blocks/ep030/rollout.mp4`
- **features:** `68` prefix tensors (`prefix`; model=``)

## Semantic timeline

| seconds | control_step | policy_step | phrase |
|---|---|---|---|
| 0.0–3.0 | 0–151 | 0–25 | lowering end-effector toward yellow block |
| 3.0–6.0 | 152–303 | 25–50 | closing gripper without holding block |
| 6.0–7.8 | 304–393 | 50–65 | moving empty gripper over wooden block |

## Failure

- **yes**
- **onset type:** obvious_mistake
- **onset:** 4.220907297830374 s (00:04.2)
- **frame / control_step:** 214 (policy_step=35, chunk_index=4)
- **coarse onset:** 4.0 s (refined=True)
- **mode:** grasp_failure
- **reason:** The robot closed its gripper above the yellow block without properly enveloping or grasping it, then moved away toward the wooden block with empty fingers.
  Summary: failed grasp on yellow block; empty gripper lift
- **recovery:** Move the end-effector back to the yellow block, open the gripper, position it fully around the block, grasp it securely, and then carry it to the wooden block.
  Summary: re-align gripper; grasp yellow block; stack on wooden block
- **prevention:** Lower the end-effector further to align the gripper fingers around the yellow block before closing them to guarantee a firm hold.
  Summary: lower gripper fully; secure block before lifting
- **justification:** At around 4.0 seconds (frame 00:04), the gripper closes in mid-air above the yellow block, failing to grasp it. The robot then proceeds to move toward the target without the block.