# t000__ep021__blocks

- **suite / variant:** `` / ``
- **instruction:** Stack the yellow block on the wooden block
- **success:** False
- **control steps:** 505  (10.0s at 50 Hz)
- **policy inferences:** 88  (replan_steps=6)
- **video:** `blocks/ep021/rollout.mp4`
- **features:** `88` prefix tensors (`prefix`; model=``)

## Semantic timeline

| seconds | control_step | policy_step | phrase |
|---|---|---|---|
| 0.0–3.0 | 0–151 | 0–25 | approaching yellow block |
| 3.0–6.0 | 152–303 | 25–50 | closing gripper on yellow block |
| 6.0–9.0 | 304–455 | 50–75 | lifting empty gripper |
| 9.0–10.0 | 456–504 | 76–84 | hovering above workspace |

## Failure

- **yes**
- **onset type:** obvious_mistake
- **onset:** 5.069306930693069 s (00:05.1)
- **frame / control_step:** 256 (policy_step=42, chunk_index=4)
- **coarse onset:** 5.5 s (refined=True)
- **mode:** grasp_failure
- **reason:** The robot gripper attempted to grasp the yellow block, but closed loosely/improperly and slipped off, lifting away without holding the block.
  Summary: failed grasp on yellow block; gripper slipped
- **recovery:** Lower the gripper back over the yellow block, close firmly around it to secure a grasp, and then stack it onto the wooden block.
  Summary: re-align gripper; regrasp yellow block; stack on wooden block
- **prevention:** Center the gripper precisely over the yellow block and ensure the fingers close completely before initiating the lift.
  Summary: align gripper centered on yellow block; secure grasp before lifting
- **justification:** None