# t000__ep012__blocks

- **suite / variant:** `` / ``
- **instruction:** Stack the yellow block on the wooden block
- **success:** False
- **control steps:** 297  (5.9s at 50 Hz)
- **policy inferences:** 52  (replan_steps=5)
- **video:** `blocks/ep012/rollout.mp4`
- **features:** `52` prefix tensors (`prefix`; model=``)

## Semantic timeline

| seconds | control_step | policy_step | phrase |
|---|---|---|---|
| 0.0–3.0 | 0–149 | 0–29 | reaching toward yellow block |
| 3.0–5.9 | 150–296 | 30–59 | closing gripper and lifting empty |

## Failure

- **yes**
- **onset type:** obvious_mistake
- **onset:** 5.02 s (00:05.0)
- **frame / control_step:** 251 (policy_step=50, chunk_index=1)
- **coarse onset:** 3.8 s (refined=True)
- **mode:** grasp_failure
- **reason:** The robot attempted to grasp the yellow block, but failed to securely grasp it, causing the end-effector to lift up empty while the yellow block remained on the table.
  Summary: failed grasp on yellow block; lifting empty gripper
- **recovery:** Re-align the end-effector above the yellow block, lower it to surround the block, close the fingers firmly, and proceed to stack it on the wooden block.
  Summary: re-align gripper; regrasp yellow block; stack on wooden block
- **prevention:** Ensure the gripper descends sufficiently low and centers around the yellow block before closing the fingers to guarantee a secure grasp.
  Summary: position lower over yellow block; secure firm grip before lifting
- **justification:** Around 3.8 seconds into the rollout, the robot closes its gripper on the yellow block but fails to establish a secure hold. It subsequently lifts away empty, leaving the block on the table.