# t000__ep008__blocks

- **suite / variant:** `` / ``
- **instruction:** Stack the yellow block on the wooden block
- **success:** False
- **control steps:** 381  (7.4s at 52 Hz)
- **policy inferences:** 66  (replan_steps=6)
- **video:** `blocks/ep008/rollout.mp4`
- **features:** `66` prefix tensors (`prefix`; model=``)

## Semantic timeline

| seconds | control_step | policy_step | phrase |
|---|---|---|---|
| 0.0–3.0 | 0–154 | 0–25 | approaching yellow block |
| 3.0–6.0 | 155–309 | 25–51 | closing gripper and missing grasp |
| 6.0–7.4 | 310–380 | 51–63 | retracting empty gripper |

## Failure

- **yes**
- **onset type:** obvious_mistake
- **onset:** 4.050387596899225 s (00:04.1)
- **frame / control_step:** 209 (policy_step=34, chunk_index=5)
- **coarse onset:** 4.0 s (refined=True)
- **mode:** grasp_failure
- **reason:** The robot closed its gripper on the yellow block, but failed to establish a secure grip, causing the block to slip out as the arm lifted.
  Summary: improper grasp alignment; failed object pick-up
- **recovery:** Re-align the gripper directly over the yellow block, close the fingers securely around it, lift it, and stack it onto the wooden block.
  Summary: re-align gripper; regrasp yellow block; stack on wooden block
- **prevention:** Ensure the gripper is properly centered and at the correct height over the yellow block before closing the fingers to guarantee a solid grasp.
  Summary: center gripper on block; close gripper securely
- **justification:** At 4.0 seconds, the robot attempts to close its gripper around the yellow block, but the block pops out of the fingers as the arm begins lifting, leaving the block on the table.