# t000__ep018__blocks

- **suite / variant:** `` / ``
- **instruction:** Stack the yellow block on the wooden block
- **success:** False
- **control steps:** 571  (11.3s at 51 Hz)
- **policy inferences:** 99  (replan_steps=6)
- **video:** `blocks/ep018/rollout.mp4`
- **features:** `99` prefix tensors (`prefix`; model=``)

## Semantic timeline

| seconds | control_step | policy_step | phrase |
|---|---|---|---|
| 0.0–3.0 | 0–151 | 0–25 | reaching toward yellow block |
| 3.0–6.0 | 152–303 | 25–50 | grasping and lifting yellow block |
| 6.0–9.0 | 304–455 | 50–75 | moving yellow block to target |
| 9.0–11.3 | 456–570 | 76–95 | lowering and releasing block |

## Failure

- **yes**
- **onset type:** obvious_mistake
- **onset:** 8.67588932806324 s (00:08.7)
- **frame / control_step:** 439 (policy_step=73, chunk_index=1)
- **coarse onset:** 9.5 s (refined=True)
- **mode:** placement_or_insertion_failure
- **reason:** The robot successfully grasped the yellow block and brought it over the wooden block, but released it with poor alignment, causing the block to rest in an unstable tilted position.
  Summary: misaligned placement; unstable block stacking
- **recovery:** Re-grasp the yellow block, align it directly over the wooden block's top surface, and place it down cleanly.
  Summary: re-grasp yellow block; align and stack on wooden block
- **prevention:** Ensure the yellow block is centered directly above the wooden block before lowering and releasing the gripper.
  Summary: center yellow block over wooden block; release carefully
- **justification:** The robot successfully picks up the yellow block and moves it to the target location. However, around 9.5 seconds into the rollout (frames 00:09–00:10), the robot lowers and releases the yellow block without proper alignment, causing it to balance instability / sit tilted on top of the wooden block rather than being properly stacked.