---
license: apache-2.0
base_model: nvidia/GR00T-H-N1.7
tags:
- robotics
- surgical-robotics
- vla
- surrol
- dvrk
- needle-reach
- surgdex
library_name: gr00t
---

# surgdex-needlereach-e8

GR00T-H-N1.7 fine-tuned for the **SurRoL `needle_reach`** task (dexterous dVRK/PSM, vision-based closed-loop) as part of the **SurgDex** project.

This is the **E8a** checkpoint: fine-tuned on a **zero-action-tail-trimmed** LeRobot dataset with **min-max** action normalization, latent aux-head disabled, 15,000 steps.

## Evaluation (closed-loop SurRoL `needle_reach`, H=8 receding horizon, denoise=16, N=25)

| Metric | Value |
|---|---|
| **success@reach** (first step within threshold — receding-horizon reach controller) | **84% (21/25)** |
| **success@hold** (strict: is_success at the end of the fixed 80-step horizon) | **0% (0/25)** |
| mean closest approach `gmin` | 0.020 (threshold = 0.025) |

### Honest caveat
The policy **reliably reaches the goal** (84%) but **does not hold** at it under the fixed-horizon strict metric: after reaching (~step 20) the arm drifts back toward the start, because the training episodes were trimmed to reach+3 steps and provide little "hold-at-goal" signal (and eval zeros the 4 latent state dims, an out-of-distribution condition at the goal). For a deployment that hands off to the next subtask on reach, `success@reach` is the operative metric.

A **hold-tail retrain (E10b)** targeting the strict `success@hold` is in progress: rebuild with a zero-action **hold tail** (zero-action fraction ~0.30 "sweet spot", vs 0.13 here and 0.67 in the undershooting predecessor E7), plus a latent-dropping ablation.

## Recipe headline (the trim fix)
- Predecessor E7 (60-step episodes, 67% zero-action padding tail) **undershot**: policy magnitude ~57% of oracle, gmin~0.099, 0% reach.
- Cropping each episode to `[0 : t_last+3]` (zero-action fraction 0.673 → 0.134) removed the diluted flow-matching marginal (active-phase action mean is 2.66x larger) and **cured the undershoot → 84% reach**.
- Remaining gap is purely **holding** at the goal → addressed by the hold-tail sweet-spot retrain.

Not a medical device. Research artifact only.