adding configuration gripper index and threshold

docs/source/vla_jepa.mdx

@@ -74,6 +74,10 @@ Key parameters in `VLAJEPAConfig`:
 | `num_inference_timesteps` | 4       | Euler integration steps for action denoising                                                                                                                                    |
 | `freeze_qwen`             | `False` | Freeze the Qwen3-VL backbone and only train the action head                                                                                                                     |
 | `reinit_modules`          | `None`  | Key prefixes allowed to be randomly re-initialised on load (for cross-embodiment transfer, see [Fine-tuning on a different embodiment](#fine-tuning-on-a-different-embodiment)) |
+| `gripper_dim`             | 6       | Index of the gripper dimension in the action vector (e.g. 6 for a 7-DoF arm with gripper as the last joint)                                                                     |
+| `gripper_threshold`       | 0.5     | Threshold used by `pre_snap_gripper_action` and `binarize_gripper_action` to binarize the gripper dimension                                                                     |
+| `pre_snap_gripper_action` | `True`  | Snap the gripper dim to {0, 1} before unnormalization. Set to `False` for robots without a binary gripper                                                                       |
+| `binarize_gripper_action` | `True`  | Binarize the gripper dim to {-1, 1} after unnormalization. Set to `False` for robots without a binary gripper                                                                   |
 
 ---
 

src/lerobot/policies/vla_jepa/configuration_vla_jepa.py

@@ -87,6 +87,8 @@ class VLAJEPAConfig(PreTrainedConfig):
     binarize_gripper_action: bool = True
     pre_snap_gripper_action: bool = True
     clip_normalized_actions: bool = True
+    gripper_dim: int = 6
+    gripper_threshold: float = 0.5
     torch_dtype: str = "bfloat16"
 
     optimizer_lr: float = 1e-4

src/lerobot/policies/vla_jepa/processor_vla_jepa.py

@@ -53,21 +53,25 @@ class ClipActionsProcessorStep(ProcessorStep):
 
 @ProcessorStepRegistry.register(name="vla_jepa_pre_snap_gripper")
 class PreSnapGripperProcessorStep(ProcessorStep):
-    """Snaps gripper dim (index 6) to {0, 1} BEFORE unnormalization.
+    """Snaps a gripper dimension to {0, 1} BEFORE unnormalization.
 
     Mirrors the original starVLA LIBERO eval:
-      normalized[:, 6] = np.where(normalized[:, 6] < 0.5, 0, 1)
+      normalized[:, gripper_dim] = np.where(normalized[:, gripper_dim] < threshold, 0, 1)
     This ensures the unnormalizer receives an exact binary value, which is
     required when the model was trained with gripper in identity (mask=False)
     space where 0=open and 1=close.
     """
 
+    def __init__(self, gripper_dim: int = 6, threshold: float = 0.5):
+        self.gripper_dim = gripper_dim
+        self.threshold = threshold
+
     def __call__(self, transition: EnvTransition) -> EnvTransition:
         action = transition.get(TransitionKey.ACTION)
-        if action is not None and action.shape[-1] >= 7:
+        if action is not None and action.shape[-1] > self.gripper_dim:
             transition = dict(transition)
             a = action.clone()
-            a[..., 6] = (a[..., 6] >= 0.5).float()
+            a[..., self.gripper_dim] = (a[..., self.gripper_dim] >= self.threshold).float()
             transition[TransitionKey.ACTION] = a
         return transition
 
@@ -77,18 +81,22 @@ class PreSnapGripperProcessorStep(ProcessorStep):
 
 @ProcessorStepRegistry.register(name="vla_jepa_binarize_gripper")
 class BinarizeGripperProcessorStep(ProcessorStep):
-    """Binarizes gripper dim (index 6) after unnormalization.
+    """Binarizes a gripper dimension after unnormalization.
 
-    Maps continuous value to {-1, 1}: > 0.5 → -1, <= 0.5 → 1 (matches starVLA convention).
-    Only applied when action has >= 7 dimensions.
+    Maps continuous value to {-1, 1}: > threshold → -1, <= threshold → 1 (matches starVLA convention).
+    Only applied when action has more dimensions than gripper_dim.
     """
 
+    def __init__(self, gripper_dim: int = 6, threshold: float = 0.5):
+        self.gripper_dim = gripper_dim
+        self.threshold = threshold
+
     def __call__(self, transition: EnvTransition) -> EnvTransition:
         action = transition.get(TransitionKey.ACTION)
-        if action is not None and action.shape[-1] >= 7:
+        if action is not None and action.shape[-1] > self.gripper_dim:
             transition = dict(transition)
             a = action.clone()
-            a[..., 6] = 1.0 - 2.0 * (a[..., 6] > 0.5).float()
+            a[..., self.gripper_dim] = 1.0 - 2.0 * (a[..., self.gripper_dim] > self.threshold).float()
             transition[TransitionKey.ACTION] = a
         return transition
 
@@ -118,7 +126,9 @@ def make_vla_jepa_pre_post_processors(
     if config.clip_normalized_actions:
         output_steps.append(ClipActionsProcessorStep())
     if config.pre_snap_gripper_action:
-        output_steps.append(PreSnapGripperProcessorStep())
+        output_steps.append(
+            PreSnapGripperProcessorStep(gripper_dim=config.gripper_dim, threshold=config.gripper_threshold)
+        )
     output_steps.append(
         UnnormalizerProcessorStep(
             features=features,
@@ -127,7 +137,9 @@ def make_vla_jepa_pre_post_processors(
         )
     )
     if config.binarize_gripper_action:
-        output_steps.append(BinarizeGripperProcessorStep())
+        output_steps.append(
+            BinarizeGripperProcessorStep(gripper_dim=config.gripper_dim, threshold=config.gripper_threshold)
+        )
     output_steps.append(DeviceProcessorStep(device="cpu"))
     return (
         PolicyProcessorPipeline[dict[str, Any], dict[str, Any]](