feat(so_follower): synchronize goal position with present position to prevent positional error during torque re-enablement

fix: update import for SO101Leader in so101_leader_follower.py
chore: include SO101LeaderFollower in exports

examples/so100_teleop/teleop.py

@@ -0,0 +1,175 @@
+#!/usr/bin/env python
+
+# Copyright 2025 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Simple SO100/SO101 leader-follower teleoperation with spacebar intervention toggle.
+
+Modes:
+  - Default (not intervening): follower holds its current position.
+    The leader arm has torque ENABLED and mirrors the follower so there is no
+    large position jump when intervention starts.
+  - Intervention (SPACE pressed): leader torque DISABLED, human moves the leader
+    freely, and the follower mirrors the leader joint-by-joint.
+
+Usage:
+    uv run python examples/so100_teleop/teleop.py
+
+Controls:
+    SPACE  — toggle intervention on/off
+    Ctrl+C — exit
+"""
+
+import logging
+import os
+import sys
+import time
+from threading import Event, Thread
+
+from lerobot.robots.so_follower import SO101Follower, SO101FollowerConfig
+from lerobot.teleoperators.so_leader import SO101Leader
+from lerobot.teleoperators.so_leader.config_so_leader import SOLeaderTeleopConfig
+from lerobot.utils.robot_utils import precise_sleep
+
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger(__name__)
+
+# ── pynput keyboard listener ─────────────────────────────────────────────────
+PYNPUT_AVAILABLE = True
+try:
+    if "DISPLAY" not in os.environ and "linux" in sys.platform:
+        raise ImportError("No DISPLAY set, pynput skipped.")
+    from pynput import keyboard as pynput_keyboard
+except Exception:
+    pynput_keyboard = None
+    PYNPUT_AVAILABLE = False
+
+# ── Configure ports ──────────────────────────────────────────────────────────
+FOLLOWER_PORT = "/dev/ttyUSB0"  # ← change to your follower port
+LEADER_PORT = "/dev/ttyUSB1"  # ← change to your leader port
+FPS = 30
+
+
+def hold_position(robot) -> dict:
+    """Read current joint positions and write them back as the goal.
+
+    This prevents the motors from snapping to a stale Goal_Position register
+    value (which can happen when torque is re-enabled after calibration).
+    Returns the current position dict for reuse.
+    """
+    current = robot.bus.sync_read("Present_Position")
+    robot.bus.sync_write("Goal_Position", current)
+    return {f"{motor}.pos": val for motor, val in current.items()}
+
+
+# ── Connect ───────────────────────────────────────────────────────────────────
+follower_config = SO101FollowerConfig(
+    port=FOLLOWER_PORT,
+    id="follower_arm",
+    use_degrees=True,
+)
+leader_config = SOLeaderTeleopConfig(
+    port=LEADER_PORT,
+    id="leader_arm",
+    use_degrees=True,
+)
+
+follower = SO101Follower(follower_config)
+leader = SO101Leader(leader_config)
+
+follower.connect()
+leader.connect()
+
+# ── CRITICAL: hold both arms at their current position before doing anything ─
+# configure() enables follower torque, and the Goal_Position register may contain
+# a stale value from a previous session. Writing current→goal prevents sudden motion.
+follower_current = hold_position(follower)
+leader_current = hold_position(leader)  # leader torque is still off here, but sets the register
+
+# ── Intervention state + keyboard listener ───────────────────────────────────
+is_intervening = False
+stop_event = Event()
+
+
+def _start_keyboard_listener():
+    if not PYNPUT_AVAILABLE:
+        logger.warning("pynput not available — spacebar toggle disabled.")
+        return None
+
+    def on_press(key):
+        global is_intervening
+        if key == pynput_keyboard.Key.space:
+            is_intervening = not is_intervening
+            state = "INTERVENTION  (leader → follower)" if is_intervening else "IDLE  (follower holds)"
+            print(f"\n[SPACE] {state}\n")
+
+    def listen():
+        with pynput_keyboard.Listener(on_press=on_press) as listener:
+            while not stop_event.is_set():
+                time.sleep(0.05)
+            listener.stop()
+
+    t = Thread(target=listen, daemon=True)
+    t.start()
+    return t
+
+
+kbd_thread = _start_keyboard_listener()
+
+# Enable leader torque AFTER writing its goal to current position, so it holds in place.
+leader.bus.sync_write("Torque_Enable", 1)
+leader_torque_on = True
+
+print("\nTeleoperation ready.")
+print("  SPACE  → toggle intervention (leader controls follower)")
+print("  Ctrl+C → exit\n")
+
+try:
+    while True:
+        t0 = time.perf_counter()
+
+        if is_intervening:
+            # ── Intervention: leader torque OFF, follower mirrors leader ──────
+            if leader_torque_on:
+                leader.bus.sync_write("Torque_Enable", 0)
+                leader_torque_on = False
+
+            leader_action = leader.get_action()  # reads present leader joints
+            follower.send_action(leader_action)  # follower tracks leader
+
+        else:
+            # ── Idle: leader torque ON, leader mirrors follower, follower holds
+            if not leader_torque_on:
+                # Before re-enabling torque, set the leader's goal to its current
+                # position so it doesn't snap to the follower position suddenly.
+                hold_position(leader)
+                leader.bus.sync_write("Torque_Enable", 1)
+                leader_torque_on = True
+
+            follower_obs = follower.get_observation()
+            # Command leader to match follower (so next intervention has no jump)
+            goal_pos = {motor: follower_obs[f"{motor}.pos"] for motor in leader.bus.motors}
+            leader.bus.sync_write("Goal_Position", goal_pos)
+            # Follower holds — no send_action call
+
+        precise_sleep(max(1.0 / FPS - (time.perf_counter() - t0), 0.0))
+
+except KeyboardInterrupt:
+    print("\nExiting...")
+finally:
+    stop_event.set()
+    leader.bus.sync_write("Torque_Enable", 0)
+    follower.disconnect()
+    leader.disconnect()

examples/so100_to_so100_EE_deltas/teleoperate.py

@@ -0,0 +1,365 @@
+# !/usr/bin/env python
+
+# Copyright 2025 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import time
+from dataclasses import dataclass
+
+import numpy as np
+import torch
+
+from lerobot.configs.types import PipelineFeatureType, PolicyFeature
+from lerobot.model.kinematics import RobotKinematics
+from lerobot.processor import (
+    ProcessorStepRegistry,
+    RobotAction,
+    RobotActionProcessorStep,
+    RobotObservation,
+    RobotProcessorPipeline,
+    TransitionKey,
+)
+from lerobot.processor.converters import (
+    create_transition,
+    identity_transition,
+)
+from lerobot.robots.robot import Robot
+from lerobot.robots.so100_follower.robot_kinematic_processor import (
+    EEBoundsAndSafety,
+    EEReferenceAndDelta,
+    GripperVelocityToJoint,
+    InverseKinematicsRLStep,
+)
+from lerobot.robots.so101_follower.config_so101_follower import SO101FollowerConfig
+from lerobot.robots.so101_follower.so101_follower import SO101Follower
+from lerobot.teleoperators.so101_leader.config_so101_leader import SO101LeaderConfig
+from lerobot.teleoperators.so101_leader.so101_leader import SO101Leader
+from lerobot.utils.robot_utils import precise_sleep
+from lerobot.utils.rotation import Rotation
+
+
+def reset_follower_position(robot_arm: Robot, target_position: np.ndarray) -> None:
+    """Reset robot arm to target position using smooth trajectory."""
+    current_position_dict = robot_arm.bus.sync_read("Present_Position")
+    current_position = np.array(
+        [current_position_dict[name] for name in current_position_dict],
+        dtype=np.float32,
+    )
+    trajectory = torch.from_numpy(
+        np.linspace(current_position, target_position, 50)
+    )  # NOTE: 30 is just an arbitrary number
+    for pose in trajectory:
+        action_dict = dict(zip(current_position_dict, pose, strict=False))
+        robot_arm.bus.sync_write("Goal_Position", action_dict)
+        precise_sleep(0.015)
+
+
+@dataclass
+class LogRobotAction(RobotActionProcessorStep):
+    def action(self, action: RobotAction) -> RobotAction:
+        print(f"Robot action: {action}")
+        return action
+
+    def transform_features(self, features):
+        # features[PipelineFeatureType.ACTION][ACTION] = PolicyFeature(
+        #     type=FeatureType.ACTION, shape=(len(self.motor_names),)
+        # )
+        return features
+
+
+@ProcessorStepRegistry.register("forward_kinematics_joints_to_ee_target_action")
+@dataclass
+class ForwardKinematicsJointsToEETargetAction(RobotActionProcessorStep):
+    """
+    Computes the end-effector pose from joint positions using forward kinematics (FK).
+
+    This step is typically used to add the robot's Cartesian pose to the observation space,
+    which can be useful for visualization or as an input to a policy.
+
+    Attributes:
+        kinematics: The robot's kinematic model.
+    """
+
+    kinematics: RobotKinematics
+    motor_names: list[str]
+    end_effector_step_sizes: dict
+    max_gripper_pos: float
+    use_ik_solution: bool = False
+
+    def action(self, action: RobotAction) -> RobotAction:
+        # return compute_forward_kinematics_joints_to_ee(action, self.kinematics, self.motor_names)
+        teleop_action = action
+        raw_joint_pos = self.transition.get(TransitionKey.OBSERVATION)
+
+        leader_pos = np.array([teleop_action[f"{motor}.pos"] for motor in self.motor_names])
+
+        leader_ee = self.kinematics.forward_kinematics(leader_pos)
+
+        if self.use_ik_solution and "IK_solution" in self.transition.get(TransitionKey.COMPLEMENTARY_DATA):
+            follower_pos = transition.get(TransitionKey.COMPLEMENTARY_DATA)["IK_solution"]
+        else:
+            follower_pos = np.array([raw_joint_pos[f"{motor}.pos"] for motor in self.motor_names])
+
+        follower_ee = self.kinematics.forward_kinematics(follower_pos)
+
+        follower_ee_pos = follower_ee[:3, 3]
+        follower_ee_rvec = Rotation.from_matrix(follower_ee[:3, :3]).as_rotvec()
+        # follower_gripper_pos = raw_joint_pos["gripper.pos"]
+        follower_gripper_pos = follower_pos[-1]  # assuming gripper is the last motor
+
+        leader_ee_pos = leader_ee[:3, 3]
+        leader_ee_rvec = Rotation.from_matrix(leader_ee[:3, :3]).as_rotvec()
+        leader_gripper_pos = np.clip(
+            teleop_action["gripper.pos"], -self.max_gripper_pos, self.max_gripper_pos
+        )
+
+        print("f pos:", follower_ee_pos)
+        print("l pos:", leader_ee_pos)
+
+        print("f rvec:", follower_ee_rvec)
+        print("l rvec:", leader_ee_rvec)
+
+        # follower_ee_pos = follower_ee[:3, 3]
+        # follower_ee_rvec = Rotation.from_matrix(follower_ee[:3, :3]).as_rotvec()
+
+        delta_pos = leader_ee_pos - follower_ee_pos
+
+        # For rotation: compute relative rotation from follower to leader
+        # R_leader = R_follower * R_delta  =>  R_delta = R_follower^T * R_leader
+        r_delta = follower_ee[:3, :3].T @ leader_ee[:3, :3]
+        delta_rvec = Rotation.from_matrix(r_delta).as_rotvec()
+        delta_gripper = leader_gripper_pos - follower_gripper_pos
+
+        desired = np.eye(4, dtype=float)
+        desired[:3, :3] = follower_ee[:3, :3] @ r_delta
+        desired[:3, 3] = follower_ee[:3, 3] + delta_pos
+
+        pos = desired[:3, 3]
+        tw = Rotation.from_matrix(desired[:3, :3]).as_rotvec()
+
+        assert np.allclose(pos, leader_ee_pos), "Position delta computation error"
+        assert np.allclose(tw, leader_ee_rvec), "Orientation delta computation error"
+        assert np.isclose(follower_gripper_pos + delta_gripper, leader_gripper_pos), (
+            "Gripper delta computation error"
+        )
+
+        # Normalize the action to the range [-1, 1]
+        delta_pos = delta_pos / np.array(
+            [
+                self.end_effector_step_sizes["x"],
+                self.end_effector_step_sizes["y"],
+                self.end_effector_step_sizes["z"],
+            ]
+        )
+        delta_rvec = delta_rvec / np.array(
+            [
+                self.end_effector_step_sizes["wx"],
+                self.end_effector_step_sizes["wy"],
+                self.end_effector_step_sizes["wz"],
+            ]
+        )
+
+        # Check if any of the normalized deltas exceed 1.0
+
+        max_normalized_pos = max(
+            abs(delta_pos[0]),
+            abs(delta_pos[1]),
+            abs(delta_pos[2]),
+        )
+
+        max_normalized_rot = max(
+            abs(delta_rvec[0]),
+            abs(delta_rvec[1]),
+            abs(delta_rvec[2]),
+        )
+
+        # Use the same scaling factor for both position and rotation
+        max_normalized = max(max_normalized_pos, max_normalized_rot)
+        if max_normalized > 1.0:
+            print(f"Warning: EE delta too large, scaling. Max normalized delta: {max_normalized_pos}")
+            print(f"Original delta_pos: {delta_pos}, delta_rvec: {delta_rvec}")
+            # Scale proportionally
+            delta_pos = delta_pos / max_normalized
+            delta_rvec = delta_rvec / max_normalized
+
+        new_action = {}
+        new_action["enabled"] = True
+        new_action["target_x"] = float(delta_pos[0])
+        new_action["target_y"] = float(delta_pos[1])
+        new_action["target_z"] = float(delta_pos[2])
+        new_action["target_wx"] = float(delta_rvec[0])
+        new_action["target_wy"] = float(delta_rvec[1])
+        new_action["target_wz"] = float(delta_rvec[2])
+        new_action["gripper_vel"] = float(
+            np.clip(delta_gripper, -self.max_gripper_pos, self.max_gripper_pos) / self.max_gripper_pos
+        )
+        return new_action
+
+    def transform_features(
+        self, features: dict[PipelineFeatureType, dict[str, PolicyFeature]]
+    ) -> dict[PipelineFeatureType, dict[str, PolicyFeature]]:
+        # TODO: implement feature transformation
+        return features
+
+
+FPS = 20
+
+# Initialize the robot and teleoperator config
+follower_config = SO101FollowerConfig(port="/dev/usb_follower_arm_a", id="follower_arm_a", use_degrees=True)
+leader_config = SO101LeaderConfig(port="/dev/usb_leader_arm_a", id="leader_arm_a", use_degrees=True)
+
+# Initialize the robot and teleoperator
+follower = SO101Follower(follower_config)
+leader = SO101Leader(leader_config)
+
+# NOTE: It is highly recommended to use the urdf in the SO-ARM100 repo: https://github.com/TheRobotStudio/SO-ARM100/blob/main/Simulation/SO101/so101_new_calib.urdf
+follower_kinematics_solver = RobotKinematics(
+    urdf_path="../SO-ARM100/Simulation/SO101/so101_new_calib.urdf",
+    target_frame_name="gripper_frame_link",
+    joint_names=list(follower.bus.motors.keys()),
+)
+
+# NOTE: It is highly recommended to use the urdf in the SO-ARM100 repo: https://github.com/TheRobotStudio/SO-ARM100/blob/main/Simulation/SO101/so101_new_calib.urdf
+leader_kinematics_solver = RobotKinematics(
+    urdf_path="../SO-ARM100/Simulation/SO101/so101_new_calib.urdf",
+    target_frame_name="gripper_frame_link",
+    joint_names=list(leader.bus.motors.keys()),
+)
+
+end_effector_step_sizes = {
+    "x": 0.004,
+    "y": 0.004,
+    "z": 0.004,
+    "wx": 5 * np.pi / 180,
+    "wy": 5 * np.pi / 180,
+    "wz": 5 * np.pi / 180,
+}
+
+
+# Build pipeline to convert teleop joints to EE action
+leader_to_ee = RobotProcessorPipeline[RobotAction, RobotAction](
+    steps=[
+        LogRobotAction(),
+        ForwardKinematicsJointsToEETargetAction(
+            kinematics=leader_kinematics_solver,
+            motor_names=list(leader.bus.motors.keys()),
+            end_effector_step_sizes=end_effector_step_sizes,
+            max_gripper_pos=30.0,
+            use_ik_solution=True,
+        ),
+        LogRobotAction(),
+    ],
+    to_transition=identity_transition,
+    to_output=identity_transition,
+)
+
+# build pipeline to convert EE action to robot joints
+ee_to_follower_joints = RobotProcessorPipeline[tuple[RobotAction, RobotObservation], RobotAction](
+    [
+        LogRobotAction(),
+        EEReferenceAndDelta(
+            kinematics=follower_kinematics_solver,
+            # end_effector_step_sizes={"x": 0.006, "y": 0.01, "z": 0.005},
+            end_effector_step_sizes=end_effector_step_sizes,
+            motor_names=list(follower.bus.motors.keys()),
+            use_latched_reference=False,
+            use_ik_solution=True,
+        ),
+        LogRobotAction(),
+        EEBoundsAndSafety(
+            end_effector_bounds={
+                "min": [-0.05, -0.55, -0.0075],
+                "max": [0.55, 0.55, 0.55],
+            },
+            # end_effector_bounds={"min": [-1.0, -1.0, -1.0], "max": [1.0, 1.0, 1.0]},
+            max_ee_step_m=0.05,
+        ),
+        LogRobotAction(),
+        GripperVelocityToJoint(
+            clip_max=30.0,
+            speed_factor=0.2,
+            discrete_gripper=False,
+            scale_velocity=True,
+            use_ik_solution=True,
+        ),
+        LogRobotAction(),
+        InverseKinematicsRLStep(
+            kinematics=follower_kinematics_solver,
+            motor_names=list(follower.bus.motors.keys()),
+            initial_guess_current_joints=False,
+        ),
+        LogRobotAction(),
+    ],
+    to_transition=identity_transition,
+    to_output=identity_transition,
+)
+
+# Connect to the robot and teleoperator
+follower.connect()
+leader.connect()
+
+reset_pose = [0.0, 10, 20, 60.00, 90.00, 10.00]
+
+start_time = time.perf_counter()
+reset_follower_position(follower, np.array(reset_pose))
+reset_follower_position(leader, np.array(reset_pose))
+precise_sleep(5.0 - (time.perf_counter() - start_time))
+# time.sleep(10)
+leader.bus.sync_write("Torque_Enable", 0)
+
+# Init rerun viewer
+# init_rerun(session_name="so100_so100_EE_teleop")
+
+transition = None
+
+print("Starting teleop loop...")
+while True:
+    print("New loop iteration")
+    t0 = time.perf_counter()
+
+    # Get robot observation
+    robot_obs = follower.get_observation()
+
+    # Get teleop observation
+    leader_joints_obs = leader.get_action()
+
+    # teleop joints -> teleop EE action
+    if transition is None:
+        transition = create_transition(action=leader_joints_obs, observation=robot_obs)
+    else:
+        transition = create_transition(
+            action=leader_joints_obs,
+            observation=robot_obs,
+            complementary_data=transition.get(TransitionKey.COMPLEMENTARY_DATA),
+        )
+
+    transition = leader_to_ee(transition)
+    leader_ee_act = transition[TransitionKey.ACTION]
+
+    # teleop EE -> robot joints
+    transition = create_transition(
+        action=leader_ee_act,
+        observation=robot_obs,
+        complementary_data=transition.get(TransitionKey.COMPLEMENTARY_DATA),
+    )
+    transition = ee_to_follower_joints(transition)
+    follower_joints_act = transition[TransitionKey.ACTION]
+
+    # Send action to robot
+    _ = follower.send_action(follower_joints_act)
+
+    # Visualize
+    # log_rerun_data(observation=leader_ee_act, action=follower_joints_act)
+
+    precise_sleep(max(1.0 / FPS - (time.perf_counter() - t0), 0.0))

src/lerobot/envs/configs.py

@@ -299,6 +299,7 @@ class HILSerlProcessorConfig:
     inverse_kinematics: InverseKinematicsConfig | None = None
     reward_classifier: RewardClassifierConfig | None = None
     max_gripper_pos: float | None = 100.0
+    gripper_speed_factor: float | None = None
 
 
 @EnvConfig.register_subclass(name="gym_manipulator")

src/lerobot/processor/__init__.py

@@ -61,6 +61,7 @@ from .hil_processor import (
     RewardClassifierProcessorStep,
     TimeLimitProcessorStep,
 )
+from .leader_follower_processor import LeaderFollowerProcessor
 from .newline_task_processor import NewLineTaskProcessorStep
 from .normalize_processor import NormalizerProcessorStep, UnnormalizerProcessorStep, hotswap_stats
 from .observation_processor import VanillaObservationProcessorStep
@@ -122,6 +123,7 @@ __all__ = [
     "ImageCropResizeProcessorStep",
     "InfoProcessorStep",
     "InterventionActionProcessorStep",
+    "LeaderFollowerProcessor",
     "make_default_processors",
     "make_default_teleop_action_processor",
     "make_default_robot_action_processor",

src/lerobot/processor/delta_action_processor.py

@@ -38,6 +38,7 @@ class MapTensorToDeltaActionDictStep(ActionProcessorStep):
     """
 
     use_gripper: bool = True
+    use_rotation: bool = False
 
     def action(self, action: PolicyAction) -> RobotAction:
         if not isinstance(action, PolicyAction):
@@ -52,7 +53,13 @@ class MapTensorToDeltaActionDictStep(ActionProcessorStep):
             "delta_y": action[1].item(),
             "delta_z": action[2].item(),
         }
-        if self.use_gripper:
+        if self.use_rotation:
+            delta_action["delta_wx"] = action[3].item()
+            delta_action["delta_wy"] = action[4].item()
+            delta_action["delta_wz"] = action[5].item()
+            if self.use_gripper:
+                delta_action["gripper"] = action[6].item()
+        elif self.use_gripper:
             delta_action["gripper"] = action[3].item()
         return delta_action
 
@@ -64,6 +71,12 @@ class MapTensorToDeltaActionDictStep(ActionProcessorStep):
                 type=FeatureType.ACTION, shape=(1,)
             )
 
+        if self.use_rotation:
+            for axis in ["wx", "wy", "wz"]:
+                features[PipelineFeatureType.ACTION][f"delta_{axis}"] = PolicyFeature(
+                    type=FeatureType.ACTION, shape=(1,)
+                )
+
         if self.use_gripper:
             features[PipelineFeatureType.ACTION]["gripper"] = PolicyFeature(
                 type=FeatureType.ACTION, shape=(1,)
@@ -90,6 +103,8 @@ class MapDeltaActionToRobotActionStep(RobotActionProcessorStep):
     # Scale factors for delta movements
     position_scale: float = 1.0
     noise_threshold: float = 1e-3  # 1 mm threshold to filter out noise
+    use_rotation: bool = False
+    rotation_scale: float = 1.0
 
     def action(self, action: RobotAction) -> RobotAction:
         # NOTE (maractingi): Action can be a dict from the teleop_devices or a tensor from the policy
@@ -97,23 +112,34 @@ class MapDeltaActionToRobotActionStep(RobotActionProcessorStep):
         delta_x = action.pop("delta_x")
         delta_y = action.pop("delta_y")
         delta_z = action.pop("delta_z")
+        if self.use_rotation:
+            delta_wx = action.pop("delta_wx")
+            delta_wy = action.pop("delta_wy")
+            delta_wz = action.pop("delta_wz")
+        else:
+            delta_wx = 0.0
+            delta_wy = 0.0
+            delta_wz = 0.0
         gripper = action.pop("gripper")
 
         # Determine if the teleoperator is actively providing input
         # Consider enabled if any significant movement delta is detected
         position_magnitude = (delta_x**2 + delta_y**2 + delta_z**2) ** 0.5  # Use Euclidean norm for position
-        enabled = position_magnitude > self.noise_threshold  # Small threshold to avoid noise
+        rotation_magnitude = (
+            delta_wx**2 + delta_wy**2 + delta_wz**2
+        ) ** 0.5  # TODO use proper magnitud for rotation
+        enabled = (
+            position_magnitude > self.noise_threshold or rotation_magnitude > self.noise_threshold
+        )  # Small threshold to avoid noise
 
         # Scale the deltas appropriately
         scaled_delta_x = delta_x * self.position_scale
         scaled_delta_y = delta_y * self.position_scale
         scaled_delta_z = delta_z * self.position_scale
 
-        # For gamepad/keyboard, we don't have rotation input, so set to 0
-        # These could be extended in the future for more sophisticated teleoperators
-        target_wx = 0.0
-        target_wy = 0.0
-        target_wz = 0.0
+        target_wx = delta_wx * self.rotation_scale
+        target_wy = delta_wy * self.rotation_scale
+        target_wz = delta_wz * self.rotation_scale
 
         # Update action with robot target format
         action = {
@@ -132,9 +158,15 @@ class MapDeltaActionToRobotActionStep(RobotActionProcessorStep):
     def transform_features(
         self, features: dict[PipelineFeatureType, dict[str, PolicyFeature]]
     ) -> dict[PipelineFeatureType, dict[str, PolicyFeature]]:
-        for axis in ["x", "y", "z", "gripper"]:
+        for axis in ["x", "y", "z"]:
             features[PipelineFeatureType.ACTION].pop(f"delta_{axis}", None)
 
+        if self.use_rotation:
+            for axis in ["wx", "wy", "wz"]:
+                features[PipelineFeatureType.ACTION].pop(f"delta_{axis}", None)
+
+        features[PipelineFeatureType.ACTION].pop("delta_gripper", None)
+
         for feat in ["enabled", "target_x", "target_y", "target_z", "target_wx", "target_wy", "target_wz"]:
             features[PipelineFeatureType.ACTION][f"{feat}"] = PolicyFeature(
                 type=FeatureType.ACTION, shape=(1,)

src/lerobot/processor/hil_processor.py

@@ -461,6 +461,7 @@ class InterventionActionProcessorStep(ProcessorStep):
 
     use_gripper: bool = False
     terminate_on_success: bool = True
+    use_rotation: bool = False
 
     def __call__(self, transition: EnvTransition) -> EnvTransition:
         """
@@ -497,6 +498,14 @@ class InterventionActionProcessorStep(ProcessorStep):
                     teleop_action.get("delta_y", 0.0),
                     teleop_action.get("delta_z", 0.0),
                 ]
+                if self.use_rotation:
+                    action_list.extend(
+                        [
+                            teleop_action.get("delta_wx", 0.0),
+                            teleop_action.get("delta_wy", 0.0),
+                            teleop_action.get("delta_wz", 0.0),
+                        ]
+                    )
                 if self.use_gripper:
                     action_list.append(teleop_action.get(GRIPPER_KEY, 1.0))
             elif isinstance(teleop_action, np.ndarray):

src/lerobot/processor/leader_follower_processor.py

@@ -0,0 +1,243 @@
+#!/usr/bin/env python
+
+# Copyright 2025 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from dataclasses import dataclass
+
+import numpy as np
+import torch
+
+from lerobot.configs.types import PipelineFeatureType, PolicyFeature
+from lerobot.model.kinematics import RobotKinematics
+from lerobot.processor.pipeline import EnvTransition, ProcessorStepRegistry, TransitionKey
+from lerobot.robots import Robot
+from lerobot.teleoperators import Teleoperator
+from lerobot.teleoperators.utils import TeleopEvents
+from lerobot.utils.rotation import Rotation
+
+from .pipeline import ProcessorStep
+
+
+@ProcessorStepRegistry.register("leader_follower_processor")
+@dataclass
+class LeaderFollowerProcessor(ProcessorStep):
+    """
+    Processor for leader-follower teleoperation mode.
+
+    This processor:
+    1. Sends follower positions to leader arm when not intervening
+    2. Computes EE delta actions from leader when intervening
+    3. Handles teleop events from the leader device
+    """
+
+    leader_device: Teleoperator
+    motor_names: list[str]
+    robot: Robot
+    kinematics: RobotKinematics
+    end_effector_step_sizes: np.ndarray | None = None
+    use_gripper: bool = True
+    # prev_leader_gripper: float | None = None
+    max_gripper_pos: float = 100.0
+    use_ik_solution: bool = False
+
+    def __call__(self, transition: EnvTransition) -> EnvTransition:
+        """Process transition with leader-follower logic."""
+        # Get current follower position from complementary data
+        # raw_joint_pos = transition.get(TransitionKey.COMPLEMENTARY_DATA, {}).get("raw_joint_positions")
+        raw_joint_pos = transition.get(TransitionKey.OBSERVATION)
+        if raw_joint_pos is not None:
+            # Send follower position to leader (for follow mode)
+            # follower_action = {
+            #     f"{motor}.pos": float(raw_joint_pos[motor])
+            #     for motor in self.motor_names
+            # }
+            self.leader_device.send_action(raw_joint_pos)
+
+        # Only compute EE action if intervention is active
+        # (AddTeleopEventsAsInfo already added IS_INTERVENTION to info)
+        info = transition.get(TransitionKey.INFO, {})
+        if info.get(TeleopEvents.IS_INTERVENTION, False):
+            # Get leader joint positions from teleop_action
+            # (AddTeleopActionAsComplimentaryData already got the action)
+            complementary = transition.get(TransitionKey.COMPLEMENTARY_DATA, {})
+            teleop_action = complementary.get("teleop_action", {})
+
+            if isinstance(teleop_action, dict) and raw_joint_pos is not None:
+                leader_pos = np.array([teleop_action[f"{motor}.pos"] for motor in self.motor_names])
+
+                leader_ee = self.kinematics.forward_kinematics(leader_pos)
+
+                if self.use_ik_solution and "IK_solution" in transition.get(TransitionKey.COMPLEMENTARY_DATA):
+                    follower_pos = transition.get(TransitionKey.COMPLEMENTARY_DATA)["IK_solution"]
+                else:
+                    follower_pos = np.array([raw_joint_pos[f"{motor}.pos"] for motor in self.motor_names])
+
+                follower_ee = self.kinematics.forward_kinematics(follower_pos)
+
+                # follower_gripper_pos = raw_joint_pos["gripper.pos"]
+                follower_gripper_pos = follower_pos[-1]  # assuming gripper is the last motor
+
+                leader_ee_pos = leader_ee[:3, 3]
+                leader_ee_rvec = Rotation.from_matrix(leader_ee[:3, :3]).as_rotvec()
+                leader_gripper_pos = np.clip(
+                    teleop_action["gripper.pos"], -self.max_gripper_pos, self.max_gripper_pos
+                )
+
+                follower_ee_pos = follower_ee[:3, 3]
+                # follower_ee_rvec = Rotation.from_matrix(follower_ee[:3, :3]).as_rotvec()
+
+                delta_pos = leader_ee_pos - follower_ee_pos
+
+                # For rotation: compute relative rotation from follower to leader
+                # R_leader = R_follower * R_delta  =>  R_delta = R_follower^T * R_leader
+                r_delta = follower_ee[:3, :3].T @ leader_ee[:3, :3]
+                delta_rvec = Rotation.from_matrix(r_delta).as_rotvec()
+
+                delta_gripper = leader_gripper_pos - follower_gripper_pos
+
+                desired = np.eye(4, dtype=float)
+                desired[:3, :3] = follower_ee[:3, :3] @ r_delta
+                desired[:3, 3] = follower_ee[:3, 3] + delta_pos
+
+                pos = desired[:3, 3]
+                tw = Rotation.from_matrix(desired[:3, :3]).as_rotvec()
+
+                assert np.allclose(pos, leader_ee_pos), "Position delta computation error"
+                assert np.allclose(tw, leader_ee_rvec), "Orientation delta computation error"
+                assert np.isclose(follower_gripper_pos + delta_gripper, leader_gripper_pos), (
+                    "Gripper delta computation error"
+                )
+
+                # Normalize the action to the range [-1, 1]
+                delta_pos = delta_pos / np.array(
+                    [
+                        self.end_effector_step_sizes["x"],
+                        self.end_effector_step_sizes["y"],
+                        self.end_effector_step_sizes["z"],
+                    ]
+                )
+                delta_rvec = delta_rvec / np.array(
+                    [
+                        self.end_effector_step_sizes["wx"],
+                        self.end_effector_step_sizes["wy"],
+                        self.end_effector_step_sizes["wz"],
+                    ]
+                )
+                max_normalized_pos = max(
+                    abs(delta_pos[0]),
+                    abs(delta_pos[1]),
+                    abs(delta_pos[2]),
+                )
+
+                normalized_rot = max(abs(delta_rvec[0]), abs(delta_rvec[1]), abs(delta_rvec[2]))
+
+                max_normalized = max(max_normalized_pos, normalized_rot)
+
+                if max_normalized > 1.0:
+                    # Scale proportionally
+                    delta_pos = delta_pos / max_normalized
+                    delta_rvec = delta_rvec / max_normalized
+
+                intervention_action = np.array(
+                    [
+                        delta_pos[0],
+                        delta_pos[1],
+                        delta_pos[2],
+                        delta_rvec[0],
+                        delta_rvec[1],
+                        delta_rvec[2],
+                        np.clip(delta_gripper, -self.max_gripper_pos, self.max_gripper_pos)
+                        / self.max_gripper_pos,
+                    ],
+                    dtype=float,
+                )
+
+                #         # Extract leader positions from teleop action dict
+                #         # leader_pos = np.array([teleop_action.get(f"{motor}.pos", 0) for motor in self.motor_names])
+                #         # follower_pos = np.array([raw_joint_pos[f"{motor}.pos"] for motor in self.motor_names])
+
+                #         teleop_action = self.leader_device.bus.sync_read("Present_Position")
+                #         raw_joint_pos = self.robot.bus.sync_read("Present_Position")
+                #         leader_pos = np.array([teleop_action.get(f"{motor}", 0) for motor in self.motor_names])
+                #         follower_pos = np.array([raw_joint_pos[f"{motor}"] for motor in self.motor_names])
+
+                #         # Compute EE positions
+                #         leader_ee_fi = self.kinematics.forward_kinematics(leader_pos)
+                #         leader_ee_pos = leader_ee_fi[:3, 3]
+                #         # leader_ee_rot = Rotation.from_matrix(leader_ee_fi[:3, :3]).as_rotvec()
+                #         leader_ee = np.concat([leader_ee_pos, [0,0,0]])
+
+                #         if "IK_solution" in transition.get(TransitionKey.COMPLEMENTARY_DATA):
+                #             follower_ee = transition.get(TransitionKey.COMPLEMENTARY_DATA)["IK_solution"]
+                #         else:
+                #             follower_pos = np.array([raw_joint_pos[f"{motor}.pos"] for motor in self.motor_names])
+                #             follower_ee_fi = self.kinematics.forward_kinematics(follower_pos)
+                #             follower_ee_pos = follower_ee_fi[:3, 3]
+                #             # follower_ee_rot = Rotation.from_matrix(follower_ee_fi[:3, :3]).as_rotvec()
+                #             follower_ee = np.concat([follower_ee_pos, [0,0,0]])
+
+                #         # Compute normalized EE delta
+                #         if self.end_effector_step_sizes is not None:
+                #             ee_delta = np.clip(
+                #                 leader_ee - follower_ee,
+                #                 -self.end_effector_step_sizes,
+                #                 self.end_effector_step_sizes
+                #             )
+                #             ee_delta_normalized = ee_delta / self.end_effector_step_sizes
+                #         else:
+                #             ee_delta_normalized = leader_ee - follower_ee
+
+                #         # Handle gripper
+                #         if self.use_gripper and len(leader_pos) > 3:
+                #             if self.prev_leader_gripper is None:
+                #                 self.prev_leader_gripper = np.clip(
+                #                     leader_pos[-1], 0, self.max_gripper_pos
+                #                 )
+
+                #             leader_gripper = leader_pos[-1]
+                #             gripper_delta = leader_gripper - self.prev_leader_gripper
+                #             normalized_delta = gripper_delta / self.max_gripper_pos
+
+                #             # Quantize gripper action
+                #             if normalized_delta >= 0.3:
+                #                 gripper_action = 2
+                #             elif normalized_delta <= -0.1:
+                #                 gripper_action = 0
+                #             else:
+                #                 gripper_action = 1
+
+                #             self.prev_leader_gripper = leader_gripper
+
+                #             # Create intervention action
+                #             intervention_action = np.append(ee_delta_normalized, gripper_action)
+                #         else:
+                #             intervention_action = ee_delta_normalized
+
+                #         # Override teleop_action with computed EE action
+                complementary["teleop_action"] = torch.from_numpy(intervention_action).float()
+                transition[TransitionKey.COMPLEMENTARY_DATA] = complementary  # type: ignore[misc]
+
+        return transition
+
+    def reset(self) -> None:
+        """Reset leader-follower state."""
+        # self.prev_leader_gripper = None
+        if hasattr(self.leader_device, "reset"):
+            self.leader_device.reset()
+
+    def transform_features(
+        self, features: dict[PipelineFeatureType, dict[str, PolicyFeature]]
+    ) -> dict[PipelineFeatureType, dict[str, PolicyFeature]]:
+        return features

src/lerobot/robots/so_follower/robot_kinematic_processor.py

@@ -18,6 +18,7 @@ from dataclasses import dataclass, field
 from typing import Any
 
 import numpy as np
+import torch
 
 from lerobot.configs import FeatureType, PipelineFeatureType, PolicyFeature
 from lerobot.model import RobotKinematics
@@ -31,6 +32,7 @@ from lerobot.processor import (
     RobotObservation,
     TransitionKey,
 )
+from lerobot.utils.constants import OBS_STATE
 from lerobot.utils.rotation import Rotation
 
 
@@ -126,9 +128,18 @@ class EEReferenceAndDelta(RobotActionProcessorStep):
                 ],
                 dtype=float,
             )
-            r_abs = Rotation.from_rotvec([wx, wy, wz]).as_matrix()
+            delta_r = np.array(
+                [
+                    wx * self.end_effector_step_sizes.get("wx", 1),
+                    wy * self.end_effector_step_sizes.get("wy", 1),
+                    wz * self.end_effector_step_sizes.get("wz", 1),
+                ],
+                dtype=float,
+            )
+
+            r_mat = Rotation.from_rotvec(delta_r).as_matrix()
             desired = np.eye(4, dtype=float)
-            desired[:3, :3] = ref[:3, :3] @ r_abs
+            desired[:3, :3] = ref[:3, :3] @ r_mat
             desired[:3, 3] = ref[:3, 3] + delta_p
 
             self._command_when_disabled = desired.copy()
@@ -361,6 +372,8 @@ class GripperVelocityToJoint(RobotActionProcessorStep):
     clip_min: float = 0.0
     clip_max: float = 100.0
     discrete_gripper: bool = False
+    scale_velocity: bool = False
+    use_ik_solution: bool = False
 
     def action(self, action: RobotAction) -> RobotAction:
         observation = self.transition.get(TransitionKey.OBSERVATION).copy()
@@ -370,14 +383,17 @@ class GripperVelocityToJoint(RobotActionProcessorStep):
         if observation is None:
             raise ValueError("Joints observation is require for computing robot kinematics")
 
-        q_raw = np.array(
-            [float(v) for k, v in observation.items() if isinstance(k, str) and k.endswith(".pos")],
-            dtype=float,
-        )
+        if self.use_ik_solution and "IK_solution" in self.transition.get(TransitionKey.COMPLEMENTARY_DATA):
+            q_raw = self.transition.get(TransitionKey.COMPLEMENTARY_DATA)["IK_solution"]
+        else:
+            q_raw = np.array(
+                [float(v) for k, v in observation.items() if isinstance(k, str) and k.endswith(".pos")],
+                dtype=float,
+            )
         if q_raw is None:
             raise ValueError("Joints observation is require for computing robot kinematics")
 
-        if self.discrete_gripper:
+        if self.discrete_gripper or self.scale_velocity:
             # Map discrete command {0=close, 1=stay, 2=open} -> signed velocity.
             # Negation accounts for SO100 sign (joint position increases on close).
             #   0 -> +clip_max (close), 1 -> 0 (stay), 2 -> -clip_max (open)
@@ -579,6 +595,7 @@ class InverseKinematicsRLStep(ProcessorStep):
 
         # Compute inverse kinematics
         q_target = self.kinematics.inverse_kinematics(self.q_curr, t_des)
+        q_target[-1] = gripper_pos  # Set gripper position
         self.q_curr = q_target
 
         # TODO: This is sentitive to order of motor_names = q_target mapping
@@ -610,3 +627,50 @@ class InverseKinematicsRLStep(ProcessorStep):
     def reset(self):
         """Resets the initial guess for the IK solver."""
         self.q_curr = None
+
+
+@dataclass
+@ProcessorStepRegistry.register("ee_observation")
+class EEObservationStep(ObservationProcessorStep):
+    use_rotation: bool = False
+
+    def observation(self, observation: dict) -> dict:
+        ee_pose_list = [
+            observation["ee.x"],
+            observation["ee.y"],
+            observation["ee.z"],
+        ]
+        if self.use_rotation:
+            ee_pose_list.extend(
+                [
+                    observation["ee.wx"],
+                    observation["ee.wy"],
+                    observation["ee.wz"],
+                ]
+            )
+        # gripper_pos = action.pop("ee.gripper_pos")
+        ee_pose = torch.tensor(ee_pose_list, dtype=torch.float32).unsqueeze(0)
+
+        current_state = observation.get(OBS_STATE)
+        if current_state is None:
+            return observation
+
+        extended_state = torch.cat([current_state, ee_pose], dim=-1)
+
+        # Create new observation dict
+        new_observation = dict(observation)
+        new_observation[OBS_STATE] = extended_state
+
+        return new_observation
+
+    def transform_features(
+        self, features: dict[PipelineFeatureType, dict[str, PolicyFeature]]
+    ) -> dict[PipelineFeatureType, dict[str, PolicyFeature]]:
+        if OBS_STATE in features[PipelineFeatureType.OBSERVATION]:
+            original_feature = features[PipelineFeatureType.OBSERVATION][OBS_STATE]
+            new_shape = (original_feature.shape[0] + 3,) + original_feature.shape[1:]
+
+            features[PipelineFeatureType.OBSERVATION][OBS_STATE] = PolicyFeature(
+                type=original_feature.type, shape=new_shape
+            )
+        return features

src/lerobot/robots/so_follower/so_follower.py

@@ -168,6 +168,12 @@ class SOFollower(Robot):
                     self.bus.write("Protection_Current", motor, 250)  # 50% of max current to avoid burnout
                     self.bus.write("Overload_Torque", motor, 25)  # 25% torque when overloaded
 
+            # Set Goal_Position = Present_Position while torque is still disabled so
+            # that when torque is re-enabled at the end of this block the motors have
+            # zero positional error and do not snap to a stale register value.
+            present = self.bus.sync_read("Present_Position")
+            self.bus.sync_write("Goal_Position", present)
+
     def setup_motors(self) -> None:
         for motor in reversed(self.bus.motors):
             input(f"Connect the controller board to the '{motor}' motor only and press enter.")

src/lerobot/teleoperators/so_leader/__init__.py

@@ -20,6 +20,7 @@ from .config_so_leader import (
     SOLeaderConfig,
     SOLeaderTeleopConfig,
 )
+from .so101_leader_follower import SO101LeaderFollower
 from .so_leader import SO100Leader, SO101Leader, SOLeader
 
 __all__ = [
@@ -27,6 +28,7 @@ __all__ = [
     "SO100LeaderConfig",
     "SO101Leader",
     "SO101LeaderConfig",
+    "SO101LeaderFollower",
     "SOLeader",
     "SOLeaderConfig",
     "SOLeaderTeleopConfig",

src/lerobot/teleoperators/so_leader/config_so_leader.py

@@ -29,6 +29,11 @@ class SOLeaderConfig:
     # Whether to use degrees for angles
     use_degrees: bool = True
 
+    # Enable leader-follower mode where leader can both lead and follow
+    leader_follower_mode: bool = False
+
+    use_gripper: bool = True
+
 
 @TeleoperatorConfig.register_subclass("so101_leader")
 @TeleoperatorConfig.register_subclass("so100_leader")

src/lerobot/teleoperators/so_leader/so101_leader_follower.py

@@ -0,0 +1,261 @@
+#!/usr/bin/env python
+
+# Copyright 2025 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+import os
+import sys
+import time
+from collections import deque
+from threading import Event, Thread
+
+import numpy as np
+
+from lerobot.teleoperators.so_leader.so_leader import SOLeader as SO101Leader
+from lerobot.teleoperators.utils import TeleopEvents
+
+PYNPUT_AVAILABLE = True
+try:
+    if ("DISPLAY" not in os.environ) and ("linux" in sys.platform):
+        logging.info("No DISPLAY set. Skipping pynput import.")
+        raise ImportError("pynput blocked intentionally due to no display.")
+
+    from pynput import keyboard
+except ImportError:
+    keyboard = None
+    PYNPUT_AVAILABLE = False
+except Exception as e:
+    keyboard = None
+    PYNPUT_AVAILABLE = False
+    logging.info(f"Could not import pynput: {e}")
+
+logger = logging.getLogger(__name__)
+
+
+class SO101LeaderFollower(SO101Leader):
+    """
+    Extended SO101 Leader that can both lead (human control) and follow (mimic follower).
+
+    This class adds leader-follower functionality where:
+    - In follow mode: The leader arm mimics the follower's position (torque enabled)
+    - In lead mode: Human controls the leader (torque disabled) and provides actions
+    """
+
+    def __init__(self, config):
+        super().__init__(config)
+
+        # Leader-follower state
+        self.is_intervening = False
+        # Initialize as False because configure() disables torque at connect time;
+        # send_action() will re-enable it on the first call when not intervening.
+        self.leader_torque_enabled = False
+
+        # Tracking error for automatic intervention detection
+        self.leader_tracking_error_queue = deque(maxlen=4)
+
+        # Keyboard event handling
+        self.keyboard_events = {
+            "intervention": False,
+            "success": False,
+            "failure": False,
+            "rerecord": False,
+        }
+        self.keyboard_thread = None
+        self.stop_event = Event()
+
+        # Store last follower position for action computation
+        self.last_follower_pos = None
+
+    @property
+    def action_features(self) -> dict:
+        if self.config.use_gripper:
+            return {
+                "dtype": "float32",
+                "shape": (7,),
+                "names": {
+                    "delta_x": 0,
+                    "delta_y": 1,
+                    "delta_z": 2,
+                    "delta_wx": 3,
+                    "delta_wy": 4,
+                    "delta_wz": 5,
+                    "gripper": 6,
+                },
+            }
+        else:
+            return {
+                "dtype": "float32",
+                "shape": (6,),
+                "names": {
+                    "delta_x": 0,
+                    "delta_y": 1,
+                    "delta_z": 2,
+                    "delta_wx": 3,
+                    "delta_wy": 4,
+                    "delta_wz": 5,
+                },
+            }
+
+    def connect(self, calibrate: bool = True) -> None:
+        """Connect and configure for leader-follower mode."""
+        super().connect(calibrate)
+
+        # Configure for leader-follower mode with lower gains
+        # Lower gains allow manual intervention without injury risk
+        # self.bus.sync_write("Torque_Enable", 1)
+        for motor in self.bus.motors:
+            self.bus.write("P_Coefficient", motor, 16)
+            self.bus.write("I_Coefficient", motor, 0)
+            self.bus.write("D_Coefficient", motor, 16)
+
+        # Start keyboard listener
+        self._start_keyboard_listener()
+
+        print("- Leader-Follower Mode:")
+        print("  - Press SPACE to toggle intervention (leader control)")
+        print("  - When not intervening, leader follows follower position")
+        print("  - When intervening, follower follows leader in end-effector space")
+        print("  - Press 's' to mark episode as success")
+        print("  - Press ESC to end episode as failure")
+        print("  - Press 'r' to re-record episode")
+
+    def _start_keyboard_listener(self):
+        """Start keyboard listener thread for intervention control."""
+
+        def on_press(key):
+            try:
+                if key == keyboard.Key.space:
+                    self.keyboard_events["intervention"] = not self.keyboard_events["intervention"]
+                    self.is_intervening = self.keyboard_events["intervention"]
+                    state = "INTERVENTION MODE" if self.is_intervening else "FOLLOWING MODE"
+                    logger.info(f"Toggled to {state}")
+                elif key == keyboard.Key.esc:
+                    self.keyboard_events["failure"] = True
+                elif hasattr(key, "char"):
+                    if key.char == "s":
+                        self.keyboard_events["success"] = True
+                    elif key.char == "r":
+                        self.keyboard_events["rerecord"] = True
+            except Exception as e:
+                logger.error(f"Error handling key press: {e}")
+
+        def listen():
+            with keyboard.Listener(on_press=on_press) as listener:
+                while not self.stop_event.is_set():
+                    time.sleep(0.1)
+                listener.stop()
+
+        self.keyboard_thread = Thread(target=listen, daemon=True)
+        self.keyboard_thread.start()
+
+    def send_action(self, action: dict[str, float]) -> None:
+        """
+        Send position commands to leader arm (follow mode).
+
+        Args:
+            action: Dictionary of motor positions to command
+        """
+        # Store follower position for later use
+        self.last_follower_pos = np.array([action.get(f"{motor}.pos", 0) for motor in self.bus.motors])
+
+        if not self.is_intervening:
+            # Follow mode: enable torque and track follower
+            if not self.leader_torque_enabled:
+                self.bus.sync_write("Torque_Enable", 1)
+                self.leader_torque_enabled = True
+
+            # Send follower positions to leader
+            goal_pos = {motor: action[f"{motor}.pos"] for motor in self.bus.motors}
+            self.bus.sync_write("Goal_Position", goal_pos)
+
+            # Track error for automatic intervention detection
+            current_pos = self.bus.sync_read("Present_Position")
+            current_array = np.array([current_pos[motor] for motor in self.bus.motors])
+            error = np.linalg.norm(self.last_follower_pos[:-1] - current_array[:-1])
+            self.leader_tracking_error_queue.append(error)
+
+    def get_action(self) -> dict[str, float]:
+        """
+        Get action from leader arm.
+
+        In follow mode: Returns neutral/current positions
+        In lead mode: Returns actual leader positions for follower to track
+        """
+        start = time.perf_counter()
+
+        if self.is_intervening:
+            # Lead mode: disable torque if needed and return leader positions
+            if self.leader_torque_enabled:
+                self.bus.sync_write("Torque_Enable", 0)
+                self.leader_torque_enabled = False
+
+            # Get current leader position
+            action = self.bus.sync_read("Present_Position")
+            action = {f"{motor}.pos": val for motor, val in action.items()}
+
+            # Track error
+            if self.last_follower_pos is not None:
+                current_array = np.array([action[f"{motor}.pos"] for motor in self.bus.motors])
+                error = np.linalg.norm(self.last_follower_pos[:-1] - current_array[:-1])
+                self.leader_tracking_error_queue.append(error)
+        else:
+            # Follow mode: return current/neutral positions
+            action = self.bus.sync_read("Present_Position")
+            action = {f"{motor}.pos": val for motor, val in action.items()}
+
+        dt_ms = (time.perf_counter() - start) * 1e3
+        logger.debug(f"{self} read action: {dt_ms:.1f}ms")
+        return action
+
+    def get_teleop_events(self) -> dict[TeleopEvents, bool]:
+        """Get current keyboard events."""
+        events = {}
+
+        # Map keyboard events to TeleopEvents
+        if self.keyboard_events["success"]:
+            events[TeleopEvents.SUCCESS] = True
+            self.keyboard_events["success"] = False
+        if self.keyboard_events["failure"]:
+            events[TeleopEvents.FAILURE] = True
+            events[TeleopEvents.TERMINATE_EPISODE] = True
+            self.keyboard_events["failure"] = False
+        if self.keyboard_events["rerecord"]:
+            events[TeleopEvents.RERECORD_EPISODE] = True
+            events[TeleopEvents.TERMINATE_EPISODE] = True
+            self.keyboard_events["rerecord"] = False
+
+        # Always report intervention state
+        events[TeleopEvents.IS_INTERVENTION] = self.is_intervening
+
+        return events
+
+    def disconnect(self) -> None:
+        """Disconnect and cleanup."""
+        self.stop_event.set()
+        if self.keyboard_thread:
+            self.keyboard_thread.join(timeout=1.0)
+        super().disconnect()
+
+    def reset(self) -> None:
+        """Reset leader-follower state."""
+        self.is_intervening = False
+        self.leader_torque_enabled = True
+        self.leader_tracking_error_queue.clear()
+        self.keyboard_events = {
+            "intervention": False,
+            "success": False,
+            "failure": False,
+            "rerecord": False,
+        }

src/lerobot/teleoperators/utils.py

@@ -52,9 +52,10 @@ def make_teleoperator_from_config(config: TeleoperatorConfig) -> "Teleoperator":
 
         return SO100Leader(config)
     elif config.type == "so101_leader":
-        from .so_leader import SO101Leader
+        from .so_leader import SO101LeaderFollower
 
-        return SO101Leader(config)
+        if getattr(config, "leader_follower_mode", False):
+            return SO101LeaderFollower(config)
     elif config.type == "mock_teleop":
         from tests.mocks.mock_teleop import MockTeleop