diff --git a/pyproject.toml b/pyproject.toml
index 0e9fba586..4b50a77f8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -108,9 +108,9 @@ training = [
     "wandb>=0.24.0,<0.25.0",
 ]
 hardware = [
-    "pynput>=1.7.8,<1.9.0",
-    "pyserial>=3.5,<4.0",
-    "deepdiff>=7.0.1,<9.0.0",
+    "lerobot[pynput-dep]",
+    "lerobot[pyserial-dep]",
+    "lerobot[deepdiff-dep]",
 ]
 viz = [
     "rerun-sdk>=0.24.0,<0.27.0",
@@ -136,10 +136,14 @@ scipy-dep = ["scipy>=1.14.0,<2.0.0"]
 diffusers-dep = ["diffusers>=0.27.2,<0.36.0"]
 qwen-vl-utils-dep = ["qwen-vl-utils>=0.0.11,<0.1.0"]
 matplotlib-dep = ["matplotlib>=3.10.3,<4.0.0", "contourpy>=1.3.0,<2.0.0"] # NOTE: Explicitly listing contourpy helps the resolver converge faster.
+pyserial-dep = ["pyserial>=3.5,<4.0"]
+deepdiff-dep = ["deepdiff>=7.0.1,<9.0.0"]
+pynput-dep = ["pynput>=1.7.8,<1.9.0"]
+pyzmq-dep = ["pyzmq>=26.2.1,<28.0.0"]
 
 # Motors
-feetech = ["feetech-servo-sdk>=1.0.0,<2.0.0"]
-dynamixel = ["dynamixel-sdk>=3.7.31,<3.9.0"]
+feetech = ["feetech-servo-sdk>=1.0.0,<2.0.0", "lerobot[pyserial-dep]", "lerobot[deepdiff-dep]"]
+dynamixel = ["dynamixel-sdk>=3.7.31,<3.9.0", "lerobot[pyserial-dep]", "lerobot[deepdiff-dep]"]
 damiao = ["lerobot[can-dep]"]
 robstride = ["lerobot[can-dep]"]
 
@@ -147,10 +151,11 @@ robstride = ["lerobot[can-dep]"]
 openarms = ["lerobot[damiao]"]
 gamepad = ["lerobot[pygame-dep]", "hidapi>=0.14.0,<0.15.0"]
 hopejr = ["lerobot[feetech]", "lerobot[pygame-dep]"]
-lekiwi = ["lerobot[feetech]", "pyzmq>=26.2.1,<28.0.0"]
+lekiwi = ["lerobot[feetech]", "lerobot[pyzmq-dep]"]
 unitree_g1 = [
     # "unitree-sdk2==1.0.1",
-    "pyzmq>=26.2.1,<28.0.0",
+    "lerobot[pyzmq-dep]",
+    "lerobot[pyserial-dep]",
     "onnxruntime>=1.16.0,<2.0.0",
     "onnx>=1.16.0,<2.0.0",
     "meshcat>=0.3.0,<0.4.0",
diff --git a/src/lerobot/cameras/reachy2_camera/reachy2_camera.py b/src/lerobot/cameras/reachy2_camera/reachy2_camera.py
index 9bef957bc..9b7e7a2e0 100644
--- a/src/lerobot/cameras/reachy2_camera/reachy2_camera.py
+++ b/src/lerobot/cameras/reachy2_camera/reachy2_camera.py
@@ -33,7 +33,7 @@ import cv2  # type: ignore  # TODO: add type stubs for OpenCV
 import numpy as np  # type: ignore  # TODO: add type stubs for numpy
 
 from lerobot.utils.decorators import check_if_not_connected
-from lerobot.utils.import_utils import _reachy2_sdk_available
+from lerobot.utils.import_utils import _reachy2_sdk_available, require_package
 
 if TYPE_CHECKING or _reachy2_sdk_available:
     from reachy2_sdk.media.camera import CameraView
@@ -76,6 +76,7 @@ class Reachy2Camera(Camera):
         Args:
             config: The configuration settings for the camera.
         """
+        require_package("reachy2_sdk", extra="reachy2")
         super().__init__(config)
 
         self.config = config
diff --git a/src/lerobot/cameras/realsense/camera_realsense.py b/src/lerobot/cameras/realsense/camera_realsense.py
index d80ec8093..6363cc0bc 100644
--- a/src/lerobot/cameras/realsense/camera_realsense.py
+++ b/src/lerobot/cameras/realsense/camera_realsense.py
@@ -19,16 +19,18 @@ Provides the RealSenseCamera class for capturing frames from Intel RealSense cam
 import logging
 import time
 from threading import Event, Lock, Thread
-from typing import Any
+from typing import TYPE_CHECKING, Any
 
 import cv2  # type: ignore  # TODO: add type stubs for OpenCV
 import numpy as np  # type: ignore  # TODO: add type stubs for numpy
 from numpy.typing import NDArray  # type: ignore  # TODO: add type stubs for numpy.typing
 
-try:
-    import pyrealsense2 as rs  # type: ignore  # TODO: add type stubs for pyrealsense2
-except Exception as e:
-    logging.info(f"Could not import realsense: {e}")
+from lerobot.utils.import_utils import _pyrealsense2_available, require_package
+
+if TYPE_CHECKING or _pyrealsense2_available:
+    import pyrealsense2 as rs
+else:
+    rs = None
 
 from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
 from lerobot.utils.errors import DeviceNotConnectedError
@@ -112,7 +114,7 @@ class RealSenseCamera(Camera):
         Args:
             config: The configuration settings for the camera.
         """
-
+        require_package("pyrealsense2", extra="intelrealsense")
         super().__init__(config)
 
         self.config = config
diff --git a/src/lerobot/cameras/zmq/camera_zmq.py b/src/lerobot/cameras/zmq/camera_zmq.py
index 2fbe50d8b..1b0be5de6 100644
--- a/src/lerobot/cameras/zmq/camera_zmq.py
+++ b/src/lerobot/cameras/zmq/camera_zmq.py
@@ -28,12 +28,19 @@ import json
 import logging
 import time
 from threading import Event, Lock, Thread
-from typing import Any
+from typing import TYPE_CHECKING, Any
 
 import cv2
 import numpy as np
 from numpy.typing import NDArray
 
+from lerobot.utils.import_utils import _zmq_available, require_package
+
+if TYPE_CHECKING or _zmq_available:
+    import zmq
+else:
+    zmq = None
+
 from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
 from lerobot.utils.errors import DeviceNotConnectedError
 
@@ -74,8 +81,8 @@ class ZMQCamera(Camera):
     """
 
     def __init__(self, config: ZMQCameraConfig):
+        require_package("pyzmq", extra="pyzmq-dep", import_name="zmq")
         super().__init__(config)
-        import zmq
 
         self.config = config
         self.server_address = config.server_address
@@ -117,8 +124,6 @@ class ZMQCamera(Camera):
         logger.info(f"Connecting to {self}...")
 
         try:
-            import zmq
-
             self.context = zmq.Context()
             self.socket = self.context.socket(zmq.SUB)
             self.socket.setsockopt_string(zmq.SUBSCRIBE, "")
@@ -180,11 +185,8 @@ class ZMQCamera(Camera):
 
         try:
             message = self.socket.recv_string()
-        except Exception as e:
-            # zmq is lazy-imported in connect(), so check by name to avoid a top-level import
-            if type(e).__name__ == "Again":
-                raise TimeoutError(f"{self} timeout after {self.timeout_ms}ms") from e
-            raise
+        except zmq.Again as e:
+            raise TimeoutError(f"{self} timeout after {self.timeout_ms}ms") from e
 
         # Decode JSON message
         data = json.loads(message)
diff --git a/src/lerobot/common/control_utils.py b/src/lerobot/common/control_utils.py
index 530955078..efbcc082f 100644
--- a/src/lerobot/common/control_utils.py
+++ b/src/lerobot/common/control_utils.py
@@ -28,6 +28,12 @@ import numpy as np
 import torch
 
 from lerobot.policies import PreTrainedPolicy, prepare_observation_for_inference
+from lerobot.utils.import_utils import _deepdiff_available, require_package
+
+if TYPE_CHECKING or _deepdiff_available:
+    from deepdiff import DeepDiff
+else:
+    DeepDiff = None
 
 if TYPE_CHECKING:
     from lerobot.datasets import LeRobotDataset
@@ -217,10 +223,7 @@ def sanity_check_dataset_robot_compatibility(
     Raises:
         ValueError: If any of the checked metadata fields do not match.
     """
-    from lerobot.utils.import_utils import require_package
-
-    require_package("deepdiff", extra="hardware")
-    from deepdiff import DeepDiff
+    require_package("deepdiff", extra="deepdiff-dep")
 
     from lerobot.utils.constants import DEFAULT_FEATURES
 
diff --git a/src/lerobot/datasets/image_writer.py b/src/lerobot/datasets/image_writer.py
index 603067757..8fb5804a5 100644
--- a/src/lerobot/datasets/image_writer.py
+++ b/src/lerobot/datasets/image_writer.py
@@ -30,13 +30,13 @@ def safe_stop_image_writer(func):
     def wrapper(*args, **kwargs):
         try:
             return func(*args, **kwargs)
-        except Exception as e:
+        except BaseException:
             dataset = kwargs.get("dataset")
             writer = getattr(dataset, "writer", None) if dataset else None
             if writer is not None and writer.image_writer is not None:
                 logger.warning("Waiting for image writer to terminate...")
                 writer.image_writer.stop()
-            raise e
+            raise
 
     return wrapper
 
diff --git a/src/lerobot/model/kinematics.py b/src/lerobot/model/kinematics.py
index 95d3b235c..01705ded5 100644
--- a/src/lerobot/model/kinematics.py
+++ b/src/lerobot/model/kinematics.py
@@ -12,8 +12,19 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
 import numpy as np
 
+from lerobot.utils.import_utils import _placo_available, require_package
+
+if TYPE_CHECKING or _placo_available:
+    import placo  # type: ignore[import-not-found]
+else:
+    placo = None
+
 
 class RobotKinematics:
     """Robot kinematics using placo library for forward and inverse kinematics."""
@@ -32,13 +43,7 @@ class RobotKinematics:
             target_frame_name (str): Name of the end-effector frame in the URDF
             joint_names (list[str] | None): List of joint names to use for the kinematics solver
         """
-        try:
-            import placo  # type: ignore[import-not-found] # C++ library with Python bindings, no type stubs available. TODO: Create stub file or request upstream typing support.
-        except ImportError as e:
-            raise ImportError(
-                "placo is required for RobotKinematics. "
-                "Please install the optional dependencies of `kinematics` in the package."
-            ) from e
+        require_package("placo", extra="placo-dep")
 
         self.robot = placo.RobotWrapper(urdf_path)
         self.solver = placo.KinematicsSolver(self.robot)
diff --git a/src/lerobot/motors/damiao/damiao.py b/src/lerobot/motors/damiao/damiao.py
index ae619f159..572741cb4 100644
--- a/src/lerobot/motors/damiao/damiao.py
+++ b/src/lerobot/motors/damiao/damiao.py
@@ -24,7 +24,7 @@ from functools import cached_property
 from typing import TYPE_CHECKING, Any, TypedDict
 
 from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
-from lerobot.utils.import_utils import _can_available
+from lerobot.utils.import_utils import _can_available, require_package
 
 if TYPE_CHECKING or _can_available:
     import can
@@ -111,6 +111,7 @@ class DamiaoMotorsBus(MotorsBusBase):
             bitrate: Nominal bitrate in bps (default: 1000000 = 1 Mbps)
             data_bitrate: Data bitrate for CAN FD in bps (default: 5000000 = 5 Mbps), ignored if use_can_fd is False
         """
+        require_package("python-can", extra="damiao", import_name="can")
         super().__init__(port, motors, calibration)
         self.port = port
         self.can_interface = can_interface
diff --git a/src/lerobot/motors/motors_bus.py b/src/lerobot/motors/motors_bus.py
index 209489bb9..4688eaa7f 100644
--- a/src/lerobot/motors/motors_bus.py
+++ b/src/lerobot/motors/motors_bus.py
@@ -356,8 +356,8 @@ class SerialMotorsBus(MotorsBusBase):
         motors: dict[str, Motor],
         calibration: dict[str, MotorCalibration] | None = None,
     ):
-        require_package("pyserial", extra="hardware", import_name="serial")
-        require_package("deepdiff", extra="hardware")
+        require_package("pyserial", extra="pyserial-dep", import_name="serial")
+        require_package("deepdiff", extra="deepdiff-dep")
         super().__init__(port, motors, calibration)
 
         self.port_handler: PortHandler
diff --git a/src/lerobot/motors/robstride/robstride.py b/src/lerobot/motors/robstride/robstride.py
index f47e41509..ecde01e9a 100644
--- a/src/lerobot/motors/robstride/robstride.py
+++ b/src/lerobot/motors/robstride/robstride.py
@@ -23,12 +23,12 @@ from types import SimpleNamespace
 from typing import TYPE_CHECKING, Any, TypedDict
 
 from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
-from lerobot.utils.import_utils import _can_available
+from lerobot.utils.import_utils import _can_available, require_package
 
 if TYPE_CHECKING or _can_available:
     import can
 else:
-    can = SimpleNamespace(Message=object, interface=None)
+    can = SimpleNamespace(Message=object, interface=None, BusABC=object)
 import numpy as np
 
 from lerobot.utils.errors import DeviceNotConnectedError
@@ -106,6 +106,7 @@ class RobstrideMotorsBus(MotorsBusBase):
             bitrate: Nominal bitrate in bps (default: 1000000 = 1 Mbps)
             data_bitrate: Data bitrate for CAN FD in bps (default: 5000000 = 5 Mbps), ignored if use_can_fd is False
         """
+        require_package("python-can", extra="robstride", import_name="can")
         super().__init__(port, motors, calibration)
         self.port = port
         self.can_interface = can_interface
diff --git a/src/lerobot/optim/schedulers.py b/src/lerobot/optim/schedulers.py
index 914edd2db..250650089 100644
--- a/src/lerobot/optim/schedulers.py
+++ b/src/lerobot/optim/schedulers.py
@@ -18,14 +18,21 @@ import logging
 import math
 from dataclasses import asdict, dataclass
 from pathlib import Path
+from typing import TYPE_CHECKING
 
 import draccus
 from torch.optim import Optimizer
 from torch.optim.lr_scheduler import LambdaLR, LRScheduler
 
 from lerobot.utils.constants import SCHEDULER_STATE
+from lerobot.utils.import_utils import _diffusers_available, require_package
 from lerobot.utils.io_utils import deserialize_json_into_object, write_json
 
+if TYPE_CHECKING or _diffusers_available:
+    from diffusers.optimization import get_scheduler
+else:
+    get_scheduler = None
+
 
 @dataclass
 class LRSchedulerConfig(draccus.ChoiceRegistry, abc.ABC):
@@ -47,10 +54,7 @@ class DiffuserSchedulerConfig(LRSchedulerConfig):
     num_warmup_steps: int | None = None
 
     def build(self, optimizer: Optimizer, num_training_steps: int) -> LambdaLR:
-        from lerobot.utils.import_utils import require_package
-
         require_package("diffusers", extra="diffusion")
-        from diffusers.optimization import get_scheduler
 
         kwargs = {**asdict(self), "num_training_steps": num_training_steps, "optimizer": optimizer}
         return get_scheduler(**kwargs)
diff --git a/src/lerobot/policies/diffusion/modeling_diffusion.py b/src/lerobot/policies/diffusion/modeling_diffusion.py
index 5b3b97571..03203ffc8 100644
--- a/src/lerobot/policies/diffusion/modeling_diffusion.py
+++ b/src/lerobot/policies/diffusion/modeling_diffusion.py
@@ -23,6 +23,7 @@ TODO(alexander-soare):
 import math
 from collections import deque
 from collections.abc import Callable
+from typing import TYPE_CHECKING
 
 import einops
 import numpy as np
@@ -32,6 +33,14 @@ import torchvision
 from torch import Tensor, nn
 
 from lerobot.utils.constants import ACTION, OBS_ENV_STATE, OBS_IMAGES, OBS_STATE
+from lerobot.utils.import_utils import _diffusers_available, require_package
+
+if TYPE_CHECKING or _diffusers_available:
+    from diffusers.schedulers.scheduling_ddim import DDIMScheduler
+    from diffusers.schedulers.scheduling_ddpm import DDPMScheduler
+else:
+    DDIMScheduler = None
+    DDPMScheduler = None
 
 from ..pretrained import PreTrainedPolicy
 from ..utils import (
@@ -64,6 +73,7 @@ class DiffusionPolicy(PreTrainedPolicy):
             dataset_stats: Dataset statistics to be used for normalization. If not passed here, it is expected
                 that they will be passed with a call to `load_state_dict` before the policy is used.
         """
+        require_package("diffusers", extra="diffusion")
         super().__init__(config)
         config.validate_features()
         self.config = config
@@ -155,11 +165,7 @@ def _make_noise_scheduler(name: str, **kwargs: dict):
     Factory for noise scheduler instances of the requested type. All kwargs are passed
     to the scheduler.
     """
-    from lerobot.utils.import_utils import require_package
-
     require_package("diffusers", extra="diffusion")
-    from diffusers.schedulers.scheduling_ddim import DDIMScheduler
-    from diffusers.schedulers.scheduling_ddpm import DDPMScheduler
 
     if name == "DDPM":
         return DDPMScheduler(**kwargs)
diff --git a/src/lerobot/policies/groot/action_head/flow_matching_action_head.py b/src/lerobot/policies/groot/action_head/flow_matching_action_head.py
index 4fda21ca5..2c1ca6014 100644
--- a/src/lerobot/policies/groot/action_head/flow_matching_action_head.py
+++ b/src/lerobot/policies/groot/action_head/flow_matching_action_head.py
@@ -204,7 +204,9 @@ class FlowmatchingActionHead(nn.Module):
             self.position_embedding = nn.Embedding(config.max_seq_len, self.input_embedding_dim)
             nn.init.normal_(self.position_embedding.weight, mean=0.0, std=0.02)
 
-        self.beta_dist = Beta(config.noise_beta_alpha, config.noise_beta_beta)
+        self._noise_beta_alpha = config.noise_beta_alpha
+        self._noise_beta_beta = config.noise_beta_beta
+        self._beta_dist = None
         self.num_timestep_buckets = config.num_timestep_buckets
         self.config = config
         self.set_trainable_parameters(config.tune_projector, config.tune_diffusion_model)
@@ -249,7 +251,9 @@ class FlowmatchingActionHead(nn.Module):
                 self.model.eval()
 
     def sample_time(self, batch_size, device, dtype):
-        sample = self.beta_dist.sample([batch_size]).to(device, dtype=dtype)
+        if self._beta_dist is None:
+            self._beta_dist = Beta(self._noise_beta_alpha, self._noise_beta_beta, validate_args=False)
+        sample = self._beta_dist.sample([batch_size]).to(device, dtype=dtype)
         return (self.config.noise_s - sample) / self.config.noise_s
 
     def prepare_input(self, batch: dict) -> BatchFeature:
diff --git a/src/lerobot/policies/groot/eagle2_hg_model/processing_eagle2_5_vl.py b/src/lerobot/policies/groot/eagle2_hg_model/processing_eagle2_5_vl.py
index 27f9b3345..7b1f67fef 100755
--- a/src/lerobot/policies/groot/eagle2_hg_model/processing_eagle2_5_vl.py
+++ b/src/lerobot/policies/groot/eagle2_hg_model/processing_eagle2_5_vl.py
@@ -222,6 +222,13 @@ class Eagle25VLProcessor(ProcessorMixin):
                         videos=None,
                         **output_kwargs["images_kwargs"],
                     )
+                    if isinstance(image_inputs["pixel_values"], list):
+                        _pv = image_inputs["pixel_values"]
+                        if _pv and isinstance(_pv[0], list):
+                            _pv = [t for sub in _pv for t in sub]
+                        image_inputs["pixel_values"] = torch.stack(
+                            [t if isinstance(t, torch.Tensor) else torch.as_tensor(t) for t in _pv]
+                        )
                     num_all_tiles = image_inputs["pixel_values"].shape[0]
                     special_placeholder = f"<image {idx_in_list + 1}>{self.image_start_token}{self.image_token * num_all_tiles * self.tokens_per_tile}{self.image_end_token}"
                     unified_frame_list.append(image_inputs)
@@ -233,6 +240,13 @@ class Eagle25VLProcessor(ProcessorMixin):
                         videos=[video_list[idx_in_list]],
                         **output_kwargs["videos_kwargs"],
                     )
+                    if isinstance(video_inputs["pixel_values"], list):
+                        _pv = video_inputs["pixel_values"]
+                        if _pv and isinstance(_pv[0], list):
+                            _pv = [t for sub in _pv for t in sub]
+                        video_inputs["pixel_values"] = torch.stack(
+                            [t if isinstance(t, torch.Tensor) else torch.as_tensor(t) for t in _pv]
+                        )
                     num_all_tiles = video_inputs["pixel_values"].shape[0]
                     image_sizes = video_inputs["image_sizes"]
                     if timestamps_list is not None and -1 not in timestamps_list:
@@ -288,8 +302,18 @@ class Eagle25VLProcessor(ProcessorMixin):
 
         text = replace_in_text(text)
         if len(unified_frame_list) > 0:
-            pixel_values = torch.cat([frame["pixel_values"] for frame in unified_frame_list])
-            image_sizes = torch.cat([frame["image_sizes"] for frame in unified_frame_list])
+
+            def _to_tensor(v):
+                if isinstance(v, torch.Tensor):
+                    return v
+                if isinstance(v, list):
+                    if v and isinstance(v[0], list):
+                        v = [t for sub in v for t in sub]
+                    return torch.stack([t if isinstance(t, torch.Tensor) else torch.as_tensor(t) for t in v])
+                return torch.as_tensor(v)
+
+            pixel_values = torch.cat([_to_tensor(frame["pixel_values"]) for frame in unified_frame_list])
+            image_sizes = torch.cat([_to_tensor(frame["image_sizes"]) for frame in unified_frame_list])
         else:
             pixel_values = None
             image_sizes = None
diff --git a/src/lerobot/policies/groot/groot_n1.py b/src/lerobot/policies/groot/groot_n1.py
index fc753839a..abcbb8a8c 100644
--- a/src/lerobot/policies/groot/groot_n1.py
+++ b/src/lerobot/policies/groot/groot_n1.py
@@ -221,6 +221,7 @@ class GR00TN15(PreTrainedModel):
         self.action_horizon = config.action_horizon
         self.action_dim = config.action_dim
         self.compute_dtype = config.compute_dtype
+        self.post_init()
 
     def validate_inputs(self, inputs):
         # NOTE -- this should be handled internally by the model
diff --git a/src/lerobot/policies/groot/modeling_groot.py b/src/lerobot/policies/groot/modeling_groot.py
index 4b612bca4..2e2e9ca89 100644
--- a/src/lerobot/policies/groot/modeling_groot.py
+++ b/src/lerobot/policies/groot/modeling_groot.py
@@ -43,6 +43,7 @@ from torch import Tensor
 
 from lerobot.configs import FeatureType, PolicyFeature
 from lerobot.utils.constants import ACTION, OBS_IMAGES
+from lerobot.utils.import_utils import require_package
 
 from ..pretrained import PreTrainedPolicy
 from .configuration_groot import GrootConfig
@@ -59,6 +60,7 @@ class GrootPolicy(PreTrainedPolicy):
 
     def __init__(self, config: GrootConfig, **kwargs):
         """Initialize Groot policy wrapper."""
+        require_package("transformers", extra="groot")
         super().__init__(config)
         config.validate_features()
         self.config = config
diff --git a/src/lerobot/policies/multi_task_dit/modeling_multi_task_dit.py b/src/lerobot/policies/multi_task_dit/modeling_multi_task_dit.py
index 8e5d1e3cb..366b271c0 100644
--- a/src/lerobot/policies/multi_task_dit/modeling_multi_task_dit.py
+++ b/src/lerobot/policies/multi_task_dit/modeling_multi_task_dit.py
@@ -36,7 +36,7 @@ import torch.nn.functional as F  # noqa: N812
 import torchvision
 from torch import Tensor
 
-from lerobot.utils.import_utils import _transformers_available
+from lerobot.utils.import_utils import _diffusers_available, _transformers_available, require_package
 
 from .configuration_multi_task_dit import MultiTaskDiTConfig
 
@@ -46,6 +46,13 @@ if TYPE_CHECKING or _transformers_available:
 else:
     CLIPTextModel = None
     CLIPVisionModel = None
+
+if TYPE_CHECKING or _diffusers_available:
+    from diffusers.schedulers.scheduling_ddim import DDIMScheduler
+    from diffusers.schedulers.scheduling_ddpm import DDPMScheduler
+else:
+    DDIMScheduler = None
+    DDPMScheduler = None
 from lerobot.utils.constants import (
     ACTION,
     OBS_IMAGES,
@@ -65,6 +72,8 @@ class MultiTaskDiTPolicy(PreTrainedPolicy):
     name = "multi_task_dit"
 
     def __init__(self, config: MultiTaskDiTConfig, **kwargs):
+        require_package("transformers", extra="multi_task_dit")
+        require_package("diffusers", extra="multi_task_dit")
         super().__init__(config)
         config.validate_features()
         self.config = config
@@ -643,12 +652,6 @@ class DiffusionObjective(nn.Module):
             "prediction_type": config.prediction_type,
         }
 
-        from lerobot.utils.import_utils import require_package
-
-        require_package("diffusers", extra="multi_task_dit")
-        from diffusers.schedulers.scheduling_ddim import DDIMScheduler
-        from diffusers.schedulers.scheduling_ddpm import DDPMScheduler
-
         if config.noise_scheduler_type == "DDPM":
             self.noise_scheduler: DDPMScheduler | DDIMScheduler = DDPMScheduler(**scheduler_kwargs)
         elif config.noise_scheduler_type == "DDIM":
diff --git a/src/lerobot/policies/pi0/modeling_pi0.py b/src/lerobot/policies/pi0/modeling_pi0.py
index 22e4e6a26..3534c7ae8 100644
--- a/src/lerobot/policies/pi0/modeling_pi0.py
+++ b/src/lerobot/policies/pi0/modeling_pi0.py
@@ -26,7 +26,7 @@ import torch
 import torch.nn.functional as F  # noqa: N812
 from torch import Tensor, nn
 
-from lerobot.utils.import_utils import _transformers_available
+from lerobot.utils.import_utils import _transformers_available, require_package
 
 # Conditional import for type checking and lazy loading
 if TYPE_CHECKING or _transformers_available:
@@ -947,6 +947,7 @@ class PI0Policy(PreTrainedPolicy):
         Args:
             config: Policy configuration class instance.
         """
+        require_package("transformers", extra="pi")
         super().__init__(config)
         config.validate_features()
         self.config = config
diff --git a/src/lerobot/policies/pi05/modeling_pi05.py b/src/lerobot/policies/pi05/modeling_pi05.py
index a44817a74..56786fbcd 100644
--- a/src/lerobot/policies/pi05/modeling_pi05.py
+++ b/src/lerobot/policies/pi05/modeling_pi05.py
@@ -26,7 +26,7 @@ import torch
 import torch.nn.functional as F  # noqa: N812
 from torch import Tensor, nn
 
-from lerobot.utils.import_utils import _transformers_available
+from lerobot.utils.import_utils import _transformers_available, require_package
 
 # Conditional import for type checking and lazy loading
 if TYPE_CHECKING or _transformers_available:
@@ -918,6 +918,7 @@ class PI05Policy(PreTrainedPolicy):
         Args:
             config: Policy configuration class instance.
         """
+        require_package("transformers", extra="pi")
         super().__init__(config)
         config.validate_features()
         self.config = config
diff --git a/src/lerobot/policies/pi0_fast/modeling_pi0_fast.py b/src/lerobot/policies/pi0_fast/modeling_pi0_fast.py
index e86b8ad27..a49828ad1 100644
--- a/src/lerobot/policies/pi0_fast/modeling_pi0_fast.py
+++ b/src/lerobot/policies/pi0_fast/modeling_pi0_fast.py
@@ -26,7 +26,7 @@ import torch
 import torch.nn.functional as F  # noqa: N812
 from torch import Tensor, nn
 
-from lerobot.utils.import_utils import _scipy_available, _transformers_available
+from lerobot.utils.import_utils import _scipy_available, _transformers_available, require_package
 
 # Conditional import for type checking and lazy loading
 if TYPE_CHECKING or _scipy_available:
@@ -35,7 +35,7 @@ else:
     idct = None
 
 if TYPE_CHECKING or _transformers_available:
-    from transformers import AutoTokenizer
+    from transformers import AutoProcessor, AutoTokenizer
     from transformers.models.auto import CONFIG_MAPPING
 
     from ..pi_gemma import (
@@ -44,6 +44,7 @@ if TYPE_CHECKING or _transformers_available:
     )
 else:
     CONFIG_MAPPING = None
+    AutoProcessor = None
     AutoTokenizer = None
     PiGemmaModel = None
     PaliGemmaForConditionalGenerationWithPiGemma = None
@@ -826,14 +827,14 @@ class PI0FastPolicy(PreTrainedPolicy):
         Args:
             config: Policy configuration class instance.
         """
+        require_package("transformers", extra="pi")
+        require_package("scipy", extra="pi")
         super().__init__(config)
         config.validate_features()
         self.config = config
 
         # Load tokenizers first
         try:
-            from transformers import AutoProcessor, AutoTokenizer
-
             # Load FAST tokenizer
             self.action_tokenizer = AutoProcessor.from_pretrained(
                 config.action_tokenizer_name, trust_remote_code=True
diff --git a/src/lerobot/policies/smolvla/modeling_smolvla.py b/src/lerobot/policies/smolvla/modeling_smolvla.py
index ee3ff4db9..8ddb023da 100644
--- a/src/lerobot/policies/smolvla/modeling_smolvla.py
+++ b/src/lerobot/policies/smolvla/modeling_smolvla.py
@@ -62,6 +62,7 @@ from torch import Tensor, nn
 
 from lerobot.utils.constants import ACTION, OBS_LANGUAGE_ATTENTION_MASK, OBS_LANGUAGE_TOKENS, OBS_STATE
 from lerobot.utils.device_utils import get_safe_dtype
+from lerobot.utils.import_utils import require_package
 
 from ..pretrained import PreTrainedPolicy
 from ..rtc.modeling_rtc import RTCProcessor
@@ -239,6 +240,7 @@ class SmolVLAPolicy(PreTrainedPolicy):
                     the configuration class is used.
         """
 
+        require_package("transformers", extra="smolvla")
         super().__init__(config)
         config.validate_features()
         self.config = config
diff --git a/src/lerobot/rl/buffer.py b/src/lerobot/rl/buffer.py
index 97aaa9caa..05b8419bd 100644
--- a/src/lerobot/rl/buffer.py
+++ b/src/lerobot/rl/buffer.py
@@ -15,6 +15,7 @@
 # limitations under the License.
 
 import functools
+import threading
 from collections.abc import Callable, Sequence
 from contextlib import suppress
 from typing import TypedDict
@@ -115,6 +116,7 @@ class ReplayBuffer:
         self.size = 0
         self.initialized = False
         self.optimize_memory = optimize_memory
+        self._lock = threading.Lock()
 
         # Track episode boundaries for memory optimization
         self.episode_ends = torch.zeros(capacity, dtype=torch.bool, device=storage_device)
@@ -198,68 +200,75 @@ class ReplayBuffer:
         complementary_info: dict[str, torch.Tensor] | None = None,
     ):
         """Saves a transition, ensuring tensors are stored on the designated storage device."""
-        # Initialize storage if this is the first transition
-        if not self.initialized:
-            self._initialize_storage(state=state, action=action, complementary_info=complementary_info)
+        with self._lock:
+            # Initialize storage if this is the first transition
+            if not self.initialized:
+                self._initialize_storage(state=state, action=action, complementary_info=complementary_info)
 
-        # Store the transition in pre-allocated tensors
-        for key in self.states:
-            self.states[key][self.position].copy_(state[key].squeeze(dim=0))
+            # Store the transition in pre-allocated tensors
+            for key in self.states:
+                self.states[key][self.position].copy_(state[key].squeeze(dim=0))
 
-            if not self.optimize_memory:
-                # Only store next_states if not optimizing memory
-                self.next_states[key][self.position].copy_(next_state[key].squeeze(dim=0))
+                if not self.optimize_memory:
+                    # Only store next_states if not optimizing memory
+                    self.next_states[key][self.position].copy_(next_state[key].squeeze(dim=0))
 
-        self.actions[self.position].copy_(action.squeeze(dim=0))
-        self.rewards[self.position] = reward
-        self.dones[self.position] = done
-        self.truncateds[self.position] = truncated
+            self.actions[self.position].copy_(action.squeeze(dim=0))
+            self.rewards[self.position] = reward
+            self.dones[self.position] = done
+            self.truncateds[self.position] = truncated
 
-        # Handle complementary_info if provided and storage is initialized
-        if complementary_info is not None and self.has_complementary_info:
-            # Store the complementary_info
-            for key in self.complementary_info_keys:
-                if key in complementary_info:
-                    value = complementary_info[key]
-                    if isinstance(value, torch.Tensor):
-                        self.complementary_info[key][self.position].copy_(value.squeeze(dim=0))
-                    elif isinstance(value, (int | float)):
-                        self.complementary_info[key][self.position] = value
+            # Handle complementary_info if provided and storage is initialized
+            if complementary_info is not None and self.has_complementary_info:
+                for key in self.complementary_info_keys:
+                    if key in complementary_info:
+                        value = complementary_info[key]
+                        if isinstance(value, torch.Tensor):
+                            self.complementary_info[key][self.position].copy_(value.squeeze(dim=0))
+                        elif isinstance(value, (int | float)):
+                            self.complementary_info[key][self.position] = value
 
-        self.position = (self.position + 1) % self.capacity
-        self.size = min(self.size + 1, self.capacity)
+            self.position = (self.position + 1) % self.capacity
+            self.size = min(self.size + 1, self.capacity)
 
     def sample(self, batch_size: int) -> BatchTransition:
         """Sample a random batch of transitions and collate them into batched tensors."""
         if not self.initialized:
             raise RuntimeError("Cannot sample from an empty buffer. Add transitions first.")
 
-        batch_size = min(batch_size, self.size)
-        high = max(0, self.size - 1) if self.optimize_memory and self.size < self.capacity else self.size
+        with self._lock:
+            batch_size = min(batch_size, self.size)
+            high = max(0, self.size - 1) if self.optimize_memory and self.size < self.capacity else self.size
 
-        # Random indices for sampling - create on the same device as storage
-        idx = torch.randint(low=0, high=high, size=(batch_size,), device=self.storage_device)
+            idx = torch.randint(low=0, high=high, size=(batch_size,), device=self.storage_device)
 
-        # Identify image keys that need augmentation
-        image_keys = [k for k in self.states if k.startswith(OBS_IMAGE)] if self.use_drq else []
+            image_keys = [k for k in self.states if k.startswith(OBS_IMAGE)] if self.use_drq else []
 
-        # Create batched state and next_state
-        batch_state = {}
-        batch_next_state = {}
+            batch_state = {}
+            batch_next_state = {}
 
-        # First pass: load all state tensors to target device
-        for key in self.states:
-            batch_state[key] = self.states[key][idx].to(self.device)
+            for key in self.states:
+                batch_state[key] = self.states[key][idx].to(self.device)
 
-            if not self.optimize_memory:
-                # Standard approach - load next_states directly
-                batch_next_state[key] = self.next_states[key][idx].to(self.device)
-            else:
-                # Memory-optimized approach - get next_state from the next index
-                next_idx = (idx + 1) % self.capacity
-                batch_next_state[key] = self.states[key][next_idx].to(self.device)
+                if not self.optimize_memory:
+                    batch_next_state[key] = self.next_states[key][idx].to(self.device)
+                else:
+                    next_idx = (idx + 1) % self.capacity
+                    batch_next_state[key] = self.states[key][next_idx].to(self.device)
+
+            # Sample other tensors
+            batch_actions = self.actions[idx].to(self.device)
+            batch_rewards = self.rewards[idx].to(self.device)
+            batch_dones = self.dones[idx].to(self.device).float()
+            batch_truncateds = self.truncateds[idx].to(self.device).float()
+
+            # Sample complementary_info if available
+            batch_complementary_info = None
+            if self.has_complementary_info:
+                batch_complementary_info = {}
+                for key in self.complementary_info_keys:
+                    batch_complementary_info[key] = self.complementary_info[key][idx].to(self.device)
 
-        # Apply image augmentation in a batched way if needed
         if self.use_drq and image_keys:
             # Concatenate all images from state and next_state
             all_images = []
@@ -280,19 +289,6 @@ class ReplayBuffer:
                 # Next states start after the states at index (i*2+1)*batch_size and also take up batch_size slots
                 batch_next_state[key] = augmented_images[(i * 2 + 1) * batch_size : (i + 1) * 2 * batch_size]
 
-        # Sample other tensors
-        batch_actions = self.actions[idx].to(self.device)
-        batch_rewards = self.rewards[idx].to(self.device)
-        batch_dones = self.dones[idx].to(self.device).float()
-        batch_truncateds = self.truncateds[idx].to(self.device).float()
-
-        # Sample complementary_info if available
-        batch_complementary_info = None
-        if self.has_complementary_info:
-            batch_complementary_info = {}
-            for key in self.complementary_info_keys:
-                batch_complementary_info[key] = self.complementary_info[key][idx].to(self.device)
-
         return BatchTransition(
             state=batch_state,
             action=batch_actions,
diff --git a/src/lerobot/rl/gym_manipulator.py b/src/lerobot/rl/gym_manipulator.py
index b6ff7155a..2190070f5 100644
--- a/src/lerobot/rl/gym_manipulator.py
+++ b/src/lerobot/rl/gym_manipulator.py
@@ -551,8 +551,8 @@ def step_env_and_process_transition(
     terminated = terminated or processed_action_transition[TransitionKey.DONE]
     truncated = truncated or processed_action_transition[TransitionKey.TRUNCATED]
     complementary_data = processed_action_transition[TransitionKey.COMPLEMENTARY_DATA].copy()
-    new_info = processed_action_transition[TransitionKey.INFO].copy()
-    new_info.update(info)
+    new_info = info.copy()
+    new_info.update(processed_action_transition[TransitionKey.INFO])
 
     new_transition = create_transition(
         observation=obs,
diff --git a/src/lerobot/robots/reachy2/robot_reachy2.py b/src/lerobot/robots/reachy2/robot_reachy2.py
index ef55f71b9..ac5c9ef2f 100644
--- a/src/lerobot/robots/reachy2/robot_reachy2.py
+++ b/src/lerobot/robots/reachy2/robot_reachy2.py
@@ -20,7 +20,7 @@ from typing import TYPE_CHECKING, Any
 
 from lerobot.cameras import make_cameras_from_configs
 from lerobot.types import RobotAction, RobotObservation
-from lerobot.utils.import_utils import _reachy2_sdk_available
+from lerobot.utils.import_utils import _reachy2_sdk_available, require_package
 
 from ..robot import Robot
 from ..utils import ensure_safe_goal_position
@@ -81,6 +81,7 @@ class Reachy2Robot(Robot):
     name = "reachy2"
 
     def __init__(self, config: Reachy2RobotConfig):
+        require_package("reachy2_sdk", extra="reachy2")
         super().__init__(config)
 
         self.config = config
diff --git a/src/lerobot/robots/unitree_g1/unitree_g1.py b/src/lerobot/robots/unitree_g1/unitree_g1.py
index 785861a5a..25ec32716 100644
--- a/src/lerobot/robots/unitree_g1/unitree_g1.py
+++ b/src/lerobot/robots/unitree_g1/unitree_g1.py
@@ -27,7 +27,7 @@ import numpy as np
 
 from lerobot.cameras import make_cameras_from_configs
 from lerobot.types import RobotAction, RobotObservation
-from lerobot.utils.import_utils import _unitree_sdk_available
+from lerobot.utils.import_utils import _unitree_sdk_available, require_package
 
 from ..robot import Robot
 from .config_unitree_g1 import UnitreeG1Config
@@ -111,6 +111,7 @@ class UnitreeG1(Robot):
     name = "unitree_g1"
 
     def __init__(self, config: UnitreeG1Config):
+        require_package("unitree-sdk2py", extra="unitree_g1", import_name="unitree_sdk2py")
         super().__init__(config)
 
         logger.info("Initialize UnitreeG1...")
diff --git a/src/lerobot/teleoperators/gamepad/gamepad_utils.py b/src/lerobot/teleoperators/gamepad/gamepad_utils.py
index 9f94b6746..c1531ca84 100644
--- a/src/lerobot/teleoperators/gamepad/gamepad_utils.py
+++ b/src/lerobot/teleoperators/gamepad/gamepad_utils.py
@@ -15,9 +15,22 @@
 # limitations under the License.
 
 import logging
+from typing import TYPE_CHECKING
+
+from lerobot.utils.import_utils import _hidapi_available, _pygame_available, require_package
 
 from ..utils import TeleopEvents
 
+if TYPE_CHECKING or _pygame_available:
+    import pygame
+else:
+    pygame = None  # type: ignore[assignment]
+
+if TYPE_CHECKING or _hidapi_available:
+    import hid
+else:
+    hid = None  # type: ignore[assignment]
+
 
 class InputController:
     """Base class for input controllers that generate motion deltas."""
@@ -199,6 +212,7 @@ class GamepadController(InputController):
     """Generate motion deltas from gamepad input."""
 
     def __init__(self, x_step_size=1.0, y_step_size=1.0, z_step_size=1.0, deadzone=0.1):
+        require_package("pygame", extra="gamepad")
         super().__init__(x_step_size, y_step_size, z_step_size)
         self.deadzone = deadzone
         self.joystick = None
@@ -206,8 +220,6 @@ class GamepadController(InputController):
 
     def start(self):
         """Initialize pygame and the gamepad."""
-        import pygame
-
         pygame.init()
         pygame.joystick.init()
 
@@ -230,8 +242,6 @@ class GamepadController(InputController):
 
     def stop(self):
         """Clean up pygame resources."""
-        import pygame
-
         if pygame.joystick.get_init():
             if self.joystick:
                 self.joystick.quit()
@@ -240,8 +250,6 @@ class GamepadController(InputController):
 
     def update(self):
         """Process pygame events to get fresh gamepad readings."""
-        import pygame
-
         for event in pygame.event.get():
             if event.type == pygame.JOYBUTTONDOWN:
                 if event.button == 3:
@@ -280,8 +288,6 @@ class GamepadController(InputController):
 
     def get_deltas(self):
         """Get the current movement deltas from gamepad state."""
-        import pygame
-
         try:
             # Read joystick axes
             # Left stick X and Y (typically axes 0 and 1)
@@ -326,6 +332,7 @@ class GamepadControllerHID(InputController):
             z_scale: Scaling factor for Z-axis movement
             deadzone: Joystick deadzone to prevent drift
         """
+        require_package("hidapi", extra="gamepad", import_name="hid")
         super().__init__(x_step_size, y_step_size, z_step_size)
         self.deadzone = deadzone
         self.device = None
@@ -342,8 +349,6 @@ class GamepadControllerHID(InputController):
 
     def find_device(self):
         """Look for the gamepad device by vendor and product ID."""
-        import hid
-
         devices = hid.enumerate()
         for device in devices:
             device_name = device["product_string"]
@@ -357,8 +362,6 @@ class GamepadControllerHID(InputController):
 
     def start(self):
         """Connect to the gamepad using HIDAPI."""
-        import hid
-
         self.device_info = self.find_device()
         if not self.device_info:
             self.running = False
diff --git a/src/lerobot/teleoperators/homunculus/homunculus_arm.py b/src/lerobot/teleoperators/homunculus/homunculus_arm.py
index 225235b59..4ceade847 100644
--- a/src/lerobot/teleoperators/homunculus/homunculus_arm.py
+++ b/src/lerobot/teleoperators/homunculus/homunculus_arm.py
@@ -45,7 +45,7 @@ class HomunculusArm(Teleoperator):
     name = "homunculus_arm"
 
     def __init__(self, config: HomunculusArmConfig):
-        require_package("pyserial", extra="hardware", import_name="serial")
+        require_package("pyserial", extra="pyserial-dep", import_name="serial")
         super().__init__(config)
         self.config = config
         self.serial = serial.Serial(config.port, config.baud_rate, timeout=1)
diff --git a/src/lerobot/teleoperators/homunculus/homunculus_glove.py b/src/lerobot/teleoperators/homunculus/homunculus_glove.py
index 655bae726..cd503c20a 100644
--- a/src/lerobot/teleoperators/homunculus/homunculus_glove.py
+++ b/src/lerobot/teleoperators/homunculus/homunculus_glove.py
@@ -71,7 +71,7 @@ class HomunculusGlove(Teleoperator):
     name = "homunculus_glove"
 
     def __init__(self, config: HomunculusGloveConfig):
-        require_package("pyserial", extra="hardware", import_name="serial")
+        require_package("pyserial", extra="pyserial-dep", import_name="serial")
         super().__init__(config)
         self.config = config
         self.serial = serial.Serial(config.port, config.baud_rate, timeout=1)
diff --git a/src/lerobot/teleoperators/keyboard/teleop_keyboard.py b/src/lerobot/teleoperators/keyboard/teleop_keyboard.py
index 0f1c7d7f1..6fc553d38 100644
--- a/src/lerobot/teleoperators/keyboard/teleop_keyboard.py
+++ b/src/lerobot/teleoperators/keyboard/teleop_keyboard.py
@@ -23,7 +23,7 @@ from typing import Any
 
 from lerobot.types import RobotAction
 from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
-from lerobot.utils.import_utils import _pynput_available
+from lerobot.utils.import_utils import _pynput_available, require_package
 
 from ..teleoperator import Teleoperator
 from ..utils import TeleopEvents
@@ -56,6 +56,7 @@ class KeyboardTeleop(Teleoperator):
     name = "keyboard"
 
     def __init__(self, config: KeyboardTeleopConfig):
+        require_package("pynput", extra="pynput-dep")
         super().__init__(config)
         self.config = config
         self.robot_type = config.type
diff --git a/src/lerobot/teleoperators/phone/teleop_phone.py b/src/lerobot/teleoperators/phone/teleop_phone.py
index f68843194..f1af248e4 100644
--- a/src/lerobot/teleoperators/phone/teleop_phone.py
+++ b/src/lerobot/teleoperators/phone/teleop_phone.py
@@ -21,14 +21,24 @@
 import logging
 import threading
 import time
+from typing import TYPE_CHECKING
 
-import hebi
 import numpy as np
-from teleop import Teleop
 
 from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
+from lerobot.utils.import_utils import _hebi_available, _teleop_available, require_package
 from lerobot.utils.rotation import Rotation
 
+if TYPE_CHECKING or _hebi_available:
+    import hebi
+else:
+    hebi = None
+
+if TYPE_CHECKING or _teleop_available:
+    from teleop import Teleop
+else:
+    Teleop = None
+
 from ..teleoperator import Teleoperator
 from .config_phone import PhoneConfig, PhoneOS
 
@@ -74,6 +84,8 @@ class IOSPhone(BasePhone, Teleoperator):
     name = "ios_phone"
 
     def __init__(self, config: PhoneConfig):
+        require_package("hebi-py", extra="phone", import_name="hebi")
+        require_package("teleop", extra="phone")
         super().__init__(config)
         self.config = config
         self._group = None
@@ -213,6 +225,8 @@ class AndroidPhone(BasePhone, Teleoperator):
     name = "android_phone"
 
     def __init__(self, config: PhoneConfig):
+        require_package("hebi-py", extra="phone", import_name="hebi")
+        require_package("teleop", extra="phone")
         super().__init__(config)
         self.config = config
         self._teleop = None
diff --git a/src/lerobot/teleoperators/reachy2_teleoperator/reachy2_teleoperator.py b/src/lerobot/teleoperators/reachy2_teleoperator/reachy2_teleoperator.py
index db076b20f..9afb34fd7 100644
--- a/src/lerobot/teleoperators/reachy2_teleoperator/reachy2_teleoperator.py
+++ b/src/lerobot/teleoperators/reachy2_teleoperator/reachy2_teleoperator.py
@@ -19,7 +19,7 @@ import logging
 import time
 from typing import TYPE_CHECKING
 
-from lerobot.utils.import_utils import _reachy2_sdk_available
+from lerobot.utils.import_utils import _reachy2_sdk_available, require_package
 
 if TYPE_CHECKING or _reachy2_sdk_available:
     from reachy2_sdk import ReachySDK
@@ -84,6 +84,7 @@ class Reachy2Teleoperator(Teleoperator):
     name = "reachy2_specific"
 
     def __init__(self, config: Reachy2TeleoperatorConfig):
+        require_package("reachy2_sdk", extra="reachy2")
         super().__init__(config)
 
         self.config = config
diff --git a/src/lerobot/teleoperators/unitree_g1/exo_calib.py b/src/lerobot/teleoperators/unitree_g1/exo_calib.py
index 05f5180ff..e977cd8b7 100644
--- a/src/lerobot/teleoperators/unitree_g1/exo_calib.py
+++ b/src/lerobot/teleoperators/unitree_g1/exo_calib.py
@@ -34,7 +34,7 @@ from typing import TYPE_CHECKING
 
 import numpy as np
 
-from lerobot.utils.import_utils import _serial_available
+from lerobot.utils.import_utils import _serial_available, require_package
 
 if TYPE_CHECKING or _serial_available:
     import serial
@@ -156,6 +156,7 @@ def run_exo_calibration(
     """
     Run interactive calibration for an exoskeleton arm.
     """
+    require_package("pyserial", extra="unitree_g1", import_name="serial")
     try:
         import cv2
         import matplotlib.pyplot as plt
diff --git a/src/lerobot/teleoperators/unitree_g1/exo_serial.py b/src/lerobot/teleoperators/unitree_g1/exo_serial.py
index 9b1c71891..ce5492537 100644
--- a/src/lerobot/teleoperators/unitree_g1/exo_serial.py
+++ b/src/lerobot/teleoperators/unitree_g1/exo_serial.py
@@ -76,7 +76,7 @@ class ExoskeletonArm:
     calibration: ExoskeletonCalibration | None = None
 
     def __post_init__(self):
-        require_package("pyserial", extra="hardware", import_name="serial")
+        require_package("pyserial", extra="unitree_g1", import_name="serial")
         if self.calibration_fpath.is_file():
             self._load_calibration()
 
diff --git a/src/lerobot/utils/import_utils.py b/src/lerobot/utils/import_utils.py
index 8cd24b0fa..1ec0b6375 100644
--- a/src/lerobot/utils/import_utils.py
+++ b/src/lerobot/utils/import_utils.py
@@ -115,6 +115,12 @@ _feetech_sdk_available = is_package_available("feetech-servo-sdk", import_name="
 _reachy2_sdk_available = is_package_available("reachy2_sdk")
 _can_available = is_package_available("python-can", "can")
 _unitree_sdk_available = is_package_available("unitree-sdk2py", "unitree_sdk2py")
+_pyrealsense2_available = is_package_available("pyrealsense2")
+_zmq_available = is_package_available("pyzmq", import_name="zmq")
+_hebi_available = is_package_available("hebi-py", import_name="hebi")
+_teleop_available = is_package_available("teleop")
+_placo_available = is_package_available("placo")
+_hidapi_available = is_package_available("hidapi", import_name="hid")
 
 # Data / serialization
 _pandas_available = is_package_available("pandas")
diff --git a/tests/policies/multi_task_dit/test_multi_task_dit.py b/tests/policies/multi_task_dit/test_multi_task_dit.py
index 5b70422d4..e4d456d19 100644
--- a/tests/policies/multi_task_dit/test_multi_task_dit.py
+++ b/tests/policies/multi_task_dit/test_multi_task_dit.py
@@ -147,6 +147,7 @@ def test_multi_task_dit_policy_forward(batch_size: int, state_dim: int, action_d
     )
 
     policy = MultiTaskDiTPolicy(config=config)
+    policy.to(config.device)
     policy.train()
 
     # Use preprocessor to handle tokenization
@@ -336,6 +337,7 @@ def test_multi_task_dit_policy_select_action(batch_size: int, state_dim: int, ac
     )
 
     policy = MultiTaskDiTPolicy(config=config)
+    policy.to(config.device)
     policy.eval()
     policy.reset()  # Reset queues before inference
 
@@ -390,6 +392,7 @@ def test_multi_task_dit_policy_diffusion_objective():
     config.validate_features()
 
     policy = MultiTaskDiTPolicy(config=config)
+    policy.to(config.device)
     policy.train()
 
     # Use preprocessor to handle tokenization
@@ -468,6 +471,7 @@ def test_multi_task_dit_policy_flow_matching_objective():
     config.validate_features()
 
     policy = MultiTaskDiTPolicy(config=config)
+    policy.to(config.device)
     policy.train()
 
     # Use preprocessor to handle tokenization
@@ -533,16 +537,12 @@ def test_multi_task_dit_policy_save_and_load(tmp_path):
     )
 
     policy = MultiTaskDiTPolicy(config=config)
+    policy.to(config.device)
     policy.eval()
 
-    # Get device before saving
-    device = next(policy.parameters()).device
-
     policy.save_pretrained(root)
     loaded_policy = MultiTaskDiTPolicy.from_pretrained(root, config=config)
-
-    # Explicitly move loaded_policy to the same device
-    loaded_policy.to(device)
+    loaded_policy.to(config.device)
     loaded_policy.eval()
 
     batch = create_train_batch(
@@ -565,10 +565,6 @@ def test_multi_task_dit_policy_save_and_load(tmp_path):
         with seeded_context(12):
             # Process batch through preprocessor
             processed_batch = preprocessor(batch)
-            # Move batch to the same device as the policy
-            for key in processed_batch:
-                if isinstance(processed_batch[key], torch.Tensor):
-                    processed_batch[key] = processed_batch[key].to(device)
             # Collect policy values before saving
             loss, _ = policy.forward(processed_batch)
 
@@ -608,6 +604,7 @@ def test_multi_task_dit_policy_get_optim_params():
     )
 
     policy = MultiTaskDiTPolicy(config=config)
+    policy.to(config.device)
     param_groups = policy.get_optim_params()
 
     # Should have 2 parameter groups: non-vision and vision encoder
diff --git a/tests/teleoperators/test_reachy2_teleoperator.py b/tests/teleoperators/test_reachy2_teleoperator.py
index dd8c5904c..f0274cb75 100644
--- a/tests/teleoperators/test_reachy2_teleoperator.py
+++ b/tests/teleoperators/test_reachy2_teleoperator.py
@@ -18,6 +18,11 @@ from unittest.mock import MagicMock, patch
 
 import pytest
 
+from lerobot.utils.import_utils import is_package_available
+
+if not is_package_available("reachy2_sdk"):
+    pytest.skip("reachy2_sdk not available", allow_module_level=True)
+
 from lerobot.teleoperators.reachy2_teleoperator import (
     REACHY2_ANTENNAS_JOINTS,
     REACHY2_L_ARM_JOINTS,