fix(eval): use FeatureType enum comparison instead of string value

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

.github/workflows/benchmark_tests.yml

@@ -167,9 +167,9 @@ jobs:
 
       # ── LIBERO TRAIN+EVAL SMOKE ──────────────────────────────────────────────
       # Train SmolVLA for 1 step (batch_size=1, dataset episode 0 only) then
-      # immediately runs eval inside the training loop (eval_freq=1, 1 episode).
+      # immediately runs eval inside the training loop (env_eval_freq=1, 1 episode).
       # Tests the full train→eval-within-training pipeline end-to-end.
-      - name: Run Libero train+eval smoke (1 step, eval_freq=1)
+      - name: Run Libero train+eval smoke (1 step, env_eval_freq=1)
         if: env.HF_USER_TOKEN != ''
         run: |
           docker run --name libero-train-smoke --gpus all \
@@ -196,7 +196,7 @@ jobs:
                 --output_dir=/tmp/train-smoke \
                 --steps=1 \
                 --batch_size=1 \
-                --eval_freq=1 \
+                --env_eval_freq=1 \
                 --eval.n_episodes=1 \
                 --eval.batch_size=1 \
                 --eval.use_async_envs=false \

Makefile

@@ -58,7 +58,7 @@ test-act-ete-train:
 		--dataset.episodes="[0]" \
 		--batch_size=2 \
 		--steps=4 \
-		--eval_freq=2 \
+		--env_eval_freq=2 \
 		--eval.n_episodes=1 \
 		--eval.batch_size=1 \
 		--save_freq=2 \
@@ -96,7 +96,7 @@ test-diffusion-ete-train:
 		--dataset.episodes="[0]" \
 		--batch_size=2 \
 		--steps=2 \
-		--eval_freq=2 \
+		--env_eval_freq=2 \
 		--eval.n_episodes=1 \
 		--eval.batch_size=1 \
 		--save_checkpoint=true \
@@ -126,7 +126,7 @@ test-tdmpc-ete-train:
 		--dataset.episodes="[0]" \
 		--batch_size=2 \
 		--steps=2 \
-		--eval_freq=2 \
+		--env_eval_freq=2 \
 		--eval.n_episodes=1 \
 		--eval.batch_size=1 \
 		--save_checkpoint=true \
@@ -161,7 +161,7 @@ test-smolvla-ete-train:
 		--dataset.episodes="[0]" \
 		--batch_size=2 \
 		--steps=4 \
-		--eval_freq=2 \
+		--env_eval_freq=2 \
 		--eval.n_episodes=1 \
 		--eval.batch_size=1 \
 		--save_freq=2 \

docs/source/hil_data_collection.mdx

@@ -57,11 +57,11 @@ The `lerobot-rollout --strategy.type=dagger` mode requires **teleoperators with
 
 **Compatible teleoperators:**
 
-- `openarm_mini` - OpenArm Mini
+- `bi_openarm_mini` - Bimanual OpenArm Mini
 - `so_leader` - SO100 / SO101 leader arm
 
 > [!IMPORTANT]
-> The provided commands default to `bi_openarm_follower` + `openarm_mini`.
+> The provided commands default to `bi_openarm_follower` + `bi_openarm_mini`.
 > `so_follower` + `so_leader` configs are also registered and can be used via CLI flags.
 
 ---
@@ -104,9 +104,9 @@ lerobot-rollout --strategy.type=dagger \
     --robot.right_arm_config.port=can0 \
     --robot.right_arm_config.side=right \
     --robot.cameras='{left_wrist: {type: opencv, index_or_path: "/dev/video0", width: 1280, height: 720, fps: 30}, right_wrist: {type: opencv, index_or_path: "/dev/video4", width: 1280, height: 720, fps: 30}, base: {type: opencv, index_or_path: "/dev/video2", width: 640, height: 480, fps: 30}}' \
-    --teleop.type=openarm_mini \
-    --teleop.port_left=/dev/ttyACM0 \
-    --teleop.port_right=/dev/ttyACM1 \
+    --teleop.type=bi_openarm_mini \
+    --teleop.left_arm_config.port=/dev/ttyACM0 \
+    --teleop.right_arm_config.port=/dev/ttyACM1 \
     --policy.path=outputs/pretrain/checkpoints/last/pretrained_model \
     --dataset.repo_id=your-username/rollout_hil_dataset \
     --dataset.single_task="Fold the T-shirt properly" \
@@ -131,9 +131,9 @@ lerobot-rollout --strategy.type=dagger \
     --robot.right_arm_config.port=can0 \
     --robot.right_arm_config.side=right \
     --robot.cameras='{left_wrist: {type: opencv, index_or_path: "/dev/video0", width: 1280, height: 720, fps: 30}, right_wrist: {type: opencv, index_or_path: "/dev/video4", width: 1280, height: 720, fps: 30}, base: {type: opencv, index_or_path: "/dev/video2", width: 640, height: 480, fps: 30}}' \
-    --teleop.type=openarm_mini \
-    --teleop.port_left=/dev/ttyACM0 \
-    --teleop.port_right=/dev/ttyACM1 \
+    --teleop.type=bi_openarm_mini \
+    --teleop.left_arm_config.port=/dev/ttyACM0 \
+    --teleop.right_arm_config.port=/dev/ttyACM1 \
     --policy.path=outputs/pretrain/checkpoints/last/pretrained_model \
     --dataset.repo_id=your-username/rollout_hil_rtc_dataset \
     --dataset.single_task="Fold the T-shirt properly" \

docs/source/hilserl.mdx

@@ -719,7 +719,7 @@ Example configuration for training the [reward classifier](https://huggingface.c
   "num_workers": 4,
   "steps": 5000,
   "log_freq": 10,
-  "eval_freq": 1000,
+  "env_eval_freq": 1000,
   "save_freq": 1000,
   "save_checkpoint": true,
   "seed": 2,

docs/source/inference.mdx

@@ -117,7 +117,7 @@ lerobot-rollout \
     --strategy.num_episodes=20 \
     --policy.path=outputs/pretrain/checkpoints/last/pretrained_model \
     --robot.type=bi_openarm_follower \
-    --teleop.type=openarm_mini \
+    --teleop.type=bi_openarm_mini \
     --dataset.repo_id=${HF_USER}/rollout_hil_data \
     --dataset.single_task="Fold the T-shirt"
 ```

docs/source/libero.mdx

@@ -143,7 +143,7 @@ lerobot-train \
   --batch_size=4 \
   --eval.batch_size=1 \
   --eval.n_episodes=1 \
-  --eval_freq=1000
+  --env_eval_freq=1000
 ```
 
 ## Reproducing published results

docs/source/libero_plus.mdx

@@ -173,7 +173,7 @@ lerobot-train \
     --batch_size=4 \
     --eval.batch_size=1 \
     --eval.n_episodes=1 \
-    --eval_freq=1000
+    --env_eval_freq=1000
 ```
 
 ## Relationship to LIBERO

docs/source/metaworld.mdx

@@ -120,11 +120,11 @@ lerobot-train \
   --batch_size=4 \
   --eval.batch_size=1 \
   --eval.n_episodes=1 \
-  --eval_freq=1000
+  --env_eval_freq=1000
 ```
 
 ## Practical tips
 
 - Use the one-hot task conditioning for multi-task training (MT10/MT50 conventions) so policies have explicit task context.
 - Inspect the dataset task descriptions and the `info["is_success"]` keys when writing post-processing or logging so your success metrics line up with the benchmark.
-- Adjust `batch_size`, `steps`, and `eval_freq` to match your compute budget.
+- Adjust `batch_size`, `steps`, and `env_eval_freq` to match your compute budget.

docs/source/molmoact2.mdx

@@ -103,7 +103,7 @@ accelerate launch \
   --batch_size=32 \
   --num_workers=4 \
   --log_freq=20 \
-  --eval_freq=-1 \
+  --env_eval_freq=-1 \
   --save_checkpoint=true \
   --save_freq=2000
 ```
@@ -142,7 +142,7 @@ accelerate launch \
   --batch_size=32 \
   --num_workers=4 \
   --log_freq=20 \
-  --eval_freq=-1 \
+  --env_eval_freq=-1 \
   --save_checkpoint=true \
   --save_freq=2000
 ```

docs/source/multi_gpu_training.mdx

@@ -113,52 +113,6 @@ accelerate launch --num_processes=2 $(which lerobot-train) \
   --policy=act
 ```
 
-## Training Large Models with FSDP
-
-DDP replicates the full model on every GPU, so a model that doesn't fit on one GPU won't fit under
-DDP either. For large models, use **FSDP** (Fully Sharded Data Parallel), which shards parameters,
-gradients, and optimizer state across GPUs. See the [accelerate FSDP guide](https://huggingface.co/docs/accelerate/usage_guides/fsdp) for background.
-
-An example on how to launch LeRobot training with FSDP across 4 GPUs (1 machine):
-
-```bash
-accelerate launch --config_file fsdp.yaml --num_processes=4 $(which lerobot-train) \
-  --dataset.repo_id=${HF_USER}/my_dataset \
-  --policy.type=<your_policy> \
-  --output_dir=outputs/train/my_policy_fsdp
-```
-
-A minimal `fsdp.yaml` (FSDP1; shards params/grads/optimizer — ZeRO-3-equivalent):
-
-```yaml
-compute_environment: LOCAL_MACHINE
-distributed_type: FSDP
-mixed_precision: bf16
-num_machines: 1
-num_processes: 4
-fsdp_config:
-  fsdp_version: 1
-  fsdp_sharding_strategy: FULL_SHARD # params + grads + optimizer (ZeRO-3)
-  fsdp_auto_wrap_policy: TRANSFORMER_BASED_WRAP
-  fsdp_transformer_layer_cls_to_wrap: <YourTransformerBlock> # repeated block class to shard
-  fsdp_use_orig_params: true # required: optimizer is built pre-prepare
-  fsdp_state_dict_type: FULL_STATE_DICT
-```
-
-Set `fsdp_transformer_layer_cls_to_wrap` to your model's repeated transformer-block class so each
-block is sharded as its own unit. `fsdp_use_orig_params: true` is required because LeRobot builds the
-optimizer before `accelerator.prepare()`.
-
-### FSDP checkpoints
-
-LeRobot gathers the full state dict across all ranks and the main process writes it as a single
-`model.safetensors`, loadable as usual with `Policy.from_pretrained(...)`. Two thigs to look out for:
-
-- With mixed precision, (`bf16`/`fp16`) FSDP keeps an fp32 master copy, so the checkpoint is fp32
-  (~2× the bf16 size on disk) and is cast back to the policy dtype on load.
-- **Optimizer state is not saved under FSDP**, so **resume-from-checkpoint is not supported**.
-  Saved weights are fully usable for evaluation and fine-tuning.
-
 ## Notes
 
 - The `--policy.use_amp` flag in `lerobot-train` is only used when **not** running with accelerate. When using accelerate, mixed precision is controlled by accelerate's configuration.

docs/source/multi_task_dit.mdx

@@ -314,7 +314,7 @@ lerobot-train \
   --steps=30000 \
   --save_freq=1000 \
   --log_freq=100 \
-  --eval_freq=1000 \
+  --env_eval_freq=1000 \
   --policy.type=multi_task_dit \
   --policy.device=cuda \
   --policy.horizon=32 \

docs/source/robocasa.mdx

@@ -166,7 +166,7 @@ lerobot-train \
   --output_dir=./outputs/smolvla_robocasa_CloseFridge \
   --steps=100000 \
   --batch_size=4 \
-  --eval_freq=5000 \
+  --env_eval_freq=5000 \
   --eval.batch_size=1 \
   --eval.n_episodes=5 \
   --save_freq=10000

docs/source/vlabench.mdx

@@ -165,7 +165,7 @@ lerobot-train \
   --output_dir=./outputs/smolvla_vlabench_primitive \
   --steps=100000 \
   --batch_size=4 \
-  --eval_freq=5000 \
+  --env_eval_freq=5000 \
   --eval.batch_size=1 \
   --eval.n_episodes=1 \
   --save_freq=10000

src/lerobot/common/train_utils.py

@@ -98,7 +98,6 @@ def save_checkpoint(
     postprocessor: PolicyProcessorPipeline | None = None,
     num_processes: int | None = None,
     batch_size: int | None = None,
-    model_state_dict: dict | None = None,
 ) -> None:
     """This function creates the following directory structure:
 
@@ -128,14 +127,9 @@ def save_checkpoint(
             resume. Defaults to None (not recorded).
         batch_size (int | None, optional): Per-process batch size to record for sample-exact
             resume. Defaults to None (not recorded).
-        model_state_dict: Pre-gathered full (unsharded) model state dict. Required under FSDP,
-            where `policy.state_dict()` would return sharded tensors; the caller gathers it via a
-            cross-rank collective and passes it here so rank 0 can write it directly. It holds
-            FSDP's fp32 master weights and is saved as-is (the loader casts to the policy dtype on
-            read). When None (DDP / single-GPU), the model is saved the normal way. Defaults to None.
     """
     pretrained_dir = checkpoint_dir / PRETRAINED_MODEL_DIR
-    policy.save_pretrained(pretrained_dir, state_dict=model_state_dict)
+    policy.save_pretrained(pretrained_dir)
     cfg.save_pretrained(pretrained_dir)
     if cfg.peft is not None:
         # When using PEFT, policy.save_pretrained will only write the adapter weights + config, not the

src/lerobot/common/wandb_utils.py

@@ -180,24 +180,32 @@ class WandBLogger:
                 self._wandb_custom_step_key.add(new_custom_key)
                 self._wandb.define_metric(new_custom_key, hidden=True)
 
+        batch_data = {}
         for k, v in d.items():
+            # Skip the custom step key here, it's added to the batch below.
+            if custom_step_key is not None and k == custom_step_key:
+                continue
+
+            if isinstance(v, list):
+                for i, elem in enumerate(v):
+                    if isinstance(elem, (int | float)):
+                        batch_data[f"{mode}/{k}_{i}"] = elem
+                continue
+
             if not isinstance(v, (int | float | str)):
                 logging.warning(
                     f'WandB logging of key "{k}" was ignored as its type "{type(v)}" is not handled by this wrapper.'
                 )
                 continue
 
-            # Do not log the custom step key itself.
-            if self._wandb_custom_step_key is not None and k in self._wandb_custom_step_key:
-                continue
+            batch_data[f"{mode}/{k}"] = v
 
+        if batch_data:
             if custom_step_key is not None:
-                value_custom_step = d[custom_step_key]
-                data = {f"{mode}/{k}": v, f"{mode}/{custom_step_key}": value_custom_step}
-                self._wandb.log(data)
-                continue
-
-            self._wandb.log(data={f"{mode}/{k}": v}, step=step)
+                batch_data[f"{mode}/{custom_step_key}"] = d[custom_step_key]
+                self._wandb.log(batch_data)
+            else:
+                self._wandb.log(data=batch_data, step=step)
 
     def log_video(self, video_path: str, step: int, mode: str = "train"):
         if mode not in {"train", "eval"}:

src/lerobot/configs/default.py

@@ -39,6 +39,8 @@ class DatasetConfig:
     # This reduces memory and speeds up DataLoader IPC. The training pipeline handles the conversion.
     return_uint8: bool = False
     streaming: bool = False
+    # Fraction of episodes held out per task for offline evaluation (0.0 = disabled).
+    eval_split: float = 0.0
 
     def __post_init__(self) -> None:
         if self.episodes is not None:
@@ -73,6 +75,8 @@ class EvalConfig:
     # `use_async_envs` specifies whether to use asynchronous environments (multiprocessing).
     # Defaults to True; automatically downgraded to SyncVectorEnv when batch_size=1.
     use_async_envs: bool = True
+    # Whether to record eval rollouts as a LeRobot v3.0 dataset on disk.
+    recording: bool = False
 
     def __post_init__(self) -> None:
         if self.batch_size == 0:

src/lerobot/configs/policies.py

@@ -79,6 +79,8 @@ class PreTrainedConfig(draccus.ChoiceRegistry, HubMixin, abc.ABC):  # type: igno
     # Either the repo ID of a model hosted on the Hub or a path to a directory containing weights
     # saved using `Policy.save_pretrained`. If not provided, the policy is initialized from scratch.
     pretrained_path: Path | None = None
+    # Optional Hub revision (commit hash, branch, or tag) to pin the pretrained model version.
+    pretrained_revision: str | None = None
 
     def __post_init__(self) -> None:
         if not self.device or not is_torch_device_available(self.device):

src/lerobot/configs/rewards.py

@@ -56,6 +56,8 @@ class RewardModelConfig(draccus.ChoiceRegistry, HubMixin, abc.ABC):
     device: str | None = None
 
     pretrained_path: str | None = None
+    # Optional Hub revision (commit hash, branch, or tag) to pin the pretrained reward model version.
+    pretrained_revision: str | None = None
 
     push_to_hub: bool = False
     repo_id: str | None = None

src/lerobot/configs/train.py

@@ -100,8 +100,13 @@ class TrainPipelineConfig(HubMixin):
     prefetch_factor: int = 4
     persistent_workers: bool = True
     steps: int = 100_000
-    eval_freq: int = 20_000
+    # Run policy in the simulation environment every N steps to measure reward/success (0 = disabled).
+    env_eval_freq: int = 20_000
     log_freq: int = 200
+    # Compute eval loss on held-out episodes every N steps (0 = disabled). Requires eval_split > 0.
+    eval_steps: int = 0
+    # Cap on total eval samples, split uniformly across tasks (0 = use all held-out data).
+    max_eval_samples: int = 0
     tolerance_s: float = 1e-4
     save_checkpoint: bool = True
     # Checkpoint is saved every `save_freq` training iterations and after the last training step.

src/lerobot/datasets/__init__.py

@@ -35,7 +35,7 @@ from .dataset_tools import (
     remove_feature,
     split_dataset,
 )
-from .factory import make_dataset, resolve_delta_timestamps
+from .factory import make_dataset, make_train_eval_datasets, resolve_delta_timestamps
 from .image_writer import safe_stop_image_writer
 from .io_utils import load_episodes, write_stats
 from .language import (
@@ -89,6 +89,7 @@ __all__ = [
     "get_feature_stats",
     "load_episodes",
     "make_dataset",
+    "make_train_eval_datasets",
     "merge_datasets",
     "modify_features",
     "modify_tasks",

src/lerobot/datasets/factory.py

@@ -14,6 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
+import math
 from pprint import pformat
 
 import torch
@@ -130,3 +131,81 @@ def make_dataset(cfg: TrainPipelineConfig) -> LeRobotDataset | MultiLeRobotDatas
                 dataset.meta.stats[key][stats_type] = torch.tensor(stats, dtype=torch.float32)
 
     return dataset
+
+
+def make_train_eval_datasets(
+    cfg: TrainPipelineConfig,
+) -> tuple[LeRobotDataset | MultiLeRobotDataset, LeRobotDataset | None]:
+    """Create train and optional eval datasets by splitting episodes based on eval_split.
+
+    The last ceil(n_episodes * eval_split) episodes per task are held out for evaluation.
+    If eval_split == 0.0, returns (full_dataset, None).
+    """
+    full_dataset = make_dataset(cfg)
+
+    if cfg.dataset.eval_split == 0.0:
+        return full_dataset, None
+
+    base_episodes = (
+        full_dataset.episodes if full_dataset.episodes is not None else list(range(full_dataset.num_episodes))
+    )
+
+    episode_tasks = full_dataset.meta.episodes["tasks"]
+    task_to_episodes: dict[str, list[int]] = {}
+    for ep_idx in base_episodes:
+        task_key = episode_tasks[ep_idx][0] if episode_tasks[ep_idx] else ""
+        task_to_episodes.setdefault(task_key, []).append(ep_idx)
+
+    train_episodes, eval_episodes = [], []
+    for eps in task_to_episodes.values():
+        n_eval = math.ceil(len(eps) * cfg.dataset.eval_split)
+        train_episodes.extend(eps[: len(eps) - n_eval])
+        eval_episodes.extend(eps[len(eps) - n_eval :])
+
+    if not train_episodes:
+        raise ValueError(
+            f"eval_split={cfg.dataset.eval_split} leaves 0 training episodes from {len(base_episodes)} total."
+        )
+
+    logging.info(
+        f"Train/eval split: {len(train_episodes)} train, {len(eval_episodes)} eval "
+        f"(eval_split={cfg.dataset.eval_split}, {len(task_to_episodes)} tasks)"
+    )
+
+    delta_timestamps = resolve_delta_timestamps(cfg.trainable_config, full_dataset.meta)
+
+    train_image_transforms = (
+        ImageTransforms(cfg.dataset.image_transforms) if cfg.dataset.image_transforms.enable else None
+    )
+
+    train_dataset = LeRobotDataset(
+        cfg.dataset.repo_id,
+        root=cfg.dataset.root,
+        episodes=train_episodes,
+        delta_timestamps=delta_timestamps,
+        image_transforms=train_image_transforms,
+        revision=cfg.dataset.revision,
+        video_backend=cfg.dataset.video_backend,
+        return_uint8=True,
+        tolerance_s=cfg.tolerance_s,
+    )
+
+    eval_dataset = LeRobotDataset(
+        cfg.dataset.repo_id,
+        root=cfg.dataset.root,
+        episodes=eval_episodes,
+        delta_timestamps=delta_timestamps,
+        image_transforms=None,
+        revision=cfg.dataset.revision,
+        video_backend=cfg.dataset.video_backend,
+        return_uint8=True,
+        tolerance_s=cfg.tolerance_s,
+    )
+
+    if cfg.dataset.use_imagenet_stats:
+        for ds in (train_dataset, eval_dataset):
+            for key in ds.meta.camera_keys:
+                for stats_type, stats in IMAGENET_STATS.items():
+                    ds.meta.stats[key][stats_type] = torch.tensor(stats, dtype=torch.float32)
+
+    return train_dataset, eval_dataset

src/lerobot/datasets/io_utils.py

@@ -153,7 +153,7 @@ def cast_stats_to_numpy(stats: dict) -> dict[str, dict[str, np.ndarray]]:
     Returns:
         dict: The statistics dictionary with values cast to numpy arrays.
     """
-    stats = {key: np.array(value) for key, value in flatten_dict(stats).items()}
+    stats = {key: np.atleast_1d(np.array(value)) for key, value in flatten_dict(stats).items()}
     return unflatten_dict(stats)
 
 

src/lerobot/datasets/lerobot_dataset.py

@@ -474,6 +474,8 @@ class LeRobotDataset(torch.utils.data.Dataset):
         if reader.hf_dataset is None:
             # One-shot load after finalize()
             reader.load_and_activate()
+        if reader._absolute_to_relative_idx is not None and idx in reader._absolute_to_relative_idx:
+            idx = reader._absolute_to_relative_idx[idx]
         return reader.get_item(idx)
 
     def select_columns(self, column_names: str | list[str]):

src/lerobot/envs/utils.py

@@ -126,6 +126,26 @@ def preprocess_observation(observations: dict[str, np.ndarray]) -> dict[str, Ten
     if "camera_obs" in observations:
         return_observations[f"{OBS_STR}.camera_obs"] = observations["camera_obs"]
 
+    # Pass through any remaining ndarray/tensor keys not already handled above,
+    # so env plugins can expose extra observation keys via get_env_processors().
+    _handled = {"pixels", "environment_state", "agent_pos", "robot_state", "policy", "camera_obs"}
+    for key, value in observations.items():
+        if key in _handled:
+            continue
+        target = f"{OBS_STR}.{key}"
+        if target in return_observations:
+            continue
+        if isinstance(value, np.ndarray):
+            val = torch.from_numpy(value).float()
+            if val.dim() == 1:
+                val = val.unsqueeze(0)
+            return_observations[target] = val
+        elif isinstance(value, Tensor):
+            val = value.float()
+            if val.dim() == 1:
+                val = val.unsqueeze(0)
+            return_observations[target] = val
+
     return return_observations
 
 

src/lerobot/policies/act/modeling_act.py

@@ -148,7 +148,7 @@ class ACTPolicy(PreTrainedPolicy):
         l1_loss = (abs_err * valid_mask).sum() / num_valid.clamp_min(1)
 
         loss_dict = {"l1_loss": l1_loss.item()}
-        if self.config.use_vae:
+        if self.config.use_vae and log_sigma_x2_hat is not None:
             # Calculate Dₖₗ(latent_pdf || standard_normal). Note: After computing the KL-divergence for
             # each dimension independently, we sum over the latent dimension to get the total
             # KL-divergence per batch element, then take the mean over the batch.

src/lerobot/policies/diffusion/modeling_diffusion.py

@@ -101,11 +101,23 @@ class DiffusionPolicy(PreTrainedPolicy):
 
     @torch.no_grad()
     def predict_action_chunk(self, batch: dict[str, Tensor], noise: Tensor | None = None) -> Tensor:
-        """Predict a chunk of actions given environment observations."""
-        # stack n latest observations from the queue
-        batch = {k: torch.stack(list(self._queues[k]), dim=1) for k in batch if k in self._queues}
-        actions = self.diffusion.generate_actions(batch, noise=noise)
+        """Predict a chunk of actions given environment observations.
 
+        Supports two modes:
+        - Online (queues populated via select_action): stacks observations from internal queues.
+        - Offline (empty queues, e.g. dataloader batch): uses the batch directly.
+        """
+        queues_populated = any(len(q) > 0 for q in self._queues.values())
+        if queues_populated:
+            batch = {k: torch.stack(list(self._queues[k]), dim=1) for k in batch if k in self._queues}
+        else:
+            batch = dict(batch)
+            if self.config.image_features:
+                for key in self.config.image_features:
+                    if batch[key].ndim == 4:
+                        batch[key] = batch[key].unsqueeze(1)
+                batch[OBS_IMAGES] = torch.stack([batch[key] for key in self.config.image_features], dim=-4)
+        actions = self.diffusion.generate_actions(batch, noise=noise)
         return actions
 
     @torch.no_grad()

src/lerobot/policies/factory.py

@@ -252,6 +252,7 @@ class ProcessorConfigKwargs(TypedDict, total=False):
 def make_pre_post_processors(
     policy_cfg: PreTrainedConfig,
     pretrained_path: str | None = None,
+    pretrained_revision: str | None = None,
     **kwargs: Unpack[ProcessorConfigKwargs],
 ) -> tuple[
     PolicyProcessorPipeline[dict[str, Any], dict[str, Any]],
@@ -309,6 +310,7 @@ def make_pre_post_processors(
             overrides=kwargs.get("preprocessor_overrides", {}),
             to_transition=batch_to_transition,
             to_output=transition_to_batch,
+            revision=pretrained_revision,
         )
         postprocessor = PolicyProcessorPipeline.from_pretrained(
             pretrained_model_name_or_path=pretrained_path,
@@ -318,6 +320,7 @@ def make_pre_post_processors(
             overrides=kwargs.get("postprocessor_overrides", {}),
             to_transition=policy_action_to_transition,
             to_output=transition_to_policy_action,
+            revision=pretrained_revision,
         )
         _reconnect_relative_absolute_steps(preprocessor, postprocessor)
         return preprocessor, postprocessor
@@ -557,6 +560,7 @@ def make_policy(
         # Load a pretrained policy and override the config if needed (for example, if there are inference-time
         # hyperparameters that we want to vary).
         kwargs["pretrained_name_or_path"] = cfg.pretrained_path
+        kwargs["revision"] = cfg.pretrained_revision
         policy = policy_cls.from_pretrained(**kwargs)
     elif cfg.pretrained_path and cfg.use_peft:
         # Load a pretrained PEFT model on top of the policy. The pretrained path points to the folder/repo

src/lerobot/policies/pretrained.py

@@ -23,7 +23,7 @@ from typing import TypedDict, TypeVar, Unpack
 
 import packaging
 import safetensors
-from huggingface_hub import HfApi, ModelCard, ModelCardData, hf_hub_download, save_torch_state_dict
+from huggingface_hub import HfApi, ModelCard, ModelCardData, hf_hub_download
 from huggingface_hub.constants import SAFETENSORS_SINGLE_FILE
 from huggingface_hub.errors import HfHubHTTPError
 from safetensors.torch import load_model as load_model_as_safetensor, save_model as save_model_as_safetensor
@@ -129,43 +129,10 @@ class PreTrainedPolicy(nn.Module, HubMixin, abc.ABC):
         if not getattr(cls, "name", None):
             raise TypeError(f"Class {cls.__name__} must define 'name'")
 
-    def save_pretrained(
-        self,
-        save_directory: str | Path,
-        *,
-        state_dict: dict[str, Tensor] | None = None,
-        repo_id: str | None = None,
-        push_to_hub: bool = False,
-        card_kwargs: dict | None = None,
-        **push_to_hub_kwargs,
-    ) -> str | None:
-        """Save the policy to a directory (and optionally push to the Hub).
-
-        Overrides `HubMixin.save_pretrained` to add a `state_dict` argument (mirroring
-        `transformers.PreTrainedModel.save_pretrained`). Under FSDP, `self.state_dict()` would
-        return sharded tensors, so the caller gathers the full state dict via a cross-rank
-        collective and passes it here for `_save_pretrained` to write directly.
-        """
-        save_directory = Path(save_directory)
-        save_directory.mkdir(parents=True, exist_ok=True)
-        self._save_pretrained(save_directory, state_dict=state_dict)
-        if push_to_hub:
-            if repo_id is None:
-                repo_id = save_directory.name
-            return self.push_to_hub(repo_id=repo_id, card_kwargs=card_kwargs, **push_to_hub_kwargs)
-        return None
-
-    def _save_pretrained(self, save_directory: Path, state_dict: dict[str, Tensor] | None = None) -> None:
+    def _save_pretrained(self, save_directory: Path) -> None:
         self.config._save_pretrained(save_directory)
         model_to_save = self.module if hasattr(self, "module") else self
-        if state_dict is None:
-            save_model_as_safetensor(model_to_save, str(save_directory / SAFETENSORS_SINGLE_FILE))
-            return
-        # A pre-gathered (e.g. FSDP full) state dict was supplied: write it directly.
-        # `save_torch_state_dict` discards shared-tensor duplicates just like `save_model` does;
-        # pin `max_shard_size` above the total size so the output stays a single `model.safetensors`
-        total_bytes = sum(t.numel() * t.element_size() for t in state_dict.values())
-        save_torch_state_dict(state_dict, str(save_directory), max_shard_size=max(total_bytes, 1))
+        save_model_as_safetensor(model_to_save, str(save_directory / SAFETENSORS_SINGLE_FILE))
 
     @classmethod
     def from_pretrained(

src/lerobot/rewards/factory.py

@@ -124,6 +124,7 @@ def make_reward_model(cfg: RewardModelConfig, **kwargs) -> PreTrainedRewardModel
 
     if cfg.pretrained_path:
         kwargs["pretrained_name_or_path"] = cfg.pretrained_path
+        kwargs["revision"] = cfg.pretrained_revision
         reward_model = reward_cls.from_pretrained(**kwargs)
     else:
         reward_model = reward_cls(**kwargs)

src/lerobot/robots/bi_openarm_follower/bi_openarm_follower.py

@@ -18,7 +18,8 @@ import logging
 from functools import cached_property
 
 from lerobot.types import RobotAction, RobotObservation
-from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
+from lerobot.utils.bimanual import BimanualMixin
+from lerobot.utils.decorators import check_if_not_connected
 
 from ..openarm_follower import OpenArmFollower, OpenArmFollowerConfig
 from ..robot import Robot
@@ -27,7 +28,7 @@ from .config_bi_openarm_follower import BiOpenArmFollowerConfig
 logger = logging.getLogger(__name__)
 
 
-class BiOpenArmFollower(Robot):
+class BiOpenArmFollower(BimanualMixin, Robot):
     """
     Bimanual OpenArm Follower Arms
     """
@@ -39,15 +40,17 @@ class BiOpenArmFollower(Robot):
         super().__init__(config)
         self.config = config
 
-        # Top-level cameras are distributed evenly: each arm's OpenArmFollower
-        # will only open the cameras assigned to it. Per-arm cameras are used
-        # as fallback when top-level cameras are empty.
-        if config.cameras:
-            left_cameras = config.cameras
-            right_cameras = {}
-        else:
-            left_cameras = config.left_arm_config.cameras
-            right_cameras = config.right_arm_config.cameras
+        # Top-level cameras are opened by `left_arm` for convenience, but their
+        # keys stay unprefixed in observations (tracked via `_top_level_cam_keys`).
+        self._top_level_cam_keys = set(config.cameras)
+        _collisions = self._top_level_cam_keys & set(
+            config.left_arm_config.cameras
+        ) | self._top_level_cam_keys & set(config.right_arm_config.cameras)
+        if _collisions:
+            raise ValueError(
+                f"Top-level camera names collide with per-arm camera names: {sorted(_collisions)}"
+            )
+        left_arm_cameras = {**config.left_arm_config.cameras, **config.cameras}
 
         left_arm_config = OpenArmFollowerConfig(
             id=f"{config.id}_left" if config.id else None,
@@ -56,7 +59,7 @@ class BiOpenArmFollower(Robot):
             disable_torque_on_disconnect=config.left_arm_config.disable_torque_on_disconnect,
             use_velocity_and_torque=config.left_arm_config.use_velocity_and_torque,
             max_relative_target=config.left_arm_config.max_relative_target,
-            cameras=left_cameras,
+            cameras=left_arm_cameras,
             side=config.left_arm_config.side,
             can_interface=config.left_arm_config.can_interface,
             use_can_fd=config.left_arm_config.use_can_fd,
@@ -75,7 +78,7 @@ class BiOpenArmFollower(Robot):
             disable_torque_on_disconnect=config.right_arm_config.disable_torque_on_disconnect,
             use_velocity_and_torque=config.right_arm_config.use_velocity_and_torque,
             max_relative_target=config.right_arm_config.max_relative_target,
-            cameras=right_cameras,
+            cameras=config.right_arm_config.cameras,
             side=config.right_arm_config.side,
             can_interface=config.right_arm_config.can_interface,
             use_can_fd=config.right_arm_config.use_can_fd,
@@ -95,22 +98,19 @@ class BiOpenArmFollower(Robot):
 
     @property
     def _motors_ft(self) -> dict[str, type]:
-        left_arm_motors_ft = self.left_arm._motors_ft
-        right_arm_motors_ft = self.right_arm._motors_ft
-
-        # Right first, then left — matches the teleoperator (OpenArmMini) ordering
-        # and the dataset feature names recorded during data collection.
         return {
-            **{f"right_{k}": v for k, v in right_arm_motors_ft.items()},
-            **{f"left_{k}": v for k, v in left_arm_motors_ft.items()},
+            **{f"left_{k}": v for k, v in self.left_arm._motors_ft.items()},
+            **{f"right_{k}": v for k, v in self.right_arm._motors_ft.items()},
         }
 
     @property
     def _cameras_ft(self) -> dict[str, tuple]:
-        # Cameras already have unique user-chosen names (e.g. "left_wrist", "base",
-        # "right_wrist"), so we merge them directly — unlike motors which need the
-        # left_/right_ prefix to disambiguate identical per-arm joint names.
-        return {**self.left_arm._cameras_ft, **self.right_arm._cameras_ft}
+        out: dict[str, tuple] = {}
+        for k, v in self.left_arm._cameras_ft.items():
+            out[k if k in self._top_level_cam_keys else f"left_{k}"] = v
+        for k, v in self.right_arm._cameras_ft.items():
+            out[f"right_{k}"] = v
+        return out
 
     @cached_property
     def observation_features(self) -> dict[str, type | tuple]:
@@ -120,27 +120,6 @@ class BiOpenArmFollower(Robot):
     def action_features(self) -> dict[str, type]:
         return self._motors_ft
 
-    @property
-    def is_connected(self) -> bool:
-        return self.left_arm.is_connected and self.right_arm.is_connected
-
-    @check_if_already_connected
-    def connect(self, calibrate: bool = True) -> None:
-        self.left_arm.connect(calibrate)
-        self.right_arm.connect(calibrate)
-
-    @property
-    def is_calibrated(self) -> bool:
-        return self.left_arm.is_calibrated and self.right_arm.is_calibrated
-
-    def calibrate(self) -> None:
-        self.left_arm.calibrate()
-        self.right_arm.calibrate()
-
-    def configure(self) -> None:
-        self.left_arm.configure()
-        self.right_arm.configure()
-
     def setup_motors(self) -> None:
         raise NotImplementedError(
             "Motor ID configuration is typically done via manufacturer tools for CAN motors."
@@ -148,21 +127,15 @@ class BiOpenArmFollower(Robot):
 
     @check_if_not_connected
     def get_observation(self) -> RobotObservation:
-        obs_dict = {}
+        obs_dict: RobotObservation = {}
 
-        # Camera keys that should NOT get the arm prefix (they already have unique names)
-        left_cam_keys = set(self.left_arm.cameras.keys())
-        right_cam_keys = set(self.right_arm.cameras.keys())
+        # Add "left_" prefix to per-arm keys; keep top-level camera keys unprefixed.
+        for key, value in self.left_arm.get_observation().items():
+            obs_dict[key if key in self._top_level_cam_keys else f"left_{key}"] = value
 
-        # Right first, then left — matches the teleoperator (OpenArmMini) ordering
-        # and the dataset feature names recorded during data collection.
-        right_obs = self.right_arm.get_observation()
-        for key, value in right_obs.items():
-            obs_dict[key if key in right_cam_keys else f"right_{key}"] = value
-
-        left_obs = self.left_arm.get_observation()
-        for key, value in left_obs.items():
-            obs_dict[key if key in left_cam_keys else f"left_{key}"] = value
+        # Add "right_" prefix
+        for key, value in self.right_arm.get_observation().items():
+            obs_dict[f"right_{key}"] = value
 
         return obs_dict
 
@@ -189,9 +162,4 @@ class BiOpenArmFollower(Robot):
         prefixed_sent_action_left = {f"left_{key}": value for key, value in sent_action_left.items()}
         prefixed_sent_action_right = {f"right_{key}": value for key, value in sent_action_right.items()}
 
-        return {**prefixed_sent_action_right, **prefixed_sent_action_left}
-
-    @check_if_not_connected
-    def disconnect(self):
-        self.left_arm.disconnect()
-        self.right_arm.disconnect()
+        return {**prefixed_sent_action_left, **prefixed_sent_action_right}

src/lerobot/robots/bi_openarm_follower/config_bi_openarm_follower.py

@@ -32,5 +32,7 @@ class BiOpenArmFollowerConfig(RobotConfig):
     left_arm_config: OpenArmFollowerConfigBase
     right_arm_config: OpenArmFollowerConfigBase
 
-    # Top-level cameras shared across both arms.
+    # Top-level cameras not attached to a specific side. Keys are kept as-is in
+    # observations (no `left_`/`right_` prefix). Per-arm cameras (declared on
+    # `{left,right}_arm_config.cameras`) are prefixed.
     cameras: dict[str, CameraConfig] = field(default_factory=dict)

src/lerobot/robots/bi_rebot_b601_follower/bi_rebot_b601_follower.py

@@ -18,7 +18,8 @@ import logging
 from functools import cached_property
 
 from lerobot.types import RobotAction, RobotObservation
-from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
+from lerobot.utils.bimanual import BimanualMixin
+from lerobot.utils.decorators import check_if_not_connected
 
 from ..rebot_b601_follower import RebotB601Follower, RebotB601FollowerRobotConfig
 from ..robot import Robot
@@ -27,7 +28,7 @@ from .config_bi_rebot_b601_follower import BiRebotB601FollowerConfig
 logger = logging.getLogger(__name__)
 
 
-class BiRebotB601Follower(Robot):
+class BiRebotB601Follower(BimanualMixin, Robot):
     """Bimanual Seeed Studio reBot B601-DM follower.
 
     Composes two single-arm :class:`RebotB601Follower` instances. Observation and
@@ -41,6 +42,18 @@ class BiRebotB601Follower(Robot):
         super().__init__(config)
         self.config = config
 
+        # Top-level cameras are opened by `left_arm` for convenience, but their
+        # keys stay unprefixed in observations (tracked via `_top_level_cam_keys`).
+        self._top_level_cam_keys = set(config.cameras)
+        _collisions = self._top_level_cam_keys & set(
+            config.left_arm_config.cameras
+        ) | self._top_level_cam_keys & set(config.right_arm_config.cameras)
+        if _collisions:
+            raise ValueError(
+                f"Top-level camera names collide with per-arm camera names: {sorted(_collisions)}"
+            )
+        left_arm_cameras = {**config.left_arm_config.cameras, **config.cameras}
+
         left_arm_config = RebotB601FollowerRobotConfig(
             id=f"{config.id}_left" if config.id else None,
             calibration_dir=config.calibration_dir,
@@ -49,7 +62,7 @@ class BiRebotB601Follower(Robot):
             dm_serial_baud=config.left_arm_config.dm_serial_baud,
             disable_torque_on_disconnect=config.left_arm_config.disable_torque_on_disconnect,
             max_relative_target=config.left_arm_config.max_relative_target,
-            cameras=config.left_arm_config.cameras,
+            cameras=left_arm_cameras,
             motor_can_ids=config.left_arm_config.motor_can_ids,
             pos_vel_velocity=config.left_arm_config.pos_vel_velocity,
             gripper_torque_ratio=config.left_arm_config.gripper_torque_ratio,
@@ -86,10 +99,12 @@ class BiRebotB601Follower(Robot):
 
     @property
     def _cameras_ft(self) -> dict[str, tuple]:
-        return {
-            **{f"left_{k}": v for k, v in self.left_arm._cameras_ft.items()},
-            **{f"right_{k}": v for k, v in self.right_arm._cameras_ft.items()},
-        }
+        out: dict[str, tuple] = {}
+        for k, v in self.left_arm._cameras_ft.items():
+            out[k if k in self._top_level_cam_keys else f"left_{k}"] = v
+        for k, v in self.right_arm._cameras_ft.items():
+            out[f"right_{k}"] = v
+        return out
 
     @cached_property
     def observation_features(self) -> dict[str, type | tuple]:
@@ -99,32 +114,13 @@ class BiRebotB601Follower(Robot):
     def action_features(self) -> dict[str, type]:
         return self._motors_ft
 
-    @property
-    def is_connected(self) -> bool:
-        return self.left_arm.is_connected and self.right_arm.is_connected
-
-    @check_if_already_connected
-    def connect(self, calibrate: bool = True) -> None:
-        self.left_arm.connect(calibrate)
-        self.right_arm.connect(calibrate)
-
-    @property
-    def is_calibrated(self) -> bool:
-        return self.left_arm.is_calibrated and self.right_arm.is_calibrated
-
-    def calibrate(self) -> None:
-        self.left_arm.calibrate()
-        self.right_arm.calibrate()
-
-    def configure(self) -> None:
-        self.left_arm.configure()
-        self.right_arm.configure()
-
     @check_if_not_connected
     def get_observation(self) -> RobotObservation:
-        obs_dict = {}
-        obs_dict.update({f"left_{k}": v for k, v in self.left_arm.get_observation().items()})
-        obs_dict.update({f"right_{k}": v for k, v in self.right_arm.get_observation().items()})
+        obs_dict: RobotObservation = {}
+        for k, v in self.left_arm.get_observation().items():
+            obs_dict[k if k in self._top_level_cam_keys else f"left_{k}"] = v
+        for k, v in self.right_arm.get_observation().items():
+            obs_dict[f"right_{k}"] = v
         return obs_dict
 
     @check_if_not_connected
@@ -143,8 +139,3 @@ class BiRebotB601Follower(Robot):
             **{f"left_{k}": v for k, v in sent_action_left.items()},
             **{f"right_{k}": v for k, v in sent_action_right.items()},
         }
-
-    @check_if_not_connected
-    def disconnect(self) -> None:
-        self.left_arm.disconnect()
-        self.right_arm.disconnect()

src/lerobot/robots/bi_rebot_b601_follower/config_bi_rebot_b601_follower.py

@@ -14,7 +14,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from dataclasses import dataclass
+from dataclasses import dataclass, field
+
+from lerobot.cameras import CameraConfig
 
 from ..config import RobotConfig
 from ..rebot_b601_follower import RebotB601FollowerConfig
@@ -27,3 +29,8 @@ class BiRebotB601FollowerConfig(RobotConfig):
 
     left_arm_config: RebotB601FollowerConfig
     right_arm_config: RebotB601FollowerConfig
+
+    # Top-level cameras not attached to a specific side. Keys are kept as-is in
+    # observations (no `left_`/`right_` prefix). Per-arm cameras (declared on
+    # `{left,right}_arm_config.cameras`) are prefixed.
+    cameras: dict[str, CameraConfig] = field(default_factory=dict)

src/lerobot/robots/bi_so_follower/bi_so_follower.py

@@ -18,7 +18,8 @@ import logging
 from functools import cached_property
 
 from lerobot.types import RobotAction, RobotObservation
-from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
+from lerobot.utils.bimanual import BimanualMixin
+from lerobot.utils.decorators import check_if_not_connected
 
 from ..robot import Robot
 from ..so_follower import SOFollower, SOFollowerRobotConfig
@@ -27,7 +28,7 @@ from .config_bi_so_follower import BiSOFollowerConfig
 logger = logging.getLogger(__name__)
 
 
-class BiSOFollower(Robot):
+class BiSOFollower(BimanualMixin, Robot):
     """
     [Bimanual SO Follower Arms](https://github.com/TheRobotStudio/SO-ARM100) designed by TheRobotStudio
     """
@@ -39,6 +40,18 @@ class BiSOFollower(Robot):
         super().__init__(config)
         self.config = config
 
+        # Top-level cameras are opened by `left_arm` for convenience, but their
+        # keys stay unprefixed in observations (tracked via `_top_level_cam_keys`).
+        self._top_level_cam_keys = set(config.cameras)
+        _collisions = self._top_level_cam_keys & set(
+            config.left_arm_config.cameras
+        ) | self._top_level_cam_keys & set(config.right_arm_config.cameras)
+        if _collisions:
+            raise ValueError(
+                f"Top-level camera names collide with per-arm camera names: {sorted(_collisions)}"
+            )
+        left_arm_cameras = {**config.left_arm_config.cameras, **config.cameras}
+
         left_arm_config = SOFollowerRobotConfig(
             id=f"{config.id}_left" if config.id else None,
             calibration_dir=config.calibration_dir,
@@ -46,7 +59,7 @@ class BiSOFollower(Robot):
             disable_torque_on_disconnect=config.left_arm_config.disable_torque_on_disconnect,
             max_relative_target=config.left_arm_config.max_relative_target,
             use_degrees=config.left_arm_config.use_degrees,
-            cameras=config.left_arm_config.cameras,
+            cameras=left_arm_cameras,
         )
 
         right_arm_config = SOFollowerRobotConfig(
@@ -77,13 +90,12 @@ class BiSOFollower(Robot):
 
     @property
     def _cameras_ft(self) -> dict[str, tuple]:
-        left_arm_cameras_ft = self.left_arm._cameras_ft
-        right_arm_cameras_ft = self.right_arm._cameras_ft
-
-        return {
-            **{f"left_{k}": v for k, v in left_arm_cameras_ft.items()},
-            **{f"right_{k}": v for k, v in right_arm_cameras_ft.items()},
-        }
+        out: dict[str, tuple] = {}
+        for k, v in self.left_arm._cameras_ft.items():
+            out[k if k in self._top_level_cam_keys else f"left_{k}"] = v
+        for k, v in self.right_arm._cameras_ft.items():
+            out[f"right_{k}"] = v
+        return out
 
     @cached_property
     def observation_features(self) -> dict[str, type | tuple]:
@@ -93,42 +105,21 @@ class BiSOFollower(Robot):
     def action_features(self) -> dict[str, type]:
         return self._motors_ft
 
-    @property
-    def is_connected(self) -> bool:
-        return self.left_arm.is_connected and self.right_arm.is_connected
-
-    @check_if_already_connected
-    def connect(self, calibrate: bool = True) -> None:
-        self.left_arm.connect(calibrate)
-        self.right_arm.connect(calibrate)
-
-    @property
-    def is_calibrated(self) -> bool:
-        return self.left_arm.is_calibrated and self.right_arm.is_calibrated
-
-    def calibrate(self) -> None:
-        self.left_arm.calibrate()
-        self.right_arm.calibrate()
-
-    def configure(self) -> None:
-        self.left_arm.configure()
-        self.right_arm.configure()
-
     def setup_motors(self) -> None:
         self.left_arm.setup_motors()
         self.right_arm.setup_motors()
 
     @check_if_not_connected
     def get_observation(self) -> RobotObservation:
-        obs_dict = {}
+        obs_dict: RobotObservation = {}
 
-        # Add "left_" prefix
-        left_obs = self.left_arm.get_observation()
-        obs_dict.update({f"left_{key}": value for key, value in left_obs.items()})
+        # Add "left_" prefix to per-arm keys; keep top-level camera keys unprefixed.
+        for key, value in self.left_arm.get_observation().items():
+            obs_dict[key if key in self._top_level_cam_keys else f"left_{key}"] = value
 
         # Add "right_" prefix
-        right_obs = self.right_arm.get_observation()
-        obs_dict.update({f"right_{key}": value for key, value in right_obs.items()})
+        for key, value in self.right_arm.get_observation().items():
+            obs_dict[f"right_{key}"] = value
 
         return obs_dict
 
@@ -151,8 +142,3 @@ class BiSOFollower(Robot):
         prefixed_sent_action_right = {f"right_{key}": value for key, value in sent_action_right.items()}
 
         return {**prefixed_sent_action_left, **prefixed_sent_action_right}
-
-    @check_if_not_connected
-    def disconnect(self):
-        self.left_arm.disconnect()
-        self.right_arm.disconnect()

src/lerobot/robots/bi_so_follower/config_bi_so_follower.py

@@ -14,7 +14,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from dataclasses import dataclass
+from dataclasses import dataclass, field
+
+from lerobot.cameras import CameraConfig
 
 from ..config import RobotConfig
 from ..so_follower import SOFollowerConfig
@@ -27,3 +29,8 @@ class BiSOFollowerConfig(RobotConfig):
 
     left_arm_config: SOFollowerConfig
     right_arm_config: SOFollowerConfig
+
+    # Top-level cameras not attached to a specific side. Keys are kept as-is in
+    # observations (no `left_`/`right_` prefix). Per-arm cameras (declared on
+    # `{left,right}_arm_config.cameras`) are prefixed.
+    cameras: dict[str, CameraConfig] = field(default_factory=dict)

src/lerobot/scripts/lerobot_calibrate.py

@@ -54,6 +54,7 @@ from lerobot.teleoperators import (  # noqa: F401
     Teleoperator,
     TeleoperatorConfig,
     bi_openarm_leader,
+    bi_openarm_mini,
     bi_rebot_102_leader,
     bi_so_leader,
     homunculus,

src/lerobot/scripts/lerobot_eval.py

@@ -72,8 +72,9 @@ from termcolor import colored
 from torch import Tensor, nn
 from tqdm import trange
 
-from lerobot.configs import parser
+from lerobot.configs import FeatureType, parser
 from lerobot.configs.eval import EvalPipelineConfig
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.envs import (
     check_env_attributes_and_types,
     close_envs,
@@ -84,7 +85,7 @@ from lerobot.envs import (
 from lerobot.policies import PreTrainedPolicy, make_policy, make_pre_post_processors
 from lerobot.processor import PolicyProcessorPipeline
 from lerobot.types import PolicyAction
-from lerobot.utils.constants import ACTION, DONE, OBS_STR, REWARD
+from lerobot.utils.constants import ACTION, DONE, OBS_IMAGE, OBS_IMAGES, OBS_STR, REWARD
 from lerobot.utils.device_utils import get_safe_torch_device
 from lerobot.utils.import_utils import register_third_party_plugins
 from lerobot.utils.io_utils import write_video
@@ -95,6 +96,81 @@ from lerobot.utils.utils import (
 )
 
 
+def _env_features_to_dataset_features(env_features: dict, raw_obs: dict | None = None) -> dict:
+    """Convert EnvConfig.features (PolicyFeature objects) to the plain dict format for LeRobotDataset.create().
+
+    If raw_obs is provided, visual feature shapes are inferred from the actual observation
+    to avoid mismatches between the env config and the real observation resolution.
+    """
+    features = {}
+    for key, ft in env_features.items():
+        if ft.type is FeatureType.VISUAL:
+            shape = tuple(ft.shape)
+            if raw_obs is not None and key in raw_obs and isinstance(raw_obs[key], np.ndarray):
+                shape = raw_obs[key].shape[1:]  # strip batch dim
+            elif raw_obs is not None and "pixels" in raw_obs:
+                pixels = raw_obs["pixels"]
+                if isinstance(pixels, dict):
+                    for cam_name, img in pixels.items():
+                        if key == f"{OBS_IMAGES}.{cam_name}" or key == cam_name:
+                            shape = img.shape[1:]  # strip batch dim
+                elif key in ("pixels", OBS_IMAGE):
+                    shape = pixels.shape[1:]  # strip batch dim
+            features[key] = {"dtype": "video", "shape": shape, "names": ["height", "width", "channel"]}
+        else:
+            shape = tuple(ft.shape)
+            if raw_obs is not None and key in raw_obs and isinstance(raw_obs[key], np.ndarray):
+                shape = raw_obs[key].shape[1:]  # strip batch dim
+            features[key] = {"dtype": "float32", "shape": shape, "names": None}
+    features["next.reward"] = {"dtype": "float32", "shape": (1,), "names": None}
+    features["next.success"] = {"dtype": "bool", "shape": (1,), "names": None}
+    features["next.done"] = {"dtype": "bool", "shape": (1,), "names": None}
+    return features
+
+
+def _build_raw_frame(
+    raw_obs: dict,
+    env_idx: int,
+    action: np.ndarray,
+    reward: float,
+    success: bool,
+    done: bool,
+    task: str,
+    env_features: dict,
+) -> dict:
+    """Build a dataset frame from raw env observations for one env index.
+
+    Keys in the frame match the keys in env_features so they align with the
+    dataset schema created by _env_features_to_dataset_features().
+    """
+    frame: dict[str, Any] = {}
+    for key in env_features:
+        if key == ACTION:
+            continue
+        if "pixels" in raw_obs and isinstance(raw_obs["pixels"], dict):
+            for cam_name, img in raw_obs["pixels"].items():
+                candidate = f"{OBS_IMAGES}.{cam_name}"
+                if candidate == key:
+                    frame[key] = img[env_idx]
+            if key in frame:
+                continue
+        if "pixels" in raw_obs and not isinstance(raw_obs["pixels"], dict) and key in ("pixels", OBS_IMAGE):
+            frame[key] = raw_obs["pixels"][env_idx]
+            continue
+        raw_key = key
+        if raw_key in raw_obs and isinstance(raw_obs[raw_key], np.ndarray):
+            val = raw_obs[raw_key][env_idx]
+            if val.dtype == np.float64:
+                val = val.astype(np.float32)
+            frame[key] = val
+    frame[ACTION] = action
+    frame["next.reward"] = np.atleast_1d(np.float32(reward))
+    frame["next.success"] = np.atleast_1d(np.bool_(success))
+    frame["next.done"] = np.atleast_1d(np.bool_(done))
+    frame["task"] = task
+    return frame
+
+
 def rollout(
     env: gym.vector.VectorEnv,
     policy: PreTrainedPolicy,
@@ -105,6 +181,7 @@ def rollout(
     seeds: list[int] | None = None,
     return_observations: bool = False,
     render_callback: Callable[[gym.vector.VectorEnv], None] | None = None,
+    recording_dataset: Any | None = None,
 ) -> dict:
     """Run a batched policy rollout once through a batch of environments.
 
@@ -145,6 +222,14 @@ def rollout(
     if render_callback is not None:
         render_callback(env)
 
+    raw_observation = deepcopy(observation) if recording_dataset is not None else None
+    task_desc = ""
+    if recording_dataset is not None:
+        try:
+            task_desc = list(env.call("task_description"))[0]
+        except (AttributeError, NotImplementedError):
+            task_desc = ""
+
     all_observations = []
     all_actions = []
     all_rewards = []
@@ -217,6 +302,26 @@ def rollout(
         else:
             successes = [False] * env.num_envs
 
+        if recording_dataset is not None and raw_observation is not None:
+            prev_done = done.copy()
+            for env_idx in range(env.num_envs):
+                if prev_done[env_idx]:
+                    continue
+                frame = _build_raw_frame(
+                    raw_observation,
+                    env_idx,
+                    action_numpy[env_idx],
+                    reward[env_idx],
+                    successes[env_idx],
+                    bool(terminated[env_idx] | truncated[env_idx]),
+                    task_desc,
+                    recording_dataset.features,
+                )
+                recording_dataset.add_frame(frame)
+                if terminated[env_idx] or truncated[env_idx]:
+                    recording_dataset.save_episode()
+            raw_observation = deepcopy(observation)
+
         # Keep track of which environments are done so far.
         # Mark the episode as done if we reach the maximum step limit.
         # This ensures that the rollout always terminates cleanly at `max_steps`,
@@ -273,6 +378,7 @@ def eval_policy(
     videos_dir: Path | None = None,
     return_episode_data: bool = False,
     start_seed: int | None = None,
+    recording_dataset: Any | None = None,
 ) -> dict:
     """
     Args:
@@ -361,6 +467,7 @@ def eval_policy(
             seeds=list(seeds) if seeds else None,
             return_observations=return_episode_data,
             render_callback=render_frame if max_episodes_rendered > 0 else None,
+            recording_dataset=recording_dataset,
         )
 
         # Figure out where in each rollout sequence the first done condition was encountered (results after
@@ -563,6 +670,10 @@ def eval_main(cfg: EvalPipelineConfig):
     # Create environment-specific preprocessor and postprocessor (e.g., for LIBERO environments)
     env_preprocessor, env_postprocessor = make_env_pre_post_processors(env_cfg=cfg.env, policy_cfg=cfg.policy)
 
+    recording_dir = Path(cfg.output_dir) / "recordings" if cfg.eval.recording else None
+    max_episodes_rendered = 0 if cfg.eval.recording else 10
+    videos_dir = None if cfg.eval.recording else Path(cfg.output_dir) / "videos"
+
     with torch.no_grad(), torch.autocast(device_type=device.type) if cfg.policy.use_amp else nullcontext():
         info = eval_policy_all(
             envs=envs,
@@ -572,10 +683,13 @@ def eval_main(cfg: EvalPipelineConfig):
             preprocessor=preprocessor,
             postprocessor=postprocessor,
             n_episodes=cfg.eval.n_episodes,
-            max_episodes_rendered=10,
-            videos_dir=Path(cfg.output_dir) / "videos",
+            max_episodes_rendered=max_episodes_rendered,
+            videos_dir=videos_dir,
+            return_episode_data=False,
             start_seed=cfg.seed,
             max_parallel_tasks=cfg.env.max_parallel_tasks,
+            recording_dir=recording_dir,
+            env_features=cfg.env.features if cfg.eval.recording else None,
         )
         print("Overall Aggregated Metrics:")
         print(info["overall"])
@@ -618,6 +732,7 @@ def eval_one(
     videos_dir: Path | None,
     return_episode_data: bool,
     start_seed: int | None,
+    recording_dataset: Any | None = None,
 ) -> TaskMetrics:
     """Evaluates one task_id of one suite using the provided vec env."""
 
@@ -635,6 +750,7 @@ def eval_one(
         videos_dir=task_videos_dir,
         return_episode_data=return_episode_data,
         start_seed=start_seed,
+        recording_dataset=recording_dataset,
     )
 
     per_episode = task_result["per_episode"]
@@ -661,6 +777,8 @@ def run_one(
     videos_dir: Path | None,
     return_episode_data: bool,
     start_seed: int | None,
+    recording_dir: Path | None = None,
+    env_features: dict | None = None,
 ):
     """
     Run eval_one for a single (task_group, task_id, env).
@@ -672,21 +790,39 @@ def run_one(
         task_videos_dir = videos_dir / f"{task_group}_{task_id}"
         task_videos_dir.mkdir(parents=True, exist_ok=True)
 
-    # Call the existing eval_one (assumed to return TaskMetrics-like dict)
-    metrics = eval_one(
-        env,
-        policy=policy,
-        env_preprocessor=env_preprocessor,
-        env_postprocessor=env_postprocessor,
-        preprocessor=preprocessor,
-        postprocessor=postprocessor,
-        n_episodes=n_episodes,
-        max_episodes_rendered=max_episodes_rendered,
-        videos_dir=task_videos_dir,
-        return_episode_data=return_episode_data,
-        start_seed=start_seed,
-    )
-    # ensure we always provide video_paths key to simplify accumulation
+    recording_dataset = None
+    if recording_dir is not None and env_features is not None:
+        task_recording_dir = recording_dir / f"{task_group}_{task_id}"
+        fps = env.unwrapped.metadata.get("render_fps", 30)
+        sample_obs, _ = env.reset()
+        features = _env_features_to_dataset_features(env_features, raw_obs=sample_obs)
+        recording_dataset = LeRobotDataset.create(
+            repo_id=f"eval_{task_group}_{task_id}",
+            fps=fps,
+            features=features,
+            root=str(task_recording_dir),
+            use_videos=True,
+        )
+
+    try:
+        metrics = eval_one(
+            env,
+            policy=policy,
+            env_preprocessor=env_preprocessor,
+            env_postprocessor=env_postprocessor,
+            preprocessor=preprocessor,
+            postprocessor=postprocessor,
+            n_episodes=n_episodes,
+            max_episodes_rendered=max_episodes_rendered,
+            videos_dir=task_videos_dir,
+            return_episode_data=return_episode_data,
+            start_seed=start_seed,
+            recording_dataset=recording_dataset,
+        )
+    finally:
+        if recording_dataset is not None:
+            recording_dataset.finalize()
+
     if max_episodes_rendered > 0:
         metrics.setdefault("video_paths", [])
     return task_group, task_id, metrics
@@ -702,6 +838,8 @@ def eval_policy_all(
     n_episodes: int,
     *,
     max_episodes_rendered: int = 0,
+    recording_dir: Path | None = None,
+    env_features: dict | None = None,
     videos_dir: Path | None = None,
     return_episode_data: bool = False,
     start_seed: int | None = None,
@@ -761,6 +899,8 @@ def eval_policy_all(
         videos_dir=videos_dir,
         return_episode_data=return_episode_data,
         start_seed=start_seed,
+        recording_dir=recording_dir,
+        env_features=env_features,
     )
 
     if max_parallel_tasks <= 1:

src/lerobot/scripts/lerobot_find_joint_limits.py

@@ -57,6 +57,7 @@ from lerobot.robots import (  # noqa: F401
 from lerobot.teleoperators import (  # noqa: F401
     TeleoperatorConfig,
     bi_openarm_leader,
+    bi_openarm_mini,
     bi_rebot_102_leader,
     bi_so_leader,
     gamepad,

src/lerobot/scripts/lerobot_record.py

@@ -137,6 +137,7 @@ from lerobot.teleoperators import (  # noqa: F401
     Teleoperator,
     TeleoperatorConfig,
     bi_openarm_leader,
+    bi_openarm_mini,
     bi_rebot_102_leader,
     bi_so_leader,
     homunculus,

src/lerobot/scripts/lerobot_rollout.py

@@ -174,6 +174,7 @@ from lerobot.teleoperators import (  # noqa: F401
     Teleoperator,
     TeleoperatorConfig,
     bi_openarm_leader,
+    bi_openarm_mini,
     bi_rebot_102_leader,
     bi_so_leader,
     homunculus,

src/lerobot/scripts/lerobot_setup_motors.py

@@ -41,6 +41,7 @@ from lerobot.robots import (  # noqa: F401
 )
 from lerobot.teleoperators import (  # noqa: F401
     TeleoperatorConfig,
+    bi_openarm_mini,
     bi_rebot_102_leader,
     bi_so_leader,
     koch_leader,

src/lerobot/scripts/lerobot_teleoperate.py

@@ -89,6 +89,7 @@ from lerobot.teleoperators import (  # noqa: F401
     Teleoperator,
     TeleoperatorConfig,
     bi_openarm_leader,
+    bi_openarm_mini,
     bi_rebot_102_leader,
     bi_so_leader,
     gamepad,

src/lerobot/scripts/lerobot_train.py

@@ -45,7 +45,8 @@ from lerobot.common.train_utils import (
 from lerobot.common.wandb_utils import WandBLogger
 from lerobot.configs import parser
 from lerobot.configs.train import TrainPipelineConfig
-from lerobot.datasets import EpisodeAwareSampler, compute_sampler_state, make_dataset
+from lerobot.datasets import EpisodeAwareSampler, compute_sampler_state
+from lerobot.datasets.factory import make_train_eval_datasets
 from lerobot.envs import close_envs, make_env, make_env_pre_post_processors
 from lerobot.optim.factory import make_optimizer_and_scheduler
 from lerobot.policies import PreTrainedPolicy, make_policy, make_pre_post_processors
@@ -189,7 +190,6 @@ def train(cfg: TrainPipelineConfig, accelerator: "Accelerator | None" = None):
 
     require_package("accelerate", extra="training")
     from accelerate import Accelerator
-    from accelerate.utils import DistributedDataParallelKwargs, DistributedType
 
     cfg.validate()
 
@@ -198,6 +198,8 @@ def train(cfg: TrainPipelineConfig, accelerator: "Accelerator | None" = None):
     # We set step_scheduler_with_optimizer=False to prevent accelerate from adjusting the lr_scheduler steps based on the num_processes
     # We set find_unused_parameters=True to handle models with conditional computation
     if accelerator is None:
+        from accelerate.utils import DistributedDataParallelKwargs
+
         ddp_kwargs = DistributedDataParallelKwargs(find_unused_parameters=True)
         # Accelerate auto-detects the device based on the available hardware and ignores the policy.device setting.
         # Force the device to be CPU when the active config's device is set to CPU (works for both policy and reward model training).
@@ -243,19 +245,19 @@ def train(cfg: TrainPipelineConfig, accelerator: "Accelerator | None" = None):
     # LeRobotDataset skips its snapshot_download when try_load() succeeds, so no rank re-downloads.
     if is_main_process:
         logging.info("Creating dataset")
-        dataset = make_dataset(cfg)
+        dataset, eval_dataset = make_train_eval_datasets(cfg)
 
     accelerator.wait_for_everyone()
 
     # Other ranks read from the shared copy populated by the main process.
     if not is_main_process:
-        dataset = make_dataset(cfg)
+        dataset, eval_dataset = make_train_eval_datasets(cfg)
 
     # Create environment used for evaluating checkpoints during training on simulation data.
     # On real-world data, no need to create an environment as evaluations are done outside train.py,
     # using the eval.py instead, with gym_dora environment and dora-rs.
     eval_env = None
-    if cfg.eval_freq > 0 and cfg.env is not None and is_main_process:
+    if cfg.env_eval_freq > 0 and cfg.env is not None and is_main_process:
         logging.info("Creating env")
         eval_env = make_env(cfg.env, n_envs=cfg.eval.batch_size, use_async_envs=cfg.eval.use_async_envs)
 
@@ -344,6 +346,7 @@ def train(cfg: TrainPipelineConfig, accelerator: "Accelerator | None" = None):
         preprocessor, postprocessor = make_pre_post_processors(
             policy_cfg=cfg.policy,
             pretrained_path=processor_pretrained_path,
+            pretrained_revision=getattr(cfg.policy, "pretrained_revision", None),
             **processor_kwargs,
         )
 
@@ -454,6 +457,31 @@ def train(cfg: TrainPipelineConfig, accelerator: "Accelerator | None" = None):
         persistent_workers=cfg.persistent_workers and cfg.num_workers > 0,
     )
 
+    # Build eval dataloader if a held-out split exists
+    eval_dataloader = None
+    if eval_dataset is not None:
+        eval_ds = eval_dataset
+        if cfg.max_eval_samples > 0 and hasattr(eval_dataset, "hf_dataset"):
+            task_indices = eval_dataset.hf_dataset["task_index"]
+            unique_tasks = sorted(set(task_indices))
+            per_task = max(1, cfg.max_eval_samples // len(unique_tasks))
+            selected: list[int] = []
+            for t in unique_tasks:
+                frames = [i for i, ti in enumerate(task_indices) if ti == t][:per_task]
+                selected.extend(frames)
+            eval_ds = torch.utils.data.Subset(eval_dataset, selected)
+
+        eval_collate_fn = lerobot_collate_fn if dataset.meta.has_language_columns else None
+        eval_dataloader = torch.utils.data.DataLoader(
+            eval_ds,
+            batch_size=cfg.batch_size,
+            shuffle=False,
+            num_workers=cfg.num_workers,
+            pin_memory=device.type == "cuda",
+            drop_last=False,
+            collate_fn=eval_collate_fn,
+        )
+
     # Prepare everything with accelerator
     accelerator.wait_for_everyone()
     policy, optimizer, dataloader, lr_scheduler = accelerator.prepare(
@@ -533,7 +561,8 @@ def train(cfg: TrainPipelineConfig, accelerator: "Accelerator | None" = None):
         train_tracker.step()
         is_log_step = cfg.log_freq > 0 and step % cfg.log_freq == 0
         is_saving_step = step % cfg.save_freq == 0 or step == cfg.steps
-        is_eval_step = cfg.eval_freq > 0 and step % cfg.eval_freq == 0
+        is_env_eval_step = cfg.env_eval_freq > 0 and step % cfg.env_eval_freq == 0
+        is_eval_step = cfg.eval_steps > 0 and eval_dataloader is not None and step % cfg.eval_steps == 0
 
         if is_log_step:
             # Collective reduce must run on every rank, before the main-process gate below.
@@ -556,32 +585,42 @@ def train(cfg: TrainPipelineConfig, accelerator: "Accelerator | None" = None):
                     wandb_logger.log_dict(wandb_log_dict, step)
             train_tracker.reset_averages()
 
+        if is_eval_step:
+            policy.eval()
+            eval_loss_sum = 0.0
+            n_eval_batches = 0
+            with torch.no_grad(), accelerator.autocast():
+                for eval_batch in eval_dataloader:
+                    for cam_key in dataset.meta.camera_keys:
+                        if cam_key in eval_batch and eval_batch[cam_key].dtype == torch.uint8:
+                            eval_batch[cam_key] = eval_batch[cam_key].to(dtype=torch.float32) / 255.0
+                    eval_batch = preprocessor(eval_batch)
+                    loss, _ = policy.forward(eval_batch)
+                    eval_loss_sum += loss.item()
+                    n_eval_batches += 1
+            eval_loss = eval_loss_sum / max(n_eval_batches, 1)
+            policy.train()
+
+            if is_main_process:
+                logging.info(f"step {step}: eval_loss={eval_loss:.4f}")
+                if wandb_logger:
+                    wandb_logger.log_dict({"eval_loss": eval_loss}, step=step, mode="eval")
+
         if cfg.save_checkpoint and is_saving_step:
-            # All ranks must call get_state_dict; rank 0 gets the
-            # full state dict, others get an empty dict.
-            is_fsdp = accelerator.distributed_type == DistributedType.FSDP
-            model_state_dict = accelerator.get_state_dict(policy)
             if is_main_process:
                 logging.info(f"Checkpoint policy after step {step}")
                 checkpoint_dir = get_step_checkpoint_dir(cfg.output_dir, cfg.steps, step)
-                if is_fsdp:
-                    # TODO(fsdp): sharded optimizer-state save/resume is not wired up yet.
-                    logging.warning(
-                        "FSDP checkpoint: saving model weights only (optimizer state skipped; "
-                        "resume-from-checkpoint not supported under FSDP yet)."
-                    )
                 save_checkpoint(
                     checkpoint_dir=checkpoint_dir,
                     step=step,
                     cfg=cfg,
                     policy=accelerator.unwrap_model(policy),
-                    optimizer=None if is_fsdp else optimizer,
+                    optimizer=optimizer,
                     scheduler=lr_scheduler,
                     preprocessor=preprocessor,
                     postprocessor=postprocessor,
                     num_processes=accelerator.num_processes,
                     batch_size=cfg.batch_size,
-                    model_state_dict=model_state_dict,
                 )
                 update_last_checkpoint(checkpoint_dir)
                 if wandb_logger:
@@ -589,7 +628,7 @@ def train(cfg: TrainPipelineConfig, accelerator: "Accelerator | None" = None):
 
             accelerator.wait_for_everyone()
 
-        if cfg.env and is_eval_step:
+        if cfg.env and is_env_eval_step:
             if is_main_process:
                 step_id = get_step_identifier(step, cfg.steps)
                 logging.info(f"Eval policy at step {step}")

src/lerobot/teleoperators/bi_openarm_leader/bi_openarm_leader.py

@@ -18,7 +18,8 @@ import logging
 from functools import cached_property
 
 from lerobot.types import RobotAction
-from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
+from lerobot.utils.bimanual import BimanualMixin
+from lerobot.utils.decorators import check_if_not_connected
 
 from ..openarm_leader import OpenArmLeader, OpenArmLeaderConfig
 from ..teleoperator import Teleoperator
@@ -27,7 +28,7 @@ from .config_bi_openarm_leader import BiOpenArmLeaderConfig
 logger = logging.getLogger(__name__)
 
 
-class BiOpenArmLeader(Teleoperator):
+class BiOpenArmLeader(BimanualMixin, Teleoperator):
     """
     Bimanual OpenArm Leader Arms
     """
@@ -86,27 +87,6 @@ class BiOpenArmLeader(Teleoperator):
     def feedback_features(self) -> dict[str, type]:
         return {}
 
-    @property
-    def is_connected(self) -> bool:
-        return self.left_arm.is_connected and self.right_arm.is_connected
-
-    @check_if_already_connected
-    def connect(self, calibrate: bool = True) -> None:
-        self.left_arm.connect(calibrate)
-        self.right_arm.connect(calibrate)
-
-    @property
-    def is_calibrated(self) -> bool:
-        return self.left_arm.is_calibrated and self.right_arm.is_calibrated
-
-    def calibrate(self) -> None:
-        self.left_arm.calibrate()
-        self.right_arm.calibrate()
-
-    def configure(self) -> None:
-        self.left_arm.configure()
-        self.right_arm.configure()
-
     def setup_motors(self) -> None:
         raise NotImplementedError(
             "Motor ID configuration is typically done via manufacturer tools for CAN motors."
@@ -129,8 +109,3 @@ class BiOpenArmLeader(Teleoperator):
     def send_feedback(self, feedback: dict[str, float]) -> None:
         # TODO: Implement force feedback
         raise NotImplementedError
-
-    @check_if_not_connected
-    def disconnect(self) -> None:
-        self.left_arm.disconnect()
-        self.right_arm.disconnect()

src/lerobot/teleoperators/bi_openarm_leader/config_bi_openarm_leader.py

@@ -23,7 +23,7 @@ from ..openarm_leader import OpenArmLeaderConfigBase
 @TeleoperatorConfig.register_subclass("bi_openarm_leader")
 @dataclass
 class BiOpenArmLeaderConfig(TeleoperatorConfig):
-    """Configuration class for Bi OpenArm Follower robots."""
+    """Configuration class for Bi OpenArm Leader teleoperators."""
 
     left_arm_config: OpenArmLeaderConfigBase
     right_arm_config: OpenArmLeaderConfigBase

src/lerobot/teleoperators/bi_openarm_mini/__init__.py

@@ -0,0 +1,20 @@
+#!/usr/bin/env python
+
+# Copyright 2026 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 .bi_openarm_mini import BiOpenArmMini
+from .config_bi_openarm_mini import BiOpenArmMiniConfig
+
+__all__ = ["BiOpenArmMini", "BiOpenArmMiniConfig"]

src/lerobot/teleoperators/bi_openarm_mini/bi_openarm_mini.py

@@ -0,0 +1,101 @@
+#!/usr/bin/env python
+
+# Copyright 2026 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
+from functools import cached_property
+
+from lerobot.types import RobotAction
+from lerobot.utils.bimanual import BimanualMixin
+from lerobot.utils.decorators import check_if_not_connected
+
+from ..openarm_mini import OpenArmMini, OpenArmMiniConfig
+from ..teleoperator import Teleoperator
+from .config_bi_openarm_mini import BiOpenArmMiniConfig
+
+logger = logging.getLogger(__name__)
+
+
+class BiOpenArmMini(BimanualMixin, Teleoperator):
+    """Bimanual OpenArm Mini teleoperator.
+
+    Composes two single-arm :class:`OpenArmMini` instances. Action and feedback
+    keys of each arm are namespaced with a ``left_`` / ``right_`` prefix, so a
+    bimanual leader can teleoperate a bimanual OpenArm follower.
+    """
+
+    config_class = BiOpenArmMiniConfig
+    name = "bi_openarm_mini"
+
+    def __init__(self, config: BiOpenArmMiniConfig):
+        super().__init__(config)
+        self.config = config
+
+        # `side` is forced to match left/right regardless of what the user passed
+        # on the per-arm base config — the bimanual wrapper owns the side semantics.
+        left_arm_config = OpenArmMiniConfig(
+            id=f"{config.id}_left" if config.id else None,
+            calibration_dir=config.calibration_dir,
+            port=config.left_arm_config.port,
+            side="left",
+            use_degrees=config.left_arm_config.use_degrees,
+        )
+
+        right_arm_config = OpenArmMiniConfig(
+            id=f"{config.id}_right" if config.id else None,
+            calibration_dir=config.calibration_dir,
+            port=config.right_arm_config.port,
+            side="right",
+            use_degrees=config.right_arm_config.use_degrees,
+        )
+
+        self.left_arm = OpenArmMini(left_arm_config)
+        self.right_arm = OpenArmMini(right_arm_config)
+
+    @cached_property
+    def action_features(self) -> dict[str, type]:
+        return {
+            **{f"left_{k}": v for k, v in self.left_arm.action_features.items()},
+            **{f"right_{k}": v for k, v in self.right_arm.action_features.items()},
+        }
+
+    @cached_property
+    def feedback_features(self) -> dict[str, type]:
+        return {
+            **{f"left_{k}": v for k, v in self.left_arm.feedback_features.items()},
+            **{f"right_{k}": v for k, v in self.right_arm.feedback_features.items()},
+        }
+
+    def setup_motors(self) -> None:
+        self.left_arm.setup_motors()
+        self.right_arm.setup_motors()
+
+    @check_if_not_connected
+    def get_action(self) -> RobotAction:
+        action: RobotAction = {}
+        for k, v in self.left_arm.get_action().items():
+            action[f"left_{k}"] = v
+        for k, v in self.right_arm.get_action().items():
+            action[f"right_{k}"] = v
+        return action
+
+    @check_if_not_connected
+    def send_feedback(self, feedback: dict[str, float]) -> None:
+        left_fb = {k.removeprefix("left_"): v for k, v in feedback.items() if k.startswith("left_")}
+        right_fb = {k.removeprefix("right_"): v for k, v in feedback.items() if k.startswith("right_")}
+        if left_fb:
+            self.left_arm.send_feedback(left_fb)
+        if right_fb:
+            self.right_arm.send_feedback(right_fb)

src/lerobot/teleoperators/bi_openarm_mini/config_bi_openarm_mini.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python
+
+# Copyright 2026 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
+
+from ..config import TeleoperatorConfig
+from ..openarm_mini import OpenArmMiniConfigBase
+
+
+@TeleoperatorConfig.register_subclass("bi_openarm_mini")
+@dataclass
+class BiOpenArmMiniConfig(TeleoperatorConfig):
+    """Configuration class for Bi OpenArm Mini teleoperators."""
+
+    left_arm_config: OpenArmMiniConfigBase
+    right_arm_config: OpenArmMiniConfigBase

src/lerobot/teleoperators/bi_rebot_102_leader/__init__.py

@@ -14,7 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from .bi_rebot_102_leader import BiRebotArm102Leader
-from .config_bi_rebot_102_leader import BiRebotArm102LeaderConfig
+from .bi_rebot_102_leader import BiRebot102Leader
+from .config_bi_rebot_102_leader import BiRebot102LeaderConfig
 
-__all__ = ["BiRebotArm102Leader", "BiRebotArm102LeaderConfig"]
+__all__ = ["BiRebot102Leader", "BiRebot102LeaderConfig"]

src/lerobot/teleoperators/bi_rebot_102_leader/bi_rebot_102_leader.py

@@ -18,16 +18,17 @@ import logging
 from functools import cached_property
 
 from lerobot.types import RobotAction
-from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
+from lerobot.utils.bimanual import BimanualMixin
+from lerobot.utils.decorators import check_if_not_connected
 
 from ..rebot_102_leader import RebotArm102Leader, RebotArm102LeaderTeleopConfig
 from ..teleoperator import Teleoperator
-from .config_bi_rebot_102_leader import BiRebotArm102LeaderConfig
+from .config_bi_rebot_102_leader import BiRebot102LeaderConfig
 
 logger = logging.getLogger(__name__)
 
 
-class BiRebotArm102Leader(Teleoperator):
+class BiRebot102Leader(BimanualMixin, Teleoperator):
     """Bimanual Seeed Studio StarArm102 / reBot Arm 102 leader.
 
     Composes two single-arm :class:`RebotArm102Leader` instances. Action keys of
@@ -35,10 +36,10 @@ class BiRebotArm102Leader(Teleoperator):
     leader can teleoperate a bimanual reBot B601 follower.
     """
 
-    config_class = BiRebotArm102LeaderConfig
+    config_class = BiRebot102LeaderConfig
     name = "bi_rebot_102_leader"
 
-    def __init__(self, config: BiRebotArm102LeaderConfig):
+    def __init__(self, config: BiRebot102LeaderConfig):
         super().__init__(config)
         self.config = config
 
@@ -76,27 +77,6 @@ class BiRebotArm102Leader(Teleoperator):
     def feedback_features(self) -> dict[str, type]:
         return {}
 
-    @property
-    def is_connected(self) -> bool:
-        return self.left_arm.is_connected and self.right_arm.is_connected
-
-    @check_if_already_connected
-    def connect(self, calibrate: bool = True) -> None:
-        self.left_arm.connect(calibrate)
-        self.right_arm.connect(calibrate)
-
-    @property
-    def is_calibrated(self) -> bool:
-        return self.left_arm.is_calibrated and self.right_arm.is_calibrated
-
-    def calibrate(self) -> None:
-        self.left_arm.calibrate()
-        self.right_arm.calibrate()
-
-    def configure(self) -> None:
-        self.left_arm.configure()
-        self.right_arm.configure()
-
     @check_if_not_connected
     def get_action(self) -> RobotAction:
         action_dict = {}
@@ -106,8 +86,3 @@ class BiRebotArm102Leader(Teleoperator):
 
     def send_feedback(self, feedback: dict[str, float]) -> None:
         raise NotImplementedError("Feedback is not implemented for the reBot Arm 102 leader.")
-
-    @check_if_not_connected
-    def disconnect(self) -> None:
-        self.left_arm.disconnect()
-        self.right_arm.disconnect()

src/lerobot/teleoperators/bi_rebot_102_leader/config_bi_rebot_102_leader.py

@@ -22,7 +22,7 @@ from ..rebot_102_leader import RebotArm102LeaderConfig
 
 @TeleoperatorConfig.register_subclass("bi_rebot_102_leader")
 @dataclass
-class BiRebotArm102LeaderConfig(TeleoperatorConfig):
+class BiRebot102LeaderConfig(TeleoperatorConfig):
     """Configuration class for the bimanual reBot Arm 102 leader teleoperator."""
 
     left_arm_config: RebotArm102LeaderConfig

src/lerobot/teleoperators/bi_so_leader/bi_so_leader.py

@@ -17,7 +17,9 @@
 import logging
 from functools import cached_property
 
-from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
+from lerobot.types import RobotAction
+from lerobot.utils.bimanual import BimanualMixin
+from lerobot.utils.decorators import check_if_not_connected
 
 from ..so_leader import SOLeader, SOLeaderTeleopConfig
 from ..teleoperator import Teleoperator
@@ -26,7 +28,7 @@ from .config_bi_so_leader import BiSOLeaderConfig
 logger = logging.getLogger(__name__)
 
 
-class BiSOLeader(Teleoperator):
+class BiSOLeader(BimanualMixin, Teleoperator):
     """
     [Bimanual SO Leader Arms](https://github.com/TheRobotStudio/SO-ARM100) designed by TheRobotStudio
     """
@@ -67,33 +69,12 @@ class BiSOLeader(Teleoperator):
     def feedback_features(self) -> dict[str, type]:
         return {}
 
-    @property
-    def is_connected(self) -> bool:
-        return self.left_arm.is_connected and self.right_arm.is_connected
-
-    @check_if_already_connected
-    def connect(self, calibrate: bool = True) -> None:
-        self.left_arm.connect(calibrate)
-        self.right_arm.connect(calibrate)
-
-    @property
-    def is_calibrated(self) -> bool:
-        return self.left_arm.is_calibrated and self.right_arm.is_calibrated
-
-    def calibrate(self) -> None:
-        self.left_arm.calibrate()
-        self.right_arm.calibrate()
-
-    def configure(self) -> None:
-        self.left_arm.configure()
-        self.right_arm.configure()
-
     def setup_motors(self) -> None:
         self.left_arm.setup_motors()
         self.right_arm.setup_motors()
 
     @check_if_not_connected
-    def get_action(self) -> dict[str, float]:
+    def get_action(self) -> RobotAction:
         action_dict = {}
 
         # Add "left_" prefix
@@ -109,8 +90,3 @@ class BiSOLeader(Teleoperator):
     def send_feedback(self, feedback: dict[str, float]) -> None:
         # TODO: Implement force feedback
         raise NotImplementedError
-
-    @check_if_not_connected
-    def disconnect(self) -> None:
-        self.left_arm.disconnect()
-        self.right_arm.disconnect()

src/lerobot/teleoperators/openarm_mini/__init__.py

@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 
-# Copyright 2025 The HuggingFace Inc. team. All rights reserved.
+# Copyright 2026 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.
@@ -14,7 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from .config_openarm_mini import OpenArmMiniConfig
+from .config_openarm_mini import OpenArmMiniConfig, OpenArmMiniConfigBase
 from .openarm_mini import OpenArmMini
 
-__all__ = ["OpenArmMini", "OpenArmMiniConfig"]
+__all__ = ["OpenArmMini", "OpenArmMiniConfig", "OpenArmMiniConfigBase"]

src/lerobot/teleoperators/openarm_mini/config_openarm_mini.py

@@ -19,12 +19,21 @@ from dataclasses import dataclass
 from ..config import TeleoperatorConfig
 
 
-@TeleoperatorConfig.register_subclass("openarm_mini")
 @dataclass
-class OpenArmMiniConfig(TeleoperatorConfig):
-    """Configuration for OpenArm Mini teleoperator with Feetech motors (dual arms)."""
+class OpenArmMiniConfigBase:
+    """Base configuration for the OpenArm Mini teleoperator (Feetech STS3215, 7DOF + gripper)."""
 
-    port_right: str = "/dev/ttyUSB0"
-    port_left: str = "/dev/ttyUSB1"
+    # Serial port for the Feetech bus (e.g., "/dev/ttyUSB0").
+    port: str
+
+    # Side of the arm: "left" or "right". Controls per-joint direction flips applied
+    # during readout. If `None`, no flipping is applied.
+    side: str | None = None
 
     use_degrees: bool = True
+
+
+@TeleoperatorConfig.register_subclass("openarm_mini")
+@dataclass
+class OpenArmMiniConfig(TeleoperatorConfig, OpenArmMiniConfigBase):
+    pass

src/lerobot/teleoperators/openarm_mini/openarm_mini.py

@@ -31,22 +31,22 @@ from .config_openarm_mini import OpenArmMiniConfig
 
 logger = logging.getLogger(__name__)
 
-# Motors whose direction is inverted during readout
-RIGHT_MOTORS_TO_FLIP = ["joint_1", "joint_2", "joint_3", "joint_4", "joint_5", "joint_7"]
-LEFT_MOTORS_TO_FLIP = ["joint_1", "joint_3", "joint_4", "joint_5", "joint_6", "joint_7"]
+# Per-side motor direction flips applied during readout.
+SIDE_MOTORS_TO_FLIP: dict[str, list[str]] = {
+    "left": ["joint_1", "joint_3", "joint_4", "joint_5", "joint_6", "joint_7"],
+    "right": ["joint_1", "joint_2", "joint_3", "joint_4", "joint_5", "joint_7"],
+}
 
-# Leader joint 6 maps to follower joint 7 and vice versa
+# Leader joint 6 ↔ follower joint 7 (symmetric — its own inverse).
 JOINT_REMAP = {"joint_6": "joint_7", "joint_7": "joint_6"}
-JOINT_REMAP_REVERSE = {"joint_7": "joint_6", "joint_6": "joint_7"}
 
 GRIPPER_TELEOP_TO_DEGREES = -0.65
 
 
 class OpenArmMini(Teleoperator):
-    """
-    OpenArm Mini Teleoperator with dual Feetech-based arms (8 motors per arm).
+    """OpenArm Mini single-arm teleoperator (Feetech STS3215, 7DOF + gripper).
 
-    Each arm has 7 joints plus a gripper, using Feetech STS3215 servos.
+    For the bimanual setup, see :class:`BiOpenArmMini` which composes two of these.
     """
 
     config_class = OpenArmMiniConfig
@@ -56,9 +56,12 @@ class OpenArmMini(Teleoperator):
         super().__init__(config)
         self.config = config
 
+        if config.side is not None and config.side not in SIDE_MOTORS_TO_FLIP:
+            raise ValueError(f"Invalid side '{config.side}'; expected 'left', 'right', or None.")
+        self._motors_to_flip: list[str] = SIDE_MOTORS_TO_FLIP.get(config.side, []) if config.side else []
+
         norm_mode_body = MotorNormMode.DEGREES
-
-        motors_right = {
+        motors = {
             "joint_1": Motor(1, "sts3215", norm_mode_body),
             "joint_2": Motor(2, "sts3215", norm_mode_body),
             "joint_3": Motor(3, "sts3215", norm_mode_body),
@@ -69,46 +72,15 @@ class OpenArmMini(Teleoperator):
             "gripper": Motor(8, "sts3215", MotorNormMode.RANGE_0_100),
         }
 
-        motors_left = {
-            "joint_1": Motor(1, "sts3215", norm_mode_body),
-            "joint_2": Motor(2, "sts3215", norm_mode_body),
-            "joint_3": Motor(3, "sts3215", norm_mode_body),
-            "joint_4": Motor(4, "sts3215", norm_mode_body),
-            "joint_5": Motor(5, "sts3215", norm_mode_body),
-            "joint_6": Motor(6, "sts3215", norm_mode_body),
-            "joint_7": Motor(7, "sts3215", norm_mode_body),
-            "gripper": Motor(8, "sts3215", MotorNormMode.RANGE_0_100),
-        }
-
-        cal_right = {
-            k.replace("right_", ""): v for k, v in (self.calibration or {}).items() if k.startswith("right_")
-        }
-        cal_left = {
-            k.replace("left_", ""): v for k, v in (self.calibration or {}).items() if k.startswith("left_")
-        }
-
-        self.bus_right = FeetechMotorsBus(
-            port=self.config.port_right,
-            motors=motors_right,
-            calibration=cal_right,
-        )
-
-        self.bus_left = FeetechMotorsBus(
-            port=self.config.port_left,
-            motors=motors_left,
-            calibration=cal_left,
+        self.bus = FeetechMotorsBus(
+            port=self.config.port,
+            motors=motors,
+            calibration=self.calibration,
         )
 
     @property
     def action_features(self) -> dict[str, type]:
-        # Right first, then left — matches the robot (BiOpenArmFollower) ordering
-        # and the dataset feature names recorded during data collection.
-        features: dict[str, type] = {}
-        for motor in self.bus_right.motors:
-            features[f"right_{motor}.pos"] = float
-        for motor in self.bus_left.motors:
-            features[f"left_{motor}.pos"] = float
-        return features
+        return {f"{motor}.pos": float for motor in self.bus.motors}
 
     @property
     def feedback_features(self) -> dict[str, type]:
@@ -116,14 +88,12 @@ class OpenArmMini(Teleoperator):
 
     @property
     def is_connected(self) -> bool:
-        return self.bus_right.is_connected and self.bus_left.is_connected
+        return self.bus.is_connected
 
     @check_if_already_connected
     def connect(self, calibrate: bool = True) -> None:
-        logger.info(f"Connecting right arm on {self.config.port_right}...")
-        self.bus_right.connect()
-        logger.info(f"Connecting left arm on {self.config.port_left}...")
-        self.bus_left.connect()
+        logger.info(f"Connecting arm on {self.config.port}...")
+        self.bus.connect()
 
         if calibrate:
             self.calibrate()
@@ -133,14 +103,14 @@ class OpenArmMini(Teleoperator):
 
     @property
     def is_calibrated(self) -> bool:
-        return self.bus_right.is_calibrated and self.bus_left.is_calibrated
+        return self.bus.is_calibrated
 
     def calibrate(self) -> None:
         """
-        Run calibration procedure for OpenArm Mini.
+        Run calibration procedure for a single OpenArm Mini arm.
 
         1. Disable torque
-        2. Ask user to position arms in hanging position with grippers closed
+        2. Ask user to position arm in hanging position with gripper closed
         3. Set this as zero position via half-turn homing
         4. Interactive gripper calibration (open/close positions)
         5. Save calibration
@@ -152,70 +122,51 @@ class OpenArmMini(Teleoperator):
             )
             if user_input.strip().lower() != "c":
                 logger.info(f"Using existing calibration for {self.id}")
-                cal_right = {
-                    k.replace("right_", ""): v for k, v in self.calibration.items() if k.startswith("right_")
-                }
-                cal_left = {
-                    k.replace("left_", ""): v for k, v in self.calibration.items() if k.startswith("left_")
-                }
-                self.bus_right.write_calibration(cal_right)
-                self.bus_left.write_calibration(cal_left)
+                self.bus.write_calibration(self.calibration)
                 return
 
         logger.info(f"\nRunning calibration for {self}")
 
-        self._calibrate_arm("right", self.bus_right)
-        self._calibrate_arm("left", self.bus_left)
+        self.bus.disable_torque()
 
-        self._save_calibration()
-        print(f"\nCalibration complete and saved to {self.calibration_fpath}")
+        logger.info("Setting Phase to 12 for all motors...")
+        for motor in self.bus.motors:
+            self.bus.write("Phase", motor, 12)
 
-    def _calibrate_arm(self, arm_name: str, bus: FeetechMotorsBus) -> None:
-        """Calibrate a single arm with Feetech motors."""
-        logger.info(f"\n=== Calibrating {arm_name.upper()} arm ===")
-
-        bus.disable_torque()
-
-        logger.info(f"Setting Phase to 12 for all motors in {arm_name.upper()} arm...")
-        for motor in bus.motors:
-            bus.write("Phase", motor, 12)
-
-        for motor in bus.motors:
-            bus.write("Operating_Mode", motor, OperatingMode.POSITION.value)
+        for motor in self.bus.motors:
+            self.bus.write("Operating_Mode", motor, OperatingMode.POSITION.value)
 
         input(
-            f"\nCalibration: Zero Position ({arm_name.upper()} arm)\n"
+            "\nCalibration: Zero Position\n"
             "Position the arm in the following configuration:\n"
             "  - Arm hanging straight down\n"
             "  - Gripper closed\n"
             "Press ENTER when ready..."
         )
 
-        homing_offsets = bus.set_half_turn_homings()
-        logger.info(f"{arm_name.capitalize()} arm zero position set.")
+        homing_offsets = self.bus.set_half_turn_homings()
+        logger.info("Arm zero position set.")
 
-        print(f"\nSetting motor ranges for {arm_name.upper()} arm\n")
+        print("\nSetting motor ranges\n")
 
         if self.calibration is None:
             self.calibration = {}
 
-        motor_resolution = bus.model_resolution_table[list(bus.motors.values())[0].model]
+        motor_resolution = self.bus.model_resolution_table[list(self.bus.motors.values())[0].model]
         max_res = motor_resolution - 1
 
-        for motor_name, motor in bus.motors.items():
-            prefixed_name = f"{arm_name}_{motor_name}"
-
+        for motor_name, motor in self.bus.motors.items():
             if motor_name == "gripper":
                 input(
-                    f"\nGripper Calibration ({arm_name.upper()} arm)\n"
-                    f"Step 1: CLOSE the gripper fully\n"
-                    f"Press ENTER when gripper is closed..."
+                    "\nGripper Calibration\n"
+                    "Step 1: CLOSE the gripper fully\n"
+                    "Press ENTER when gripper is closed..."
                 )
-                closed_pos = bus.read("Present_Position", motor_name, normalize=False)
+                closed_pos = self.bus.read("Present_Position", motor_name, normalize=False)
                 logger.info(f"  Gripper closed position recorded: {closed_pos}")
 
                 input("\nStep 2: OPEN the gripper fully\nPress ENTER when gripper is fully open...")
-                open_pos = bus.read("Present_Position", motor_name, normalize=False)
+                open_pos = self.bus.read("Present_Position", motor_name, normalize=False)
                 logger.info(f"  Gripper open position recorded: {open_pos}")
 
                 if closed_pos < open_pos:
@@ -228,16 +179,16 @@ class OpenArmMini(Teleoperator):
                     drive_mode = 1
 
                 logger.info(
-                    f"  {prefixed_name}: range set to [{range_min}, {range_max}] "
+                    f"  {motor_name}: range set to [{range_min}, {range_max}] "
                     f"(0=closed, 100=open, drive_mode={drive_mode})"
                 )
             else:
                 range_min = 0
                 range_max = max_res
                 drive_mode = 0
-                logger.info(f"  {prefixed_name}: range set to [0, {max_res}] (full motor range)")
+                logger.info(f"  {motor_name}: range set to [0, {max_res}] (full motor range)")
 
-            self.calibration[prefixed_name] = MotorCalibration(
+            self.calibration[motor_name] = MotorCalibration(
                 id=motor.id,
                 drive_mode=drive_mode,
                 homing_offset=homing_offsets[motor_name],
@@ -245,108 +196,68 @@ class OpenArmMini(Teleoperator):
                 range_max=range_max,
             )
 
-        cal_for_bus = {
-            k.replace(f"{arm_name}_", ""): v
-            for k, v in self.calibration.items()
-            if k.startswith(f"{arm_name}_")
-        }
-        bus.write_calibration(cal_for_bus)
+        self.bus.write_calibration(self.calibration)
+        self._save_calibration()
+        print(f"\nCalibration complete and saved to {self.calibration_fpath}")
 
     def configure(self) -> None:
-        self.bus_right.disable_torque()
-        self.bus_right.configure_motors()
-        for motor in self.bus_right.motors:
-            self.bus_right.write("Operating_Mode", motor, OperatingMode.POSITION.value)
-
-        self.bus_left.disable_torque()
-        self.bus_left.configure_motors()
-        for motor in self.bus_left.motors:
-            self.bus_left.write("Operating_Mode", motor, OperatingMode.POSITION.value)
+        self.bus.disable_torque()
+        self.bus.configure_motors()
+        for motor in self.bus.motors:
+            self.bus.write("Operating_Mode", motor, OperatingMode.POSITION.value)
 
     def setup_motors(self) -> None:
-        print("\nSetting up RIGHT arm motors...")
-        for motor in reversed(self.bus_right.motors):
-            input(f"Connect the controller board to the RIGHT '{motor}' motor only and press enter.")
-            self.bus_right.setup_motor(motor)
-            print(f"RIGHT '{motor}' motor id set to {self.bus_right.motors[motor].id}")
-
-        print("\nSetting up LEFT arm motors...")
-        for motor in reversed(self.bus_left.motors):
-            input(f"Connect the controller board to the LEFT '{motor}' motor only and press enter.")
-            self.bus_left.setup_motor(motor)
-            print(f"LEFT '{motor}' motor id set to {self.bus_left.motors[motor].id}")
+        for motor in reversed(self.bus.motors):
+            input(f"Connect the controller board to the '{motor}' motor only and press enter.")
+            self.bus.setup_motor(motor)
+            print(f"'{motor}' motor id set to {self.bus.motors[motor].id}")
 
     @check_if_not_connected
     def get_action(self) -> RobotAction:
-        """Get current action from both arms (read positions from all motors)."""
+        """Get current action (read positions from all motors)."""
         start = time.perf_counter()
 
-        right_positions = self.bus_right.sync_read("Present_Position")
-        left_positions = self.bus_left.sync_read("Present_Position")
+        positions = self.bus.sync_read("Present_Position")
 
-        # Right first, then left — matches the robot (BiOpenArmFollower) ordering
-        # and the dataset feature names recorded during data collection.
         # Joint 6↔7 remap: leader joint_6 → follower joint_7 and vice versa.
+        # Per-side direction flip is applied based on the configured `side`.
         action: dict[str, Any] = {}
-        for motor, val in right_positions.items():
+        for motor, val in positions.items():
             target = JOINT_REMAP.get(motor, motor)
             if motor == "gripper":
                 # Convert gripper from teleop 0-100 to openarms degrees: 0→0°, 100→-65°
-                action[f"right_{target}.pos"] = val * GRIPPER_TELEOP_TO_DEGREES
+                action[f"{target}.pos"] = val * GRIPPER_TELEOP_TO_DEGREES
             else:
-                action[f"right_{target}.pos"] = -val if motor in RIGHT_MOTORS_TO_FLIP else val
-        for motor, val in left_positions.items():
-            target = JOINT_REMAP.get(motor, motor)
-            if motor == "gripper":
-                action[f"left_{target}.pos"] = val * GRIPPER_TELEOP_TO_DEGREES
-            else:
-                action[f"left_{target}.pos"] = -val if motor in LEFT_MOTORS_TO_FLIP else val
+                action[f"{target}.pos"] = -val if motor in self._motors_to_flip else val
 
         dt_ms = (time.perf_counter() - start) * 1e3
         logger.debug(f"{self} read action: {dt_ms:.1f}ms")
         return action
 
     def enable_torque(self) -> None:
-        """Enable torque on both arms for position control."""
-        self.bus_right.enable_torque()
-        self.bus_left.enable_torque()
+        self.bus.enable_torque()
 
     def disable_torque(self) -> None:
-        """Disable torque on both arms for free movement."""
-        self.bus_right.disable_torque()
-        self.bus_left.disable_torque()
+        self.bus.disable_torque()
 
     def write_goal_positions(self, positions: dict[str, float]) -> None:
         """Write goal positions to motors (inverse of get_action flip/gripper/remap logic)."""
-        right_goals: dict[str, float] = {}
-        left_goals: dict[str, float] = {}
-
+        goals: dict[str, float] = {}
         for key, val in positions.items():
             if not key.endswith(".pos"):
                 continue
-            motor_name = key.removesuffix(".pos")
-            if motor_name.startswith("right_"):
-                base = motor_name.removeprefix("right_")
-                # Reverse remap: follower joint_7 → leader joint_6 and vice versa
-                target = JOINT_REMAP_REVERSE.get(base, base)
-                if base == "gripper":
-                    # Convert robot degrees to teleop 0-100: 0°→0, -65°→100
-                    right_goals[target] = val / GRIPPER_TELEOP_TO_DEGREES
-                else:
-                    # Un-flip using the ORIGINAL motor name (target = leader motor)
-                    right_goals[target] = -val if target in RIGHT_MOTORS_TO_FLIP else val
-            elif motor_name.startswith("left_"):
-                base = motor_name.removeprefix("left_")
-                target = JOINT_REMAP_REVERSE.get(base, base)
-                if base == "gripper":
-                    left_goals[target] = val / GRIPPER_TELEOP_TO_DEGREES
-                else:
-                    left_goals[target] = -val if target in LEFT_MOTORS_TO_FLIP else val
+            base = key.removesuffix(".pos")
+            # JOINT_REMAP is symmetric (its own inverse).
+            target = JOINT_REMAP.get(base, base)
+            if base == "gripper":
+                # Convert robot degrees to teleop 0-100: 0°→0, -65°→100
+                goals[target] = val / GRIPPER_TELEOP_TO_DEGREES
+            else:
+                # Un-flip using the ORIGINAL motor name (target = leader motor)
+                goals[target] = -val if target in self._motors_to_flip else val
 
-        if right_goals:
-            self.bus_right.sync_write("Goal_Position", right_goals)
-        if left_goals:
-            self.bus_left.sync_write("Goal_Position", left_goals)
+        if goals:
+            self.bus.sync_write("Goal_Position", goals)
 
     @check_if_not_connected
     def send_feedback(self, feedback: dict[str, float]) -> None:
@@ -354,6 +265,5 @@ class OpenArmMini(Teleoperator):
 
     @check_if_not_connected
     def disconnect(self) -> None:
-        self.bus_right.disconnect()
-        self.bus_left.disconnect()
+        self.bus.disconnect()
         logger.info(f"{self} disconnected.")

src/lerobot/teleoperators/utils.py

@@ -99,14 +99,18 @@ def make_teleoperator_from_config(config: TeleoperatorConfig) -> "Teleoperator":
         from .openarm_mini import OpenArmMini
 
         return OpenArmMini(config)
+    elif config.type == "bi_openarm_mini":
+        from .bi_openarm_mini import BiOpenArmMini
+
+        return BiOpenArmMini(config)
     elif config.type == "rebot_102_leader":
         from .rebot_102_leader import RebotArm102Leader
 
         return RebotArm102Leader(config)
     elif config.type == "bi_rebot_102_leader":
-        from .bi_rebot_102_leader import BiRebotArm102Leader
+        from .bi_rebot_102_leader import BiRebot102Leader
 
-        return BiRebotArm102Leader(config)
+        return BiRebot102Leader(config)
     else:
         try:
             return cast("Teleoperator", make_device_from_device_class(config))

src/lerobot/utils/bimanual.py

@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+
+# Copyright 2026 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 typing import Any
+
+from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
+
+
+class BimanualMixin:
+    """Lifecycle delegation for bimanual robots and teleoperators.
+
+    Concrete subclasses must populate ``self.left_arm`` and ``self.right_arm`` in
+    their own ``__init__``. They retain ownership of feature dicts and the
+    data-routing methods (``get_action`` / ``send_action`` / ``get_observation`` /
+    ``send_feedback``), which vary per-embodiment.
+
+    Inherit before the ``Robot`` / ``Teleoperator`` base so the mixin's methods
+    take precedence in the MRO::
+
+        class BiFooFollower(BimanualMixin, Robot): ...
+    """
+
+    left_arm: Any
+    right_arm: Any
+
+    @property
+    def is_connected(self) -> bool:
+        return self.left_arm.is_connected and self.right_arm.is_connected
+
+    @property
+    def is_calibrated(self) -> bool:
+        return self.left_arm.is_calibrated and self.right_arm.is_calibrated
+
+    @check_if_already_connected
+    def connect(self, calibrate: bool = True) -> None:
+        self.left_arm.connect(calibrate)
+        self.right_arm.connect(calibrate)
+
+    def calibrate(self) -> None:
+        self.left_arm.calibrate()
+        self.right_arm.calibrate()
+
+    def configure(self) -> None:
+        self.left_arm.configure()
+        self.right_arm.configure()
+
+    @check_if_not_connected
+    def disconnect(self) -> None:
+        self.left_arm.disconnect()
+        self.right_arm.disconnect()

src/lerobot/utils/import_utils.py

@@ -216,9 +216,15 @@ def register_third_party_plugins() -> None:
 
     This function uses `importlib.metadata` to find packages installed in the environment
     (including editable installs) starting with 'lerobot_robot_', 'lerobot_camera_',
-    'lerobot_teleoperator_', or 'lerobot_policy_' and imports them.
+    'lerobot_teleoperator_', 'lerobot_policy_', or 'lerobot_env_' and imports them.
     """
-    prefixes = ("lerobot_robot_", "lerobot_camera_", "lerobot_teleoperator_", "lerobot_policy_")
+    prefixes = (
+        "lerobot_robot_",
+        "lerobot_camera_",
+        "lerobot_teleoperator_",
+        "lerobot_policy_",
+        "lerobot_env_",
+    )
     imported: list[str] = []
     failed: list[str] = []
 

tests/policies/test_policies.py

@@ -23,7 +23,6 @@ import torch
 
 pytest.importorskip("datasets", reason="datasets is required (install lerobot[dataset])")
 
-from huggingface_hub.constants import SAFETENSORS_SINGLE_FILE
 from packaging import version
 from safetensors.torch import load_file
 
@@ -301,29 +300,6 @@ def test_save_and_load_pretrained(dummy_dataset_metadata, tmp_path, policy_name:
     torch.testing.assert_close(list(policy.parameters()), list(loaded_policy.parameters()), rtol=0, atol=0)
 
 
-def test_save_pretrained_with_state_dict(dummy_dataset_metadata, tmp_path):
-    """Exercise the FSDP checkpoint path: save_pretrained with a pre-gathered state_dict."""
-    policy_cls = get_policy_class("act")
-    policy_cfg = make_policy_config("act")
-    features = dataset_to_policy_features(dummy_dataset_metadata.features)
-    policy_cfg.output_features = {key: ft for key, ft in features.items() if ft.type is FeatureType.ACTION}
-    policy_cfg.input_features = {
-        key: ft for key, ft in features.items() if key not in policy_cfg.output_features
-    }
-    policy = policy_cls(policy_cfg)
-    policy.to(policy_cfg.device)
-
-    save_dir = tmp_path / "fsdp_state_dict"
-    policy.save_pretrained(save_dir, state_dict=policy.state_dict())
-
-    # A single, unsharded safetensors file (no sharded set + index).
-    assert (save_dir / SAFETENSORS_SINGLE_FILE).is_file()
-    assert not (save_dir / f"{SAFETENSORS_SINGLE_FILE}.index.json").exists()
-
-    loaded_policy = policy_cls.from_pretrained(save_dir, config=policy_cfg)
-    torch.testing.assert_close(list(policy.parameters()), list(loaded_policy.parameters()), rtol=0, atol=0)
-
-
 @pytest.mark.parametrize("multikey", [True, False])
 def test_multikey_construction(multikey: bool):
     """

tests/teleoperators/test_rebot_102_leader.py

@@ -18,7 +18,7 @@ from unittest.mock import MagicMock, patch
 
 import pytest
 
-from lerobot.teleoperators.bi_rebot_102_leader import BiRebotArm102Leader, BiRebotArm102LeaderConfig
+from lerobot.teleoperators.bi_rebot_102_leader import BiRebot102Leader, BiRebot102LeaderConfig
 from lerobot.teleoperators.rebot_102_leader import (
     RebotArm102Leader,
     RebotArm102LeaderConfig,
@@ -91,11 +91,11 @@ def test_send_feedback_not_implemented(leader):
 
 def test_bimanual_prefixes_features():
     with patch(f"{_MODULE}.require_package", lambda *a, **kw: None):
-        cfg = BiRebotArm102LeaderConfig(
+        cfg = BiRebot102LeaderConfig(
             left_arm_config=RebotArm102LeaderConfig(port="/dev/null0"),
             right_arm_config=RebotArm102LeaderConfig(port="/dev/null1"),
         )
-        teleop = BiRebotArm102Leader(cfg)
+        teleop = BiRebot102Leader(cfg)
     assert any(k.startswith("left_") for k in teleop.action_features)
     assert any(k.startswith("right_") for k in teleop.action_features)
     assert "left_gripper.pos" in teleop.action_features

tests/training/test_multi_gpu.py

@@ -134,7 +134,7 @@ class TestMultiGPUTraining:
                 f"--output_dir={output_dir}",
                 "--batch_size=4",
                 "--steps=10",
-                "--eval_freq=-1",
+                "--env_eval_freq=-1",
                 "--log_freq=5",
                 "--save_freq=10",
                 "--seed=42",
@@ -177,7 +177,7 @@ class TestMultiGPUTraining:
                 f"--output_dir={output_dir}",
                 "--batch_size=4",
                 "--steps=20",
-                "--eval_freq=-1",
+                "--env_eval_freq=-1",
                 "--log_freq=5",
                 "--save_freq=10",
                 "--seed=42",