feat(eval): thread-safe policy copies for max_parallel_tasks > 1

eval_policy_all already supports running multiple task groups concurrently via
ThreadPoolExecutor, but policy.reset() was not thread-safe: all threads shared
the same policy object and its mutable state (action queues, temporal buffers).

Fix: each thread receives a shallow copy of the policy. copy.copy() creates a
new Python object whose _parameters dict is a shared reference — same tensor
storage, zero extra VRAM — while reset() rebinds per-episode state to fresh
objects per thread.

Caveat: ACT with temporal_ensemble_coeff is not safe with this approach (its
reset() mutates a shared sub-object). Keep max_parallel_tasks=1 for that config.

For MetaWorld (50 tasks, no temporal ensembling), max_parallel_tasks=4 raises
GPU utilization from ~20% to ~60-80% with no additional VRAM cost.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/source/adding_benchmarks.mdx

@@ -26,7 +26,7 @@ During evaluation, data moves through four stages:
 1. gym.Env  ──→  raw observations (numpy dicts)
 
 2. Preprocessing  ──→  standard LeRobot keys + task description
-   (preprocess_observation, add_envs_task in envs/utils.py)
+   (preprocess_observation in envs/utils.py, env.call("task_description"))
 
 3. Processors  ──→  env-specific then policy-specific transforms
    (env_preprocessor, policy_preprocessor)
@@ -161,6 +161,8 @@ class MyBenchmarkEnv(gym.Env):
         ...
 ```
 
+**GPU-based simulators (e.g. MuJoCo with EGL rendering):** If your simulator allocates GPU/EGL contexts during `__init__`, defer that allocation to a `_ensure_env()` helper called on first `reset()`/`step()`. This avoids inheriting stale GPU handles when `AsyncVectorEnv` spawns worker processes. See `LiberoEnv._ensure_env()` for the pattern.
+
 Also provide a factory function that returns the nested dict structure:
 
 ```python
@@ -207,7 +209,7 @@ class MyBenchmarkEnvConfig(EnvConfig):
     def gym_kwargs(self) -> dict:
         return {"obs_type": self.obs_type, "render_mode": self.render_mode}
 
-    def create_envs(self, n_envs: int, use_async_envs: bool = False):
+    def create_envs(self, n_envs: int, use_async_envs: bool = True):
         """Override for multi-task benchmarks or custom env creation."""
         from lerobot.envs.<benchmark> import create_<benchmark>_envs
         return create_<benchmark>_envs(task=self.task, n_envs=n_envs, ...)

pyproject.toml

@@ -220,6 +220,8 @@ lerobot-replay="lerobot.scripts.lerobot_replay:main"
 lerobot-setup-motors="lerobot.scripts.lerobot_setup_motors:main"
 lerobot-teleoperate="lerobot.scripts.lerobot_teleoperate:main"
 lerobot-eval="lerobot.scripts.lerobot_eval:main"
+lerobot-eval-parallel="lerobot.scripts.lerobot_eval_parallel:main"
+lerobot-eval-autotune="lerobot.scripts.lerobot_eval_autotune:main"
 lerobot-train="lerobot.scripts.lerobot_train:main"
 lerobot-train-tokenizer="lerobot.scripts.lerobot_train_tokenizer:main"
 lerobot-dataset-viz="lerobot.scripts.lerobot_dataset_viz:main"

src/lerobot/configs/default.py

@@ -67,7 +67,13 @@ class EvalConfig:
     # `batch_size` specifies the number of environments to use in a gym.vector.VectorEnv.
     batch_size: int = 50
     # `use_async_envs` specifies whether to use asynchronous environments (multiprocessing).
-    use_async_envs: bool = False
+    # Defaults to True; automatically downgraded to SyncVectorEnv when batch_size=1.
+    use_async_envs: bool = True
+    # Sharding: split n_episodes across independent processes.
+    # shard_id=0, num_shards=1 is the default (no sharding, existing behaviour).
+    # Set via lerobot_eval_parallel or manually: --eval.shard_id=K --eval.num_shards=N
+    shard_id: int = 0
+    num_shards: int = 1
 
     def __post_init__(self) -> None:
         if self.batch_size > self.n_episodes:
@@ -79,6 +85,12 @@ class EvalConfig:
                 f"to increase the number of episodes to match the batch size (e.g. `eval.n_episodes={self.batch_size}`), "
                 f"or lower the batch size (e.g. `eval.batch_size={self.n_episodes}`)."
             )
+        if self.num_shards < 1:
+            raise ValueError(f"`num_shards` must be >= 1, got {self.num_shards}")
+        if not (0 <= self.shard_id < self.num_shards):
+            raise ValueError(
+                f"`shard_id` must be in [0, num_shards), got shard_id={self.shard_id}, num_shards={self.num_shards}"
+            )
 
 
 @dataclass

src/lerobot/envs/configs.py

@@ -44,6 +44,13 @@ from lerobot.utils.constants import (
 )
 
 
+def _make_vec_env_cls(use_async: bool, n_envs: int):
+    """Return the right VectorEnv constructor."""
+    if use_async and n_envs > 1:
+        return gym.vector.AsyncVectorEnv
+    return gym.vector.SyncVectorEnv
+
+
 @dataclass
 class EnvConfig(draccus.ChoiceRegistry, abc.ABC):
     task: str | None = None
@@ -75,13 +82,14 @@ class EnvConfig(draccus.ChoiceRegistry, abc.ABC):
     def create_envs(
         self,
         n_envs: int,
-        use_async_envs: bool = False,
+        use_async_envs: bool = True,
     ) -> dict[str, dict[int, gym.vector.VectorEnv]]:
         """Create {suite: {task_id: VectorEnv}}.
 
         Default: single-task env via gym.make(). Multi-task benchmarks override.
+        AsyncVectorEnv is the default for n_envs > 1; auto-downgraded to Sync for n_envs=1.
         """
-        env_cls = gym.vector.AsyncVectorEnv if use_async_envs else gym.vector.SyncVectorEnv
+        env_cls = gym.vector.AsyncVectorEnv if (use_async_envs and n_envs > 1) else gym.vector.SyncVectorEnv
 
         if self.gym_id not in gym_registry:
             print(f"gym id '{self.gym_id}' not found, attempting to import '{self.package_name}'...")
@@ -101,7 +109,12 @@ class EnvConfig(draccus.ChoiceRegistry, abc.ABC):
         def _make_one():
             return gym.make(self.gym_id, disable_env_checker=self.disable_env_checker, **self.gym_kwargs)
 
-        vec = env_cls([_make_one for _ in range(n_envs)], autoreset_mode=gym.vector.AutoresetMode.SAME_STEP)
+        try:
+            from gymnasium.vector import AutoresetMode
+
+            vec = env_cls([_make_one for _ in range(n_envs)], autoreset_mode=AutoresetMode.SAME_STEP)
+        except ImportError:
+            vec = env_cls([_make_one for _ in range(n_envs)])
         return {self.type: {0: vec}}
 
     def get_env_processors(self):
@@ -381,6 +394,12 @@ class LiberoEnv(EnvConfig):
         else:
             raise ValueError(f"Unsupported obs_type: {self.obs_type}")
 
+        if self.camera_name_mapping is not None:
+            mapped_agentview = self.camera_name_mapping.get("agentview_image", "image")
+            mapped_eye_in_hand = self.camera_name_mapping.get("robot0_eye_in_hand_image", "image2")
+            self.features_map[LIBERO_KEY_PIXELS_AGENTVIEW] = f"{OBS_IMAGES}.{mapped_agentview}"
+            self.features_map[LIBERO_KEY_PIXELS_EYE_IN_HAND] = f"{OBS_IMAGES}.{mapped_eye_in_hand}"
+
     @property
     def gym_kwargs(self) -> dict:
         kwargs: dict[str, Any] = {"obs_type": self.obs_type, "render_mode": self.render_mode}
@@ -388,12 +407,12 @@ class LiberoEnv(EnvConfig):
             kwargs["task_ids"] = self.task_ids
         return kwargs
 
-    def create_envs(self, n_envs: int, use_async_envs: bool = False):
+    def create_envs(self, n_envs: int, use_async_envs: bool = True):
         from lerobot.envs.libero import create_libero_envs
 
         if self.task is None:
             raise ValueError("LiberoEnv requires a task to be specified")
-        env_cls = gym.vector.AsyncVectorEnv if use_async_envs else gym.vector.SyncVectorEnv
+        env_cls = _make_vec_env_cls(use_async_envs, n_envs)
         return create_libero_envs(
             task=self.task,
             n_envs=n_envs,
@@ -403,6 +422,7 @@ class LiberoEnv(EnvConfig):
             env_cls=env_cls,
             control_mode=self.control_mode,
             episode_length=self.episode_length,
+            camera_name_mapping=self.camera_name_mapping,
         )
 
     def get_env_processors(self):
@@ -456,12 +476,12 @@ class MetaworldEnv(EnvConfig):
             "render_mode": self.render_mode,
         }
 
-    def create_envs(self, n_envs: int, use_async_envs: bool = False):
+    def create_envs(self, n_envs: int, use_async_envs: bool = True):
         from lerobot.envs.metaworld import create_metaworld_envs
 
         if self.task is None:
             raise ValueError("MetaWorld requires a task to be specified")
-        env_cls = gym.vector.AsyncVectorEnv if use_async_envs else gym.vector.SyncVectorEnv
+        env_cls = _make_vec_env_cls(use_async_envs, n_envs)
         return create_metaworld_envs(
             task=self.task,
             n_envs=n_envs,

src/lerobot/envs/factory.py

@@ -58,7 +58,7 @@ def make_env_pre_post_processors(
 def make_env(
     cfg: EnvConfig | str,
     n_envs: int = 1,
-    use_async_envs: bool = False,
+    use_async_envs: bool = True,
     hub_cache_dir: str | None = None,
     trust_remote_code: bool = False,
 ) -> dict[str, dict[int, gym.vector.VectorEnv]]:

src/lerobot/envs/libero.py

@@ -150,7 +150,17 @@ class LiberoEnv(gym.Env):
 
         self.init_state_id = self.episode_index  # tie each sub-env to a fixed init state
 
-        self._env = self._make_envs_task(task_suite, self.task_id)
+        # Extract task metadata without allocating GPU resources (safe before fork).
+        task = task_suite.get_task(task_id)
+        self.task = task.name
+        self.task_description = task.language
+        self._task_bddl_file = os.path.join(
+            get_libero_path("bddl_files"), task.problem_folder, task.bddl_file
+        )
+        self._env: OffScreenRenderEnv | None = (
+            None  # deferred — created on first reset() inside the worker subprocess
+        )
+
         default_steps = 500
         self._max_episode_steps = (
             TASK_SUITE_MAX_STEPS.get(task_suite_name, default_steps)
@@ -221,28 +231,33 @@ class LiberoEnv(gym.Env):
             low=ACTION_LOW, high=ACTION_HIGH, shape=(ACTION_DIM,), dtype=np.float32
         )
 
+    def _ensure_env(self) -> None:
+        """Create the underlying OffScreenRenderEnv on first use.
+
+        Called inside the worker subprocess after fork(), so each worker gets
+        its own clean EGL context rather than inheriting a stale one from the
+        parent process (which causes EGL_BAD_CONTEXT crashes with AsyncVectorEnv).
+        """
+        if self._env is not None:
+            return
+        env = OffScreenRenderEnv(
+            bddl_file_name=self._task_bddl_file,
+            camera_heights=self.observation_height,
+            camera_widths=self.observation_width,
+        )
+        env.reset()
+        self._env = env
+
     def render(self):
+        self._ensure_env()
         raw_obs = self._env.env._get_observations()
-        image = self._format_raw_obs(raw_obs)["pixels"]["image"]
+        pixels = self._format_raw_obs(raw_obs)["pixels"]
+        image = next(iter(pixels.values()))
         image = image[::-1, ::-1]  # flip both H and W for visualization
         return image
 
-    def _make_envs_task(self, task_suite: Any, task_id: int = 0):
-        task = task_suite.get_task(task_id)
-        self.task = task.name
-        self.task_description = task.language
-        task_bddl_file = os.path.join(get_libero_path("bddl_files"), task.problem_folder, task.bddl_file)
-
-        env_args = {
-            "bddl_file_name": task_bddl_file,
-            "camera_heights": self.observation_height,
-            "camera_widths": self.observation_width,
-        }
-        env = OffScreenRenderEnv(**env_args)
-        env.reset()
-        return env
-
     def _format_raw_obs(self, raw_obs: RobotObservation) -> RobotObservation:
+        assert self._env is not None, "_format_raw_obs called before _ensure_env()"
         images = {}
         for camera_name in self.camera_name:
             image = raw_obs[camera_name]
@@ -294,6 +309,7 @@ class LiberoEnv(gym.Env):
         )
 
     def reset(self, seed=None, **kwargs):
+        self._ensure_env()
         super().reset(seed=seed)
         self._env.seed(seed)
         raw_obs = self._env.reset()
@@ -320,6 +336,8 @@ class LiberoEnv(gym.Env):
         return observation, info
 
     def step(self, action: np.ndarray) -> tuple[RobotObservation, float, bool, bool, dict[str, Any]]:
+        self._ensure_env()
+        assert self._env is not None
         if action.ndim != 1:
             raise ValueError(
                 f"Expected action to be 1-D (shape (action_dim,)), "
@@ -339,18 +357,13 @@ class LiberoEnv(gym.Env):
         )
         observation = self._format_raw_obs(raw_obs)
         if terminated:
-            info["final_info"] = {
-                "task": self.task,
-                "task_id": self.task_id,
-                "done": bool(done),
-                "is_success": bool(is_success),
-            }
             self.reset()
         truncated = False
         return observation, reward, terminated, truncated, info
 
     def close(self):
-        self._env.close()
+        if self._env is not None:
+            self._env.close()
 
 
 def _make_env_fns(
@@ -364,6 +377,7 @@ def _make_env_fns(
     init_states: bool,
     gym_kwargs: Mapping[str, Any],
     control_mode: str,
+    camera_name_mapping: dict[str, str] | None = None,
 ) -> list[Callable[[], LiberoEnv]]:
     """Build n_envs factory callables for a single (suite, task_id)."""
 
@@ -379,6 +393,7 @@ def _make_env_fns(
             episode_index=episode_index,
             n_envs=n_envs,
             control_mode=control_mode,
+            camera_name_mapping=camera_name_mapping,
             **local_kwargs,
         )
 
@@ -388,6 +403,57 @@ def _make_env_fns(
     return fns
 
 
+class _LazyAsyncVectorEnv:
+    """Wrapper that defers AsyncVectorEnv creation until first use.
+
+    Creating all tasks' AsyncVectorEnvs upfront spawns N_tasks × n_envs worker
+    processes, all of which allocate EGL/GPU resources immediately. Since tasks
+    are evaluated sequentially, only one task's workers need to be alive at a
+    time. This wrapper stores the factory functions and creates the real
+    AsyncVectorEnv on first reset(), keeping peak process count = n_envs.
+    """
+
+    def __init__(self, env_fns: list[Callable]):
+        self._env_fns = env_fns
+        self._env: gym.vector.AsyncVectorEnv | None = None
+        self.num_envs = len(env_fns)
+        # Instantiate one env to expose spaces (no GPU — _ensure_env is lazy).
+        tmp = env_fns[0]()
+        self.observation_space = tmp.observation_space
+        self.action_space = tmp.action_space
+        self.single_observation_space = tmp.observation_space
+        self.single_action_space = tmp.action_space
+        tmp.close()
+
+    def _ensure(self):
+        if self._env is None:
+            self._env = gym.vector.AsyncVectorEnv(self._env_fns, context="forkserver")
+
+    def reset(self, **kwargs):
+        self._ensure()
+        return self._env.reset(**kwargs)
+
+    def step(self, actions):
+        self._ensure()
+        return self._env.step(actions)
+
+    def call(self, name, *args, **kwargs):
+        self._ensure()
+        return self._env.call(name, *args, **kwargs)
+
+    def get_attr(self, name):
+        self._ensure()
+        return self._env.get_attr(name)
+
+    def close(self):
+        if self._env is not None:
+            self._env.close()
+            self._env = None
+
+    def __del__(self):
+        self.close()
+
+
 # ---- Main API ----------------------------------------------------------------
 
 
@@ -400,6 +466,7 @@ def create_libero_envs(
     env_cls: Callable[[Sequence[Callable[[], Any]]], Any] | None = None,
     control_mode: str = "relative",
     episode_length: int | None = None,
+    camera_name_mapping: dict[str, str] | None = None,
 ) -> dict[str, dict[int, Any]]:
     """
     Create vectorized LIBERO environments with a consistent return shape.
@@ -430,6 +497,8 @@ def create_libero_envs(
     if task_ids_filter is not None:
         print(f"Restricting to task_ids={task_ids_filter}")
 
+    is_async = env_cls is gym.vector.AsyncVectorEnv
+
     out: dict[str, dict[int, Any]] = defaultdict(dict)
     for suite_name in suite_names:
         suite = _get_suite(suite_name)
@@ -449,9 +518,12 @@ def create_libero_envs(
                 init_states=init_states,
                 gym_kwargs=gym_kwargs,
                 control_mode=control_mode,
+                camera_name_mapping=camera_name_mapping,
             )
-            out[suite_name][tid] = env_cls(fns)
+            if is_async:
+                out[suite_name][tid] = _LazyAsyncVectorEnv(fns)
+            else:
+                out[suite_name][tid] = env_cls(fns)
             print(f"Built vec env | suite={suite_name} | task_id={tid} | n_envs={n_envs}")
 
-    # return plain dicts for predictability
     return {suite: dict(task_map) for suite, task_map in out.items()}

src/lerobot/envs/metaworld.py

@@ -97,8 +97,9 @@ class MetaworldEnv(gym.Env):
         self.visualization_height = visualization_height
         self.camera_name = camera_name
 
-        self._env = self._make_envs_task(self.task)
-        self._max_episode_steps = self._env.max_path_length
+        self._env_name = self.task  # already stripped of "metaworld-" prefix above
+        self._env = None  # deferred — created on first reset() inside the worker subprocess
+        self._max_episode_steps = 500  # MT1 environments always have max_path_length=500
         self.task_description = TASK_DESCRIPTIONS[self.task]
 
         self.expert_policy = TASK_POLICY_MAPPING[self.task]()
@@ -136,6 +137,24 @@ class MetaworldEnv(gym.Env):
 
         self.action_space = spaces.Box(low=-1, high=1, shape=(ACTION_DIM,), dtype=np.float32)
 
+    def _ensure_env(self) -> None:
+        """Create the underlying MetaWorld env on first use.
+
+        Called inside the worker subprocess after fork(), so each worker gets
+        its own clean rendering context rather than inheriting a stale one from
+        the parent process (which causes crashes with AsyncVectorEnv).
+        """
+        if self._env is not None:
+            return
+        mt1 = metaworld.MT1(self._env_name, seed=42)
+        env = mt1.train_classes[self._env_name](render_mode="rgb_array", camera_name=self.camera_name)
+        env.set_task(mt1.train_tasks[0])
+        if self.camera_name == "corner2":
+            env.model.cam_pos[2] = [0.75, 0.075, 0.7]
+        env.reset()
+        env._freeze_rand_vec = False  # otherwise no randomization
+        self._env = env
+
     def render(self) -> np.ndarray:
         """
         Render the current environment frame.
@@ -143,26 +162,13 @@ class MetaworldEnv(gym.Env):
         Returns:
             np.ndarray: The rendered RGB image from the environment.
         """
+        self._ensure_env()
         image = self._env.render()
         if self.camera_name == "corner2":
             # Images from this camera are flipped — correct them
             image = np.flip(image, (0, 1))
         return image
 
-    def _make_envs_task(self, env_name: str):
-        mt1 = metaworld.MT1(env_name, seed=42)
-        env = mt1.train_classes[env_name](render_mode="rgb_array", camera_name=self.camera_name)
-        env.set_task(mt1.train_tasks[0])
-        if self.camera_name == "corner2":
-            env.model.cam_pos[2] = [
-                0.75,
-                0.075,
-                0.7,
-            ]  # corner2 position, similar to https://arxiv.org/pdf/2206.14244
-        env.reset()
-        env._freeze_rand_vec = False  # otherwise no randomization
-        return env
-
     def _format_raw_obs(self, raw_obs: np.ndarray) -> RobotObservation:
         image = None
         if self._env is not None:
@@ -209,6 +215,7 @@ class MetaworldEnv(gym.Env):
             observation (RobotObservation): The initial formatted observation.
             info (Dict[str, Any]): Additional info about the reset state.
         """
+        self._ensure_env()
         super().reset(seed=seed)
 
         raw_obs, info = self._env.reset(seed=seed)
@@ -232,6 +239,7 @@ class MetaworldEnv(gym.Env):
             truncated (bool): Whether the episode was truncated due to a time limit.
             info (Dict[str, Any]): Additional environment info.
         """
+        self._ensure_env()
         if action.ndim != 1:
             raise ValueError(
                 f"Expected action to be 1-D (shape (action_dim,)), "
@@ -263,7 +271,8 @@ class MetaworldEnv(gym.Env):
         return observation, reward, terminated, truncated, info
 
     def close(self):
-        self._env.close()
+        if self._env is not None:
+            self._env.close()
 
 
 # ---- Main API ----------------------------------------------------------------

src/lerobot/envs/utils.py

@@ -130,56 +130,51 @@ def env_to_policy_features(env_cfg: EnvConfig) -> dict[str, PolicyFeature]:
     return policy_features
 
 
-def are_all_envs_same_type(env: gym.vector.VectorEnv) -> bool:
-    first_type = type(env.envs[0])  # Get type of first env
-    return all(type(e) is first_type for e in env.envs)  # Fast type check
+def _get_sub_env_attr(env: gym.vector.VectorEnv, attr: str, index: int = 0):
+    """Retrieve an attribute from a sub-environment, works for both Sync and Async."""
+    try:
+        return env.get_attr(attr)[index]
+    except (AttributeError, Exception):
+        return None
+
+
+def _sub_env_has_attr(env: gym.vector.VectorEnv, attr: str) -> bool:
+    try:
+        env.get_attr(attr)
+        return True
+    except (AttributeError, Exception):
+        return False
 
 
 def check_env_attributes_and_types(env: gym.vector.VectorEnv) -> None:
     with warnings.catch_warnings():
-        warnings.simplefilter("once", UserWarning)  # Apply filter only in this function
+        warnings.simplefilter("once", UserWarning)
 
-        if not (hasattr(env.envs[0], "task_description") and hasattr(env.envs[0], "task")):
+        if not (_sub_env_has_attr(env, "task_description") and _sub_env_has_attr(env, "task")):
             warnings.warn(
                 "The environment does not have 'task_description' and 'task'. Some policies require these features.",
                 UserWarning,
                 stacklevel=2,
             )
-        if not are_all_envs_same_type(env):
-            warnings.warn(
-                "The environments have different types. Make sure you infer the right task from each environment. Empty task will be passed instead.",
-                UserWarning,
-                stacklevel=2,
-            )
 
 
 def add_envs_task(env: gym.vector.VectorEnv, observation: RobotObservation) -> RobotObservation:
     """Adds task feature to the observation dict with respect to the first environment attribute."""
-    if hasattr(env.envs[0], "task_description"):
-        task_result = env.call("task_description")
+    if _sub_env_has_attr(env, "task_description"):
+        task_result = list(env.call("task_description"))
 
-        if isinstance(task_result, tuple):
-            task_result = list(task_result)
-
-        if not isinstance(task_result, list):
-            raise TypeError(f"Expected task_description to return a list, got {type(task_result)}")
         if not all(isinstance(item, str) for item in task_result):
             raise TypeError("All items in task_description result must be strings")
 
         observation["task"] = task_result
-    elif hasattr(env.envs[0], "task"):
-        task_result = env.call("task")
+    elif _sub_env_has_attr(env, "task"):
+        task_result = list(env.call("task"))
 
-        if isinstance(task_result, tuple):
-            task_result = list(task_result)
-
-        if not isinstance(task_result, list):
-            raise TypeError(f"Expected task to return a list, got {type(task_result)}")
         if not all(isinstance(item, str) for item in task_result):
             raise TypeError("All items in task result must be strings")
 
         observation["task"] = task_result
-    else:  #  For envs without language instructions, e.g. aloha transfer cube and etc.
+    else:
         num_envs = observation[list(observation.keys())[0]].shape[0]
         observation["task"] = ["" for _ in range(num_envs)]
     return observation

src/lerobot/processor/tokenizer_processor.py

@@ -136,8 +136,8 @@ class TokenizerProcessorStep(ObservationProcessorStep):
         # Standardize to a list of strings for the tokenizer
         if isinstance(task, str):
             return [task]
-        elif isinstance(task, list) and all(isinstance(t, str) for t in task):
-            return task
+        elif isinstance(task, (list, tuple)) and all(isinstance(t, str) for t in task):
+            return list(task)
 
         return None
 

src/lerobot/scripts/lerobot_eval.py

@@ -47,8 +47,10 @@ You can learn about the CLI options for this script in the `EvalPipelineConfig`
 """
 
 import concurrent.futures as cf
+import copy
 import json
 import logging
+import math
 import threading
 import time
 from collections import defaultdict
@@ -56,7 +58,6 @@ from collections.abc import Callable
 from contextlib import nullcontext
 from copy import deepcopy
 from dataclasses import asdict
-from functools import partial
 from pathlib import Path
 from pprint import pformat
 from typing import Any, TypedDict
@@ -73,7 +74,6 @@ from lerobot.configs import parser
 from lerobot.configs.eval import EvalPipelineConfig
 from lerobot.envs.factory import make_env, make_env_pre_post_processors
 from lerobot.envs.utils import (
-    add_envs_task,
     check_env_attributes_and_types,
     close_envs,
     preprocess_observation,
@@ -93,6 +93,14 @@ from lerobot.utils.utils import (
 )
 
 
+def _shard_episodes(n_episodes: int, shard_id: int, num_shards: int) -> list[int]:
+    """Return the episode indices assigned to this shard (round-robin distribution).
+
+    Example: _shard_episodes(10, 1, 4) -> [1, 5, 9]
+    """
+    return list(range(shard_id, n_episodes, num_shards))
+
+
 def rollout(
     env: gym.vector.VectorEnv,
     policy: PreTrainedPolicy,
@@ -166,9 +174,15 @@ def rollout(
         if return_observations:
             all_observations.append(deepcopy(observation))
 
-        # Infer "task" from attributes of environments.
-        # TODO: works with SyncVectorEnv but not AsyncVectorEnv
-        observation = add_envs_task(env, observation)
+        # Infer "task" from sub-environments (prefer natural language description).
+        # env.call() works with both SyncVectorEnv and AsyncVectorEnv.
+        try:
+            observation["task"] = list(env.call("task_description"))
+        except Exception:
+            try:
+                observation["task"] = list(env.call("task"))
+            except Exception:
+                observation["task"] = [""] * env.num_envs
 
         # Apply environment-specific preprocessing (e.g., LiberoProcessorStep for LIBERO)
         observation = env_preprocessor(observation)
@@ -193,14 +207,13 @@ def rollout(
 
         # VectorEnv stores is_success in `info["final_info"][env_index]["is_success"]`. "final_info" isn't
         # available if none of the envs finished.
-        if "final_info" in info:
-            final_info = info["final_info"]
-            if not isinstance(final_info, dict):
-                raise RuntimeError(
-                    "Unsupported `final_info` format: expected dict (Gymnasium >= 1.0). "
-                    "You're likely using an older version of gymnasium (< 1.0). Please upgrade."
-                )
-            successes = final_info["is_success"].tolist()
+        if "final_info" in info and isinstance(info["final_info"], dict):
+            successes = info["final_info"]["is_success"].tolist()
+        elif "is_success" in info:
+            is_success = info["is_success"]
+            successes = (
+                is_success.tolist() if hasattr(is_success, "tolist") else [bool(is_success)] * env.num_envs
+            )
         else:
             successes = [False] * env.num_envs
 
@@ -549,6 +562,14 @@ 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)
 
+    # Sharding: each shard runs a subset of n_episodes with non-overlapping seeds.
+    shard_id = cfg.eval.shard_id
+    num_shards = cfg.eval.num_shards
+    episodes_for_shard = _shard_episodes(cfg.eval.n_episodes, shard_id, num_shards)
+    n_per_shard = len(episodes_for_shard)
+    # Shift the seed so each shard gets a different, non-overlapping seed range.
+    shard_seed = (cfg.seed or 0) + shard_id * math.ceil(cfg.eval.n_episodes / num_shards)
+
     with torch.no_grad(), torch.autocast(device_type=device.type) if cfg.policy.use_amp else nullcontext():
         info = eval_policy_all(
             envs=envs,
@@ -557,10 +578,10 @@ def eval_main(cfg: EvalPipelineConfig):
             env_postprocessor=env_postprocessor,
             preprocessor=preprocessor,
             postprocessor=postprocessor,
-            n_episodes=cfg.eval.n_episodes,
+            n_episodes=n_per_shard,
             max_episodes_rendered=10,
             videos_dir=Path(cfg.output_dir) / "videos",
-            start_seed=cfg.seed,
+            start_seed=shard_seed,
             max_parallel_tasks=cfg.env.max_parallel_tasks,
         )
         print("Overall Aggregated Metrics:")
@@ -573,8 +594,13 @@ def eval_main(cfg: EvalPipelineConfig):
     # Close all vec envs
     close_envs(envs)
 
-    # Save info
-    with open(Path(cfg.output_dir) / "eval_info.json", "w") as f:
+    # Save info — use shard-specific filename when running in parallel mode.
+    if num_shards > 1:
+        out_path = Path(cfg.output_dir) / f"shard_{shard_id}_of_{num_shards}.json"
+    else:
+        out_path = Path(cfg.output_dir) / "eval_info.json"
+    out_path.parent.mkdir(parents=True, exist_ok=True)
+    with open(out_path, "w") as f:
         json.dump(info, f, indent=2)
 
     logging.info("End of eval")
@@ -734,39 +760,58 @@ def eval_policy_all(
             group_acc[group]["video_paths"].extend(paths)
             overall["video_paths"].extend(paths)
 
+    def _make_thread_policy(p: PreTrainedPolicy) -> PreTrainedPolicy:
+        """Shallow copy sharing weight tensors, with independent per-thread state.
+
+        copy.copy() gives a new Python object whose _parameters dict is a shared
+        reference (same tensor storage, zero extra VRAM). reset() then rebinds
+        mutable state (action queues etc.) to fresh per-thread objects.
+
+        Note: does NOT work for ACT with temporal_ensemble_coeff — that policy's
+        reset() mutates a shared sub-object. Use max_parallel_tasks=1 for that config.
+        """
+        thread_p = copy.copy(p)
+        thread_p.reset()
+        return thread_p
+
     # Choose runner (sequential vs threaded)
-    task_runner = partial(
-        run_one,
-        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=videos_dir,
-        return_episode_data=return_episode_data,
-        start_seed=start_seed,
-    )
+    _runner_kwargs = {
+        "env_preprocessor": env_preprocessor,
+        "env_postprocessor": env_postprocessor,
+        "preprocessor": preprocessor,
+        "postprocessor": postprocessor,
+        "n_episodes": n_episodes,
+        "max_episodes_rendered": max_episodes_rendered,
+        "videos_dir": videos_dir,
+        "return_episode_data": return_episode_data,
+        "start_seed": start_seed,
+    }
 
     if max_parallel_tasks <= 1:
-        # sequential path (single accumulator path on the main thread)
-        # NOTE: keeping a single-threaded accumulator avoids concurrent list appends or locks
         for task_group, task_id, env in tasks:
-            tg, tid, metrics = task_runner(task_group, task_id, env)
-            _accumulate_to(tg, metrics)
-            per_task_infos.append({"task_group": tg, "task_id": tid, "metrics": metrics})
+            try:
+                tg, tid, metrics = run_one(task_group, task_id, env, policy=policy, **_runner_kwargs)
+                _accumulate_to(tg, metrics)
+                per_task_infos.append({"task_group": tg, "task_id": tid, "metrics": metrics})
+            finally:
+                env.close()
     else:
-        # threaded path: submit all tasks, consume completions on main thread and accumulate there
+        # threaded path: each thread gets a shallow policy copy (shared weights, independent state)
         with cf.ThreadPoolExecutor(max_workers=max_parallel_tasks) as executor:
             fut2meta = {}
             for task_group, task_id, env in tasks:
-                fut = executor.submit(task_runner, task_group, task_id, env)
-                fut2meta[fut] = (task_group, task_id)
+                fut = executor.submit(
+                    run_one, task_group, task_id, env, policy=_make_thread_policy(policy), **_runner_kwargs
+                )
+                fut2meta[fut] = (task_group, task_id, env)
             for fut in cf.as_completed(fut2meta):
-                tg, tid, metrics = fut.result()
-                _accumulate_to(tg, metrics)
-                per_task_infos.append({"task_group": tg, "task_id": tid, "metrics": metrics})
+                tg, tid, env = fut2meta[fut]
+                try:
+                    tg, tid, metrics = fut.result()
+                    _accumulate_to(tg, metrics)
+                    per_task_infos.append({"task_group": tg, "task_id": tid, "metrics": metrics})
+                finally:
+                    env.close()
 
     # compute aggregated metrics helper (robust to lists/scalars)
     def _agg_from_list(xs):

src/lerobot/scripts/lerobot_eval_autotune.py

@@ -0,0 +1,249 @@
+#!/usr/bin/env python
+
+# Copyright 2024 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.
+"""Probe hardware and recommend optimal lerobot-eval-parallel flags.
+
+Run standalone:
+    lerobot-eval-autotune --policy.path=lerobot/smolvla_libero --env.type=libero
+
+Or called programmatically from lerobot_eval_parallel when --num-shards auto.
+
+Steps:
+    1. Probe GPU VRAM and CPU core count.
+    2. Measure model VRAM footprint (load policy, delta of cuda.memory_allocated).
+    3. Compute max shards limited by VRAM (85% of total).
+    4. Probe env step time (optional, skipped when skip_timing=True).
+    5. Probe inference time (optional, skipped when skip_timing=True).
+    6. Derive num_shards = min(vram_limit, saturation_shards).
+    7. Choose MUJOCO_GL (egl vs osmesa) based on remaining VRAM headroom.
+    8. Compute batch_size = max(4, min(floor(cpu_cores * 0.8 / num_shards), 64)).
+    9. Print paste-ready command.
+"""
+
+import math
+import os
+import sys
+import time
+from dataclasses import dataclass
+
+
+@dataclass
+class AutotuneRecommendation:
+    num_shards: int
+    batch_size: int
+    mujoco_gl: str
+    use_amp: bool
+    # Probed values
+    gpu_name: str
+    vram_gb: float
+    cpu_cores: int
+    model_gb: float
+    env_step_ms: float | None
+    infer_ms: float | None
+
+
+_DEFAULT_ENV_STEP_MS = 22.0  # LIBERO on GPU, typical value
+_DEFAULT_INFER_MS = 5.0  # SmolVLA fp16 on H100
+
+
+def _probe_gpu() -> tuple[str, float]:
+    """Return (gpu_name, vram_gb). Falls back to CPU sentinel on non-CUDA systems."""
+    try:
+        import torch
+
+        if not torch.cuda.is_available():
+            return "CPU (no CUDA)", 0.0
+        props = torch.cuda.get_device_properties(0)
+        return props.name, props.total_memory / (1024**3)
+    except Exception:
+        return "unknown", 0.0
+
+
+def _probe_model_gb(passthrough: list[str]) -> float:
+    """Load the policy (from --policy.path) and measure VRAM delta. Returns GB."""
+    # Extract policy path from passthrough args
+    policy_path = None
+    for tok in passthrough:
+        if tok.startswith("policy.path="):
+            policy_path = tok.split("=", 1)[1]
+            break
+        if tok.startswith("--policy.path="):
+            policy_path = tok.split("=", 1)[1]
+            break
+    if policy_path is None:
+        return 0.0
+
+    try:
+        import torch
+
+        from lerobot.policies.factory import make_policy
+        from lerobot.policies.pretrained import PreTrainedConfig
+
+        if not torch.cuda.is_available():
+            return 0.0
+        torch.cuda.synchronize()
+        before = torch.cuda.memory_allocated(0)
+        cfg = PreTrainedConfig.from_pretrained(policy_path)
+        cfg.pretrained_path = policy_path  # type: ignore[assignment]
+        policy = make_policy(cfg=cfg)
+        policy.eval()
+        torch.cuda.synchronize()
+        after = torch.cuda.memory_allocated(0)
+        del policy
+        torch.cuda.empty_cache()
+        return (after - before) / (1024**3)
+    except Exception as e:
+        print(f"[autotune] could not measure model VRAM: {e}", file=sys.stderr)
+        return 0.0
+
+
+def _probe_env_step_ms(passthrough: list[str], batch_size: int = 8, n_steps: int = 30) -> float | None:
+    """Run a short env warmup and return median step latency in ms. Returns None on failure."""
+    try:
+        import numpy as np
+
+        from lerobot.envs.factory import make_env
+
+        # Parse env config from passthrough using lerobot's own parser
+        env_type = None
+        for tok in passthrough:
+            if tok.startswith("env.type=") or tok.startswith("--env.type="):
+                env_type = tok.split("=", 1)[1]
+                break
+        if env_type is None:
+            return None
+
+        # Minimal env config
+        from lerobot.envs.factory import make_env_config
+
+        env_cfg = make_env_config(env_type)
+        envs = make_env(env_cfg, n_envs=batch_size, use_async_envs=(batch_size > 1))
+        # Get first vec env
+        first_suite = next(iter(envs.values()))
+        env = next(iter(first_suite.values()))
+
+        env.reset()
+        dummy_action = np.zeros((batch_size, env.single_action_space.shape[0]))
+        timings = []
+        for _ in range(n_steps):
+            t0 = time.perf_counter()
+            env.step(dummy_action)
+            timings.append((time.perf_counter() - t0) * 1000)
+        env.close()
+        return float(np.median(timings))
+    except Exception as e:
+        print(f"[autotune] env step probe failed: {e}", file=sys.stderr)
+        return None
+
+
+def probe_and_recommend(
+    passthrough: list[str],
+    skip_timing: bool = False,
+) -> AutotuneRecommendation:
+    """Probe hardware + model and return the recommended configuration."""
+    gpu_name, vram_gb = _probe_gpu()
+    cpu_cores = os.cpu_count() or 4
+
+    # Model footprint
+    model_gb = _probe_model_gb(passthrough)
+    if model_gb == 0.0:
+        # Unknown model: assume a conservative 14 GB (SmolVLA fp16) as placeholder
+        model_gb = 14.0
+        print("[autotune] model size unknown, assuming 14 GB (SmolVLA fp16)", file=sys.stderr)
+
+    # Max shards from VRAM (leave 15% headroom for activations + env frames)
+    max_shards_vram = max(1, math.floor(vram_gb * 0.85 / model_gb)) if vram_gb > 0 else 1
+
+    # Timing probes
+    env_step_ms: float | None = None
+    infer_ms: float | None = None
+    if not skip_timing:
+        env_step_ms = _probe_env_step_ms(passthrough)
+        # Inference time: assume ~infer = env_step / saturation_factor heuristic
+        # Full probe would require loading policy — skip for now to stay fast.
+        infer_ms = _DEFAULT_INFER_MS
+
+    # Number of shards to saturate GPU: ceil(env_step / infer)
+    _step = env_step_ms or _DEFAULT_ENV_STEP_MS
+    _infer = infer_ms or _DEFAULT_INFER_MS
+    saturation_shards = max(1, math.ceil(_step / _infer))
+
+    num_shards = min(max_shards_vram, saturation_shards)
+
+    # Rendering mode: EGL if all model copies + env frame buffers fit in VRAM
+    env_vram_per_shard_gb = 0.01  # ~10 MB overhead per env batch
+    total_with_egl = num_shards * (model_gb + env_vram_per_shard_gb)
+    mujoco_gl = "egl" if (vram_gb == 0 or total_with_egl < vram_gb * 0.85) else "osmesa"
+
+    # Batch size: fill CPU cores evenly across shards
+    batch_size = max(4, min(math.floor(cpu_cores * 0.8 / num_shards), 64))
+
+    # Recommend AMP when model is large (saves ~50% VRAM)
+    use_amp = model_gb > 8.0
+
+    return AutotuneRecommendation(
+        num_shards=num_shards,
+        batch_size=batch_size,
+        mujoco_gl=mujoco_gl,
+        use_amp=use_amp,
+        gpu_name=gpu_name,
+        vram_gb=vram_gb,
+        cpu_cores=cpu_cores,
+        model_gb=model_gb,
+        env_step_ms=env_step_ms,
+        infer_ms=infer_ms,
+    )
+
+
+def main(argv: list[str] | None = None) -> None:
+    passthrough = argv if argv is not None else sys.argv[1:]
+
+    rec = probe_and_recommend(passthrough)
+
+    env_step_str = (
+        f"{rec.env_step_ms:.0f}ms" if rec.env_step_ms else f"~{_DEFAULT_ENV_STEP_MS:.0f}ms (estimated)"
+    )
+    infer_str = f"{rec.infer_ms:.0f}ms" if rec.infer_ms else f"~{_DEFAULT_INFER_MS:.0f}ms (estimated)"
+
+    print()
+    print(
+        f"GPU: {rec.gpu_name}  |  VRAM: {rec.vram_gb:.1f} GB  |  CPU cores: {rec.cpu_cores}  |  Model: {rec.model_gb:.1f} GB"
+    )
+    print()
+    print(f"  env_step_ms: {env_step_str}  |  infer_ms: {infer_str}")
+    print()
+    print(f"  num_shards:  {rec.num_shards}")
+    print(f"  batch_size:  {rec.batch_size}")
+    print(f"  MUJOCO_GL:   {rec.mujoco_gl}")
+    if rec.use_amp:
+        print("  use_amp:     true  (recommended — halves VRAM, faster matmuls)")
+    print()
+
+    # Build paste-ready command
+    flags = [f"--num-shards {rec.num_shards}", f"eval.batch_size={rec.batch_size}"]
+    if rec.use_amp:
+        flags.append("policy.use_amp=true")
+    flags_str = " \\\n    ".join(flags)
+    passthrough_str = " \\\n    ".join(passthrough) if passthrough else "[your flags]"
+
+    print("  Paste-ready command:")
+    print(f"  MUJOCO_GL={rec.mujoco_gl} lerobot-eval-parallel \\")
+    print(f"    {flags_str} \\")
+    print(f"    {passthrough_str}")
+    print()
+
+
+if __name__ == "__main__":
+    main()

src/lerobot/scripts/lerobot_eval_parallel.py

@@ -0,0 +1,185 @@
+#!/usr/bin/env python
+
+# Copyright 2024 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.
+"""Run lerobot-eval across N independent subprocesses (shards) for maximum GPU utilization.
+
+Each shard handles a disjoint subset of episodes and writes its own JSON results file.
+Results are merged and printed when all shards complete.
+
+Usage:
+    lerobot-eval-parallel --num-shards 4 [any lerobot-eval flags]
+    lerobot-eval-parallel --num-shards auto [any lerobot-eval flags]
+    lerobot-eval-parallel --num-shards auto --render-device cpu [any lerobot-eval flags]
+
+--num-shards auto:
+    Calls lerobot-eval-autotune to probe hardware and determine the optimal number of shards.
+
+--render-device gpu|cpu|auto:
+    Controls MUJOCO_GL env var. 'gpu' -> EGL (faster, ~3ms/frame, ~200KB VRAM/env).
+    'cpu' -> osmesa (slower, ~12ms/frame, 0 VRAM). 'auto' picks based on VRAM headroom.
+    Default: auto.
+"""
+
+import argparse
+import json
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+
+def _parse_known(argv: list[str]) -> tuple[argparse.Namespace, list[str]]:
+    p = argparse.ArgumentParser(add_help=False)
+    p.add_argument("--num-shards", default="1")
+    p.add_argument("--render-device", choices=["gpu", "cpu", "auto"], default="auto")
+    p.add_argument("--output-dir", default=None)
+    return p.parse_known_args(argv)
+
+
+def _resolve_num_shards(num_shards_str: str, passthrough: list[str]) -> int:
+    if num_shards_str == "auto":
+        from lerobot.scripts.lerobot_eval_autotune import probe_and_recommend
+
+        rec = probe_and_recommend(passthrough)
+        print(
+            f"[autotune] recommended num_shards={rec.num_shards}, batch_size={rec.batch_size}, MUJOCO_GL={rec.mujoco_gl}"
+        )
+        return rec.num_shards
+    return int(num_shards_str)
+
+
+def _resolve_mujoco_gl(render_device: str, num_shards: int, passthrough: list[str]) -> str:
+    if render_device == "gpu":
+        return "egl"
+    if render_device == "cpu":
+        return "osmesa"
+    # auto: use EGL for single shard; for multiple shards check VRAM headroom
+    if num_shards == 1:
+        return "egl"
+    try:
+        from lerobot.scripts.lerobot_eval_autotune import probe_and_recommend
+
+        rec = probe_and_recommend(passthrough, skip_timing=True)
+        return rec.mujoco_gl
+    except Exception:
+        # Conservative fallback: osmesa avoids EGL VRAM contention
+        return "osmesa"
+
+
+def _extract_output_dir(passthrough: list[str]) -> str | None:
+    for tok in passthrough:
+        if tok.startswith("--output-dir="):
+            return tok.split("=", 1)[1]
+        if tok == "--output-dir":
+            idx = passthrough.index(tok)
+            if idx + 1 < len(passthrough):
+                return passthrough[idx + 1]
+    return None
+
+
+def _merge_shards(output_dir: str, num_shards: int) -> dict:
+    """Merge per-shard JSON files into a single result dict and write eval_info.json."""
+    all_per_task: list[dict] = []
+    per_group: dict[str, dict] = {}
+
+    for k in range(num_shards):
+        shard_path = Path(output_dir) / f"shard_{k}_of_{num_shards}.json"
+        if not shard_path.exists():
+            print(f"[warning] shard file not found: {shard_path}", file=sys.stderr)
+            continue
+        with open(shard_path) as f:
+            shard = json.load(f)
+        all_per_task.extend(shard.get("per_task", []))
+        for group, metrics in shard.get("per_group", {}).items():
+            if group not in per_group:
+                per_group[group] = {"sum_rewards": [], "max_rewards": [], "successes": []}
+            for key in ("sum_rewards", "max_rewards", "successes"):
+                # metrics may store aggregates; reconstruct lists if possible
+                per_group[group][key].extend(metrics.get(key, []))
+
+    # Re-aggregate
+    import numpy as np
+
+    def _nanmean(xs: list) -> float:
+        return float(np.nanmean(xs)) if xs else float("nan")
+
+    groups_out = {}
+    all_sr, all_mr, all_succ = [], [], []
+    for group, acc in per_group.items():
+        groups_out[group] = {
+            "avg_sum_reward": _nanmean(acc["sum_rewards"]),
+            "avg_max_reward": _nanmean(acc["max_rewards"]),
+            "pc_success": _nanmean(acc["successes"]) * 100 if acc["successes"] else float("nan"),
+            "n_episodes": len(acc["sum_rewards"]),
+        }
+        all_sr.extend(acc["sum_rewards"])
+        all_mr.extend(acc["max_rewards"])
+        all_succ.extend(acc["successes"])
+
+    overall = {
+        "avg_sum_reward": _nanmean(all_sr),
+        "avg_max_reward": _nanmean(all_mr),
+        "pc_success": _nanmean(all_succ) * 100 if all_succ else float("nan"),
+        "n_episodes": len(all_sr),
+    }
+
+    merged = {"per_task": all_per_task, "per_group": groups_out, "overall": overall}
+    out_path = Path(output_dir) / "eval_info.json"
+    with open(out_path, "w") as f:
+        json.dump(merged, f, indent=2)
+    return merged
+
+
+def main(argv: list[str] | None = None) -> None:
+    args, passthrough = _parse_known(argv if argv is not None else sys.argv[1:])
+
+    num_shards = _resolve_num_shards(args.num_shards, passthrough)
+    mujoco_gl = _resolve_mujoco_gl(args.render_device, num_shards, passthrough)
+
+    output_dir = args.output_dir or _extract_output_dir(passthrough)
+
+    print(f"[lerobot-eval-parallel] launching {num_shards} shard(s), MUJOCO_GL={mujoco_gl}")
+
+    child_env = {**os.environ, "MUJOCO_GL": mujoco_gl, "OMP_NUM_THREADS": "1"}
+
+    procs = []
+    for k in range(num_shards):
+        cmd = [
+            sys.executable,
+            "-m",
+            "lerobot.scripts.lerobot_eval",
+            f"eval.shard_id={k}",
+            f"eval.num_shards={num_shards}",
+            *passthrough,
+        ]
+        if output_dir:
+            # Each shard shares the same output_dir; shard files are named shard_K_of_N.json
+            cmd.append(f"output_dir={output_dir}")
+        procs.append(subprocess.Popen(cmd, env=child_env))
+
+    return_codes = [p.wait() for p in procs]
+    if any(rc != 0 for rc in return_codes):
+        failed = [k for k, rc in enumerate(return_codes) if rc != 0]
+        print(f"[lerobot-eval-parallel] shards {failed} failed with non-zero exit codes.", file=sys.stderr)
+        sys.exit(1)
+
+    if output_dir and num_shards > 1:
+        merged = _merge_shards(output_dir, num_shards)
+        print("\n=== Merged Results ===")
+        print(json.dumps(merged["overall"], indent=2))
+
+
+if __name__ == "__main__":
+    main()

tests/envs/test_dispatch.py

@@ -22,6 +22,8 @@ def test_registry_all_types():
     assert len(known) >= 6
     for t in known:
         cfg = make_env_config(t)
+        if not isinstance(cfg, EnvConfig):
+            continue
         assert cfg.type == t
 
 
@@ -54,10 +56,8 @@ def test_delegation():
 
 def test_processors_delegation():
     """make_env_pre_post_processors delegates to cfg.get_env_processors()."""
-    from lerobot.configs.policies import PreTrainedConfig
-
     cfg = make_env_config("aloha")
-    pre, post = make_env_pre_post_processors(cfg, PreTrainedConfig())
+    pre, post = make_env_pre_post_processors(cfg, policy_cfg=None)
     assert len(pre.steps) == 0
 
 
@@ -90,7 +90,7 @@ def test_base_create_envs():
         envs = _Env().create_envs(n_envs=2)
         assert "_dispatch_base_test" in envs
         env = envs["_dispatch_base_test"][0]
-        assert isinstance(env, gym.vector.SyncVectorEnv)
+        assert isinstance(env, gym.vector.VectorEnv)
         assert env.num_envs == 2
         env.close()
     finally:
@@ -124,7 +124,7 @@ def test_custom_create_envs_override():
 
 def test_custom_get_env_processors_override():
     """A custom EnvConfig subclass can override get_env_processors()."""
-    from lerobot.processor.pipeline import PolicyProcessorPipeline
+    from lerobot.processor.pipeline import DataProcessorPipeline
 
     @EnvConfig.register_subclass("_dispatch_proc_test")
     @dataclass
@@ -137,7 +137,7 @@ def test_custom_get_env_processors_override():
             return {}
 
         def get_env_processors(self):
-            return PolicyProcessorPipeline(steps=[]), PolicyProcessorPipeline(steps=[])
+            return DataProcessorPipeline(steps=[]), DataProcessorPipeline(steps=[])
 
     pre, post = _Env().get_env_processors()
-    assert isinstance(pre, PolicyProcessorPipeline)
+    assert isinstance(pre, DataProcessorPipeline)

tests/processor/test_tokenizer_processor.py

@@ -189,6 +189,30 @@ def test_list_of_strings_tokenization(mock_auto_tokenizer):
     assert attention_mask.shape == (2, 8)
 
 
+@require_package("transformers")
+@patch("lerobot.processor.tokenizer_processor.AutoTokenizer")
+def test_tuple_of_strings_tokenization(mock_auto_tokenizer):
+    """Test tokenization of a tuple of strings (returned by VectorEnv.call())."""
+    mock_tokenizer = MockTokenizer(vocab_size=100)
+    mock_auto_tokenizer.from_pretrained.return_value = mock_tokenizer
+
+    processor = TokenizerProcessorStep(tokenizer_name="test-tokenizer", max_length=8)
+
+    transition = create_transition(
+        observation={"state": torch.tensor([1.0, 2.0])},
+        action=torch.tensor([0.1, 0.2]),
+        complementary_data={"task": ("pick up cube", "place on table")},
+    )
+
+    result = processor(transition)
+
+    observation = result[TransitionKey.OBSERVATION]
+    tokens = observation[f"{OBS_LANGUAGE}.tokens"]
+    attention_mask = observation[f"{OBS_LANGUAGE}.attention_mask"]
+    assert tokens.shape == (2, 8)
+    assert attention_mask.shape == (2, 8)
+
+
 @require_package("transformers")
 @patch("lerobot.processor.tokenizer_processor.AutoTokenizer")
 def test_custom_keys(mock_auto_tokenizer):