chore(deps): bump pytest in the uv group across 1 directory

Bumps the uv group with 1 update in the / directory: [pytest](https://github.com/pytest-dev/pytest).


Updates `pytest` from 8.4.2 to 9.0.3
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/main/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/pytest/compare/8.4.2...9.0.3)

---
updated-dependencies:
- dependency-name: pytest
  dependency-version: 9.0.3
  dependency-type: direct:production
  dependency-group: uv
...

Signed-off-by: dependabot[bot] <support@github.com>

AGENTS.md

@@ -51,6 +51,7 @@ pre-commit run --all-files                           # Lint + format (ruff, typo
 ## Notes
 
 - **Mypy is gradual**: strict only for `lerobot.envs`, `lerobot.configs`, `lerobot.optim`, `lerobot.model`, `lerobot.cameras`, `lerobot.motors`, `lerobot.transport`. Add type annotations when modifying these modules.
-- **Optional dependencies**: many policies, envs, and robots are behind extras (e.g., `lerobot[aloha]`). New imports for optional packages must be guarded or lazy. See `pyproject.toml [project.optional-dependencies]`.
+- **Imports**: prefer top-level imports; relative (`from .sibling import X`) across sibling files within a module, absolute (`from lerobot.module import X`) across modules.
+- **Optional dependencies**: many policies, envs, and robots are behind extras (e.g., `lerobot[aloha]`, see `pyproject.toml`). Guard optional imports with `TYPE_CHECKING or _foo_available` at module top + a `require_package(...)` check at use time. Reuse the `_foo_available` flags in `utils/import_utils.py`; don't call `is_package_available`.
 - **Video decoding**: datasets can store observations as video files. `LeRobotDataset` handles frame extraction, but tests need ffmpeg installed.
 - **Prioritize use of `uv run`** to execute Python commands (not raw `python` or `pip`).

docs/source/bring_your_own_policies.mdx

@@ -165,6 +165,8 @@ Batches are flat dictionaries keyed by the constants in [`lerobot.utils.constant
 
 LeRobot uses `PolicyProcessorPipeline`s to normalize inputs and de-normalize outputs around your policy. For a concrete reference, see [`processor_act.py`](https://github.com/huggingface/lerobot/blob/main/src/lerobot/policies/act/processor_act.py) or [`processor_diffusion.py`](https://github.com/huggingface/lerobot/blob/main/src/lerobot/policies/diffusion/processor_diffusion.py).
 
+Pay close attention here: processors are the most common reproducibility pain point. A mismatch in normalization mode (`IDENTITY` vs `MEAN_STD` vs `MIN_MAX` vs `QUANTILES`/`QUANTILE10`) or in which features get normalized will train and eval without erroring, yet silently wreck results. Make sure the modes match how the checkpoint was trained, that the required stats exist (e.g. `QUANTILES` needs `q01`/`q99`), and that the pre- and post-processors stay consistent.
+
 ```python
 # processor_my_policy.py
 from typing import Any
@@ -304,7 +306,9 @@ Mirror an existing policy that's structurally similar to yours; the diff is smal
 
 ### Heavy / optional dependencies
 
-Most policies need a heavy backbone (transformers, diffusers, a specific VLM SDK). The convention is **two-step gating**: a `TYPE_CHECKING`-guarded import at module top, and a `require_package` runtime check in the constructor. [`modeling_diffusion.py`](https://github.com/huggingface/lerobot/blob/main/src/lerobot/policies/diffusion/modeling_diffusion.py) is the canonical reference:
+Most policies need a heavy backbone (transformers, diffusers, a specific VLM SDK). Wherever one exists, prefer loading it e.g from `transformers` or `diffusers` rather than re-implementing the architecture in-tree.
+
+The convention is **two-step gating**: a `TYPE_CHECKING`-guarded import at module top, and a `require_package` runtime check in the constructor. [`modeling_diffusion.py`](https://github.com/huggingface/lerobot/blob/main/src/lerobot/policies/diffusion/modeling_diffusion.py) is the canonical reference:
 
 ```python
 from typing import TYPE_CHECKING
@@ -374,6 +378,7 @@ The general expectations are in [`CONTRIBUTING.md`](https://github.com/huggingfa
 - [ ] Optional deps live behind a `[project.optional-dependencies]` extra and the `TYPE_CHECKING + require_package` guard.
 - [ ] `tests/policies/` updated; backward-compat artifact committed & policy-specific tests.
 - [ ] `src/lerobot/policies/<name>/README.md` symlinked into `docs/source/policy_<name>_README.md`; user-facing `docs/source/<name>.mdx` written and added to `_toctree.yml`.
+- [ ] `lerobot-train --policy.type my_policy ...` runs end-to-end for at least a few steps + save a checkpoint that can be loaded and run by `lerobot-eval` or `lerobot-rollout`.
 - [ ] `templates/lerobot_modelcard_template.md` has a description entry and a `policy_docs` link for your policy.
 - [ ] The models table in the root `README.md` lists your policy in the right category, linking to your doc page.
 - [ ] At least one reproducible benchmark eval in the policy MDX with a published checkpoint (sim benchmark, or real-robot dataset + checkpoint).

pyproject.toml

@@ -155,7 +155,7 @@ accelerate-dep = ["accelerate>=1.14.0,<2.0.0"]
 can-dep = ["python-can>=4.2.0,<5.0.0"]
 peft-dep = ["peft>=0.18.0,<1.0.0"]
 scipy-dep = ["scipy>=1.14.0,<2.0.0"]
-diffusers-dep = ["diffusers>=0.27.2,<0.36.0"]
+diffusers-dep = ["diffusers>=0.38.0,<0.40.0"]
 qwen-vl-utils-dep = ["qwen-vl-utils>=0.0.11,<0.1.0"]
 matplotlib-dep = ["matplotlib>=3.10.3,<4.0.0", "contourpy>=1.3.0,<2.0.0"] # NOTE: Explicitly listing contourpy helps the resolver converge faster.
 pyserial-dep = ["pyserial>=3.5,<4.0"]
@@ -261,7 +261,7 @@ annotations = [
 # Development
 dev = ["pre-commit>=3.7.0,<5.0.0", "debugpy>=1.8.1,<1.9.0", "lerobot[grpcio-dep]", "grpcio-tools>=1.73.1,<2.0.0", "mypy>=1.19.1", "ruff>=0.14.1", "lerobot[notebook]"]
 notebook = ["jupyter>=1.0.0,<2.0.0", "ipykernel>=6.0.0,<7.0.0"]
-test = ["pytest>=8.1.0,<9.0.0", "pytest-timeout>=2.4.0,<3.0.0", "pytest-cov>=5.0.0,<8.0.0", "mock-serial>=0.0.1,<0.1.0 ; sys_platform != 'win32'"]
+test = ["pytest>=8.1.0,<10.0.0", "pytest-timeout>=2.4.0,<3.0.0", "pytest-cov>=5.0.0,<8.0.0", "mock-serial>=0.0.1,<0.1.0 ; sys_platform != 'win32'"]
 video_benchmark = ["scikit-image>=0.23.2,<0.26.0", "pandas>=2.2.2,<2.4.0"]
 
 # Simulation

src/lerobot/policies/gaussian_actor/configuration_gaussian_actor.py

@@ -37,19 +37,13 @@ def is_image_feature(key: str) -> bool:
 @dataclass
 class ConcurrencyConfig:
     """Configuration for the concurrency of the actor and learner.
-
     Possible values are:
     - "threads": Use threads for the actor and learner.
     - "processes": Use processes for the actor and learner.
-
-    ``multiprocessing_context`` selects the process-wide start method when
-    processes are used. Set it to ``None`` to preserve Python's default or a
-    method already selected by the embedding application.
     """
 
     actor: str = "threads"
     learner: str = "threads"
-    multiprocessing_context: str | None = "spawn"
 
 
 @dataclass

src/lerobot/rl/actor.py

@@ -91,7 +91,7 @@ from lerobot.robots import so_follower  # noqa: F401
 from lerobot.teleoperators import gamepad, so_leader  # noqa: F401
 from lerobot.teleoperators.utils import TeleopEvents
 from lerobot.utils.device_utils import get_safe_torch_device
-from lerobot.utils.process import ProcessSignalHandler, ensure_multiprocessing_start_method
+from lerobot.utils.process import ProcessSignalHandler
 from lerobot.utils.random_utils import set_seed
 from lerobot.utils.robot_utils import precise_sleep
 from lerobot.utils.transition import (
@@ -124,7 +124,9 @@ def actor_cli(cfg: TrainRLServerPipelineConfig):
     cfg.validate()
     display_pid = False
     if not use_threads(cfg):
-        ensure_multiprocessing_start_method(cfg.policy.concurrency.multiprocessing_context)
+        import torch.multiprocessing as mp
+
+        mp.set_start_method("spawn")
         display_pid = True
 
     # Create logs directory to ensure it exists

src/lerobot/rl/learner.py

@@ -102,7 +102,7 @@ from lerobot.utils.constants import (
 )
 from lerobot.utils.device_utils import get_safe_torch_device
 from lerobot.utils.io_utils import load_json, write_json
-from lerobot.utils.process import ProcessSignalHandler, ensure_multiprocessing_start_method
+from lerobot.utils.process import ProcessSignalHandler
 from lerobot.utils.random_utils import set_seed
 from lerobot.utils.utils import (
     format_big_number,
@@ -123,7 +123,9 @@ def train_cli(cfg: TrainRLServerPipelineConfig):
     # Fail fast with a friendly error if the optional ``hilserl`` extra is missing.
     require_package("grpcio", extra="hilserl", import_name="grpc")
     if not use_threads(cfg):
-        ensure_multiprocessing_start_method(cfg.policy.concurrency.multiprocessing_context)
+        import torch.multiprocessing as mp
+
+        mp.set_start_method("spawn")
 
     # Use the job_name from the config
     train(

src/lerobot/robots/bi_so_follower/bi_so_follower.py

@@ -58,6 +58,9 @@ class BiSOFollower(BimanualMixin, Robot):
             port=config.left_arm_config.port,
             disable_torque_on_disconnect=config.left_arm_config.disable_torque_on_disconnect,
             max_relative_target=config.left_arm_config.max_relative_target,
+            position_p_coefficient=config.left_arm_config.position_p_coefficient,
+            position_i_coefficient=config.left_arm_config.position_i_coefficient,
+            position_d_coefficient=config.left_arm_config.position_d_coefficient,
             use_degrees=config.left_arm_config.use_degrees,
             cameras=left_arm_cameras,
         )
@@ -68,6 +71,9 @@ class BiSOFollower(BimanualMixin, Robot):
             port=config.right_arm_config.port,
             disable_torque_on_disconnect=config.right_arm_config.disable_torque_on_disconnect,
             max_relative_target=config.right_arm_config.max_relative_target,
+            position_p_coefficient=config.right_arm_config.position_p_coefficient,
+            position_i_coefficient=config.right_arm_config.position_i_coefficient,
+            position_d_coefficient=config.right_arm_config.position_d_coefficient,
             use_degrees=config.right_arm_config.use_degrees,
             cameras=config.right_arm_config.cameras,
         )

src/lerobot/robots/so_follower/config_so_follower.py

@@ -41,6 +41,11 @@ class SOFollowerConfig:
     # Set to `True` for backward compatibility with previous policies/dataset
     use_degrees: bool = True
 
+    # Position-mode PID gains written to Feetech STS3215 motors at connect time.
+    position_p_coefficient: int = 16
+    position_i_coefficient: int = 0
+    position_d_coefficient: int = 32
+
 
 @RobotConfig.register_subclass("so101_follower")
 @RobotConfig.register_subclass("so100_follower")

src/lerobot/robots/so_follower/so_follower.py

@@ -161,11 +161,9 @@ class SOFollower(Robot):
             self.bus.configure_motors()
             for motor in self.bus.motors:
                 self.bus.write("Operating_Mode", motor, OperatingMode.POSITION.value)
-                # Set P_Coefficient to lower value to avoid shakiness (Default is 32)
-                self.bus.write("P_Coefficient", motor, 16)
-                # Set I_Coefficient and D_Coefficient to default value 0 and 32
-                self.bus.write("I_Coefficient", motor, 0)
-                self.bus.write("D_Coefficient", motor, 32)
+                self.bus.write("P_Coefficient", motor, self.config.position_p_coefficient)
+                self.bus.write("I_Coefficient", motor, self.config.position_i_coefficient)
+                self.bus.write("D_Coefficient", motor, self.config.position_d_coefficient)
 
                 if motor == "gripper":
                     self.bus.write("Max_Torque_Limit", motor, 500)  # 50% of max torque to avoid burnout

src/lerobot/utils/process.py

@@ -16,39 +16,11 @@
 # limitations under the License.
 
 import logging
-import multiprocessing
 import os
 import signal
 import sys
 
 
-def ensure_multiprocessing_start_method(start_method: str | None) -> None:
-    """Set a multiprocessing start method once, or verify the existing method matches.
-
-    Passing ``None`` leaves Python's process-wide default untouched. This is useful
-    when LeRobot is embedded in an application that owns multiprocessing setup.
-    """
-    if start_method is None:
-        return
-
-    available_methods = multiprocessing.get_all_start_methods()
-    if start_method not in available_methods:
-        raise ValueError(
-            f"Multiprocessing start method must be one of {available_methods} on this platform, "
-            f"got {start_method!r}."
-        )
-
-    current_method = multiprocessing.get_start_method(allow_none=True)
-    if current_method is None:
-        multiprocessing.set_start_method(start_method)
-    elif current_method != start_method:
-        raise RuntimeError(
-            f"Multiprocessing start method is already {current_method!r}; cannot change it to "
-            f"{start_method!r}. Set the configured multiprocessing context to null to keep the "
-            "application's existing method, or launch LeRobot in a fresh process."
-        )
-
-
 class ProcessSignalHandler:
     """Utility class to attach graceful shutdown signal handlers.
 

tests/policies/test_gaussian_actor_config.py

@@ -113,7 +113,6 @@ def test_gaussian_actor_config_default_initialization():
     # Concurrency configuration
     assert config.concurrency.actor == "threads"
     assert config.concurrency.learner == "threads"
-    assert config.concurrency.multiprocessing_context == "spawn"
 
     assert isinstance(config.actor_network_kwargs, ActorNetworkConfig)
     assert isinstance(config.policy_kwargs, PolicyConfig)
@@ -153,7 +152,6 @@ def test_concurrency_config():
     config = ConcurrencyConfig()
     assert config.actor == "threads"
     assert config.learner == "threads"
-    assert config.multiprocessing_context == "spawn"
 
 
 def test_gaussian_actor_config_custom_initialization():

tests/robots/test_so100_follower.py

@@ -109,3 +109,22 @@ def test_send_action(follower):
 
     goal_pos = {m: (i + 1) * 10 for i, m in enumerate(follower.bus.motors)}
     follower.bus.sync_write.assert_called_once_with("Goal_Position", goal_pos)
+
+
+def test_configure_writes_position_pid_coefficients():
+    bus_mock = _make_bus_mock()
+    bus_mock.motors = ["shoulder_pan"]
+    robot = MagicMock()
+    robot.bus = bus_mock
+    robot.config = SO100FollowerConfig(
+        port="/dev/null",
+        position_p_coefficient=32,
+        position_i_coefficient=1,
+        position_d_coefficient=16,
+    )
+
+    SO100Follower.configure(robot)
+
+    bus_mock.write.assert_any_call("P_Coefficient", "shoulder_pan", 32)
+    bus_mock.write.assert_any_call("I_Coefficient", "shoulder_pan", 1)
+    bus_mock.write.assert_any_call("D_Coefficient", "shoulder_pan", 16)