diff --git a/docs/sphinx/source/zh_CN/5-reference/5-support_matrix.md b/docs/sphinx/source/zh_CN/5-reference/5-support_matrix.md
index 60f8c83a7..66d1f113f 100644
--- a/docs/sphinx/source/zh_CN/5-reference/5-support_matrix.md
+++ b/docs/sphinx/source/zh_CN/5-reference/5-support_matrix.md
@@ -77,13 +77,14 @@ uv run scripts/generate_support_matrix.py --write
 | APPO (torch) | `g1_flip_tracking` (G1 flip tracking) | Tested | - | Tested | - | - | - | - | - |
 | APPO (torch) | `allegro_inhand` (Allegro in-hand) | Tested | - | Tested | - | - | - | - | - |
 | SAC (torch) | `g1_walk_flat` (G1 walk flat) | Tested | Tested | Tested | Tested | Tested | Configured | Tested | - |
-| SAC (torch) | `g1_motion_tracking` (G1 motion tracking) | Tested | Configured | Tested | - | - | - | - | - |
+| SAC (torch) | `g1_motion_tracking` (G1 motion tracking) | Tested | Configured | Tested | - | Registered | - | Registered | - |
 | SAC (torch) | `g1_flip_tracking` (G1 flip tracking) | Tested | - | Registered | - | - | - | - | - |
 | SAC (torch) | `g1_wbt_obs` (g1 wbt obs) | Tested | - | Registered | - | - | - | - | - |
 | TD3 (torch) | `go2_joystick_flat` (Go2 joystick) | Registered | - | Tested | - | - | - | - | Registered |
 | TD3 (torch) | `g1_walk_flat` (G1 walk flat) | Tested | Registered | Registered | Registered | Registered | Registered | Registered | - |
 | FlashSAC (torch) | `go2_joystick_flat` (Go2 joystick) | Tested | - | Registered | - | - | - | - | Registered |
 | FlashSAC (torch) | `g1_walk_flat` (G1 walk flat) | Tested | Configured | Tested | Registered | Registered | Registered | Registered | - |
+| FlashSAC (torch) | `g1_motion_tracking` (G1 motion tracking) | Tested | Configured | Tested | - | Configured | - | Configured | - |
 
 ### Source Index
 
diff --git a/pyproject.toml b/pyproject.toml
index 6e061b4d0..69d2f55bc 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -40,8 +40,10 @@ dependencies = [
     "numpy",
     # Physics implementations are provided by the independently released
     # unisim-core package. Version 1.5.0 provides the M2 physical entity,
-    # immutable variant, layout and selected-reset contracts.
-    "unisim-core>=1.5.0",
+    # immutable variant, layout and selected-reset contracts; 1.5.1 adds
+    # get_motion_body_ids on the newton/genesis adapters and fixes the
+    # subprocess motion-id offset (unilabsim/unisim#137).
+    "unisim-core>=1.5.1",
     # RL algorithms and async runtimes (PPO/APPO/SAC/TD3 runners,
     # collectors, IPC, logging) live in the independently released uni-rl
     # package (distribution name ``unilab-rl``), consumed via the injected
@@ -169,7 +171,7 @@ viser = ["viser>=1.0.26", "trimesh>=3.21.7"]
 # required-environments; elsewhere the extra is empty and the CLI reports a
 # targeted runtime diagnostic.
 superdex = [
-    "unisim-core[superdex]>=1.5.0 ; python_version >= '3.12' and sys_platform == 'linux' and platform_machine == 'x86_64'",
+    "unisim-core[superdex]>=1.5.1 ; python_version >= '3.12' and sys_platform == 'linux' and platform_machine == 'x86_64'",
 ]
 
 [dependency-groups]
diff --git a/src/unilab/conf/flashsac/config.yaml b/src/unilab/conf/flashsac/config.yaml
index 14e9a6173..0e837a40a 100644
--- a/src/unilab/conf/flashsac/config.yaml
+++ b/src/unilab/conf/flashsac/config.yaml
@@ -88,6 +88,10 @@ training:
   log_root: null
   log_dir: null
   env_steps_per_sync: 1
+  # Seconds the learner waits for each collector inference tick before
+  # failing. Tick 0 includes collector env construction, whose cost is
+  # backend-owned; slow-start backends raise this in their task owner YAML.
+  inference_request_timeout_sec: 30.0
   trace_enabled: false
   trace_output_dir: null
   trace_thread_time: false
diff --git a/src/unilab/conf/flashsac/task/g1_motion_tracking/base.yaml b/src/unilab/conf/flashsac/task/g1_motion_tracking/base.yaml
new file mode 100644
index 000000000..c0fa03002
--- /dev/null
+++ b/src/unilab/conf/flashsac/task/g1_motion_tracking/base.yaml
@@ -0,0 +1,253 @@
+# @package _global_
+# Canonical G1 Whole-Body Tracking (WBT) Manager-Based task declaration for
+# FlashSAC owners. Env/reward identity matches
+# conf/sac/task/g1_motion_tracking/mujoco.yaml verbatim so the sim2sim
+# DENYLIST contract keeps parity across algos and backends; backend owner
+# leaves inherit this file and only override backend/algo tuning.
+env:
+  seed: null
+  scene:
+    model_file: src/unilab/assets/robots/g1/scene_flat.xml
+    default_keyframe_name: stand
+    entities:
+      robot:
+        root_body_name: pelvis
+        joint_names: &g1_joints
+          - left_hip_pitch_joint
+          - left_hip_roll_joint
+          - left_hip_yaw_joint
+          - left_knee_joint
+          - left_ankle_pitch_joint
+          - left_ankle_roll_joint
+          - right_hip_pitch_joint
+          - right_hip_roll_joint
+          - right_hip_yaw_joint
+          - right_knee_joint
+          - right_ankle_pitch_joint
+          - right_ankle_roll_joint
+          - waist_yaw_joint
+          - waist_roll_joint
+          - waist_pitch_joint
+          - left_shoulder_pitch_joint
+          - left_shoulder_roll_joint
+          - left_shoulder_yaw_joint
+          - left_elbow_joint
+          - left_wrist_roll_joint
+          - left_wrist_pitch_joint
+          - left_wrist_yaw_joint
+          - right_shoulder_pitch_joint
+          - right_shoulder_roll_joint
+          - right_shoulder_yaw_joint
+          - right_elbow_joint
+          - right_wrist_roll_joint
+          - right_wrist_pitch_joint
+          - right_wrist_yaw_joint
+        actuator_names: *g1_joints
+        body_names: &tracked_bodies
+          - pelvis
+          - left_hip_roll_link
+          - left_knee_link
+          - left_ankle_roll_link
+          - right_hip_roll_link
+          - right_knee_link
+          - right_ankle_roll_link
+          - torso_link
+          - left_shoulder_roll_link
+          - left_elbow_link
+          - left_wrist_yaw_link
+          - right_shoulder_roll_link
+          - right_elbow_link
+          - right_wrist_yaw_link
+  sim_dt: 0.006666666666666667
+  ctrl_dt: 0.02
+  max_episode_seconds: 10.0
+  observations:
+    actor:
+      enable_corruption: true
+      terms:
+        command: &command_obs
+          func: unilab.envs.mdp.generated_commands
+          params: {command_name: motion}
+        motion_anchor_pos_b: &anchor_pos_obs
+          func: unilab.tasks.motion_tracking.common.manager_terms.motion_anchor_pos_b
+          params: {command_name: motion}
+        motion_anchor_ori_b: &anchor_ori_obs
+          func: unilab.tasks.motion_tracking.common.manager_terms.motion_anchor_ori_b
+          params: {command_name: motion}
+        base_lin_vel: &base_lin_vel_obs
+          func: unilab.envs.mdp.builtin_sensor
+          params: {sensor_name: pelvis_local_linvel}
+          noise:
+            _target_: unilab.managers._noise.UniformNoiseCfg
+            n_min: -0.1
+            n_max: 0.1
+        base_ang_vel: &base_ang_vel_obs
+          func: unilab.envs.mdp.builtin_sensor
+          params: {sensor_name: torso_gyro}
+          noise:
+            _target_: unilab.managers._noise.UniformNoiseCfg
+            n_min: -0.2
+            n_max: 0.2
+        joint_pos: &joint_pos_obs
+          func: unilab.tasks.motion_tracking.common.manager_terms.motion_joint_pos_rel
+          params: {command_name: motion}
+          noise:
+            _target_: unilab.managers._noise.UniformNoiseCfg
+            n_min: -0.01
+            n_max: 0.01
+        joint_vel: &joint_vel_obs
+          func: unilab.envs.mdp.joint_vel_rel
+          noise:
+            _target_: unilab.managers._noise.UniformNoiseCfg
+            n_min: -1.5
+            n_max: 1.5
+        actions: &actions_obs
+          func: unilab.envs.mdp.last_action
+    critic:
+      terms:
+        command: *command_obs
+        motion_anchor_pos_b: *anchor_pos_obs
+        motion_anchor_ori_b: *anchor_ori_obs
+        base_lin_vel: *base_lin_vel_obs
+        base_ang_vel: *base_ang_vel_obs
+        joint_pos: *joint_pos_obs
+        joint_vel: *joint_vel_obs
+        actions: *actions_obs
+        body_pos:
+          func: unilab.tasks.motion_tracking.common.manager_terms.robot_body_pos_b
+          params: {command_name: motion}
+        body_ori:
+          func: unilab.tasks.motion_tracking.common.manager_terms.robot_body_ori_b
+          params: {command_name: motion}
+        sac_base_lin_vel:
+          func: unilab.envs.mdp.builtin_sensor
+          params: {sensor_name: pelvis_local_linvel}
+  actions:
+    joint_pos:
+      _target_: unilab.tasks.motion_tracking.common.manager_terms.MotionJointPositionActionCfg
+      entity_name: robot
+      actuator_names: [".*"]
+      scale: 2.0
+      use_default_offset: true
+      command_name: motion
+  commands:
+    motion:
+      _target_: unilab.tasks.motion_tracking.common.manager_terms.MotionCommandCfg
+      entity_name: robot
+      resampling_time_range: [1.0e9, 1.0e9]
+      params:
+        motion_file: motions/g1/dance1_subject2_part.npz
+        anchor_body_name: torso_link
+        body_names: *tracked_bodies
+        sampling_mode: adaptive
+        sampling_start_ratio: 0.0
+        truncate_on_clip_end: true
+        pose_range:
+          x: [-0.05, 0.05]
+          y: [-0.05, 0.05]
+          z: [-0.01, 0.01]
+          roll: [-0.1, 0.1]
+          pitch: [-0.1, 0.1]
+          yaw: [-0.2, 0.2]
+        velocity_range:
+          x: [-0.5, 0.5]
+          y: [-0.5, 0.5]
+          z: [-0.2, 0.2]
+          roll: [-0.52, 0.52]
+          pitch: [-0.52, 0.52]
+          yaw: [-0.78, 0.78]
+        joint_position_range: [-0.1, 0.1]
+        joint_default_position_range: [0.0, 0.0]
+  terminations:
+    time_out:
+      func: unilab.envs.mdp.time_out
+      time_out: true
+    motion_clip_end:
+      func: unilab.tasks.motion_tracking.common.manager_terms.motion_clip_end
+      time_out: true
+      params: {command_name: motion}
+    anchor_pos:
+      func: unilab.tasks.motion_tracking.common.manager_terms.bad_anchor_pos_z_only
+      params: {command_name: motion, threshold: 0.5}
+    anchor_ori:
+      func: unilab.tasks.motion_tracking.common.manager_terms.bad_anchor_ori
+      params:
+        command_name: motion
+        threshold: 0.8
+        asset_cfg:
+          _target_: unilab.managers.SceneEntityCfg
+          name: robot
+    ee_body_pos:
+      func: unilab.tasks.motion_tracking.common.manager_terms.bad_motion_body_pos_z_only
+      params:
+        command_name: motion
+        threshold: 0.5
+        body_names:
+          - left_ankle_roll_link
+          - right_ankle_roll_link
+          - left_wrist_yaw_link
+          - right_wrist_yaw_link
+  policy_observation_group: actor
+  critic_observation_group: critic
+
+reward:
+  motion_global_root_pos:
+    func: unilab.tasks.motion_tracking.common.manager_terms.motion_global_anchor_position_error_exp
+    weight: 1.0
+    params: {command_name: motion, std: 0.3}
+  motion_global_root_ori:
+    func: unilab.tasks.motion_tracking.common.manager_terms.motion_global_anchor_orientation_error_exp
+    weight: 0.5
+    params: {command_name: motion, std: 0.4}
+  motion_body_pos:
+    func: unilab.tasks.motion_tracking.common.manager_terms.motion_relative_body_position_error_exp
+    weight: 2.0
+    params: {command_name: motion, std: 0.3}
+  motion_body_ori:
+    func: unilab.tasks.motion_tracking.common.manager_terms.motion_relative_body_orientation_error_exp
+    weight: 1.0
+    params: {command_name: motion, std: 0.4}
+  motion_body_lin_vel:
+    func: unilab.tasks.motion_tracking.common.manager_terms.motion_global_body_linear_velocity_error_exp
+    weight: 1.0
+    params: {command_name: motion, std: 1.0}
+  motion_body_ang_vel:
+    func: unilab.tasks.motion_tracking.common.manager_terms.motion_global_body_angular_velocity_error_exp
+    weight: 1.0
+    params: {command_name: motion, std: 3.14}
+  motion_joint_pos:
+    func: unilab.tasks.motion_tracking.common.manager_terms.motion_joint_position_error_exp
+    weight: 0.0
+    params: {command_name: motion, std: 0.2}
+  motion_joint_vel:
+    func: unilab.tasks.motion_tracking.common.manager_terms.motion_joint_velocity_error_exp
+    weight: 0.0
+    params: {command_name: motion, std: 1.0}
+  action_rate_l2:
+    func: unilab.envs.mdp.action_rate_l2
+    weight: -0.1
+  joint_limit:
+    func: unilab.tasks.motion_tracking.common.manager_terms.joint_pos_limits
+    weight: -2.0
+    params:
+      asset_cfg:
+        _target_: unilab.managers.SceneEntityCfg
+        name: robot
+        joint_names: ".*"
+  undesired_contacts:
+    func: unilab.tasks.motion_tracking.common.manager_terms.undesired_body_contacts
+    weight: -0.1
+    params:
+      command_name: motion
+      threshold: 0.05
+      body_names:
+        - pelvis
+        - left_hip_roll_link
+        - left_knee_link
+        - right_hip_roll_link
+        - right_knee_link
+        - torso_link
+        - left_shoulder_roll_link
+        - left_elbow_link
+        - right_shoulder_roll_link
+        - right_elbow_link
diff --git a/src/unilab/conf/flashsac/task/g1_motion_tracking/genesis.yaml b/src/unilab/conf/flashsac/task/g1_motion_tracking/genesis.yaml
new file mode 100644
index 000000000..74a516e5a
--- /dev/null
+++ b/src/unilab/conf/flashsac/task/g1_motion_tracking/genesis.yaml
@@ -0,0 +1,29 @@
+# @package _global_
+# FlashSAC Genesis owner for G1 WBT (in-process backend, genesis-world==1.3.3).
+# Keeps DENYLIST parity with the MuJoCo owner so cross-backend play transfers
+# 1:1. Genesis drops the MJCF global <option> block at import (REPORT #1372
+# §3.3), so the integrator g1.xml declares is re-declared here: the timestep
+# flows through the existing base.yaml sim_dt -> ctrl_dt chain, and the
+# integrator through the env field below. Requires unisim-core>=1.5.1 for the
+# motion body id capability (unilabsim/unisim#137). Playback uses Genesis
+# native rendering: with a display, play_render_mode=auto opens the
+# interactive viewer; headless hosts fall back to offscreen camera recording.
+defaults:
+  - /task/g1_motion_tracking/mujoco
+  - _self_
+
+training:
+  task_name: G1MotionTrackingSAC
+  sim_backend: genesis
+  play_render_mode: auto
+  # First tick includes collector env construction; genesis JIT startup exceeds
+  # the 30s default (same override as sac g1_walk_flat/genesis).
+  inference_request_timeout_sec: 180.0
+env:
+  # GPU device id for the process-wide Genesis session. Multi-GPU training
+  # overrides this cold-path field from the rank topology; zero preserves the
+  # single-device owner default.
+  genesis_device_id: 0
+  # Re-declares the MJCF <option integrator="implicitfast"> that Genesis drops
+  # at import; the remaining global options keep the Genesis defaults.
+  genesis_integrator: implicitfast
diff --git a/src/unilab/conf/flashsac/task/g1_motion_tracking/mjwarp.yaml b/src/unilab/conf/flashsac/task/g1_motion_tracking/mjwarp.yaml
new file mode 100644
index 000000000..97c5fd42e
--- /dev/null
+++ b/src/unilab/conf/flashsac/task/g1_motion_tracking/mjwarp.yaml
@@ -0,0 +1,15 @@
+# @package _global_
+# FlashSAC mjwarp (GPU) owner for G1 WBT. Inherits the MuJoCo owner verbatim
+# so sim2sim DENYLIST fields keep parity and run metrics stay directly
+# comparable with logs/fast_sac/G1MotionTrackingSAC; offline record reuses
+# MuJoCo rendering.
+# NOTE: mjwarp rejects reset/interval domain randomization and push terms;
+# this owner inherits the DR-free base, so no extra disables are needed.
+defaults:
+  - /task/g1_motion_tracking/mujoco
+  - _self_
+
+training:
+  task_name: G1MotionTrackingSAC
+  sim_backend: mjwarp
+  play_render_mode: record
diff --git a/src/unilab/conf/flashsac/task/g1_motion_tracking/motrix.yaml b/src/unilab/conf/flashsac/task/g1_motion_tracking/motrix.yaml
new file mode 100644
index 000000000..edc3e0575
--- /dev/null
+++ b/src/unilab/conf/flashsac/task/g1_motion_tracking/motrix.yaml
@@ -0,0 +1,9 @@
+# @package _global_
+# Motrix is the sim2sim eval owner for MuJoCo-trained FlashSAC WBT checkpoints.
+defaults:
+  - /task/g1_motion_tracking/mujoco
+  - _self_
+
+training:
+  task_name: G1MotionTrackingSAC
+  sim_backend: motrix
diff --git a/src/unilab/conf/flashsac/task/g1_motion_tracking/mujoco.yaml b/src/unilab/conf/flashsac/task/g1_motion_tracking/mujoco.yaml
new file mode 100644
index 000000000..ff863e20b
--- /dev/null
+++ b/src/unilab/conf/flashsac/task/g1_motion_tracking/mujoco.yaml
@@ -0,0 +1,21 @@
+# @package _global_
+# FlashSAC MuJoCo owner for G1 WBT. Carries the FlashSAC training budget
+# aligned with the FastSAC owner (2048 envs x 25000 iterations, gamma 0.99)
+# so run metrics are directly comparable across algos; FlashSAC algo-specific
+# knobs (batch_size, num_atoms, temp/n_step params) stay at the
+# conf/flashsac/config.yaml defaults.
+defaults:
+  - /task/g1_motion_tracking/base
+  - _self_
+
+training:
+  task_name: G1MotionTrackingSAC
+  sim_backend: mujoco
+algo:
+  num_envs: 2048
+  max_iterations: 25000
+  save_interval: 1000
+  gamma: 0.99
+  tau: 0.05
+  updates_per_step: 4
+  policy_frequency: 2
diff --git a/src/unilab/conf/flashsac/task/g1_motion_tracking/newton.yaml b/src/unilab/conf/flashsac/task/g1_motion_tracking/newton.yaml
new file mode 100644
index 000000000..6812345a4
--- /dev/null
+++ b/src/unilab/conf/flashsac/task/g1_motion_tracking/newton.yaml
@@ -0,0 +1,26 @@
+# @package _global_
+# FlashSAC Newton owner for G1 WBT. Newton's runtime is optional and shares
+# the MuJoCo 3.11 / MuJoCo-Warp 3.11 / Warp 1.16 line with the mujoco/mjwarp
+# extras; process device binding supplies the rank-local CUDA device when
+# ``newton_device`` is left unset. Requires unisim-core>=1.5.1 for the motion
+# body id capability (unilabsim/unisim#137). Native ViewerGL rendering
+# (offline record + interactive) is provided by the backend; playback inherits
+# auto mode.
+defaults:
+  - /task/g1_motion_tracking/mujoco
+  - _self_
+
+training:
+  task_name: G1MotionTrackingSAC
+  sim_backend: newton
+  # First tick includes collector env construction; newton startup exceeds the
+  # 30s default (same override as sac g1_walk_flat/newton).
+  inference_request_timeout_sec: 180.0
+env:
+  # A null device is intentional: the off-policy collector binder injects the
+  # rank-local CUDA device before materialization. 320/512 leaves headroom
+  # over the observed fall-contact demand measured on g1_walk_flat.
+  newton_device: null
+  newton_nconmax: 320
+  newton_njmax: 512
+  newton_capacity_check_steps: 1
diff --git a/src/unilab/tasks/motion_tracking/g1/__init__.py b/src/unilab/tasks/motion_tracking/g1/__init__.py
index 10e488009..696754207 100644
--- a/src/unilab/tasks/motion_tracking/g1/__init__.py
+++ b/src/unilab/tasks/motion_tracking/g1/__init__.py
@@ -24,5 +24,11 @@
 # mujoco/motrix until their mjwarp paths are validated.
 registry.register_env("G1MotionTrackingSAC", make_manager_based_rl_env, sim_backend="mjwarp")
 
+# genesis/newton implement the motion-body-id capability since unisim-core 1.5.1
+# (unilabsim/unisim#137); isaacgym/isaacsim stay unregistered until their
+# body-state publish/reset paths are fixed (unilabsim/unisim#141).
+for _backend in ("genesis", "newton"):
+    registry.register_env("G1MotionTrackingSAC", make_manager_based_rl_env, sim_backend=_backend)
+
 
 __all__ = ["BoxMotionData", "BoxMotionLoader", "G1_MOTION_TASKS"]
diff --git a/tests/base/test_backend_pre_step_control.py b/tests/base/test_backend_pre_step_control.py
index 8500ee270..283c9ae6e 100644
--- a/tests/base/test_backend_pre_step_control.py
+++ b/tests/base/test_backend_pre_step_control.py
@@ -142,6 +142,11 @@ def _fake_mujoco_backend(pre_step_control_fn=None):
     backend._refresh_pre_step_body_state = True
     backend._pre_step_control_fn = pre_step_control_fn
     backend._tracked_sensor_copyout_range = None
+    backend._tracked_sensor_slices = ()
+    backend._tracked_body_state_dirty = np.zeros(1, dtype=bool)
+    # Matches the 1.4.3 constructor default; the pre-step-control tests pin the
+    # refreshing behavior the flag gates.
+    backend._refresh_pre_step_body_state = True
     backend._num_envs = 1
     backend._np_dtype = np.float32
     backend.nq = pool._nq
diff --git a/tests/benchmark/test_replay_buffer_placement_benchmark.py b/tests/benchmark/test_replay_buffer_placement_benchmark.py
index 6ba406cdc..7ec993577 100644
--- a/tests/benchmark/test_replay_buffer_placement_benchmark.py
+++ b/tests/benchmark/test_replay_buffer_placement_benchmark.py
@@ -53,7 +53,8 @@ def test_replay_shape_packed_width_includes_critic_fields() -> None:
 
 def test_wbt_owner_config_is_only_included_when_present() -> None:
     assert bench._owner_config_exists("sac", "g1_motion_tracking", "mujoco")
-    assert not bench._owner_config_exists("flashsac", "g1_motion_tracking", "mujoco")
+    assert bench._owner_config_exists("flashsac", "g1_motion_tracking", "mujoco")
+    assert not bench._owner_config_exists("td3", "g1_motion_tracking", "mujoco")
 
 
 def test_default_discovery_includes_existing_offpolicy_mujoco_tasks() -> None:
@@ -69,7 +70,8 @@ def test_default_discovery_includes_existing_offpolicy_mujoco_tasks() -> None:
     assert ("flashsac", "g1_walk_flat") in targets
     assert ("flashsac", "go2_joystick_flat") in targets
     assert ("td3", "g1_walk_flat") in targets
-    assert ("flashsac", "g1_motion_tracking") not in targets
+    assert ("flashsac", "g1_motion_tracking") in targets
+    assert ("td3", "g1_motion_tracking") not in targets
 
 
 def test_td3_is_an_allowed_benchmark_algo() -> None:
diff --git a/tests/envs/test_env_configs.py b/tests/envs/test_env_configs.py
index 2c8a2adf3..eb173843c 100644
--- a/tests/envs/test_env_configs.py
+++ b/tests/envs/test_env_configs.py
@@ -723,10 +723,11 @@ def test_g1_motion_core_registrations_are_manager_only() -> None:
             "config_factory": "ManagerBasedRlEnvCfg",
             "available_backends": ["mujoco", "motrix"],
         }
-    # mjwarp is registered for G1MotionTrackingSAC only (benchmark scope, #1292).
+    # mjwarp is registered for G1MotionTrackingSAC only (benchmark scope, #1292);
+    # genesis/newton extend the same SAC contract (unisim-core>=1.5.1, #137).
     assert metadata["G1MotionTrackingSAC"] == {
         "config_factory": "ManagerBasedRlEnvCfg",
-        "available_backends": ["mujoco", "motrix", "mjwarp"],
+        "available_backends": ["mujoco", "motrix", "mjwarp", "genesis", "newton"],
     }
 
 
diff --git a/tests/scripts/test_train_scripts.py b/tests/scripts/test_train_scripts.py
index 6b6770d13..e28e579df 100644
--- a/tests/scripts/test_train_scripts.py
+++ b/tests/scripts/test_train_scripts.py
@@ -2210,6 +2210,22 @@ def test_offpolicy_flashsac_g1_walk_flat_task_composes() -> None:
     assert cfg.training.sim_backend == "mujoco"
 
 
+def test_offpolicy_flashsac_g1_motion_tracking_mjwarp_task_composes() -> None:
+    cfg = _offpolicy_cfg(["task=g1_motion_tracking/mjwarp"], algo="flashsac")
+    assert cfg.training.task_name == "G1MotionTrackingSAC"
+    assert cfg.training.sim_backend == "mjwarp"
+    assert cfg.training.play_render_mode == "record"
+
+
+@pytest.mark.parametrize("backend", ["mujoco", "motrix", "newton", "genesis"])
+def test_offpolicy_flashsac_g1_motion_tracking_task_composes(backend: str) -> None:
+    cfg = _offpolicy_cfg([f"task=g1_motion_tracking/{backend}"], algo="flashsac")
+    assert cfg.training.task_name == "G1MotionTrackingSAC"
+    assert cfg.training.sim_backend == backend
+    assert cfg.algo.num_envs == 2048
+    assert cfg.algo.max_iterations == 25000
+
+
 def test_offpolicy_rejects_algo_argument_mismatch():
     """build_runner must reject an algo argument inconsistent with cfg.algo.algo."""
     cfg = _offpolicy_cfg(["task=g1_walk_flat/mujoco"])
diff --git a/uv.lock b/uv.lock
index db10bbfa6..de163ea49 100644
--- a/uv.lock
+++ b/uv.lock
@@ -5240,8 +5240,8 @@ requires-dist = [
     { name = "trimesh", marker = "extra == 'viser'", specifier = ">=3.21.7" },
     { name = "typing-extensions" },
     { name = "unilab-rl", specifier = "==1.2.1" },
-    { name = "unisim-core", specifier = ">=1.5.0" },
-    { name = "unisim-core", extras = ["superdex"], marker = "python_full_version >= '3.12' and platform_machine == 'x86_64' and sys_platform == 'linux' and extra == 'superdex'", specifier = ">=1.5.0" },
+    { name = "unisim-core", specifier = ">=1.5.1" },
+    { name = "unisim-core", extras = ["superdex"], marker = "python_full_version >= '3.12' and platform_machine == 'x86_64' and sys_platform == 'linux' and extra == 'superdex'", specifier = ">=1.5.1" },
     { name = "viser", marker = "extra == 'viser'", specifier = ">=1.0.26" },
     { name = "wandb" },
     { name = "warp-lang", marker = "extra == 'mjwarp'", specifier = "==1.16.0" },
@@ -5284,13 +5284,13 @@ wheels = [
 
 [[package]]
 name = "unisim-core"
-version = "1.5.0"
+version = "1.5.1"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
     { name = "numpy", version = "2.2.6", source = { registry = "https://pypi.org/simple" }, marker = "python_full_version < '3.11'" },
     { name = "numpy", version = "2.4.4", source = { registry = "https://pypi.org/simple" }, marker = "python_full_version >= '3.11'" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/1c/d8/e142031c7aeb29653ba04b882f5f8df57a7fc5603a7bae682b08121e005f/unisim_core-1.5.0.tar.gz", hash = "sha256:4fd0f276af7f1905812f9189e11422889993423e00a331abdecaa00a8cdd118c", size = 354365, upload-time = "2026-09-17T04:39:54.318Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/ce/a5/aaa2505237af593ee495963a537893e71a7452fb376e6881d8fb5e4d7695/unisim_core-1.5.1.tar.gz", hash = "sha256:49c5b178ba2e513a0eeebd0c42048a56d72fa1d563f2c66457268130a26ba5af", size = 354707, upload-time = "2026-09-17T04:56:46.441Z" }
 
 [package.optional-dependencies]
 superdex = [