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name: sim2sim description: "Route safe, source-backed MuJoCo sim2sim validation for the AgiBot X1 DH stand policy, including JIT/model contracts, XML assets, timing, controller mapping, and backend-gated interactive execution." disable-model-invocation: true metadata: disco-role: operating license: NO_LICENSE

X1 sim2sim

Use this sub-skill to validate an exported X1 DH stand policy against the bundled MuJoCo model, or to prepare the guarded native sim2sim.py handoff. The supported task is x1_dh_stand. Start with workflows, then use model-and-asset-validation for shape/XML checks and troubleshooting for fail-closed diagnosis.

Hard backend and safety boundary

The full native script is currently BLOCKED_REQUIRED_BACKEND until NVIDIA Isaac Gym Preview 4 is installed and verified. Although it uses MuJoCo, it imports humanoid.envs before parsing arguments; that import chain requires Isaac Gym. A working modern MuJoCo install alone does not make the native workflow runnable. The native path also requires the repository's documented Python 3.8 / PyTorch 1.13.1 + CUDA 11.7 stack, mujoco==2.3.6, mujoco-python-viewer, pygame, an X1 checkout with its meshes, and a valid exported policy.

Until that gate is cleared, perform only isolated XML, URDF, filesystem, JIT container, and metadata checks. Run the bundled scripts/sim2sim_preflight.py; it never imports humanoid or Isaac Gym, opens a viewer, initializes pygame, loads TorchScript, or steps a simulator. Do not launch a viewer by default and do not treat a preflight pass as a sim2sim behavior result. The helper's --compile-mujoco option compiles XML in a child process only; it does not render or step.

Operating invariants

• Native invocation is python humanoid/scripts/sim2sim.py --task=x1_dh_stand --load_model=<timestamp-directory>. --task is required. In the source, --load_model is a child name under logs/<task>/exported_policies/, not a free-form absolute model file; if omitted, the source selects the last lexicographically sorted directory. Inside that directory it takes the last os.listdir entry, so pin a directory containing exactly one artifact.
• The exported artifact is a TorchScript file normally named policy_dh.jit, written by the DH exporter under a timestamp directory. It accepts a float32 tensor shaped [batch, 3102] and returns [batch, 12]. The 3102 values are 66 history frames × 47 features. The export wrapper takes the final 235 values (5 × 47) for the state estimator, reshapes the full input as [-1, 66, 47] for the long-history encoder, concatenates estimator and compressed history with the short history, and emits 12 action means.
• Each 47-value frame is: 5 command/gait values (sin phase, cos phase, scaled vx, scaled vy, scaled yaw), 12 DOF-position offsets, 12 DOF velocities, 12 previous actions, 3 body angular-velocity values, and 3 Euler-angle values. The X1 config has num_actions=12, num_single_obs=47, frame_stack=66, short_frame_stack=5, and num_observations=3102.
• The 12 action order is left hip pitch/roll/yaw, left knee pitch, left ankle pitch/roll, then the corresponding six right-leg joints. The MuJoCo actuator and URDF revolute order must agree with that order. Actions are clipped by the configured action limit, scaled by 0.5, offset by the 12 default joint angles, and passed through position PD; do not pass a runner checkpoint or an ONNX file to sim2sim.
• The sim loop uses a MuJoCo timestep of 0.001 seconds and decimation 10: physics advances at 1 kHz and the policy/observation update occurs every 10 low-level steps (100 Hz). The source sets model.opt.timestep from this value, runs for 100 seconds by default, applies PD torques at every physics step, and renders every step. Native rendering is interactive and must be explicitly authorized after all gates pass.

Controller and native handoff

The README documents a Logitech F710 button-4 gate, but the current native thread does not implement that gate. It continuously reads axes every 100 ms: x_vel_cmd = -axis(1), y_vel_cmd = -axis(0), and yaw_vel_cmd = -axis(3). The README's intended semantic mapping is button 4 + stick 1− forward, 1+ backward, 0− left, 0+ right, 3− counterclockwise, and 3+ clockwise. Treat button gating as an operator procedure, not an implemented safety interlock; center the controller and begin with one small command.

After a successful training run, hand off checkpoints to training only for provenance or repair. Hand a runner checkpoint to export to produce policy_dh.jit; only then return here. Hand a JIT path to this sub-skill, and hand any interactive Isaac Gym checkpoint playback to playback. Do not make this route train, export, or replace a missing backend with a fake simulator.

Bundled runtime files

• workflows.md: guarded execution, artifact selection, timing, and sibling handoffs.
• model-and-asset-validation.md: distilled JIT, observation/action, MJCF, mesh, URDF, and timing contracts.
• troubleshooting.md: backend, policy, XML, observation, controller, and viewer failure recovery.
• scripts/sim2sim_preflight.py: safe static preflight and optional no-viewer XML compilation.