Returns JSON: {session_id, source, nq, nv, nu, nsensor, nkey, timestep,
joints: [names], actuators: [names], sensors: [names], keyframes: [names]}.
The name arrays define the element order of qpos/qvel/ctrl vectors used by every other tool.
Next: mujoco_step to advance physics, mujoco_get_state to read, mujoco_model_info for ranges/types.

Returns JSON: {session_id, source, sizes: {nq, nv, nu, na, nbody, njnt, ngeom, nsensor, nkey},
options: {timestep, gravity, integrator},
joints: [{name, type, range|null, qpos_adr, dof_adr}],
actuators: [{name, ctrlrange|null, gear}],
sensors: [{name, type, dim}], bodies: [names], keyframes: [names]}.
Use before choosing ctrl values (respect ctrlrange) or interpreting qpos/qvel layout.

Without a keyframe, restores the configured seeded start (if any), else model defaults.
Clears force guard and runtime errors. Identical full states and control sequences
reproduce trajectories with the same model, engine and stepping schedule.
Returns the post-reset state JSON (same shape as mujoco_get_state).

Returns the post-step state JSON: {session_id, time, steps_taken, qpos, qvel, ctrl, sensors, ...}
filtered by `include`. Batch steps in one call (e.g. nsteps=500 for 1s at timestep 0.002)
instead of many single-step calls. Errors and suggests mujoco_reset if the state diverges.

Returns JSON with the requested blocks: qpos/qvel/ctrl (vectors in model order),
sensors ({name: value}), bodies ({name: {pos, quat}} world-frame), contacts
({ncon, listed, contacts: [{geom1, geom2, pos, dist, normal_force}]}, capped at 20).

Only provided fields change. Runs mj_forward so sensors/body poses reflect the new state
without advancing time. Returns the resulting state JSON. Useful for setting initial
conditions or visual replay. Use snapshots, not rounded state views, for exact continuation.

Returns JSON: {count, sessions: [{session_id, source, time, steps_taken, nq, nu}]}.

Returns JSON: {closed, remaining: [session_ids]}.

Starts paused; call mujoco_step or mujoco_set_running next. One window per
server: close the current viewer before displaying another session. This
opens a new controlled window; it does not attach to the standalone DMG app.
On macOS launch the server via start.sh or mjpython.

Open a viewer first. Optional ctrl changes persist; this can update controls
during playback. Pause before deterministic mujoco_step calls. Closing the
window or resetting pauses playback. Instability pauses automatically and
appears in runtime_error; call mujoco_reset to recover.

Stops at the first force-limit exceedance. guard.peak_force_N is the maximum
summed contact load on body_name (including descendants); opposite contact
forces do not cancel. World-frame resultant force and torque are also returned.
The guard detects an exceedance, it cannot guarantee zero overshoot. No hard
real-time or physical safety certification is implied. A tripped session is
latched until reset or snapshot restore. Optional record_every samples a JSON
trace every N steps (0 disables; maximum 2000 frames). Initial, terminal and
trip states are always captured; peak_force_N tracks all steps, not samples.
Persist returned trace/provenance in the consuming project for replay/evidence.

Raw resultant force (N) and torque (N m) are in world axes. Torque is about
the requested body's origin. force_N sums contact magnitudes (opposing forces
do not cancel). This is contact-only, not a general wrist F/T sensor.
observed_force_xyz_N adds configured noise; raw force and guard stay unchanged.

Close viewer first. Supports named geom friction [sliding,torsional,rolling],
named explicit pair_friction [sliding1,sliding2,torsional,rolling1,rolling2],
hinge/slide initial joint_offsets and Gaussian joint_noise_std (rad/m), mocap
body poses (m, wxyz), additive ctrl_bias in actuator input units, and named
sensor_noise_std in each sensor's units. Noise affects observations only;
physical state and force guarding remain raw. Missing options return to model
defaults. Repeating the same config reproduces initial conditions. metadata
stores caller tags such as trial_id/param_version, without enforcing policy.

Includes act, warm-start, applied forces, mocap and other integration inputs,
beyond qpos/qvel. Persist this JSON in your project. Pause before capture.