MuJoCo Complete Guide 2026 — MJCF, Gymnasium RL, Menagerie & Isaac Lab

The definitive MuJoCo 3.x reference guide: installation, MJCF format, contact physics, actuators, Python API, Gymnasium RL, and the Menagerie robot library. 11 sections.

Section 1: pip install mujoco (not mujoco-py)
Section 2: MJCF format — world, body, joint, actuator
Section 3: Soft contact model and friction
Section 4: Actuators, tendons, and cables
Section 5: Python API — mj_step, mj_data, mj_model
Section 6: Gymnasium RL environments
Section 7: EGL headless rendering
Section 8: MuJoCo Menagerie robot library
Section 9: MJX — GPU-accelerated MuJoCo on JAX
Section 10: Isaac Lab and MuJoCo integration
Section 11: 9 common errors and fixes