> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tryreflex.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Robot interface

> Three methods. The same contract for simulation, mock, and real hardware.

Every robot implements three methods:

```python theme={null}
obs = robot.observe()   # {"state": Tensor(1, N), "images": ...}
robot.act(action)       # Tensor(1, N)
robot.reset()
```

This contract is the seam between policy code and the world. A policy that
works against a `MockRobot` works against a `SimRobot` works against a
`RealRobot` — no changes to the policy.

## Built-in robots

```python theme={null}
# Real hardware
robot = rfx.RealRobot(rfx.SO101_CONFIG)

# Simulation
robot = rfx.SimRobot.from_config("so101.yaml", backend="genesis", viewer=True)
robot = rfx.SimRobot.from_config("go2.yaml",   backend="mjx",     num_envs=4096)

# Mock (zero dependencies)
robot = rfx.MockRobot(state_dim=12, action_dim=6)
```

## Contract guarantees

<CardGroup cols={2}>
  <Card title="observe()" icon="eye">
    Returns a `Dict[str, Tensor]`. Keys are stable — `state`, `images`, and
    any sensor keys declared in the robot config. Shapes and dtypes follow
    the config.
  </Card>

  <Card title="act(action)" icon="arrow-right">
    Accepts a `Tensor` in the action space declared by the robot config.
    Indexing by name (via `MotorCommands`) is supported for readable code.
  </Card>

  <Card title="reset()" icon="rotate-left">
    Returns the robot to a known-safe home state. Called once per episode.
  </Card>

  <Card title="disconnect()" icon="plug">
    Releases hardware resources. Always call during cleanup, or use a
    context manager.
  </Card>
</CardGroup>

## Custom robots

Implement `observe()` / `act()` / `reset()` directly, or supply a YAML config
that declares joints, sensors, and control rate. Hardware adapters handle the
transport layer; the contract stays the same.