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Architecture

Four-layer stack - Agent, Policies, Backends, Robots - with green action signals flowing down and cyan observation signals flowing back up 
graph TB
    subgraph user[Your code]
        AGENT["Strands Agent"]
        FACTORY["Robot('so100')"]
    end

    subgraph factory_layer[Robot factory  -  strands_robots/robot.py]
        ROBOT["Robot()"]
        REGISTRY["registry/robots.json<br/>68 robots, 8 categories"]
        ROBOT --> REGISTRY
    end

    subgraph backends[Backends]
        SIM["Simulation<br/>simulation/mujoco/simulation.py"]
        HW["HardwareRobot<br/>hardware_robot.py"]
        SIM_ABC["SimEngine ABC<br/>simulation/base.py"]
        SIM -.implements.-> SIM_ABC
    end

    subgraph policies[Policy layer  -  strands_robots/policies]
        POLICY_ABC["Policy ABC<br/>policies/base.py"]
        MOCK["MockPolicy"]
        GROOT["Gr00tPolicy"]
        LEROBOT["LerobotLocalPolicy"]
        COSMOS3["Cosmos3Policy"]
        FACTORY_FN["create_policy()"]
        MOCK -.implements.-> POLICY_ABC
        GROOT -.implements.-> POLICY_ABC
        LEROBOT -.implements.-> POLICY_ABC
        COSMOS3 -.implements.-> POLICY_ABC
        FACTORY_FN --> POLICY_ABC
    end

    subgraph extras[Cross-cutting]
        TOOLS["Tools<br/>tools/*.py"]
        RECORDER["DatasetRecorder<br/>dataset_recorder.py"]
        BENCH["Benchmarks<br/>benchmarks/libero"]
    end

    AGENT --> FACTORY
    FACTORY --> ROBOT
    ROBOT -->|mode='sim' default| SIM
    ROBOT -->|mode='real'| HW

    SIM --> POLICY_ABC
    HW --> POLICY_ABC
    SIM --> RECORDER
    HW --> RECORDER

    AGENT --> TOOLS

    classDef user fill:#2ea44f,stroke:#1b7735,color:#fff
    classDef factory fill:#0969da,stroke:#044289,color:#fff
    classDef backend fill:#bf8700,stroke:#875e00,color:#fff
    classDef policy fill:#8250df,stroke:#5a32a3,color:#fff
    classDef cross fill:#cf222e,stroke:#86181d,color:#fff

    class AGENT,FACTORY user
    class ROBOT,REGISTRY factory
    class SIM,HW,SIM_ABC backend
    class POLICY_ABC,MOCK,GROOT,LEROBOT,COSMOS3,FACTORY_FN policy
    class TOOLS,RECORDER,BENCH cross

Modules

Module What it owns Key types
strands_robots/robot.py Factory Robot(name, mode, backend, **kwargs). Name resolution, sim/real dispatch, mesh attach. Robot() function
strands_robots/registry/ 68 robots, 106 aliases, 8 categories. robots.json is source of truth. list_robots(), resolve_name(), get_robot()
strands_robots/simulation/ MuJoCo AgentTool - 60+ actions. Simulation, SimWorld, SimRobot, SimObject, SimCamera
strands_robots/simulation/base.py Backend ABC for future Isaac/Newton backends. SimEngine
strands_robots/hardware_robot.py Real-servo path. Async task execution + status. Robot (class), TaskStatus, RobotTaskState
strands_robots/policies/ ABC + 4 providers + factory + JSON registry. Policy, create_policy()
strands_robots/dataset_recorder.py LeRobot v3 writer. DatasetRecorder
strands_robots/tools/ 8 @tool-decorated helpers. lerobot_calibrate, serial_tool, etc.
strands_robots/benchmarks/libero/ LIBERO benchmark adapter. LiberoSuite

ABCs

Policy - get_actions(observation_dict, instruction) -> list[dict] (async), set_robot_state_keys(keys), provider_name property, requires_images property (default True), reset(seed) (default no-op). Four implementations: MockPolicy, Gr00tPolicy, LerobotLocalPolicy, Cosmos3Policy.

SimEngine - create_world(), step(), 30+ abstract actions. Today: MuJoCo CPU. Roadmap: Isaac Sim, Newton.

Strands AgentTool - Simulation and HardwareRobot are both AgentTool subclasses. Agent(tools=[robot]) calls actions through the tool dispatcher.

The one rule

Lazy imports everywhere. strands_robots/__init__.py exports Policy, MockPolicy, create_policy eagerly. Everything else (Robot, Simulation, Gr00tPolicy, the tools) is behind __getattr__. Enforced by tests/test_init.py.

Extras

Extra Pulls in When
[sim-mujoco] mujoco, numpy, imageio, imageio-ffmpeg Robot(mode="sim")
[lerobot] lerobot>=0.5.0,<0.6.0, torch Real hardware OR LerobotLocalPolicy
[groot-service] pyzmq, msgpack Gr00tPolicy ZMQ
[cosmos3-service] msgpack, websockets Cosmos3Policy WebSocket
[mesh] eclipse-zenoh, json5 Multi-robot mesh
[mesh-iot] above + awsiotsdk, awscrt, boto3 AWS IoT Core transport
[all] union CI / exploration

See also