Two Control Paths - Bedrock Dynamics

roz provides two complementary control paths. The agent chooses which path to use based on the task, and can combine both in the same session.

                          ┌─────────────────────┐
                          │     LLM Agent        │
                          │  (Claude, GPT-4, …)  │
                          └──────┬──────┬────────┘
                                 │      │
                   ┌─────────────┘      └──────────────┐
                   │                                    │
          Path A: MCP Tools                   Path B: WASM Controllers
              (1-3 Hz)                             (100 Hz)
                   │                                    │
                   ▼                                    ▼
        ┌──────────────────┐               ┌────────────────────┐
        │  MCP Server      │               │  wasmtime Sandbox  │
        │  (in sim Docker) │               │  process(tick)     │
        │                  │               │                    │
        │  move_to_pose()  │               │  state::get(i)     │
        │  takeoff()       │               │  command::set(i,v) │
        │  navigate_to()   │               │                    │
        └──────────────────┘               └────────────────────┘
                   │                                    │
                   ▼                                    ▼
        ┌──────────────────┐               ┌────────────────────┐
        │  Robot Middleware │               │   Safety Filter    │
        │  (MoveIt2, PX4,  │               │   (per-channel     │
        │   Nav2, …)       │               │    clamping)       │
        └──────────────────┘               └────────────────────┘
                   │                                    │
                   └──────────────┬─────────────────────┘
                                  ▼
                         ┌─────────────────┐
                         │  Robot / Sim     │
                         └─────────────────┘

Path A: MCP Tools

The agent calls high-level tools through the Model Context Protocol. Each sim container bundles its own MCP server with robot-specific tools like move_to_pose, get_joint_state, takeoff, or navigate_to. MCP tools handle motion planning, collision checking, and middleware coordination internally. The agent says what to do, and the tool handles how. Rate: 1-3 Hz (one tool call per LLM turn). Best for:

Discrete actions (go to a waypoint, pick up an object, land)
Positioning and setup before a precision task
Tasks where the middleware’s built-in planner is sufficient

Agent: "Move the arm to the packing position"
  → move_to_pose(x: 0.3, y: 0.0, z: 0.4, ...)
  → MoveIt2 plans and executes the trajectory
  → Tool returns success + final joint state

Path B: WASM Controllers

The agent writes WAT (WebAssembly Text) code implementing a process(tick) function. The code is compiled to WASM, verified in a sandbox, and deployed to a 100 Hz Copper control loop. Each tick, the controller reads sensor state and writes motor commands through the channel interface. The agent has direct, continuous control over the robot’s actuators. Rate: 100 Hz (10 ms per tick). Best for:

Continuous control (smooth trajectories, oscillation, impedance control)
Reactive behaviors that need fast sensor feedback
Custom motion patterns the middleware does not support

Agent: "Oscillate joint 0 with a sine wave at 0.5 Hz"
  → Writes WAT code: process(tick) { command::set(0, sin(tick * 0.031)) }
  → deploy_controller compiles, verifies 100 ticks, deploys
  → Controller runs at 100 Hz until replaced or halted

When to Use Which

	MCP Tools (Path A)	WASM Controllers (Path B)
Control rate	1-3 Hz	100 Hz
Agent writes	Tool call parameters	WAT/WASM code
Motion planning	Handled by middleware	Agent implements directly
Sensor feedback	Snapshot per tool call	Every tick (10 ms)
Safety	Middleware enforces limits	Safety filter clamps per tick
Use case	Go-to-pose, pick-and-place	Trajectory tracking, force control
Latency	Seconds (LLM round-trip)	10 ms (WASM tick)

Combining Both Paths

The agent can use both paths in the same session. A typical pattern:

Position with MCP

Use move_to_pose to move the arm to a starting configuration.

Deploy WASM controller

Write and deploy a WAT controller for the precision task (e.g., a circular polishing motion).

Monitor and iterate

Read sensor state via MCP tools to check progress. If the controller needs adjustment, deploy an updated version.

Halt and return

Stop the controller and use MCP tools to move back to a safe home position.

Both control paths go through the safety filter before reaching the robot. MCP tools are checked by the middleware’s own safety layer. WASM commands are clamped per-channel by SafetyFilterTask at 100 Hz.

Source

Control path architecture: roz-local/src/runtime.rs
MCP tool registration: roz-local/src/tools/
WASM deployment: roz-local/src/tools/deploy_controller.rs

​Path A: MCP Tools

​Path B: WASM Controllers

​When to Use Which

​Combining Both Paths

​Source

Path A: MCP Tools

Path B: WASM Controllers

When to Use Which

Combining Both Paths

Source