OpenCastor

Open-source robot runtime — connect any AI model to any robot hardware through a single YAML config.

94,438 lines of Python · 7,334 tests · Python 3.10–3.13

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What is OpenCastor

OpenCastor is an open-source runtime for embodied AI. It implements the RCAN open protocol and handles the hard parts: safety gates, multi-provider AI routing, hardware drivers, messaging channels, and fleet management.

Point it at any LLM (Gemini, GPT-4.1, Claude, Ollama, and 13 more) and any robot body (Raspberry Pi, Jetson, Arduino, ESP32, LEGO) via a single YAML config. Your robot answers to WhatsApp, Telegram, Discord, Slack, and Home Assistant — and learns from its own experience through the Sisyphus self-improvement loop.

RCAN ≠ OpenCastor. RCAN is an independent open protocol — like DNS and ICANN, but for robotics. Any robot can implement RCAN without using OpenCastor. OpenCastor is one implementation that helped inform the spec.

Quick Start

1. Install

pip install opencastor==2026.4.1.0

2. Run the setup wizard

castor setup

The wizard will:

• Name your robot and assign an RRN (Robot Registration Number)
• Generate a config file at ~/.config/opencastor/<name>.rcan.yaml
• Show a QR code to connect to the Fleet UI at app.opencastor.com
• Configure your AI brain provider (Gemini, Claude, OpenAI, or local Ollama)

3. Start your robot

# Start the AI brain + REST API (port 8000)
castor gateway --config ~/.config/opencastor/bob.rcan.yaml

# Start the cloud bridge (connects robot to Fleet UI — outbound-only)
castor bridge --config ~/.config/opencastor/bob.rcan.yaml

4. One-command systemd setup

castor bridge setup   # generates and optionally installs systemd services

Docker

docker run -it \
  -v ~/.config/opencastor:/config \
  -e OPENCASTOR_CONFIG=/config/bob.rcan.yaml \
  ghcr.io/craigm26/opencastor:2026.4.1.0 \
  castor gateway

Profile	Description	Requires
apple_native	Mac with Apple Silicon (M1–M4) — runs models on-device via Apple Foundation Models. No API key needed.	macOS, Apple Silicon
mlx_local_vision	Mac with Apple Silicon — open-source models via MLX (Llama, Mistral, Qwen). More model choice than apple_native.	macOS, Apple Silicon
ollama_universal_local	Any machine — runs local models via Ollama. Works on Mac, Linux, and Windows.	Ollama installed

On Apple Silicon, apple_native is the default. The wizard will ask which Apple model profile fits your use case:

Apple Profile	Use case	Guardrails
apple-balanced ⭐	General chat and robot commands — best starting point	Default
apple-creative	Creative tasks, less restrictive output	Permissive Content Transformations
apple-tagging	Classifying or labeling objects/scenes	Default

Features

• Protocol 66 safety — ESTOP never blocked, local safety always wins, confidence gates run on-device
• RCAN v1.6 — replay prevention, federation, constrained transport (BLE/LoRa), multi-modal payloads, Level of Assurance
• Multi-provider AI — Gemini, Claude, OpenAI, Ollama, MLX (Apple Silicon), Groq, DeepSeek, and 7 more; hot-swap via YAML
• Fleet UI — real-time fleet dashboard at app.opencastor.com; no port forwarding needed
• SO-ARM101 arm support — auto-detected via USB, guided setup for follower/leader/bimanual configurations
• 18 hardware presets — Raspberry Pi, Jetson, Arduino, ESP32, LEGO Mindstorms, OAK-D, LeRobot SO-ARM101, and more
• Self-improving loop — Sisyphus PM→Dev→QA→Apply pipeline learns from every episode
• Messaging channels — WhatsApp, Telegram, Discord, Slack, Home Assistant, MQTT
• castor setup wizard — guided onboarding with QR codes; works headless on Pi

Architecture

[ app.opencastor.com / Fleet UI ]
          │  Firebase / Firestore
          │
   [ Cloud Functions ]            R2RAM enforcement + rate limiting
          │
   [ castor bridge ]              outbound-only Firestore connection
          │
   [ castor gateway ]             FastAPI REST + messaging channels
          │
   ┌──────────────────────┐
   │   Protocol 66 Safety │       ESTOP | confidence gates | bounds
   └──────────────────────┘
          │
   [ Tiered Brain ]               Gemini / Claude / GPT / Ollama / …
          │
   [ RCAN Config + Drivers ]      .rcan.yaml → hardware abstraction
          │
   [ Robot Hardware ]             Pi / Jetson / Arduino / SO-ARM101 / …

RCAN v1.6 Features

Feature	Description
Replay prevention	Sliding-window msg_id cache; stale messages rejected
Federation	Cross-registry consent, DNS trust anchors, JWT verification
Constrained transport	Compact CBOR (512B), 32-byte ESTOP minimal for BLE/LoRa
Multi-modal payloads	Inline or referenced media chunks; streaming sensor data
Level of Assurance	LoA 1/2/3 on operator JWTs; configurable minimum per scope

castor CLI Reference

Command	Description
castor setup	Interactive onboarding wizard — config, RRN, Fleet UI QR code
castor gateway	Start AI brain + REST API + messaging channels
castor bridge	Start cloud bridge (Fleet UI connection)
castor scan	Auto-detect connected hardware (USB, I2C, V4L2)
castor doctor	System health check — providers, channels, hardware
castor fix	Auto-fix common configuration issues
castor status	Provider and channel readiness summary
castor improve	Run Sisyphus self-improvement on recent episodes
castor audit --verify	Verify audit chain integrity
castor approvals	Review and approve pending high-risk commands
castor deploy	Push config to a remote robot over SSH
castor fleet	Discover and monitor all robots on the local network
castor upgrade	Pull latest version + pip install + service restart

Full reference: docs.opencastor.com/runtime/cli

Configuration

Minimal bob.rcan.yaml:

rcan_version: "1.6"
metadata:
  robot_name: bob
agent:
  provider: google
  model: gemini-2.5-flash
drivers:
  - id: wheels
    protocol: pca9685
channels: {}

That's it. castor gateway --config bob.rcan.yaml starts the REST API, messaging channels, and the self-improving loop.

Swap the AI brain with one line:

agent:
  provider: anthropic
  model: claude-sonnet-4-6

Protocol 66

Protocol 66 is RCAN's mandatory safety layer. Current OpenCastor conformance: 94%.

Key invariants:

• ESTOP delivered at QoS 2 (EXACTLY_ONCE) — never blocked by backpressure
• Local safety always wins — cloud commands pass through the same confidence gates as local commands
• Audit chain required for all flagged commands
• GuardianAgent has veto authority over unsafe actions

P66 manifest: sbom/ · Full spec: rcan.dev/docs/safety/

Fleet UI

app.opencastor.com — sign in with Google to see your fleet.

• Real-time status cards for all registered robots
• Robot detail: telemetry, command history, chat-scope instructions
• ESTOP button on every screen
• Consent management — approve/deny R2RAM access requests
• Revocation display — shows if a robot's identity has been revoked
• LoA display — shows operator Level of Assurance on control commands

Robots connect via castor bridge (outbound-only Firestore). No open ports on the robot side.

SO-ARM101 Arm Support

The LeRobot SO-ARM101 6-DOF serial bus servo arm is auto-detected via USB VID/PID (CH340, 0x1A86/0x7523).

pip install opencastor[lerobot]
castor scan                          # detects arm + suggests preset
castor wizard --preset so_arm101     # guided config: follower / leader / bimanual
castor gateway --config so_arm101.rcan.yaml

castor scan counts connected Feetech boards and automatically suggests the right preset: single arm (follower or leader), or bimanual pair (ALOHA-style). Koch arms use the same detection path.

Ecosystem

Project	Version	Purpose
OpenCastor (this)	v2026.3.17.13	Robot runtime, RCAN reference implementation
Fleet UI	live	Web fleet dashboard
RCAN Protocol	v1.6.0	Open robot communication standard
rcan-py	v0.6.0	Python RCAN SDK
rcan-ts	v0.6.0	TypeScript RCAN SDK
Robot Registry Foundation	v1.6.0	Global robot identity registry

Contributing

OpenCastor is Apache 2.0 and community-driven.

• Discord: discord.gg/jMjA8B26Bq
• Issues: github.com/craigm26/OpenCastor/issues
• PRs: See CONTRIBUTING.md
• Docs: docs/claude/ — structure, API reference, env vars

License

Apache 2.0 · by Craig Merry

Implements the RCAN open protocol. RCAN is an independent open standard — any robot or runtime can implement it.