OpenCastor

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

Peer runtime: opencastor and robot-md are first-class peer RCAN 3.x runtimes against a single ROBOT.md — see PEER_RUNTIMES.md for the side-by-side.

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 3.0 — hybrid signing (ML-DSA-65 + Ed25519), mandatory LoA, canonical JSON wire format, §22-26 compliance builders, BLE/LoRa/MQTT carriers
• 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 3.0 Features

• Replay prevention — hybrid signatures (ML-DSA-65 + Ed25519) over canonical JSON bodies
• Level of Assurance (LoA) — mandatory under 3.0+; gates control-plane operations behind HiTL authorization
• Canonical JSON wire format — rcan.canonical_json(body) produces byte-identical serialization across Python and TypeScript SDKs
• §22-26 compliance artifacts — emit §23 safety benchmarks, §24 IFU, §25 post-market incident reports, §26 EU register entries via rcan.build_* builders
• Federation + constrained transport — BLE / LoRa / MQTT carriers; RRN-based identity resolution via rcan.dev
• Post-quantum ready — NIST FIPS 204 ML-DSA-65 is the primary signing scheme (Q-Day 2029 is NOW)

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: "3.0"
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.

Where this fits in the stack

OpenCastor is the reference runtime — one implementation of the RCAN protocol. Everything else is independent; adopt one, or all seven.

Layer	Piece	What it is
Declaration	ROBOT.md	The file a robot ships at its root. YAML frontmatter + markdown prose. Declares identity, capabilities, safety gates. Spec + Python CLI.
Agent bridge	robot-md-mcp	MCP server that exposes a ROBOT.md to Claude Code, Claude Desktop, Cursor, Zed, Gemini CLI — any MCP-aware agent.
Wire protocol	RCAN	How robots, gateways, and planners talk. Signed envelopes, LoA enforcement, PQC crypto. Think HTTP for robots.
Python SDK	rcan-py	pip install rcan — RCANMessage, RobotURI, ConfidenceGate, HiTLGate, AuditChain.
TypeScript SDK	rcan-ts	npm install rcan-ts — same API surface for Node + browser.
Registry	Robot Registry Foundation	Permanent RRN identities. Public resolver at /r/<rrn>. Like ICANN for robots.
Reference runtime ← this	OpenCastor	This repo. Open-source robot runtime — connects LLM brains to hardware bodies. Implements RCAN, adds safety gates, multi-provider AI routing, 18+ hardware drivers, messaging channels, fleet management.

See also: the ROBOT.md quickstart — one command puts a Bob-class robot in Claude Code via the MCP bridge.

Ecosystem (versions)

Project	Version
OpenCastor (this)	v2026.4.17.0
Fleet UI	live
RCAN Protocol	v3.0
rcan-py	v2.0.0
rcan-ts	v2.0.0
ROBOT.md	v0.2.0 (schema v1.1)
robot-md-mcp	v0.1.3
Robot Registry Foundation	v3.0

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.