For OpenClaw v2026.2 | This article is for users who have completed basic setup and want to understand the architecture in depth. We recommend completing the first 3 tutorials first.

TL;DR: Gateway is OpenClaw’s core control plane. Session is the conversation context container (main/channel/group), Message Router decides message routing, Tool Registry manages tool permissions, Skills are pre-packaged capability extensions. WebSocket endpoint: ws://127.0.0.1:18789/ws, common commands: openclaw gateway/doctor/config. Understanding these concepts is the foundation for advanced configuration.

Architecture Overview

Overall Architecture

flowchart TB
    subgraph Clients["Client Layer"]
        WA[WhatsApp]
        TG[Telegram]
        DC[Discord]
        SL[Slack]
        WC[WebChat]
        CLI[CLI]
        MAC[macOS App]
        IOS[iOS Node]
        AND[Android Node]
    end
    
    subgraph Gateway["Gateway Layer"]
        WS[WebSocket Server]
        HTTP[HTTP Server]
        MR[Message Router]
        SM[Session Manager]
        TR[Tool Registry]
        EM[Event Manager]
        CFG[Config Store]
    end
    
    subgraph Agent["Agent Layer"]
        PI[Pi Agent]
        PROMPT[Prompt Engine]
        TOOLS[Tool Executor]
        SKILLS[Skills Manager]
    end
    
    subgraph External["External Services"]
        FS[File System]
        BR[Browser]
        API[API Services]
        DB[Database]
        CAL[Cron Scheduler]
    end
    
    Clients --> WS
    Clients --> HTTP
    WS --> MR
    HTTP --> MR
    MR --> SM
    SM --> PI
    PI --> PROMPT
    PI --> TOOLS
    PI --> SKILLS
    TOOLS --> TR
    TR --> External
    EM --> MR
    CFG --> SM
    CFG --> TR

Component Responsibilities

Data Flow

sequenceDiagram
    participant U as User
    participant C as Channel
    participant WS as WebSocket
    participant MR as Router
    participant SM as Session
    participant A as Agent
    participant T as Tools
    
    U->>C: Send message
    C->>WS: Push message
    WS->>MR: Route request
    MR->>SM: Find/create session
    SM-->>MR: Return session
    MR->>A: Deliver message
    A->>A: Process message
    A->>T: Invoke tool (optional)
    T-->>A: Return result
    A-->>MR: Generate response
    MR->>WS: Send response
    WS->>C: Push response
    C-->>U: Display message

Session Model

What is a Session?

Session is one of the most core concepts in OpenClaw. Each Session represents an independent conversation context, containing:

Session Types

{
  "sessions": {
    "main": {
      "type": "main",
      "model": "anthropic/claude-opus-4-6",
      "thinkingLevel": "high",
      "channel": null,
      "created": "2026-02-26T10:00:00Z"
    },
    "telegram:user:123456789": {
      "type": "channel",
      "model": "anthropic/claude-opus-4-6",
      "thinkingLevel": "normal",
      "channel": "telegram",
      "sender": "123456789",
      "created": "2026-02-26T10:05:00Z"
    },
    "telegram:group:-100123456789": {
      "type": "group",
      "model": "anthropic/claude-sonnet-4",
      "thinkingLevel": "minimal",
      "channel": "telegram",
      "groupId": "-100123456789",
      "created": "2026-02-26T10:10:00Z"
    }
  }
}

Session Lifecycle

stateDiagram-v2
    [*] --> Created: Message arrives
    Created --> Active: First response
    Active --> Active: Message interaction
    Active --> Idle: No activity
    Idle --> Active: New message
    Idle --> Compacted: Auto compress
    Compacted --> Active: Continue conversation
    Active --> Reset: /reset command
    Reset --> Created: Start over
    Active --> Pruned: Session cleanup
    Idle --> Pruned: Timeout cleanup
    Pruned --> [*]

Session Commands

Send the following commands in chat to manage sessions:

Session Configuration

{
  "sessionPruning": {
    "enabled": true,
    "maxAge": 86400000,
    "maxSize": 100,
    "pruneOnStartup": true
  },
  "sessionCompression": {
    "enabled": true,
    "threshold": 50000,
    "targetRatio": 0.3
  }
}

Message Router

Routing Rules

Message Router is responsible for routing incoming messages to the correct Session:

flowchart TB
    MSG[Message arrives] --> CH{Channel type?}
    CH -->|Private chat| DM[Extract sender ID]
    CH -->|Group chat| GRP[Extract group ID]
    CH -->|WebChat/CLI| MAIN[Use main session]
    
    DM --> SID[Session: channel:user:id]
    GRP --> GID[Session: channel:group:id]
    
    SID --> EXISTS{Session exists?}
    GID --> EXISTS
    
    EXISTS -->|Yes| LOAD[Load session]
    EXISTS -->|No| CREATE[Create new session]
    
    CREATE --> LOAD
    LOAD --> AGENT[Deliver to Agent]

Routing Configuration

{
  "messageRouting": {
    "defaultSession": "main",
    "channelMapping": {
      "telegram": {
        "userPrefix": "telegram:user",
        "groupPrefix": "telegram:group"
      },
      "whatsapp": {
        "userPrefix": "whatsapp:user",
        "groupPrefix": "whatsapp:group"
      }
    },
    "groupActivation": {
      "mode": "mention",
      "mentionPatterns": ["@bot", "/bot"]
    }
  }
}

Group Activation Strategies

{
  "channels": {
    "telegram": {
      "groups": {
        "*": {
          "requireMention": true
        },
        "-100WORKGROUP": {
          "requireMention": false,
          "activationMode": "always"
        }
      }
    }
  }
}

Tool Registry

Built-in Tools

OpenClaw includes a rich set of built-in tools:

Tool Permission Control

{
  "agents": {
    "defaults": {
      "sandbox": {
        "mode": "off",
        "allowlist": ["read", "write", "bash", "web_search"],
        "denylist": []
      }
    }
  }
}

Sandbox Configuration Details

{
  "agents": {
    "defaults": {
      "sandbox": {
        "mode": "non-main",
        "allowlist": [
          "read",
          "write",
          "edit",
          "bash",
          "web_search",
          "sessions_list",
          "sessions_history"
        ],
        "denylist": [
          "browser",
          "canvas",
          "camera",
          "screen_record"
        ]
      }
    }
  }
}

Skills System

Skills Architecture

flowchart LR
    subgraph Skills["Skills Directory"]
        S1[gmail/SKILL.md]
        S2[calendar/SKILL.md]
        S3[home-assistant/SKILL.md]
    end
    
    subgraph Manager["Skills Manager"]
        DISC[Discover]
        LOAD[Load]
        EXEC[Execute]
    end
    
    subgraph Agent["Agent"]
        PROMPT[Inject Prompt]
        TOOLS[Register Tools]
        RES[Return Result]
    end
    
    Skills --> DISC
    DISC --> LOAD
    LOAD --> PROMPT
    LOAD --> TOOLS
    PROMPT --> Agent
    TOOLS --> Agent
    Agent --> EXEC
    EXEC --> RES

Skills Directory Structure

~/.openclaw/workspace/skills/
├── gmail/
│   ├── SKILL.md          # Skill definition
│   ├── package.json      # Dependencies (optional)
│   └── src/
│       └── index.js      # Implementation (optional)
├── calendar/
│   └── SKILL.md
└── my-custom-skill/
    └── SKILL.md

SKILL.md Structure

# Gmail Skill

## Description
Send and read Gmail messages through OpenClaw.

## Triggers
- email
- gmail
- mail
- send email
- read email

## Instructions
When the user wants to send an email:
1. Ask for recipient, subject, and body
2. Use the gmail_send tool
3. Confirm the email was sent

When the user wants to check emails:
1. Use the gmail_list tool
2. Summarize the results

## Tools
- gmail_list: List recent emails
- gmail_send: Send an email
- gmail_read: Read a specific email

## Examples
User: "Check my email"
Action: Use gmail_list tool

User: "Send an email to [email protected]"
Action: Ask for subject and body, then use gmail_send

Skills Installation

# Install from ClawHub
openclaw skill install gmail

# Install from GitHub
openclaw skill install github:user/repo/skill-name

# Manual install
git clone https://github.com/user/skill-repo.git ~/.openclaw/workspace/skills/skill-name

Skills Configuration

{
  "skills": {
    "bundled": true,
    "managed": true,
    "workspace": true,
    "installGating": true
  }
}

WebSocket Protocol

Connection Endpoint

ws://127.0.0.1:18789/ws

Message Format

{
  "type": "message_type",
  "id": "unique_message_id",
  "data": {
    // Message content
  }
}

Client Message Types

Server Message Types

Example: Sending a Message

// Connect WebSocket
const ws = new WebSocket('ws://127.0.0.1:18789/ws');

// Send message
ws.send(JSON.stringify({
  type: 'agent.send',
  id: 'msg-001',
  data: {
    session: 'main',
    message: 'Hello, please introduce yourself'
  }
}));

// Receive response
ws.onmessage = (event) => {
  const msg = JSON.parse(event.data);
  console.log(msg);
  
  // Output example:
  // {
  //   type: 'agent.response',
  //   id: 'msg-001',
  //   data: {
  //     content: 'Hello! I am your OpenClaw assistant...',
  //     session: 'main'
  //   }
  // }
};

Event System

Built-in Events

Webhook Configuration

{
  "webhooks": [
    {
      "url": "https://your-server.com/webhook/openclaw",
      "events": ["message.received", "tool.invoked"],
      "secret": "your_webhook_secret",
      "headers": {
        "X-Custom-Header": "value"
      }
    }
  ]
}

Webhook Payload

{
  "event": "message.received",
  "timestamp": "2026-02-26T10:30:00Z",
  "data": {
    "channel": "telegram",
    "sender": "123456789",
    "session": "telegram:user:123456789",
    "message": "Hello",
    "metadata": {
      "messageId": "msg_abc123",
      "timestamp": "2026-02-26T10:30:00Z"
    }
  },
  "signature": "sha256=..."
}

Cron Scheduled Tasks

Configuration Example

{
  "cron": [
    {
      "id": "daily-briefing",
      "schedule": "0 9 * * *",
      "session": "main",
      "message": "Please give me today's schedule",
      "enabled": true
    },
    {
      "id": "weekly-summary",
      "schedule": "0 18 * * 5",
      "session": "main",
      "message": "Generate this week's work summary",
      "enabled": true
    }
  ]
}

Cron Expression

┌───────────── minute (0 - 59)
│ ┌───────────── hour (0 - 23)
│ │ ┌───────────── day of month (1 - 31)
│ │ │ ┌───────────── month (1 - 12)
│ │ │ │ ┌───────────── day of week (0 - 6, 0 = Sunday)
│ │ │ │ │
* * * * *

Common Examples

Configuration Hierarchy and Priority

Priority Order

CLI args > Environment variables > Config file > Defaults

Configuration Sources

Configuration Merge Example

// ~/.openclaw/openclaw.json
{
  "agent": {
    "model": "anthropic/claude-opus-4-6"
  }
}

# Environment variable override
export OPENCLAW_AGENT_MODEL="anthropic/claude-sonnet-4"

# CLI arg override (highest priority)
openclaw gateway --model "anthropic/claude-opus-4"

Config Hot Reload

# Update config (no restart)
openclaw config set agent.model "anthropic/claude-sonnet-4"

# Reload config file
openclaw config reload

# Validate config
openclaw config get agent.model

Command Quick Reference

Gateway Management

# Start Gateway
openclaw gateway

# Specify port
openclaw gateway --port 18790

# Run in background
openclaw gateway --daemon

# Verbose logging
openclaw gateway --verbose

# Health check
openclaw health

Session Management

# List all sessions
openclaw session list

# View session details
openclaw session show main
openclaw session show telegram:user:123456789

# Reset session
openclaw session reset main

# Delete session
openclaw session delete telegram:user:123456789

Config Management

# View config
openclaw config get agent.model
openclaw config get channels.telegram.botToken

# Set config
openclaw config set agent.thinkingLevel high

# List all config
openclaw config list

# Validate config
openclaw config validate

Diagnostic Tools

# Full diagnostic
openclaw doctor

# Check specific item
openclaw doctor --check gateway
openclaw doctor --check config
openclaw doctor --check channels

# View logs
openclaw logs
openclaw logs --follow
openclaw logs --level error

Troubleshooting

Gateway Won’t Start

# Check port usage
lsof -i :18789
netstat -tlnp | grep 18789

# Check config syntax
openclaw config validate

# View detailed errors
openclaw gateway --verbose 2>&1 | tee gateway.log

Session Lost

# Check session directory
ls -la ~/.openclaw/sessions/

# Check cleanup config
openclaw config get sessionPruning

# Disable auto cleanup
openclaw config set sessionPruning.enabled false

Tool Invocation Failed

# Check sandbox config
openclaw config get agents.defaults.sandbox

# Temporarily disable sandbox
openclaw config set agents.defaults.sandbox.mode off

# View tool logs
openclaw logs --filter tool

WebSocket Connection Failed

# Check Gateway status
curl http://127.0.0.1:18789/health

# Check WebSocket endpoint
wscat -c ws://127.0.0.1:18789/ws

# Check firewall
sudo ufw status
sudo iptables -L -n | grep 18789

Summary

Understanding Gateway core concepts is key to mastering OpenClaw:

• Session: Conversation context container with type isolation
• Message Router: Core of message routing, determines message destination
• Tool Registry: Tool registration center, controls Agent capabilities
• Skills: Capability extension system for quick feature enhancement
• WebSocket: Real-time communication protocol, supports custom clients
• Event System: Event dispatch mechanism, supports Webhook and Cron

These concepts will appear throughout subsequent articles. A deep understanding will help you configure and use OpenClaw more effectively.

Article Summary:

• Mastered Gateway overall architecture and component responsibilities
• Understood Session model and lifecycle
• Learned message routing and group activation strategies
• Explored tool permissions and sandbox configuration
• Mastered WebSocket protocol and event system

Changelog:

• 2026-02-26: Initial release, based on OpenClaw v2026.2

Series Navigation:

• ← Previous: Channel Setup: Starting with Telegram
• → Next: Multi-Model Configuration and Switching