Imported from junhaochoo/Before-you- (.claude/skills/03-nexus/SKILL.md). Install upstream with npx skills add junhaochoo/Before-you- --skill 03-nexus. Copyright stays with the author.

Kailash Nexus - Multi-Channel Platform Framework

Nexus is a zero-config multi-channel platform built on Kailash Core SDK that deploys workflows as API + CLI + MCP simultaneously.

Features

Nexus transforms workflows into a complete platform with:

• Zero Configuration: Deploy workflows instantly without boilerplate code
• Multi-Channel Access: API, CLI, and MCP from single deployment
• Unified Sessions: Consistent session management across all channels
• Enterprise Features: Health monitoring, plugins, event system, comprehensive logging
• DataFlow Integration: Automatic CRUD API generation from database models
• Production Ready: Deployment patterns, monitoring, troubleshooting guides
• Multi-Channel Platform: Workflow-based platform without manual route definition
• Async-First: Uses kailash.Runtime by default for optimal performance

Quick Start

from kailash.nexus import NexusApp, NexusConfig

# Create app with custom port (or use defaults: host=0.0.0.0, port=3000)
app = NexusApp(config=NexusConfig(port=3000))

# Register handler - deployed to all channels at once
@app.handler(name="greet", description="Greet a user")
async def greet(name: str) -> dict:
    return {"message": f"Hello, {name}!"}

# Start the server (no arguments - host/port come from NexusConfig)
app.start()

# Now available via:
# - HTTP API: POST http://localhost:3000/api/greet
# - CLI: nexus run greet --name "World"
# - MCP: Connect via MCP client (Claude Desktop, etc.)

Reference Documentation

Getting Started

• nexus-quickstart - Quick start guide
• nexus-installation - Installation and setup
• nexus-architecture - Architecture overview
• README - Framework overview
• nexus-comparison - Nexus vs alternatives

Core Concepts

• nexus-workflow-registration - Registering workflows
• nexus-multi-channel - Multi-channel architecture
• nexus-sessions - Session management
• nexus-config-options - Configuration options

Channel-Specific Patterns

• nexus-api-patterns - HTTP API patterns
• nexus-api-input-mapping - API input handling
• nexus-cli-patterns - CLI usage patterns
• nexus-mcp-channel - MCP channel configuration

Integration

• nexus-dataflow-integration - DataFlow + Nexus patterns
• nexus-plugins - Plugin system
• nexus-event-system - Event-driven architecture

Production & Operations

• nexus-production-deployment - Production deployment
• nexus-health-monitoring - Health checks and monitoring
• nexus-enterprise-features - Enterprise capabilities
• nexus-troubleshooting - Common issues and solutions

Additional Skills

• nexus-handler-support - @app.handler() decorator for direct function registration
• nexus-auth-plugin - NexusAuthPlugin unified auth (JWT, RBAC, SSO, rate limiting, tenant, audit)
• golden-patterns-catalog - Top 7 production-validated codegen patterns
• codegen-decision-tree - Decision tree, anti-patterns, scaffolding templates

Key Concepts

Zero-Config Platform

Nexus eliminates boilerplate:

• No manual routes - Automatic API generation from workflows
• No CLI arg parsing - Automatic CLI creation
• No MCP server setup - Automatic MCP integration
• Unified deployment - One command for all channels

Multi-Channel Architecture

Single deployment, three access methods:

1. HTTP API: RESTful JSON endpoints
2. CLI: Command-line interface
3. MCP: Model Context Protocol server

Unified Sessions

Consistent session management:

• Cross-channel session tracking
• Session state persistence
• Session-scoped workflows
• Concurrent session support

Enterprise Features

Production-ready capabilities:

• Health monitoring endpoints
• Plugin system for extensibility
• Event system for integrations
• Comprehensive logging and metrics
• Correct channel initialization flow
• Proper workflow registration

When to Use This Skill

Use Nexus when you need to:

• Deploy workflows as production platforms
• Provide multiple access methods (API/CLI/MCP)
• Build enterprise platforms quickly
• Auto-generate CRUD APIs (with DataFlow)
• Build multi-channel platforms quickly
• Create multi-channel applications
• Deploy AI agent platforms (with Kaizen)

Integration Patterns

With DataFlow (Database-Backed Handlers)

from kailash.nexus import NexusApp, NexusConfig
import kailash

# Initialize DataFlow
df = kailash.DataFlow("postgresql://user:pass@localhost/db")

@db.model
class User:
    id: str
    name: str

# Create Nexus app and register database-backed handlers
app = NexusApp(config=NexusConfig(port=3000))

@app.handler(name="create_user", description="Create a new user")
async def create_user(name: str) -> dict:
    reg = kailash.NodeRegistry()
    builder = kailash.WorkflowBuilder()
    builder.add_node("CreateUser", "create", {"data": {"name": name}})
    rt = kailash.Runtime(reg)
    result = rt.execute(builder.build(reg))
    return result["results"]["create"]["result"]

app.start()

With Kaizen (Agent Platform)

from kailash.nexus import NexusApp
from kailash.kaizen import BaseAgent

# Deploy agents via all channels using handlers
app = NexusApp()

@app.handler(name="agent_chat", description="Chat with AI agent")
async def agent_chat(message: str) -> dict:
    agent = BaseAgent()
    result = agent.execute(message)
    return {"response": result.get("output", "")}

app.start()  # Agents accessible via API, CLI, and MCP

With Core SDK (Custom Workflows)

from kailash.nexus import NexusApp, NexusConfig
import kailash

app = NexusApp(config=NexusConfig(port=3000))

# Register workflow execution as handlers
@app.handler(name="process_data", description="Run data processing workflow")
async def process_data(input_text: str) -> dict:
    reg = kailash.NodeRegistry()
    builder = kailash.WorkflowBuilder()
    builder.add_node("EmbeddedPythonNode", "process", {
        "code": "result = {'processed': True}",
        "output_vars": ["result"]
    })
    rt = kailash.Runtime(reg)
    result = rt.execute(builder.build(reg))
    return result["results"]["process"]["outputs"]

app.start()

Standalone Platform

from kailash.nexus import NexusApp, NexusConfig, Preset

# Complete platform with enterprise preset and custom config
app = NexusApp(
    config=NexusConfig(host="0.0.0.0", port=3000),
    preset="enterprise",  # or Preset.enterprise()
)

# Add middleware
app.add_cors(origins=["https://app.example.com"])
app.add_rate_limit(max_requests=100, window_secs=60)

# Register handlers
@app.handler(name="status", description="Platform status")
async def status() -> dict:
    return app.health_check()

app.start()  # Host/port configured via NexusConfig

Critical Rules

• Use Nexus for workflow platforms
• Register workflows, not individual routes
• Leverage unified sessions across channels
• Enable health monitoring in production
• Use plugins for custom behavior
• Nexus uses kailash.Runtime by default (correct for Docker)
• NEVER bypass Nexus with raw framework routes
• NEVER implement manual API/CLI/MCP servers when Nexus can do it
• NEVER skip health checks in production

Deployment Patterns

Development

from kailash.nexus import NexusApp

app = NexusApp()  # Defaults: host=0.0.0.0, port=3000

@app.handler(name="hello", description="Hello world")
async def hello(name: str = "World") -> dict:
    return {"message": f"Hello, {name}!"}

app.start()

Production (Docker)

from kailash.nexus import NexusApp, NexusConfig

app = NexusApp(
    config=NexusConfig(host="0.0.0.0", port=3000),
    preset="enterprise",
)
app.add_cors(origins=["https://app.example.com"])
app.add_rate_limit(max_requests=100, window_secs=60)

# Register production handlers...

app.start()

With Load Balancer

# Deploy multiple Nexus instances behind nginx/traefik
docker-compose up --scale nexus=3

Channel Comparison

DataFlowEventBridge (NP-023)

Feature-gated behind dataflow-bridge. Bridges DataFlow model change events to the Nexus EventBus, enabling Nexus subscribers (SSE clients, plugin hooks, monitoring) to react to DataFlow writes without direct coupling.

kailash-nexus = { version = "...", features = ["dataflow-bridge"] }

NexusEvent::DataFlowEvent variant

Subscribes to topics: model.created, model.updated, model.deleted, model.upserted, model.bulk_created.

Usage

use kailash_nexus::Nexus;
use std::sync::Arc;

// domain_bus is the DomainEventBus from DataFlow
let mut nexus = Nexus::new(config);
nexus.bridge_dataflow(domain_bus);

Nexus::bridge_dataflow(&mut self, domain_bus: Arc<dyn DomainEventBus>) -> &mut Self registers the bridge as a background service. The bridge converts each DomainEvent into a NexusEvent::DataFlowEvent and publishes it on the Nexus EventBus.

Source: crates/kailash-nexus/src/bridge.rs, crates/kailash-nexus/src/events/mod.rs

Related Skills

• 01-core-sdk - Core workflow patterns
• 02-dataflow - Auto CRUD API generation
• 04-kaizen - AI agent deployment
• 05-kailash-mcp - MCP channel details
• 17-gold-standards - Best practices

Support

For Nexus-specific questions, invoke:

• nexus-specialist - Nexus implementation and deployment
• release-specialist - Production deployment patterns
• ``decide-framework skill - When to use Nexus vs other approaches