Build your first multi-language Motia app in minutes. This guide walks you through creating, running, and understanding a Motia app using JavaScript, TypeScript, and Python.

Build Your First Motia App

Get up and running with Motia in just a few minutes! This guide shows you how to create a Motia app that connects JavaScript, TypeScript, and Python as steps.

What You'll Build

A simple data processing Motia app:

TypeScript API endpoint receives data with validation
TypeScript bridges and notifies with proper types
Python processes the data with proper logging
JavaScript generates final summary and metrics

All connected automatically with zero configuration and strict type safety.

Step 1: Create Your Motia App

# Create a new Motia app
npx motia@latest create -i

Create App Command

# Change directory to my-app
cd my-app

run dev command

### Start the development environment
npx motia dev

run starter app

✅ That's it! You now have a working Motia app with a visual debugger at http://localhost:3000

Step 2: Add Environment Variables (Optional)

If you want to use external APIs, create a .env file:

.env

# Only add these if you need external services
OPENAI_API_KEY=sk-your-api-key-here
DISCORD_WEBHOOK_URL=https://discord.com/api/webhooks/your-webhook

The basic tutorial works without any API keys. Add environment variables only if you want to integrate external services.

➡️ Learn about Environment Variables

Step 3: Add Your Logic Steps

TypeScript API Endpoint (App Starter)

// File: 01-starter.step.ts

import { Handlers } from 'motia'
import { z } from 'zod'
import { StartAppRequest, StartAppResponse, AppData } from '../types'
 
const bodySchema = z.object({
  data: z.record(z.unknown()).optional(),
  message: z.string().optional()
})
 
// Basic app starter - TypeScript API endpoint
export const config = {
  type: 'api',
  name: 'appStarter',
  description: 'Start the basic multi-language app',
 
  method: 'POST',
  path: '/start-app',
 
  emits: ['app.started'],
  flows: ['data-processing'],
  
  bodySchema,
  responseSchema: {
    200: z.object({
      message: z.string(),
      appId: z.number(),
      traceId: z.string()
    })
  }
} as const
 
export const handler: Handlers['appStarter'] = async (req, { logger, emit, traceId }) => {
  logger.info('🚀 Starting basic app', { body: req.body, traceId })
  
  const validationResult = bodySchema.safeParse(req.body)
  
  if (!validationResult.success) {
    logger.error('Invalid request body', { errors: validationResult.error.errors })
    return { 
      status: 400, 
      body: { 
        message: 'Invalid request body', 
        errors: validationResult.error.errors 
      } 
    }
  }
  
  const appData: AppData = {
    id: Date.now(),
    input: validationResult.data.data || {},
    started_at: new Date().toISOString(),
    traceId: traceId
  }
  
  // Emit to start the app
  await emit({
    topic: 'app.started',
    data: appData
  })
  
  logger.info('app initiated successfully', { appId: appData.id })
  
  const response: StartAppResponse = {
    message: 'Basic app started successfully',
    appId: appData.id,
    traceId: traceId
  }
  
  return {
    status: 200,
    body: response
  }
}

TypeScript Bridge Step

// File: 02-bridge.step.ts

import { Handlers } from 'motia'
import { AppData, ProcessedResult } from '../types'
 
// Bridge step to connect app starter to Python processing
export const config = {
  type: 'event',
  name: 'appBridge',
  description: 'Bridge between app start and Python processing',
  
  subscribes: ['app.started'],
  emits: ['data.processed'],
  
  flows: ['data-processing']
} as const
 
export const handler: Handlers['appBridge'] = async (input, { logger, emit }) => {
  logger.info('🌉 Processing app data and sending to Python', { appId: input.id })
  
  // Process data for Python step
  const processedResult: ProcessedResult = {
    original_id: input.id,
    processed_at: input.started_at,
    result: `Processed: ${JSON.stringify(input.input)}`,
    confidence: 0.95,
    model_version: 'v2.1-ts'
  }
  
  // Send to Python step for async processing
  await emit({
    topic: 'data.processed',
    data: processedResult
  })
  
  logger.info('Data sent to Python step for processing', { dataId: processedResult.original_id })
}

Python Data Processor

// File: simple-python.step.py

# process-data.step.py
config = {
    'type': 'event',
    'name': 'ProcessDataPython',
    'description': 'Process incoming data and emit python.done',
    'subscribes': ['data.processed'],
    'emits': ['python.done'],
    'flows': ['data-processing']
}
 
async def handler(input_data, context):
    """
    Process data received from TypeScript bridge step
    
    Args:
        input_data: ProcessedResult with original_id, processed_at, result, confidence, model_version
        context: Motia context with emit, logger, etc.
    """
    try:
        # Validate required fields
        required_fields = ['original_id', 'processed_at', 'result']
        for field in required_fields:
            if field not in input_data:
                raise ValueError(f"Missing required field: {field}")
        
        context.logger.info("🐍 Processing data", {
            "id": input_data['original_id'],
            "confidence_level": input_data.get('confidence', 'N/A'),
            "model_version": input_data.get('model_version', 'unknown'),
        })
 
        # Process the data (simulate complex Python processing)
        python_result = {
            'id': input_data['original_id'],
            'python_message': f"Python processed: {input_data['result']}",
            'processed_by': 'python-step',
            'timestamp': input_data['processed_at']
        }
 
        context.logger.info(f"🐍 Processing complete, emitting python.done event")
 
        # Emit with topic and data in dictionary format
        await context.emit({"topic": "python.done", "data": python_result})
 
        context.logger.info("🐍 Event emitted successfully", { "id": python_result['id'] })
 
        # Return the payload so Motia passes it along automatically
        return python_result
        
    except Exception as e:
        context.logger.error(f"🐍 Error processing data: {str(e)}")
        # Re-raise the exception to let Motia handle it
        raise

TypeScript Notification Step

// File: notify.step.ts

import { Handlers } from 'motia'
import { PythonResult, NotificationData } from '../types'
 
export const config = {
  type: 'event',
  name: 'NotificationHandler',
  description: 'Send notifications after Python processing',
  
  subscribes: ['python.done'],
  emits: ['notification.sent'],
  
  flows: ['data-processing']
} as const
 
export const handler: Handlers['NotificationHandler'] = async (input, { logger, emit }) => {
  logger.info('📧 Sending notifications after Python processing:', { id: input.id })
  
  // Simulate sending notifications (email, slack, etc.)
  const notification: NotificationData = {
    id: input.id,
    message: `Notification: ${input.python_message}`,
    processed_by: input.processed_by,
    sent_at: new Date().toISOString()
  }
  
  // Trigger final step
  await emit({
    topic: 'notification.sent',
    data: notification
  })
  
  logger.info('Notification sent successfully', notification)
}

TypeScript Finalizer Step

// File: 04-final.step.ts

import { Handlers } from 'motia'
import { NotificationData, AppSummary } from '../types'
 
// Final step to complete the app - TypeScript
export const config = {
  type: 'event',
  name: 'appFinalizer',
  description: 'Complete the basic app and log final results',
  
  subscribes: ['notification.sent'],
  emits: ['app.completed'],
  
  flows: ['data-processing']
} as const
 
export const handler: Handlers['appFinalizer'] = async (input, { logger, emit }) => {
  logger.info('🏁 Finalizing app', { 
    notificationId: input.id,
    message: input.message 
  })
  
  // Create final app summary
  const summary: AppSummary = {
    appId: input.id,
    status: 'completed',
    completed_at: new Date().toISOString(),
    steps_executed: [
      'appStarter (TypeScript)',
      'appBridge (TypeScript)', 
      'ProcessDataPython (Python)',
      'NotificationHandler (TypeScript)',
      'appFinalizer (TypeScript)',
      'summaryGenerator (JavaScript)'
    ],
    result: input.message
  }
  
  // Emit completion event
  await emit({
    topic: 'app.completed',
    data: summary
  })
  
  logger.info('✅ Basic app completed successfully', summary)
}

JavaScript Summary Generator

// File: 05-summary.step.js

// Final summary step - JavaScript
export const config = {
  type: 'event',
  name: 'summaryGenerator',
  description: 'Generate final summary in JavaScript',
  
  subscribes: ['app.completed'],
  emits: ['summary.generated'],
  
  flows: ['data-processing']
}
 
export const handler = async (input, { logger, emit }) => {
  logger.info('📊 Generating final summary in JavaScript', { 
    appId: input.appId,
    status: input.status 
  })
  
  // Calculate processing metrics
  const processingTime = new Date() - new Date(input.completed_at)
  const stepsCount = input.steps_executed.length
  
  // Create comprehensive summary
  const summary = {
    appId: input.appId,
    finalStatus: input.status,
    totalSteps: stepsCount,
    processingTimeMs: Math.abs(processingTime),
    languages: ['TypeScript', 'Python', 'JavaScript'],
    summary: `Multi-language app completed successfully with ${stepsCount} steps`,
    result: input.result,
    completedAt: new Date().toISOString(),
    generatedBy: 'javascript-summary-step'
  }
  
  // Emit final summary
  await emit({
    topic: 'summary.generated',
    data: summary
  })
  
  logger.info('✨ Final summary generated successfully', summary)
  
  return summary
}

What Happens Next?

motia-build-your-app

Watch in the Workbench (http://localhost:3000) as your data flows through:

TypeScript API receives and validates the request
TypeScript bridge processes and forwards data
Python processes it with proper logging (access to numpy, pandas, torch, etc.)
TypeScript handles notifications with full type safety
JavaScript generates final summary with metrics

All languages working together in one unified system with:

✅ Automatic observability - see every step in real-time
✅ Built-in error handling - retry logic included
✅ Shared state - pass data between languages effortlessly
✅ Hot reload - edit any file and see changes instantly
✅ Type safety - proper TypeScript types throughout
✅ Input validation - Zod schema validation for APIs
✅ Multi-language - JavaScript, TypeScript, and Python working together

Deploy and Extend

You just built a production-ready multi-language Motia app!

Extend your app:

Add scheduled jobs with cron steps
Create UI components with React/Vue steps
Connect to databases, APIs, and external services
Scale to handle millions of requests

Ready to deploy? Check out Motia Cloud deployment for one-click production deployments.

Ready to build more? Check out our Getting Started Guide for more details.

The bottom line: Motia eliminates the complexity of managing separate runtimes. Write each piece in the best language for the job, and Motia handles the rest.

Need help? See our Community Resources for questions, examples, and discussions.

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