# 1. Scaffold project
npm create cloudflare@latest my-workflow -- --template cloudflare/workflows-starter --git --deploy false
cd my-workflow

# 2. Configure wrangler.jsonc
{
  "name": "my-workflow",
  "main": "src/index.ts",
  "compatibility_date": "2025-11-25",
  "workflows": [{
    "name": "my-workflow",
    "binding": "MY_WORKFLOW",
    "class_name": "MyWorkflow"
  }]
}

# 3. Create workflow (src/index.ts)
import { WorkflowEntrypoint, WorkflowStep, WorkflowEvent } from 'cloudflare:workers';

export class MyWorkflow extends WorkflowEntrypoint<Env, Params> {
  async run(event: WorkflowEvent<Params>, step: WorkflowStep) {
    const result = await step.do('process', async () => { /* work */ });
    await step.sleep('wait', '1 hour');
    await step.do('continue', async () => { /* more work */ });
  }
}

# 4. Deploy and test
npm run deploy
npx wrangler workflows instances list my-workflow

export class MyWorkflow extends WorkflowEntrypoint<Env, Params> {
  async run(event: WorkflowEvent<Params>, step: WorkflowStep) {
    for (let i = 0; i < 3; i++) {
      try {
        const evt = await step.waitForEvent(`wait-${i}`, {
          type: 'user-action',
          timeout: '5 seconds'
        });
        console.log(`Iteration ${i}: Received event`);
      } catch {
        console.log(`Iteration ${i}: Timeout`);
      }
    }
  }
}
// In wrangler dev:
// - Iteration 1: ✅ receives event
// - Iteration 2: ⏱️ times out (expected)
// - Iteration 3: ❌ does not receive event (BUG - event is sent but ignored)

// Workaround: Separate config for CLI scripts
// wrangler.cli.jsonc (no workflows)
{
  "name": "my-worker",
  "main": "src/index.ts",
  "compatibility_date": "2025-01-20"
  // workflows commented out
}

// Use in script:
import { getPlatformProxy } from 'wrangler';
const { env } = await getPlatformProxy({ configPath: './wrangler.cli.jsonc' });

export default {
  async fetch(req: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    const workflow = await env.MY_WORKFLOW.create({ params: { userId: '123' } });

    // ✅ Ensure workflow initialization completes
    ctx.waitUntil(workflow.status());

    return Response.redirect('/dashboard', 302);
  }
};

const instance = await env.MY_WORKFLOW.get(instanceId);

// ❌ Fails in wrangler dev
await instance.restart();    // Error: Not implemented yet
await instance.terminate();  // Error: Not implemented yet

// ✅ Works in production

// ❌ Bad - I/O outside step
const response = await fetch('https://api.example.com/data');
const data = await response.json();

await step.do('use data', async () => {
  return data;  // This will fail!
});

// ✅ Good - I/O inside step
const data = await step.do('fetch data', async () => {
  const response = await fetch('https://api.example.com/data');
  return await response.json();
});

// ❌ Retries in dev, exits in prod
throw new NonRetryableError('');

// ✅ Exits in both environments
throw new NonRetryableError('Validation failed');

// ❌ BAD - In-memory variable lost on hibernation
let counter = 0;
export class MyWorkflow extends WorkflowEntrypoint<Env, Params> {
  async run(event: WorkflowEvent<Params>, step: WorkflowStep) {
    counter = await step.do('increment', async () => counter + 1);
    await step.sleep('wait', '1 hour'); // ← Hibernates here, in-memory state lost
    console.log(counter); // ❌ Will be 0, not 1!
  }
}

// ✅ GOOD - State from step.do() return values persists
export class MyWorkflow extends WorkflowEntrypoint<Env, Params> {
  async run(event: WorkflowEvent<Params>, step: WorkflowStep) {
    const counter = await step.do('increment', async () => 1);
    await step.sleep('wait', '1 hour');
    console.log(counter); // ✅ Still 1
  }
}

// ❌ BAD - Non-deterministic step name
await step.do(`fetch-data-${Date.now()}`, async () => {
  return await fetchExpensiveData();
});
// Every execution creates new cache key → step always re-runs

// ✅ GOOD - Deterministic step name
await step.do('fetch-data', async () => {
  return await fetchExpensiveData();
});
// Same cache key → result reused on restart/retry

// ❌ BAD - Race outside step
const fastest = await Promise.race([fetchA(), fetchB()]);
await step.do('use result', async () => fastest);
// On restart: race runs again, different promise might win

// ✅ GOOD - Race inside step
const fastest = await step.do('fetch fastest', async () => {
  return await Promise.race([fetchA(), fetchB()]);
});
// On restart: cached result used, consistent behavior

// ❌ BAD - Side effect outside step
console.log('Workflow started'); // ← Logs multiple times on restart
await step.do('work', async () => { /* work */ });

// ✅ GOOD - Side effects inside step
await step.do('log start', async () => {
  console.log('Workflow started'); // ← Logs once (cached)
});

// ❌ BAD - Charge customer without check
await step.do('charge', async () => {
  return await stripe.charges.create({ amount: 1000, customer: customerId });
});
// If step times out after charge succeeds, retry charges AGAIN!

// ✅ GOOD - Check for existing charge first
await step.do('charge', async () => {
  const existing = await stripe.charges.list({ customer: customerId, limit: 1 });
  if (existing.data.length > 0) return existing.data[0]; // Idempotent
  return await stripe.charges.create({ amount: 1000, customer: customerId });
});

step.do<T>(name: string, config?: WorkflowStepConfig, callback: () => Promise<T>): Promise<T>

const result = await step.do('call API', { retries: { limit: 10, delay: '10s', backoff: 'exponential' }, timeout: '5 min' }, async () => {
  return await fetch('https://api.example.com/data').then(r => r.json());
});

step.sleep(name: string, duration: WorkflowDuration): Promise<void>

await step.sleep('wait 5 minutes', '5 minutes');
await step.sleep('wait 1 hour', '1 hour');
await step.sleep('wait 2 days', '2 days');
await step.sleep('wait 30 seconds', 30000);  // milliseconds

step.sleepUntil(name: string, timestamp: Date | number): Promise<void>

await step.sleepUntil('wait for launch', new Date('2025-12-25T00:00:00Z'));
await step.sleepUntil('wait until time', Date.parse('24 Oct 2024 13:00:00 UTC'));

step.waitForEvent<T>(name: string, options: { type: string; timeout?: string | number }): Promise<T>

export class PaymentWorkflow extends WorkflowEntrypoint<Env, Params> {
  async run(event: WorkflowEvent<Params>, step: WorkflowStep) {
    await step.do('create payment', async () => { /* Stripe API */ });

    const webhookData = await step.waitForEvent<StripeWebhook>(
      'wait for payment confirmation',
      { type: 'stripe-webhook', timeout: '1 hour' }
    );

    if (webhookData.status === 'succeeded') {
      await step.do('fulfill order', async () => { /* fulfill */ });
    }
  }
}

// Worker sends event to workflow
export default {
  async fetch(req: Request, env: Env): Promise<Response> {
    if (req.url.includes('/webhook/stripe')) {
      const instance = await env.PAYMENT_WORKFLOW.get(instanceId);
      await instance.sendEvent({ type: 'stripe-webhook', payload: await req.json() });
      return new Response('OK');
    }
  }
};

try {
  const event = await step.waitForEvent('wait for user', { type: 'user-submitted', timeout: '10 minutes' });
} catch (error) {
  await step.do('send reminder', async () => { /* reminder */ });
}

interface WorkflowStepConfig {
  retries?: {
    limit: number;          // Max attempts (Infinity allowed)
    delay: string | number; // Delay between retries
    backoff?: 'constant' | 'linear' | 'exponential';
  };
  timeout?: string | number; // Max time per attempt
}

// Constant: 30s, 30s, 30s
{ retries: { limit: 3, delay: '30 seconds', backoff: 'constant' } }

// Linear: 1m, 2m, 3m, 4m, 5m
{ retries: { limit: 5, delay: '1 minute', backoff: 'linear' } }

// Exponential (recommended): 10s, 20s, 40s, 80s, 160s
{ retries: { limit: 10, delay: '10 seconds', backoff: 'exponential' }, timeout: '5 minutes' }

// Unlimited retries
{ retries: { limit: Infinity, delay: '1 minute', backoff: 'exponential' } }

// No retries
{ retries: { limit: 0 } }

import { WorkflowEntrypoint, WorkflowStep, WorkflowEvent } from 'cloudflare:workers';
import { NonRetryableError } from 'cloudflare:workflows';

export class MyWorkflow extends WorkflowEntrypoint<Env, Params> {
  async run(event: WorkflowEvent<Params>, step: WorkflowStep) {
    await step.do('validate input', async () => {
      if (!event.payload.userId) {
        throw new NonRetryableError('userId is required');
      }

      // Validate user exists
      const user = await this.env.DB.prepare(
        'SELECT * FROM users WHERE id = ?'
      ).bind(event.payload.userId).first();

      if (!user) {
        // Terminal error - retrying won't help
        throw new NonRetryableError('User not found');
      }

      return user;
    });
  }
}

export class MyWorkflow extends WorkflowEntrypoint<Env, Params> {
  async run(event: WorkflowEvent<Params>, step: WorkflowStep) {
    await step.do('process payment', async () => { /* critical */ });

    try {
      await step.do('send email', async () => { /* optional */ });
    } catch (error) {
      await step.do('log failure', async () => {
        await this.env.DB.prepare('INSERT INTO failed_emails VALUES (?, ?)').bind(event.payload.userId, error.message).run();
      });
    }

    await step.do('update status', async () => { /* continues */ });
  }
}

let result;
try {
  result = await step.do('call primary API', async () => await callPrimaryAPI());
} catch {
  result = await step.do('call backup API', async () => await callBackupAPI());
}

{
  "workflows": [{
    "name": "my-workflow",
    "binding": "MY_WORKFLOW",
    "class_name": "MyWorkflow",
    "script_name": "workflow-worker"  // If workflow in different Worker
  }]
}

const instance = await env.MY_WORKFLOW.create({ params: { userId: '123' } });
return Response.json({ id: instance.id, status: await instance.status() });

const instance = await env.MY_WORKFLOW.get(instanceId);
const status = await instance.status();  // { status: 'running'|'complete'|'errored'|'queued', error, output }
await instance.sendEvent({ type: 'user-action', payload: { action: 'approved' } });
await instance.pause();
await instance.resume();
await instance.terminate();

// ✅ Good
const result = await step.do('fetch data', async () => ({
  users: [{ id: 1, name: 'Alice' }],
  timestamp: Date.now(),
  metadata: null
}));

// ❌ Bad - function not serializable
const bad = await step.do('bad', async () => ({ data: [1, 2, 3], transform: (x) => x * 2 }));  // Throws error!

const userData = await step.do('fetch user', async () => ({ id: 123, email: 'user@example.com' }));
const orderData = await step.do('create order', async () => ({ userId: userData.id, orderId: 'ORD-456' }));
await step.do('send email', async () => sendEmail({ to: userData.email, subject: `Order ${orderData.orderId}` }));

const instance = await env.MY_WORKFLOW.get(instanceId);
const status = await instance.status();

console.log(status);
// {
//   status: 'complete' | 'running' | 'errored' | 'queued' | 'waiting' | 'unknown',
//   error: string | null,
//   output: { userId: '123', status: 'processed' }
// }

// wrangler.jsonc
{ "limits": { "cpu_ms": 300000 } }  // 5 minutes max (default: 30 seconds)

npm install -D vitest@latest @cloudflare/vitest-pool-workers@latest

import { defineWorkersConfig } from '@cloudflare/vitest-pool-workers/config';
export default defineWorkersConfig({ test: { poolOptions: { workers: { miniflare: { bindings: { MY_WORKFLOW: { scriptName: 'workflow' } } } } } } });

import { env, introspectWorkflowInstance } from 'cloudflare:test';

it('should complete workflow', async () => {
  const instance = await introspectWorkflowInstance(env.MY_WORKFLOW, 'test-123');

  try {
    await instance.modify(async (m) => {
      await m.disableSleeps();  // Skip all sleeps
      await m.mockStepResult({ name: 'fetch data' }, { users: [{ id: 1 }] });  // Mock step result
      await m.mockEvent({ type: 'approval', payload: { approved: true } });  // Send mock event
      await m.mockStepError({ name: 'call API' }, new Error('Network timeout'), 1);  // Force error once
    });

    await env.MY_WORKFLOW.create({ id: 'test-123' });
    await expect(instance.waitForStatus('complete')).resolves.not.toThrow();
  } finally {
    await instance.dispose();  // Cleanup
  }
});