Inngest Events

Inngest Events

Master Inngest event design and delivery patterns. Events are the foundation of Inngest - learn to design robust event schemas, implement idempotency, leverage fan-out patterns, and handle system events effectively.

These skills are focused on TypeScript. For Python or Go, refer to the Inngest documentation for language-specific guidance. Core concepts apply across all languages.

Event Payload Format

Every Inngest event is a JSON object with required and optional properties:

Required Properties

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type Event = {
  name: string; // Event type (triggers functions)
  data: object; // Payload data (any nested JSON)
};

Complete Schema

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type EventPayload = {
  name: string; // Required: event type
  data: Record<string, any>; // Required: event data
  id?: string; // Optional: deduplication ID
  ts?: number; // Optional: timestamp (Unix ms)
  v?: string; // Optional: schema version
};

Basic Event Example

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await inngest.send({
  name: "billing/invoice.paid",
  data: {
    customerId: "cus_NffrFeUfNV2Hib",
    invoiceId: "in_1J5g2n2eZvKYlo2C0Z1Z2Z3Z",
    userId: "user_03028hf09j2d02",
    amount: 1000,
    metadata: {
      accountId: "acct_1J5g2n2eZvKYlo2C0Z1Z2Z3Z",
      accountName: "Acme.ai",
    },
  },
});

Event Naming Conventions

Use the Object-Action pattern: domain/noun.verb

Recommended Patterns

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// ✅ Good: Clear object-action pattern
"billing/invoice.paid";
"user/profile.updated";
"order/item.shipped";
"ai/summary.completed";

// ✅ Good: Domain prefixes for organization
"stripe/customer.created";
"intercom/conversation.assigned";
"slack/message.posted";

// ❌ Avoid: Unclear or inconsistent
"payment"; // What happened?
"user_update"; // Use dots, not underscores
"invoiceWasPaid"; // Too verbose

Naming Guidelines

• Past tense: Events describe what happened (created, updated, failed)
• Dot notation: Use dots for hierarchy (billing/invoice.paid)
• Prefixes: Group related events (api/user.created, webhook/stripe.received)
• Consistency: Establish patterns and stick to them

Event IDs and Idempotency

When to use IDs: Prevent duplicate processing when events might be sent multiple times.

Basic Deduplication

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await inngest.send({
  id: "cart-checkout-completed-ed12c8bde", // Unique per event type
  name: "storefront/cart.checkout.completed",
  data: {
    cartId: "ed12c8bde",
    items: ["item1", "item2"],
  },
});

ID Best Practices

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// ✅ Good: Specific to event type and instance
id: `invoice-paid-${invoiceId}`;
id: `user-signup-${userId}-${timestamp}`;
id: `order-shipped-${orderId}-${trackingNumber}`;

// ❌ Bad: Generic IDs shared across event types
id: invoiceId; // Could conflict with other events
id: "user-action"; // Too generic
id: customerId; // Same customer, different events

Deduplication window: 24 hours from first event reception

See inngest-durable-functions for idempotency configuration.

The ts Parameter for Delayed Delivery

When to use: Schedule events for future processing or maintain event ordering.

Future Scheduling

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const oneHourFromNow = Date.now() + 60 * 60 * 1000;

await inngest.send({
  name: "trial/reminder.send",
  ts: oneHourFromNow, // Deliver in 1 hour
  data: {
    userId: "user_123",
    trialExpiresAt: "2024-02-15T12:00:00Z",
  },
});

Maintaining Event Order

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// Events with timestamps are processed in chronological order
const events = [
  {
    name: "user/action.performed",
    ts: 1640995200000, // Earlier
    data: { action: "login" },
  },
  {
    name: "user/action.performed",
    ts: 1640995260000, // Later
    data: { action: "purchase" },
  },
];

await inngest.send(events);

Fan-Out Patterns

Use case: One event triggers multiple independent functions for reliability and parallel processing.

Basic Fan-Out Implementation

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// Send single event
await inngest.send({
  name: "user/signup.completed",
  data: {
    userId: "user_123",
    email: "user@example.com",
    plan: "pro",
  },
});

// Multiple functions respond to same event
const sendWelcomeEmail = inngest.createFunction(
  { id: "send-welcome-email", triggers: [{ event: "user/signup.completed" }] },
  async ({ event, step }) => {
    await step.run("send-email", async () => {
      return sendEmail({
        to: event.data.email,
        template: "welcome",
      });
    });
  },
);

const createTrialSubscription = inngest.createFunction(
  { id: "create-trial", triggers: [{ event: "user/signup.completed" }] },
  async ({ event, step }) => {
    await step.run("create-subscription", async () => {
      return stripe.subscriptions.create({
        customer: event.data.stripeCustomerId,
        trial_period_days: 14,
      });
    });
  },
);

const addToCrm = inngest.createFunction(
  { id: "add-to-crm", triggers: [{ event: "user/signup.completed" }] },
  async ({ event, step }) => {
    await step.run("crm-sync", async () => {
      return crm.contacts.create({
        email: event.data.email,
        plan: event.data.plan,
      });
    });
  },
);

Fan-Out Benefits

• Independence: Functions run separately; one failure doesn't affect others
• Parallel execution: All functions run simultaneously
• Selective replay: Re-run only failed functions
• Cross-service: Trigger functions in different codebases/languages

Advanced Fan-Out with waitForEvent

In expressions, event = the original triggering event, async = the new event being matched. See Expression Syntax Reference for full details.

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const orchestrateOnboarding = inngest.createFunction(
  {
    id: "orchestrate-onboarding",
    triggers: [{ event: "user/signup.completed" }],
  },
  async ({ event, step }) => {
    // Fan out to multiple services
    await step.sendEvent("fan-out", [
      { name: "email/welcome.send", data: event.data },
      { name: "subscription/trial.create", data: event.data },
      { name: "crm/contact.add", data: event.data },
    ]);

    // Wait for all to complete
    const [emailResult, subResult, crmResult] = await Promise.all([
      step.waitForEvent("email-sent", {
        event: "email/welcome.sent",
        timeout: "5m",
        if: `event.data.userId == async.data.userId`,
      }),
      step.waitForEvent("subscription-created", {
        event: "subscription/trial.created",
        timeout: "5m",
        if: `event.data.userId == async.data.userId`,
      }),
      step.waitForEvent("crm-synced", {
        event: "crm/contact.added",
        timeout: "5m",
        if: `event.data.userId == async.data.userId`,
      }),
    ]);

    // Complete onboarding
    await step.run("complete-onboarding", async () => {
      return completeUserOnboarding(event.data.userId);
    });
  },
);

See inngest-steps for additional patterns including step.invoke.

System Events

Inngest emits system events for function lifecycle monitoring:

Available System Events

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// Function execution events
"inngest/function.failed"; // Function failed after retries
"inngest/function.finished"; // Function finished - completed or failed
"inngest/function.cancelled"; // Function cancelled before completion

Handling Failed Functions

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const handleFailures = inngest.createFunction(
  {
    id: "handle-failed-functions",
    triggers: [{ event: "inngest/function.failed" }],
  },
  async ({ event, step }) => {
    const { function_id, run_id, error } = event.data;

    await step.run("log-failure", async () => {
      logger.error("Function failed", {
        functionId: function_id,
        runId: run_id,
        error: error.message,
        stack: error.stack,
      });
    });

    // Alert on critical function failures
    if (function_id.includes("critical")) {
      await step.run("send-alert", async () => {
        return alerting.sendAlert({
          title: `Critical function failed: ${function_id}`,
          severity: "high",
          runId: run_id,
        });
      });
    }

    // Auto-retry certain failures
    if (error.code === "RATE_LIMIT_EXCEEDED") {
      await step.run("schedule-retry", async () => {
        return inngest.send({
          name: "retry/function.requested",
          ts: Date.now() + 5 * 60 * 1000, // Retry in 5 minutes
          data: { originalRunId: run_id },
        });
      });
    }
  },
);

Sending Events

Client Setup

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// inngest/client.ts
import { Inngest } from "inngest";

export const inngest = new Inngest({
  id: "my-app",
});
// You must set INNGEST_EVENT_KEY environment variable in production

Single Event

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const result = await inngest.send({
  name: "order/placed",
  data: {
    orderId: "ord_123",
    customerId: "cus_456",
    amount: 2500,
    items: [
      { id: "item_1", quantity: 2 },
      { id: "item_2", quantity: 1 },
    ],
  },
});

// Returns event IDs for tracking
console.log(result.ids); // ["01HQ8PTAESBZPBDS8JTRZZYY3S"]

Batch Events

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const orderItems = await getOrderItems(orderId);

// Convert to events
const events = orderItems.map((item) => ({
  name: "inventory/item.reserved",
  data: {
    itemId: item.id,
    orderId: orderId,
    quantity: item.quantity,
    warehouseId: item.warehouseId,
  },
}));

// Send all at once (up to 512kb)
await inngest.send(events);

Sending from Functions

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inngest.createFunction(
  { id: "process-order", triggers: [{ event: "order/placed" }] },
  async ({ event, step }) => {
    // Use step.sendEvent() instead of inngest.send() in functions
    // for reliability and deduplication
    await step.sendEvent("trigger-fulfillment", {
      name: "fulfillment/order.received",
      data: {
        orderId: event.data.orderId,
        priority: event.data.customerTier === "premium" ? "high" : "normal",
      },
    });
  },
);

Event Design Best Practices

Schema Versioning

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// Use version field to track schema changes
await inngest.send({
  name: "user/profile.updated",
  v: "2024-01-15.1", // Schema version
  data: {
    userId: "user_123",
    changes: {
      email: "new@example.com",
      preferences: { theme: "dark" },
    },
    // New field in v2 schema
    auditInfo: {
      changedBy: "user_456",
      reason: "user_requested",
    },
  },
});

Rich Context Data

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// Include enough context for all consumers
await inngest.send({
  name: "payment/charge.succeeded",
  data: {
    // Primary identifiers
    chargeId: "ch_123",
    customerId: "cus_456",

    // Amount details
    amount: 2500,
    currency: "usd",

    // Context for different consumers
    subscription: {
      id: "sub_789",
      plan: "pro_monthly",
    },
    invoice: {
      id: "inv_012",
      number: "INV-2024-001",
    },

    // Metadata for debugging
    paymentMethod: {
      type: "card",
      last4: "4242",
      brand: "visa",
    },
    metadata: {
      source: "stripe_webhook",
      environment: "production",
    },
  },
});

Event design principles:

1. Self-contained: Include all data consumers need
2. Immutable: Never modify event schemas after sending
3. Traceable: Include correlation IDs and audit trails
4. Actionable: Provide enough context for business logic
5. Debuggable: Include metadata for troubleshooting

This Repository

These upstream Inngest instructions are vendored for agent tooling and integration work in this monorepo.

Repository Triggers

Use this skill when inngest-events matches the current Inngest task. If the right skill is unclear, start with docs/ai/skills/inngest/SKILL.md.

Repository Workflow

1. Confirm whether the request is agent-tooling guidance or product runtime integration.
2. Use inngest-brownfield-audit before changing existing app workflows or fragile background work.
3. Follow this upstream guidance under OpenSpec, root AGENTS.md, repo rulebooks, framework docs, and runtime evidence.
4. Keep runtime packages, app code, migrations, and INNGEST_* env requirements out of agent-tooling-only changes.

Repository Checklist

• The task has explicit product-runtime scope before adding Inngest app code or dependencies.
• Existing workflows were audited before introducing or changing durable workflow behavior.
• Any MCP usage is backed by a running Inngest dev server on the configured port.
• Upstream source and license attribution remain documented in docs/ai/skills/inngest/references/upstream.md.