Commet Webhooks

Receive real-time HTTP notifications when billing events happen in Commet -- subscriptions activating, payments failing, invoices being created, and more.

Quick Start

// app/api/webhooks/commet/route.ts
import { Webhooks } from "@commet/next";

export const POST = Webhooks({
  webhookSecret: process.env.COMMET_WEBHOOK_SECRET!,

  onSubscriptionActivated: async (payload) => {
    await sendWelcomeEmail(payload.data.externalId);
  },

  onSubscriptionCanceled: async (payload) => {
    await sendCancellationEmail(payload.data.externalId);
  },
});

Install the handler package:

npm install @commet/next

Key Gotcha: Query State Directly

Webhooks are for background tasks (sending emails, provisioning resources, logging). They should never be the source of truth for access control or subscription state.

Always query the SDK directly when you need to check a customer's status:

import { Commet } from "@commet/node";

const commet = new Commet({ apiKey: process.env.COMMET_API_KEY! });

// Check subscription status -- do this, not webhook state sync
const { data: sub } = await commet.subscriptions.get("user_123");
if (sub?.status === "active" || sub?.status === "trialing") {
  // grant access
}

// Check feature access
const { data } = await commet.features.check({
  code: "advanced_analytics",
  customerId: "user_123",
});

Event Types

Event	When Fired	Common Use
subscription.created	New subscription created, before payment	Logging, analytics
subscription.activated	Payment successful, subscription active	Welcome email, provision resources
subscription.canceled	Subscription canceled	Cancellation email, schedule cleanup
subscription.updated	Subscription details changed	Sync external systems
subscription.plan_changed	Plan upgrade/downgrade	Notify of plan change, adjust resources
payment.received	Recurring payment processed	Receipt email, update accounting
payment.failed	Recurring charge failed	Alert customer, dunning flow
invoice.created	New invoice generated	Custom invoice handling

See references/events.md for full payload shapes and examples.

Payload Envelope

Every webhook delivers a JSON payload with this structure:

{
  "event": "subscription.activated",
  "timestamp": "2026-03-25T14:30:00.000Z",
  "organizationId": "org_abc123",
  "data": { }
}

Headers

Header	Description
X-Commet-Signature	HMAC-SHA256 hex signature of the raw body
X-Commet-Event	The event type
X-Commet-Timestamp	ISO 8601 datetime when the event was emitted

When to Load References

• Setting up webhooks or verifying signatures -> references/setup.md
• Event payload shapes and fields -> references/events.md
• Next.js, Express, or Better Auth handlers -> references/framework-handlers.md