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Hookflo Tern

Use this skill for requests touching webhooks, event-driven infrastructure, or real-time HTTP callba

Rating
4.9 (188 reviews)
Downloads
507 downloads
Version
1.0.0

Overview

Use this skill for requests touching webhooks, event-driven infrastructure, or real-time HTTP callbacks.

Complete Documentation

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Hookflo + Tern Webhook Skill

This skill covers two tightly related tools in the Hookflo ecosystem:

  • Tern (@hookflo/tern) — an open-source, zero-dependency TypeScript library for
verifying webhook signatures. Algorithm-agnostic, supports all major platforms.
  • Hookflo — a hosted webhook event alerting and logging platform. Sends real-time
Slack/email alerts when webhooks fire. No code required on their end; you point your provider at Hookflo's URL and configure alerts in the dashboard.


Mental Model

text
Incoming Webhook Request
        │
        ▼
  [Tern] verify signature  ←── your server/edge function
        │
    isValid?
        │
   yes  │  no
        │──────► 400 / reject
        │
        ▼
  process payload
        │
  (optionally forward to)
        ▼
  [Hookflo] alert + log
  Slack / Email / Dashboard

Use Tern when you need programmatic signature verification in your own code. Use Hookflo when you want no-code / low-code alerting and centralized event logs. They can be used together or independently.


Part 1 — Tern (Webhook Verification Library)

Installation

bash
npm install @hookflo/tern

No other dependencies required. Full TypeScript support.

Core API

#### WebhookVerificationService.verify(request, config) The primary method. Returns a WebhookVerificationResult.

ts
import { WebhookVerificationService } from '@hookflo/tern';

const result = await WebhookVerificationService.verify(request, {
  platform: 'stripe',
  secret: process.env.STRIPE_WEBHOOK_SECRET!,
  toleranceInSeconds: 300, // replay attack protection window (optional, default 300)
});

if (result.isValid) {
  console.log('Verified payload:', result.payload);
  console.log('Metadata:', result.metadata); // timestamp, id, etc.
} else {
  console.error('Rejected:', result.error);
  // return 400
}

#### WebhookVerificationService.verifyWithPlatformConfig(request, platform, secret, tolerance?) Shorthand that accepts just a platform name + secret.

ts
const result = await WebhookVerificationService.verifyWithPlatformConfig(
  request,
  'github',
  process.env.GITHUB_WEBHOOK_SECRET!
);

#### WebhookVerificationService.verifyTokenBased(request, webhookId, webhookToken) For token-based platforms (Supabase, GitLab).

ts
const result = await WebhookVerificationService.verifyTokenBased(
  request,
  process.env.SUPABASE_WEBHOOK_ID!,
  process.env.SUPABASE_WEBHOOK_TOKEN!
);

WebhookVerificationResult type

ts
interface WebhookVerificationResult {
  isValid: boolean;
  error?: string;
  platform: WebhookPlatform;
  payload?: any;             // parsed JSON body
  metadata?: {
    timestamp?: string;
    id?: string | null;
    [key: string]: any;
  };
}


Built-in Platform Configs

PlatformAlgorithmSignature HeaderFormat
stripeHMAC-SHA256stripe-signaturet={ts},v1={sig}
githubHMAC-SHA256x-hub-signature-256sha256={sig}
clerkHMAC-SHA256 (base64)svix-signaturev1,{sig}
supabaseToken-basedcustom
gitlabToken-basedx-gitlab-token
shopifyHMAC-SHA256x-shopify-hmac-sha256raw
vercelHMAC-SHA256custom
polarHMAC-SHA256custom
dodoHMAC-SHA256 (svix)webhook-signaturev1,{sig}
Always use the lowercase string name (e.g., 'stripe', 'github').


Custom Platform Configuration

For any provider not in the list, supply a full signatureConfig:

ts
import { WebhookVerificationService } from '@hookflo/tern';

// Standard HMAC-SHA256 with prefix
const result = await WebhookVerificationService.verify(request, {
  platform: 'acmepay',
  secret: 'your_secret',
  signatureConfig: {
    algorithm: 'hmac-sha256',
    headerName: 'x-acme-signature',
    headerFormat: 'prefixed',
    prefix: 'sha256=',
    payloadFormat: 'raw',
  },
});

// Timestamped payload (signs "{timestamp}.{body}")
const result2 = await WebhookVerificationService.verify(request, {
  platform: 'mypay',
  secret: 'your_secret',
  signatureConfig: {
    algorithm: 'hmac-sha256',
    headerName: 'x-webhook-signature',
    headerFormat: 'raw',
    timestampHeader: 'x-webhook-timestamp',
    timestampFormat: 'unix',
    payloadFormat: 'timestamped',
  },
});

// Svix/StandardWebhooks compatible (Clerk, Dodo, etc.)
const result3 = await WebhookVerificationService.verify(request, {
  platform: 'my-svix-platform',
  secret: 'whsec_abc123...',
  signatureConfig: {
    algorithm: 'hmac-sha256',
    headerName: 'webhook-signature',
    headerFormat: 'raw',
    timestampHeader: 'webhook-timestamp',
    timestampFormat: 'unix',
    payloadFormat: 'custom',
    customConfig: {
      payloadFormat: '{id}.{timestamp}.{body}',
      idHeader: 'webhook-id',
    },
  },
});

SignatureConfig fields:

  • algorithm: 'hmac-sha256' | 'hmac-sha1' | 'hmac-sha512' | custom
  • headerName: the HTTP header that carries the signature
  • headerFormat: 'raw' | 'prefixed' | 'comma-separated' | 'space-separated'
  • prefix: string prefix to strip before comparing (e.g. 'sha256=')
  • timestampHeader: header name for the timestamp (if any)
  • timestampFormat: 'unix' | 'iso' | 'ms'
  • payloadFormat: 'raw' | 'timestamped' | 'custom'
  • customConfig.payloadFormat: template like '{id}.{timestamp}.{body}'
  • customConfig.idHeader: header supplying the {id} value
  • customConfig.encoding: 'base64' if the provider base64-encodes the key

Framework Integration

#### Express.js

ts
import express from 'express';
import { WebhookVerificationService } from '@hookflo/tern';

const app = express();

// IMPORTANT: use raw body parser for webhook routes
app.post(
  '/webhooks/stripe',
  express.raw({ type: 'application/json' }),
  async (req, res) => {
    const result = await WebhookVerificationService.verifyWithPlatformConfig(
      req,
      'stripe',
      process.env.STRIPE_WEBHOOK_SECRET!
    );

    if (!result.isValid) {
      return res.status(400).json({ error: result.error });
    }

    const event = result.payload;
    // handle event.type, e.g. 'payment_intent.succeeded'

    res.json({ received: true });
  }
);

Common mistake: Express's default json() middleware consumes and re-serializes
the body, breaking HMAC. Always use express.raw() on webhook endpoints.

#### Next.js App Router (Route Handler)

ts
// app/api/webhooks/github/route.ts
import { NextRequest, NextResponse } from 'next/server';
import { WebhookVerificationService } from '@hookflo/tern';

export async function POST(req: NextRequest) {
  const result = await WebhookVerificationService.verifyWithPlatformConfig(
    req,
    'github',
    process.env.GITHUB_WEBHOOK_SECRET!
  );

  if (!result.isValid) {
    return NextResponse.json({ error: result.error }, { status: 400 });
  }

  const event = req.headers.get('x-github-event');
  // handle event

  return NextResponse.json({ received: true });
}

// Disable body parsing so Tern gets the raw body
export const config = { api: { bodyParser: false } };

#### Cloudflare Workers

ts
addEventListener('fetch', (event) => {
  event.respondWith(handleRequest(event.request));
});

async function handleRequest(request: Request): Promise<Response> {
  if (request.method === 'POST' && new URL(request.url).pathname === '/webhooks/clerk') {
    const result = await WebhookVerificationService.verifyWithPlatformConfig(
      request,
      'clerk',
      CLERK_WEBHOOK_SECRET
    );

    if (!result.isValid) {
      return new Response(JSON.stringify({ error: result.error }), {
        status: 400,
        headers: { 'Content-Type': 'application/json' },
      });
    }

    return new Response(JSON.stringify({ received: true }));
  }

  return new Response('Not Found', { status: 404 });
}


Platform Manager (Advanced)

ts
import { platformManager } from '@hookflo/tern';

// Verify using the platform manager directly
const result = await platformManager.verify(request, 'stripe', 'whsec_...');

// Get the config for a platform (for inspection)
const config = platformManager.getConfig('stripe');

// Get docs/metadata for a platform
const docs = platformManager.getDocumentation('stripe');

// Run built-in tests for a platform
const passed = await platformManager.runPlatformTests('stripe');


Testing

bash
npm test                       # run all tests
npm run test:platform stripe   # test one platform
npm run test:all               # test all platforms


Part 2 — Hookflo (Hosted Alerting Platform)

Hookflo requires no library installation. The integration is:

  • Create a webhook endpoint in the Hookflo Dashboard → get a Webhook URL + Secret
  • Point your provider (Stripe, Supabase, Clerk, GitHub, etc.) at that URL
  • Configure Slack/email notifications in the dashboard

How to Set Up a Hookflo Integration

Step 1 — Go to hookflo.com/dashboard and create a new webhook. You'll receive:

  • Webhook URL — paste into your provider's webhook settings
  • Webhook ID — used for token-based platforms
  • Secret Token — used by Hookflo to verify incoming events
  • Notification channel settings — configure Slack or email
Step 2 — Set up the provider to send to that Hookflo URL:

ProviderWhere to paste the URL
StripeDashboard → Developers → Webhooks → Add endpoint
SupabaseDashboard → Database → Webhooks → Create webhook
ClerkDashboard → Webhooks → Add endpoint
GitHubRepo/Org Settings → Webhooks → Add webhook
Step 3 — In the Hookflo dashboard, configure:
  • Which event types to alert on (e.g., payment_intent.succeeded, user.created)
  • Notification channels (Slack workspace/channel, email addresses)
  • Digest frequency if you want batched summaries instead of per-event alerts

Hookflo Platform Docs

Hookflo + Tern Together

If you want both programmatic verification (Tern) AND logging/alerting (Hookflo), use a proxy pattern:

ts
// Your server receives the webhook, verifies it with Tern, then forwards to Hookflo
app.post('/webhooks/stripe', express.raw({ type: 'application/json' }), async (req, res) => {
  // 1. Verify with Tern
  const result = await WebhookVerificationService.verifyWithPlatformConfig(
    req, 'stripe', process.env.STRIPE_WEBHOOK_SECRET!
  );
  if (!result.isValid) return res.status(400).json({ error: result.error });

  // 2. Process locally
  handleStripeEvent(result.payload);

  // 3. Forward to Hookflo for alerting/logging (optional)
  await fetch(process.env.HOOKFLO_WEBHOOK_URL!, {
    method: 'POST',
    headers: { ...req.headers, 'Content-Type': 'application/json' },
    body: req.body,
  });

  res.json({ received: true });
});

Alternatively, point Stripe directly at your Hookflo URL and keep Tern for a different endpoint.


Common Pitfalls & Best Practices

Raw Body Requirement

HMAC signatures are computed over the exact raw bytes of the request body. Any re-serialization (e.g., by a JSON body parser) will break verification. Always ensure:
  • Express: use express.raw({ type: 'application/json' }) on webhook routes
  • Next.js Pages Router: set export const config = { api: { bodyParser: false } }
  • Next.js App Router: Tern reads the body directly from the Request object

Replay Attack Protection

Always pass toleranceInSeconds (default is 300 = 5 minutes). This rejects requests with timestamps too far in the past, preventing replay attacks.

Secrets Management

  • Never hardcode secrets in source code
  • Use environment variables: process.env.STRIPE_WEBHOOK_SECRET
  • For Cloudflare Workers: use wrangler secret put STRIPE_WEBHOOK_SECRET
  • For Vercel: add secrets in project settings

Error Responses

Always return HTTP 400 (not 500) for failed verification — this signals to the sender that the request was rejected (not that your server crashed).

HTTPS Only

Webhook endpoints must use HTTPS in production. Never accept webhook traffic over HTTP.


Troubleshooting

SymptomLikely CauseFix
isValid: false, error about signatureBody was parsed before TernUse raw body parser
isValid: false, error about timestampClock skew or replay attackCheck server clock; increase tolerance if dev
isValid: false for ClerkMissing svix headersEnsure svix-id, svix-timestamp, svix-signature are forwarded
isValid: false for GitHubWrong secretRe-copy secret from GitHub Webhooks settings
Tern not finding platformTypo in platform nameUse lowercase: 'stripe', 'github', 'clerk'
Hookflo not receiving eventsWrong URL pastedRe-copy URL from Hookflo dashboard

Key Links

  • Tern GitHub: https://github.com/Hookflo/tern
  • Tern npm: https://www.npmjs.com/package/@hookflo/tern
  • Tern docs: https://tern.hookflo.com
  • Hookflo homepage: https://hookflo.com
  • Hookflo dashboard: https://hookflo.com/dashboard
  • Hookflo docs: https://docs.hookflo.com
  • Hookflo Discord: https://discord.com/invite/SNmCjU97nr

Installation

Terminal bash

openclaw install hookflo-tern
    
Copied!

💻Code Examples

Slack / Email / Dashboard

-slack--email--dashboard.txt
Use **Tern** when you need programmatic signature verification in your own code.
Use **Hookflo** when you want no-code / low-code alerting and centralized event logs.
They can be used together or independently.

---

## Part 1 — Tern (Webhook Verification Library)

### Installation

npm install @hookflo/tern

npm-install-hookflotern.txt
No other dependencies required. Full TypeScript support.

### Core API

#### `WebhookVerificationService.verify(request, config)`
The primary method. Returns a `WebhookVerificationResult`.

}

.txt
#### `WebhookVerificationService.verifyWithPlatformConfig(request, platform, secret, tolerance?)`
Shorthand that accepts just a platform name + secret.

);

.txt
#### `WebhookVerificationService.verifyTokenBased(request, webhookId, webhookToken)`
For token-based platforms (Supabase, GitLab).

}

.txt
---

### Built-in Platform Configs

| Platform | Algorithm | Signature Header | Format |
|---|---|---|---|
| `stripe` | HMAC-SHA256 | `stripe-signature` | `t={ts},v1={sig}` |
| `github` | HMAC-SHA256 | `x-hub-signature-256` | `sha256={sig}` |
| `clerk` | HMAC-SHA256 (base64) | `svix-signature` | `v1,{sig}` |
| `supabase` | Token-based | custom | — |
| `gitlab` | Token-based | `x-gitlab-token` | — |
| `shopify` | HMAC-SHA256 | `x-shopify-hmac-sha256` | raw |
| `vercel` | HMAC-SHA256 | custom | — |
| `polar` | HMAC-SHA256 | custom | — |
| `dodo` | HMAC-SHA256 (svix) | `webhook-signature` | `v1,{sig}` |

Always use the lowercase string name (e.g., `'stripe'`, `'github'`).

---

### Custom Platform Configuration

For any provider not in the list, supply a full `signatureConfig`:

});

.txt
**`SignatureConfig` fields:**
- `algorithm`: `'hmac-sha256'` | `'hmac-sha1'` | `'hmac-sha512'` | custom
- `headerName`: the HTTP header that carries the signature
- `headerFormat`: `'raw'` | `'prefixed'` | `'comma-separated'` | `'space-separated'`
- `prefix`: string prefix to strip before comparing (e.g. `'sha256='`)
- `timestampHeader`: header name for the timestamp (if any)
- `timestampFormat`: `'unix'` | `'iso'` | `'ms'`
- `payloadFormat`: `'raw'` | `'timestamped'` | `'custom'`
- `customConfig.payloadFormat`: template like `'{id}.{timestamp}.{body}'`
- `customConfig.idHeader`: header supplying the `{id}` value
- `customConfig.encoding`: `'base64'` if the provider base64-encodes the key

---

### Framework Integration

#### Express.js

);

.txt
> **Common mistake**: Express's default `json()` middleware consumes and re-serializes
> the body, breaking HMAC. Always use `express.raw()` on webhook endpoints.

#### Next.js App Router (Route Handler)

}

.txt
---

### Platform Manager (Advanced)

const passed = await platformManager.runPlatformTests('stripe');

const-passed--await-platformmanagerrunplatformtestsstripe.txt
---

### Testing

npm run test:all # test all platforms

npm-run-testall--test-all-platforms.txt
---

## Part 2 — Hookflo (Hosted Alerting Platform)

Hookflo requires **no library installation**. The integration is:
1. Create a webhook endpoint in the Hookflo Dashboard → get a Webhook URL + Secret
2. Point your provider (Stripe, Supabase, Clerk, GitHub, etc.) at that URL
3. Configure Slack/email notifications in the dashboard

### How to Set Up a Hookflo Integration

**Step 1** — Go to [hookflo.com/dashboard](https://hookflo.com/dashboard/webhooks) and create a new webhook.
You'll receive:
- **Webhook URL** — paste into your provider's webhook settings
- **Webhook ID** — used for token-based platforms
- **Secret Token** — used by Hookflo to verify incoming events
- **Notification channel settings** — configure Slack or email

**Step 2** — Set up the provider to send to that Hookflo URL:

| Provider | Where to paste the URL |
|---|---|
| Stripe | Dashboard → Developers → Webhooks → Add endpoint |
| Supabase | Dashboard → Database → Webhooks → Create webhook |
| Clerk | Dashboard → Webhooks → Add endpoint |
| GitHub | Repo/Org Settings → Webhooks → Add webhook |

**Step 3** — In the Hookflo dashboard, configure:
- Which event types to alert on (e.g., `payment_intent.succeeded`, `user.created`)
- Notification channels (Slack workspace/channel, email addresses)
- Digest frequency if you want batched summaries instead of per-event alerts

### Hookflo Platform Docs

- **Stripe**: [docs.hookflo.com/webhook-platforms/stripe](https://docs.hookflo.com/webhook-platforms/stripe)
- **Supabase**: [docs.hookflo.com/webhook-platforms/supabase](https://docs.hookflo.com/webhook-platforms/supabase)
- **Clerk**: [docs.hookflo.com/webhook-platforms/clerk](https://docs.hookflo.com/webhook-platforms/clerk)
- **GitHub**: [docs.hookflo.com/webhook-platforms/github](https://docs.hookflo.com/webhook-platforms/github)
- **Slack notifications**: [docs.hookflo.com/notification-channels/slack](https://docs.hookflo.com/notification-channels/slack)

### Hookflo + Tern Together

If you want both programmatic verification (Tern) AND logging/alerting (Hookflo), use a proxy pattern:

Tags

#web_and-frontend-development #web

Quick Info

Category Development
Model Claude 3.5
Complexity One-Click
Author prateek32177
Last Updated 3/10/2026
🚀
Optimized for
Claude 3.5
🧠

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openclaw install hookflo-tern