@profullstack/webhooks

Standard Webhooks signing, verification and delivery with retries. Zero dependencies.

Every app in the fleet that sends or receives a webhook does it the same way: a CloudEvents 1.0 JSON body, signed per the Standard Webhooks spec. This package is that one way, so nobody hand-rolls HMAC again.

• Plain ESM JavaScript with hand-written types. No runtime dependencies.
• Works in Node >= 20 and Bun (uses node:crypto, fetch, Request, Response).
• Matches the Standard Webhooks reference test vector, so any spec-compliant library (Svix, standardwebhooks, etc.) can talk to it.

npm i @profullstack/webhooks
# or
bun add @profullstack/webhooks

Make a secret

import { generateSecret } from '@profullstack/webhooks';

generateSecret(); // 'whsec_3j1V...=' (base64 of 32 random bytes)

Store it in the vault on both sides. Secrets are accepted in two forms:

• whsec_<base64>: the spec form. The HMAC key is the decoded base64.
• any other string: used as its UTF-8 bytes. This is what older fleet senders (autoblog) did, so existing shared secrets keep working.

Send

import { createEvent, sendWebhook } from '@profullstack/webhooks';

const event = createEvent('com.profullstack.ai.prompt.run.v1', { prompt: 'Summarize the repo' }, {
  source: 'https://ai.profullstack.com',
  subject: 'run:42',
});

const result = await sendWebhook('https://agent.example.com/webhooks', event, {
  secret: process.env.WEBHOOK_SECRET,
  onAttempt: ({ attempt, status, error, ms }) => log.info({ attempt, status, error, ms }),
});
// { ok: true, status: 204, attempts: 1, id: '<event.id>' }

createEvent(type, data, { source, subject, id, time }) returns:

{
  "specversion": "1.0",
  "id": "8f0c...",
  "type": "com.profullstack.ai.prompt.run.v1",
  "source": "https://ai.profullstack.com",
  "subject": "run:42",
  "time": "2026-10-06T12:00:00.000Z",
  "datacontenttype": "application/json",
  "data": { "prompt": "Summarize the repo" }
}

source defaults to urn:profullstack:webhooks, id to a random UUID and time to now. sendWebhook also accepts any plain object or a pre-serialised string as the event.

Receive in Hono (Bun)

import { Hono } from 'hono';
import { honoHandler } from '@profullstack/webhooks';

const app = new Hono();

app.post('/webhooks', honoHandler({
  secret: process.env.WEBHOOK_SECRET,
  onEvent: async (event, c) => {
    await queue.add(event.type, event.data, { jobId: event.id });
  },
}));

The handler reads the raw body from c.req.raw, verifies it, and calls onEvent(event, c). It answers:

Status	When
204	verified and onEvent returned
401	missing headers, bad signature, or timestamp outside tolerance
400	signature fine but the body is not a JSON object
405	not a POST
500	onEvent threw (so the sender retries)

Return a Response from onEvent to send something else (for example a 202). It does not import hono. For Bun.serve, Workers or Deno use fetchHandler({ secret, onEvent }), which takes a plain Request.

Receive in Node (node:http)

The signature is over the bytes as received, so read the raw body. Never verify JSON.stringify(await req.json()).

import http from 'node:http';
import { verifyAndParse } from '@profullstack/webhooks';

http.createServer(async (req, res) => {
  const chunks = [];
  for await (const chunk of req) chunks.push(chunk);
  const body = Buffer.concat(chunks).toString('utf8');

  const r = verifyAndParse({ headers: req.headers, body, secret: process.env.WEBHOOK_SECRET });
  if (!r.ok) {
    res.writeHead(r.status, { 'content-type': 'application/json' });
    return res.end(JSON.stringify({ error: r.reason }));
  }
  await handle(r.event); // r.id is the webhook-id, dedupe on it
  res.writeHead(204).end();
}).listen(8787);

verifyAndParse returns { ok: true, event, id } or { ok: false, reason, status } with status 401 for an auth failure and 400 for bad JSON. If you only need the signature check, verifySignature returns { ok: true, id, timestamp } or { ok: false, reason }. Both take headers as a Headers instance or a plain object (any case).

Header format

Three headers, per the Standard Webhooks spec:

webhook-id: 8f0c2d1e-...            the event id, identical on every retry
webhook-timestamp: 1791288000       unix seconds, fresh on every attempt
webhook-signature: v1,K5oZfzN95Z9UVu1EsfQmfVNQhnkZ2pj9o9NDN/H/pI4=

The signature is v1, plus the base64 HMAC-SHA256 of ${webhook-id}.${webhook-timestamp}.${body}, keyed with the secret. Comparison is constant time.

• Replay window: a timestamp more than toleranceSeconds (default 300) away from the receiver's clock, either way, is rejected.
• Key rotation: the signature header may hold several space-separated signatures (v1,abc v1,def). A receiver accepts if any one matches its secret, so sign with old and new keys during a rotation. Entries with a version other than v1 are ignored.
• Idempotency: retries reuse the same webhook-id. Receivers should treat a repeated id as already handled.

signRequest({ id, timestamp, body, secret }) builds these headers if you want to manage transport yourself.

Requests also carry content-type: application/cloudevents+json (or application/json for a non-CloudEvents body) and user-agent: @profullstack/webhooks. Extra headers you pass are merged in, but can never replace the webhook-* ones.

Retry policy

sendWebhook(url, event, { secret, retryDelaysMs, timeoutMs, fetchImpl, headers, onAttempt })

• retryDelaysMs (default [0, 10_000, 60_000]) has one entry per attempt: the wait before that attempt. The default is three attempts over about 70 seconds. [0] means a single attempt.
• Retried: network errors, timeouts, 408, 429 and any 5xx.
• Not retried: any other 4xx. The receiver has said the request itself is wrong, and sending it again will not change that.
• Any 2xx is success.
• timeoutMs (default 10 s) bounds each attempt, not the whole delivery.
• onAttempt({ attempt, status, error, ms }) runs after every attempt, for a delivery log. status is null for a network error or timeout.
• The result is { ok, status, attempts, id, error? }. It never throws for a failed delivery; it throws only for a missing url or secret.

Delays run in-process. For deliveries that must survive a restart, put them on a queue (BullMQ, etc.) with retryDelaysMs: [0] and let the queue retry.

License

MIT, Profullstack, LLC