Stripe

Stripe signs with its own scheme, not Standard Webhooks: a Stripe-Signature header carrying t=<unix> and one or more v1=<hex> HMAC-SHA256 signatures over `${t}.${body}`. Stripe(secret) implements it as an ordinary Verifier:

import { Postel, Stripe } from "@postel/core";

export const postel = Postel({
  inbound: {
    stripe: { verify: Stripe(process.env.STRIPE_WEBHOOK_SECRET!) },
  },
});

Wire it through any web adapter — the gate, raw-body handling, and error→status mapping are identical to every other source:

import { NextjsWebAdapter } from "@postel/nextjs";
import { postel } from "@/lib/postel";

export const { POST } = NextjsWebAdapter(postel).inbound.stripe.post((result) => {
  // result.event.type: "payment_intent.succeeded", "invoice.paid", …
  return Response.json({ received: true });
});

Scheme details

Gotchas

• The secret is literal key material. Pass the whsec_... value exactly as Stripe issues it — prefix included. Unlike Standard Webhooks Secret(...), it is not base64-decoded first.
• Raw bytes matter as much as ever. Stripe signs the exact body it sent; a JSON middleware that re-serializes breaks verification. The adapters handle this — hand-rolled routes should read Raw bytes.
• Rotating your endpoint secret? verify accepts an array: verify: [Stripe(newSecret), Stripe(oldSecret)] — same rotation window pattern as everything else.

Testing locally

Use the Stripe CLI: stripe listen --forward-to localhost:3000/api/webhooks/stripe forwards real, correctly-signed events to your dev server, and stripe trigger payment_intent.succeeded fires one on demand. (signFixture signs Standard Webhooks only — it can't fabricate Stripe signatures.)