BlindPay Webhooks Skill

BlindPay is a stablecoin and fiat payins/payouts API. It pushes customer, bank account, wallet, payin, payout, virtual account, transfer, limit-increase and payable changes to endpoints you register per instance, delivered through Svix, which implements Standard Webhooks. Every delivery is an HTTP POST with a JSON body and three signature headers: svix-id, svix-timestamp, and svix-signature. The body is flat: webhook_event holds the event name, followed by the resource's own fields (no wrapper object).

When to Use This Skill

• How do I receive BlindPay webhooks?
• How do I verify BlindPay webhook signatures (svix-signature)?
• How do I handle payin.complete, payout.complete or customer.update events?
• How do I detect a stablecoin deposit (wallet.inbound) or a finished transfer (transfer.complete)?
• Why is my BlindPay webhook signature verification failing, or rejecting Hookdeck retries?

Verification (core)

Signed content is {svix-id}.{svix-timestamp}.{raw body}. Svix signs it with HMAC-SHA256 using the base64-decoded secret (the part after whsec_), base64-encodes the result, and sends one or more space-separated v1,<signature> entries. Use the official svix library, which compares in constant time. Read the svix-* headers, and when svix-id is absent fall back to the webhook-* headers (webhook-id, webhook-timestamp, webhook-signature), as Hookdeck does.

import { Webhook } from 'svix'; // svix 2.x is ESM-only

const prefix = req.headers['svix-id'] ? 'svix' : 'webhook';
const id = req.headers[`${prefix}-id`];
const timestamp = req.headers[`${prefix}-timestamp`];
const signature = req.headers[`${prefix}-signature`];
// rawBody: the raw Buffer/string, never re-serialized JSON
new Webhook(process.env.BLINDPAY_WEBHOOK_SECRET).verify(rawBody, {
  'svix-id': id, 'svix-timestamp': timestamp, 'svix-signature': signature,
  'webhook-id': id, 'webhook-timestamp': timestamp, 'webhook-signature': signature,
}); // throws on a bad signature or a timestamp outside the window
const event = JSON.parse(rawBody.toString('utf8')); // parse only after verify passes

from svix.webhooks import Webhook, WebhookVerificationError

wh = Webhook(os.environ["BLINDPAY_WEBHOOK_SECRET"])  # "whsec_..."
wh.verify(raw_body, {"svix-id": id, "svix-timestamp": ts, "svix-signature": sig,
                     "webhook-id": id, "webhook-timestamp": ts, "webhook-signature": sig})

For complete handlers with tests, see examples/express/, examples/nextjs/, examples/fastapi/.

The signing secret has the form whsec_<base64>. Fetch it with GET /v1/instances/{instance}/webhook-endpoints/{we_id}/secret (returns { "key": "whsec_..." }) or from the dashboard (instance > Webhooks > the endpoint's menu > Get secret). Keep the full whsec_... value in BLINDPAY_WEBHOOK_SECRET. Handlers fail closed: with the variable unset they return 500 instead of accepting anything. BlindPay stresses using the exact raw body: "Never modify the request body before verification".

Hookdeck retries and replays hit the 5-minute window

The svix library always enforces a fixed 5-minute timestamp window, and it can't be configured. Hookdeck retries and replays resend the original svix-timestamp, so the library rejects any retry or replay that happens more than 5 minutes after the original delivery. If you verify behind Hookdeck (or replay old events), use the manual verifier in references/verification.md, where the window can be dropped or widened. Deduplicate on svix-id (stable across retries) instead of relying on the timestamp.

Event Types

The handlers route on the top-level webhook_event field. BlindPay documents 26 events (the list may not be exhaustive, so acknowledge unknown events with 200):

payin.complete fires when a payin finishes in any way (sent, refunded or failed), while a failed payout fires payout.update, not payout.complete. Check status on the payload. See references/overview.md for when each event fires and the payload shape.

Environment Variables

# Signing secret for the webhook endpoint (Svix format, starts with whsec_)
BLINDPAY_WEBHOOK_SECRET=whsec_xxxxx

Local Development

# Start tunnel (no account needed)
npx hookdeck-cli listen 3000 blindpay --path /webhooks/blindpay

Register the tunnel URL as a webhook endpoint on your instance (BlindPay requires https) and copy the signing secret into .env. See references/setup.md.

Reference Materials

• references/overview.md - BlindPay webhook concepts, events, payload, delivery rules
• references/setup.md - Register an endpoint (API or dashboard), get the signing secret
• references/verification.md - Svix verification details, header fallback, manual verifier, timestamp window