> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sayvyai.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Webhooks

> Setting up Meta Cloud API webhooks and signature verification

# Webhooks

*This page covers the webhook infrastructure, cryptographic verification, and inbound event routing for the Meta Cloud API.*

***

## Webhook Verification Challenge

*Content coming soon.*

* Meta handshake parameters (`hub.mode`, `hub.challenge`, `hub.verify_token`)
* Handshake endpoint validation

***

## Cryptographic Security (HMAC-SHA256)

*Content coming soon.*

* Verifying the `X-Hub-Signature-256` header
* Meta App Secret hashing
* Constant-time string comparison (`timingSafeEqual`) to prevent timing attacks

***

## Idempotency & Deduplication

*Content coming soon.*

* Handling Meta's at-least-once delivery guarantees
* Redis-based locking and message ID (`wamid`) deduplication
* Asynchronous queueing for inbound message processors


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