The 24-hour window

It's the rule that confuses newcomers to official WhatsApp the most, and the most common cause of 422 meta_error in production.

You can only send free-form messages within 24 hours of the customer's last message to you. Outside that window, WhatsApp accepts only previously approved templates.

How the window opens and closes

Only the customer's message opens the window. Your own messages don't extend it — sending ten in a row buys no extra time.

The error when the window is closed

422 Unprocessable Entity

{
  "error": {
    "message": "The Meta Cloud API rejected the request.",
    "type": "meta_error",
    "meta": {
      "error": {
        "message": "(#131047) Re-engagement message",
        "code": 131047,
        "error_subcode": 2494010,
        "fbtrace_id": "AbCdEfGhIjK"
      }
    }
  }
}

Code 131047 is the tell. Retrying won't help — the fix is to send a template.

Tracking the window in your system

The API has no "is this window open?" endpoint. You track it from the webhooks: every incoming message carries a Unix timestamp.

// On receiving a `messages` webhook with a customer message:
const openUntil = Number(message.timestamp) * 1000 + 24 * 60 * 60 * 1000;
await db.conversations.upsert({ waId: message.from, windowOpenUntil: new Date(openUntil) });

// Before sending:
const conversation = await db.conversations.find({ waId: recipient });
const canSendFreeForm = conversation && conversation.windowOpenUntil > new Date();

Leave a few minutes of margin: the clock that counts is Meta's, not yours.

A practical strategy

Inside the window — use whatever you like: text, media, buttons, lists. It's cheaper and needs no approval.

Outside the window — send a template. It reopens the conversation; as soon as the customer replies, you're back to free-form content.

When in doubt — send the template. A message that arrives costs less than an error that doesn't.

Templates worth keeping approved

A small approved library keeps you from being held hostage by approval times:

Situation	Category
Reviving a stalled conversation	UTILITY
Confirming an order, delivery or appointment	UTILITY
Sending a verification code	AUTHENTICATION
Announcing a promotion	MARKETING

Creation details and variable rules are in Templates.

Cost

Meta bills per conversation, not per message. A conversation opened by a MARKETING template costs more than a UTILITY one, and customer-initiated conversations (SERVICE) are the cheapest — often free.

That changes how you design the integration: a flow that gets the customer to write first is cheaper than one that fires marketing templates.