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

# WhatsApp Channel

A WhatsApp chat agent answers inbound messages on one of your WhatsApp Business numbers. This is the fullest version of a chat agent — templates, media, calls and follow-ups are all WhatsApp features.

## Before you start

<Steps>
  <Step title="A connected WhatsApp Business account">
    See [WhatsApp signup](/whatsapp/signup).
  </Step>

  <Step title="A registered phone number">
    Only **CLOUD\_API** numbers can have a chat agent assigned. If your number shows "Register via Actions" in the table, [register it first](/whatsapp/phone-numbers#registering-phone-numbers).
  </Step>

  <Step title="A saved chat agent">
    Built and saved, ideally with a published version. See [Create a chat agent](/chat-agents/create-a-chat-agent).
  </Step>
</Steps>

## Assign the agent to a number

<Steps>
  <Step title="Open the numbers table">
    **Dashboard → WhatsApp → Phone Numbers**.
  </Step>

  <Step title="Click the WhatsApp Agent cell">
    Find your number and click its **WhatsApp Agent** cell.
  </Step>

  <Step title="Pick the agent and save">
    Select your chat agent and save.
  </Step>
</Steps>

You can also do this from the other end: the **WhatsApp Phone Number** column in the Chat Agents table opens the same assignment.

<Note>
  **One agent per number.** Each WhatsApp number has a single inbound chat agent. To run different agents for different products, use different numbers.
</Note>

From that point on, every inbound message to that number is handled by the agent's **published** version.

## Per-contact assignment

Besides the number-wide assignment, an individual contact can be attached to a specific chat agent — for example when a voice call ends and the contact is handed to a chat agent to continue on WhatsApp.

Those explicit assignments are visible in their effect, and can be removed from the [Inbox](/chat-agents/monitoring) with **De-assign**, which clears the assignment for that contact on that number without deleting any messages.

## The 24-hour rule

WhatsApp only allows free-form messages inside a 24-hour window that opens when the customer messages you. Outside it, only approved templates may be sent.

This shapes what a chat agent can do:

| Situation                            | What works                                                      |
| ------------------------------------ | --------------------------------------------------------------- |
| Customer messaged recently           | Normal replies, media, everything                               |
| Window has closed                    | Only a [template](/chat-agents/functions/send-template)         |
| Starting a conversation from scratch | A template — normally through a [campaign](/whatsapp/campaigns) |

<Tip>
  This is why the follow-up gap and the 24-hour window interact: a follow-up an hour later is inside the window and can be a normal message; one the next day is not.
</Tip>

## Related

<CardGroup cols={2}>
  <Card title="WhatsApp phone numbers" icon="hashtag" href="/whatsapp/phone-numbers">
    Registering numbers and assigning agents
  </Card>

  <Card title="Templates" icon="file-lines" href="/whatsapp/templates">
    What the agent sends outside the window
  </Card>

  <Card title="Inbox" icon="inbox" href="/whatsapp/inbox">
    Watching live conversations
  </Card>

  <Card title="Campaigns" icon="bullhorn" href="/whatsapp/campaigns">
    Starting conversations at scale
  </Card>
</CardGroup>