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

# Channels: One Session Model Across Every Medium

> Chat, SMS, voice, and email all map to the same Feather conversation. Learn how channel, surface, and identity fit together.

Feather runs every customer interaction through the same [conversation](/concepts/conversations) model, regardless of how the customer reaches you. A conversation is classified by a few server-assigned facts that together describe where and how it runs.

## How a conversation is classified

| Attribute | Values                                                                                    | Meaning                           |
| --------- | ----------------------------------------------------------------------------------------- | --------------------------------- |
| `channel` | `chat`, `sms`, `voice`, `email`                                                           | The medium                        |
| `surface` | `webchat_widget`, `direct_api`, `mcp`, `dashboard`, `simulation`, `phone_line`, `mailbox` | Where the session physically runs |

You don't set `channel` or `surface` directly — Feather assigns them based on how the conversation is created. Creating one over the API (`POST /v1/conversations`) always yields a `chat` conversation on the `direct_api` surface.

***

## Where each channel is created

Each channel has its own entry point, but they all produce the same conversation object with the same turns, transcript, analytics, and HITL behavior.

<CardGroup cols={2}>
  <Card title="Chat" icon="comments" href="/guides/run-a-conversation">
    Created with `POST /v1/conversations`. Powers your own app (surface `direct_api`) and the embeddable webchat widget (surface `webchat_widget`).
  </Card>

  <Card title="SMS" icon="mobile" href="/guides/sms-channel">
    Outbound via `POST /v1/sms/send`; inbound arrives on your Twilio number. Each number maps to a conversation per end user.
  </Card>

  <Card title="Voice" icon="phone" href="/guides/voice-calls">
    Created by inbound calls to a bound number or by `POST /v1/voice/outbound` — over the phone (SIP) or in the browser (web).
  </Card>

  <Card title="Email" icon="envelope" href="/guides/email-channel">
    Inbound mail creates or continues a thread on the `mailbox` surface; replies go out from your connected mailbox.
  </Card>
</CardGroup>

***

## Identity across channels

Every conversation resolves to an `end_user_id`. How that happens depends on what you provide at creation:

* **`end_user_id`** — reference a known end user directly.
* **`org_external_end_user_id`** — pass your own stable identifier (a customer ID, or a persisted anonymous browser token). Feather get-or-creates an end user and, when possible, **bridges** it to the same person's existing email or phone identity.
* **Nothing** — Feather resolves the authenticated caller as the end user.

Because a phone number, an email address, and your own customer ID can all resolve to the same end user, an assistant gets a unified view of that person across channels — a customer who texts today and emails next week shares one history and one memory.

### Thread keys

Within a channel, `external_id` distinguishes concurrent threads for the same user. Reusing a value resumes that thread; a new value opens another. `external_id` is unique per organization, which also makes conversation creation idempotent under retries.

<Note>
  For anonymous webchat visitors, send a **stable per-visitor token** in
  `org_external_end_user_id`. A new value on every page load creates a new
  identity and loses history and memory.
</Note>

***

## Next steps

<CardGroup cols={2}>
  <Card title="Conversations" icon="comment-dots" href="/concepts/conversations">
    The full conversation object, status lifecycle, and turn model.
  </Card>

  <Card title="Embed the webchat widget" icon="window-maximize" href="/guides/webchat-widget">
    Drop a Feather assistant onto your website with the embeddable widget.
  </Card>
</CardGroup>