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

# Authentication

## Channel ID

Every request must include an `X-Channel-Id` header. This identifies which merchant's storefront you're accessing — it determines the outlets, menus, branding, and payment configuration the diner sees

You receive the channel ID when a merchant is onboarded to Atlas. It is a fixed identifier, not a secret

## Sessions

Start by calling `GET /channel` with your channel ID. This creates a session and returns it in the `X-Session-Id` response header

```bash theme={null}
curl -sD - https://api.atlas.kitchen/storefronts/v1/channel \
  -H "X-Channel-Id: your-channel-id"
```

```
# Response header — save this
X-Session-Id: b7ac755d301dc5d23c790ccd7bb6dadf
```

Include both headers on all subsequent requests:

| Header         | What it is                       | Where it comes from        |
| -------------- | -------------------------------- | -------------------------- |
| `X-Channel-Id` | Merchant's storefront identifier | Provided during onboarding |
| `X-Session-Id` | Diner's session (tracks cart)    | Returned by `GET /channel` |

<Warning>
  `GET /channel` is the only endpoint that creates a session. All other endpoints require a valid `X-Session-Id` header — calling them without one returns `401 Unauthorized`
</Warning>

Read-only endpoints (menus, stocks, timeslots, availabilities, announcements, banners, popups) work with just `X-Channel-Id` — no session needed

## Session lifecycle

A session holds a reference to the diner's active cart. There's always exactly one active cart per session at any time.

* **Creation**: the first `GET /channel` call creates a session and returns `X-Session-Id`
* **Reuse**: pass the same `X-Session-Id` on subsequent `GET /channel` calls to keep the same session (and cart). Send no session, and a new one is minted
* **After checkout**: when `POST /cart/order` succeeds, the session's active cart is marked `is_checked_out: true` and a fresh empty cart is created for the same session. The session ID stays valid — reuse it for the diner's next order

<Tip>
  Persist `X-Session-Id` in local storage. As long as it's valid, returning diners keep their cart across page reloads.
</Tip>