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

# Authentication

> API keys and environments for the Cesto SDK.

The SDK authenticates with a **secret API key**. Keys look like `cesto_sk_…` and are sent
automatically with every request — you never set headers yourself.

## Getting a key

<Note>
  API keys are issued by the Cesto team — there's no self-serve portal yet.

  **Contact us to request a key:** reach out on our
  [community](https://t.me/cesto_co) or through your Cesto contact, and let us know which
  environment (Production or Beta) you need.
</Note>

Keys are **environment-specific**: a Production key only works against the Production backend,
and a Beta key only against Beta. Request the key for the environment you're integrating with.

## Providing the key

Pass it explicitly, or set the `CESTO_API_KEY` environment variable and omit it:

<CodeGroup>
  ```ts Explicit theme={null}
  const cesto = new Cesto({ apiKey: 'cesto_sk_…' });
  ```

  ```ts From env theme={null}
  // reads process.env.CESTO_API_KEY
  const cesto = new Cesto();
  ```
</CodeGroup>

If no key is found, the constructor throws.

## Environments

Select the backend with the `environment` option — you choose an environment, not a URL.

| `environment`            | Backend                        |
| ------------------------ | ------------------------------ |
| `PRODUCTION` *(default)* | `https://backend.cesto.co`     |
| `BETA`                   | `https://dev.backend.cesto.co` |

```ts theme={null}
const cesto = new Cesto({
  apiKey: process.env.CESTO_API_KEY,
  environment: 'BETA',
});
```

## Keep your key safe

<Warning>
  Treat the key like a password — keep it server-side, store it in a secret manager or
  environment variable, and never commit it to source control. To rotate or revoke a key,
  contact the Cesto team.
</Warning>