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

# Configuration

> Every constructor option, the environment table, and how to build a client from the environment.

```ts theme={null}
import { Brickken } from 'brickken-sdk'

new Brickken({
  env: 'sandbox',            // 'sandbox' | 'production'
  baseUrl,                   // overrides env
  apiKey,
  signer,
  rpcUrl,                    // client-broadcast writes, receipt polling, and on-chain token metadata
  timeoutMs: 30_000,
  retry: { attempts: 3, baseDelayMs: 500, jitter: true },
  payment: { maxAmountBaseUnits: '50000' },
  fetch,                     // inject your own
})
```

Every option is optional. `new Brickken()` with no arguments is a valid anonymous sandbox client.

| Option      | Type                        | Default                                           | Purpose                                                                        |
| ----------- | --------------------------- | ------------------------------------------------- | ------------------------------------------------------------------------------ |
| `env`       | `'sandbox' \| 'production'` | `'sandbox'`                                       | Selects the base URL                                                           |
| `baseUrl`   | `string`                    | —                                                 | Overrides `env`. Use for any non-public deployment                             |
| `apiKey`    | `string`                    | —                                                 | Selects API-key mode; sent as `x-api-key`                                      |
| `signer`    | `Signer`                    | —                                                 | Selects x402 mode when no key is set. See [Signers](/sdk/signers)              |
| `rpcUrl`    | `string`                    | —                                                 | JSON-RPC endpoint for `client-broadcast`, `waitForReceipt`, and token metadata |
| `timeoutMs` | `number`                    | `30000`                                           | Per-request timeout                                                            |
| `retry`     | `RetryPolicy`               | `{ attempts: 3, baseDelayMs: 500, jitter: true }` | See [Errors](/sdk/errors#retries)                                              |
| `payment`   | `PaymentPolicy`             | `{}`                                              | Spending controls. See [Payments](/sdk/payments)                               |
| `fetch`     | `typeof fetch`              | `globalThis.fetch`                                | Injectable for tests, proxies, or a runtime whose global you do not want       |

The constructor throws a `TypeError` if no `fetch` implementation is available — use Node 20 or newer, or pass one explicitly.

## Environments

| Environment | API base URL                       | App URL                             |
| ----------- | ---------------------------------- | ----------------------------------- |
| Sandbox     | `https://api.sandbox.brickken.com` | `https://dapp.sandbox.brickken.com` |
| Production  | `https://api.brickken.com`         | `https://dapp.brickken.com`         |

<Note>
  Sandbox and production are separate deployments with separate databases. An API key issued for one does not work on the other.
</Note>

| `env`        | Base URL                           |
| ------------ | ---------------------------------- |
| `sandbox`    | `https://api.sandbox.brickken.com` |
| `production` | `https://api.brickken.com`         |

An internal `forge` environment exists for Brickken pre-release QA — contact `tech@brickken.com` for its base URL and pass it as `baseUrl`.

Read back what the client resolved:

```ts theme={null}
bkn.baseUrl          // 'https://api.sandbox.brickken.com'
bkn.credentialMode   // 'api-key' | 'x402' | 'anonymous'
```

## From the environment

`Brickken.fromEnv` reads the same variables the CLI and MCP server already document, including the `BKN_*` aliases.

```ts theme={null}
const bkn = Brickken.fromEnv(process.env)
```

| Variable            | Alias          | Purpose                                                            |
| ------------------- | -------------- | ------------------------------------------------------------------ |
| `BRICKKEN_API_KEY`  | `BKN_API_KEY`  | Brickken API key                                                   |
| `BRICKKEN_ENV`      | `BKN_ENV`      | `sandbox` or `production`                                          |
| `BRICKKEN_BASE_URL` | `BKN_BASE_URL` | Override the API base URL                                          |
| `BRICKKEN_RPC_URL`  | `BKN_RPC_URL`  | JSON-RPC used for `client-broadcast`, receipts, and token metadata |

An empty string is treated as unset, and an unrecognised `BRICKKEN_ENV` is ignored rather than guessed at.

`BRICKKEN_PRIVATE_KEY` is deliberately **not** read. Turning a key into a signer is an explicit choice, never an implicit one — pass it as an override:

```ts theme={null}
import { fromPrivateKey } from 'brickken-sdk/adapters/private-key'

const bkn = Brickken.fromEnv(process.env, {
  signer: fromPrivateKey(process.env.BRICKKEN_PRIVATE_KEY!),
  payment: { maxAmountBaseUnits: '50000' },
})
```

Overrides win over the environment, so this composes cleanly with a `.env` file.

## Injecting `fetch`

Useful for a proxy, for request logging, or for a test that must not touch the network:

```ts theme={null}
const bkn = new Brickken({
  env: 'sandbox',
  apiKey,
  fetch: async (input, init) => {
    console.log('→', input)
    return await undici.fetch(input, init)
  },
})
```

The injected implementation is used for API requests, for JSON-RPC broadcasting, and for receipt polling.

<Card title="Namespaces" icon="sitemap" href="/sdk/namespaces">
  Every method the configured client exposes.
</Card>