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

# Client Configuration

> Every parameter you can pass when initializing an Ostium SDK client — shared options, per-mode fields, and build-only variants.

This page is the complete reference for the parameters accepted by the `OstiumClient` factory methods. Every factory returns a `Promise<OstiumClient>` and is `async`, so always `await` it.

```ts theme={null}
import { OstiumClient } from '@ostium/builder-sdk';

const client = await OstiumClient.createSelfAndSelf({
  traderPrivateKey: process.env.TRADER_PRIVATE_KEY as `0x${string}`,
  rpcUrl: process.env.ARB_RPC_URL!,
  // shared options below are accepted by every write mode
  testnet: false,
  slippageBps: 25,
  builder: { address: '0xBuilderAddress', feeBps: 10 },
  alchemyApiKey: process.env.ALCHEMY_API_KEY!,
});
```

## Shared options (all write modes)

These optional fields are accepted by `createSelfAndSelf`, `createSelfAndGasless`, `createDelegatedAndSelf`, and `createDelegatedAndGasless`.

| Option          | Type                                  | Default                                  | Description                                                                                                                                                                                                     |
| --------------- | ------------------------------------- | ---------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `testnet`       | `boolean`                             | `false`                                  | Use Arbitrum Sepolia. Switches the contracts, subgraph endpoint, builder API endpoint, and the default Pimlico sponsor URL. See [Testnet](/developer/client-modes/testnet).                                     |
| `slippageBps`   | `number`                              | `25`                                     | Default slippage tolerance in basis points (`25` = 0.25%). Used when a call does not pass its own slippage.                                                                                                     |
| `builder`       | `{ address: string; feeBps: number }` | —                                        | Builder fee sharing. `feeBps` is in basis points, range `0`–`50` (0%–0.5%), in steps of `0.01` bps. Can be overridden per `openTrade()` call.                                                                   |
| `subgraphUrl`   | `string`                              | mainnet/testnet subgraph                 | Override the Ostium subgraph endpoint used by read methods (`getPairs`, `getOpenPositions`, …). Mainnet default is `https://builder.prod.bedrock.ostium.io/v1/subgraph/gn`.                                     |
| `builderApiUrl` | `string`                              | `https://builder.prod.bedrock.ostium.io` | Override the builder API base URL used for live prices, OHLC candles, and the WebSocket price stream.                                                                                                           |
| `alchemyApiKey` | `string`                              | —                                        | Alchemy API key used by [`streamAccountUpdates()`](/developer/reference/stream-account-updates) for the Arbitrum contract-log overlay. Required to start an account stream; can also be passed per stream call. |

`alchemyApiKey` is only needed if you call `streamAccountUpdates()`. Set it once at client creation, or pass it per call: `client.streamAccountUpdates({ alchemyApiKey })`. Without an Alchemy key (from either place), the stream throws `INVALID_CONFIG`.

## Submit-capable vs build-only

Every write mode can be created two ways:

* **Submit-capable** — pass a private key; the SDK signs and submits.
* **Build-only** — pass addresses only; use `get*Tx()` to return unsigned transaction data for your own wallet or Safe flow. No key ever touches the SDK.

The fields below differ between the two variants of each mode.

## `createSelfAndSelf`

The trader EOA owns funds, signs, and pays gas. See [Self + Self](/developer/client-modes/self-and-self).

**Submit-capable**

| Field              | Type          | Required | Description                                                          |
| ------------------ | ------------- | -------- | -------------------------------------------------------------------- |
| `traderPrivateKey` | `0x${string}` | Yes      | Private key of the trader EOA. Holds USDC, owns positions, pays gas. |
| `rpcUrl`           | `string`      | Yes      | Arbitrum One (or Sepolia) RPC URL.                                   |

**Build-only**

| Field           | Type          | Required | Description                                                       |
| --------------- | ------------- | -------- | ----------------------------------------------------------------- |
| `traderAddress` | `0x${string}` | Yes      | Trader EOA address. Used to build unsigned EOA transactions.      |
| `rpcUrl`        | `string`      | No       | RPC URL for reads/simulation. Defaults to the chain's public RPC. |

## `createSelfAndGasless`

The trader EOA owns funds and signs; a Safe derived from the key submits gaslessly. See [Self + Gasless](/developer/client-modes/self-and-gasless).

**Submit-capable**

| Field                 | Type          | Required | Description                                                                                                                                                 |
| --------------------- | ------------- | -------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `traderPrivateKey`    | `0x${string}` | Yes      | Private key of the trader EOA. A Safe is derived from this key to relay trades gaslessly.                                                                   |
| `pimlicoUrl`          | `string`      | No       | Pimlico-compatible bundler/paymaster RPC URL. Defaults to the Ostium sponsor URL (`…/v1/pimlico/sponsor?chainId=42161`, or the Sepolia variant on testnet). |
| `rpcUrl`              | `string`      | No       | RPC URL for reads/simulation. Defaults to the public Arbitrum RPC.                                                                                          |
| `sponsorshipPolicyId` | `string`      | No       | Pimlico sponsorship policy ID.                                                                                                                              |

**Build-only**

| Field           | Type          | Required | Description                                                       |
| --------------- | ------------- | -------- | ----------------------------------------------------------------- |
| `traderAddress` | `0x${string}` | Yes      | Trader EOA that owns USDC and positions.                          |
| `safeAddress`   | `0x${string}` | Yes      | Safe smart-account address that will submit delegated calls.      |
| `rpcUrl`        | `string`      | No       | RPC URL for reads/simulation. Defaults to the chain's public RPC. |

## `createDelegatedAndSelf`

A delegate EOA signs and pays gas on behalf of a separate trader. See [Delegated + Self](/developer/client-modes/delegated-and-self).

**Submit-capable**

| Field                | Type          | Required | Description                                                                                |
| -------------------- | ------------- | -------- | ------------------------------------------------------------------------------------------ |
| `delegatePrivateKey` | `0x${string}` | Yes      | Private key of the delegate EOA. Signs and pays gas for all transactions.                  |
| `traderAddress`      | `0x${string}` | Yes      | Trader this delegate acts for. The trader must have called `setDelegate(delegateAddress)`. |
| `rpcUrl`             | `string`      | Yes      | Arbitrum One (or Sepolia) RPC URL.                                                         |

**Build-only**

| Field             | Type          | Required | Description                                                       |
| ----------------- | ------------- | -------- | ----------------------------------------------------------------- |
| `traderAddress`   | `0x${string}` | Yes      | Trader this delegate acts for.                                    |
| `delegateAddress` | `0x${string}` | Yes      | Delegate EOA that will submit the transaction.                    |
| `rpcUrl`          | `string`      | No       | RPC URL for reads/simulation. Defaults to the chain's public RPC. |

## `createDelegatedAndGasless`

A Safe derived from the delegate key submits sponsored user operations on behalf of the trader. See [Delegated + Gasless](/developer/client-modes/delegated-and-gasless).

**Submit-capable**

| Field                 | Type          | Required | Description                                                                                                                                                                               |
| --------------------- | ------------- | -------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `delegatePrivateKey`  | `0x${string}` | Yes      | Private key of the delegate EOA. A Safe is derived from this key and submits user operations via Pimlico.                                                                                 |
| `traderAddress`       | `0x${string}` | Yes      | Trader this delegate acts for. The trader must have called `setDelegate(safeAddress)`, where `safeAddress` is the Safe derived from the delegate key (`client.getSmartAccountAddress()`). |
| `pimlicoUrl`          | `string`      | No       | Pimlico bundler/paymaster RPC URL. Defaults to the Ostium sponsor URL (chain-aware).                                                                                                      |
| `rpcUrl`              | `string`      | No       | RPC URL for reads/simulation. Defaults to the public Arbitrum RPC.                                                                                                                        |
| `sponsorshipPolicyId` | `string`      | No       | Pimlico sponsorship policy ID.                                                                                                                                                            |

**Build-only**

| Field             | Type          | Required | Description                                                       |
| ----------------- | ------------- | -------- | ----------------------------------------------------------------- |
| `traderAddress`   | `0x${string}` | Yes      | Trader this delegate acts for.                                    |
| `delegateAddress` | `0x${string}` | Yes      | Delegate EOA that owns the Safe.                                  |
| `safeAddress`     | `0x${string}` | Yes      | Safe smart-account address that will submit delegated calls.      |
| `rpcUrl`          | `string`      | No       | RPC URL for reads/simulation. Defaults to the chain's public RPC. |

## `createReadOnly`

No signer, no submitter, no private key. All read methods work; write methods throw `INVALID_CONFIG`. See [Read-only](/developer/client-modes/read-only).

| Field           | Type      | Required | Description                                                                                  |
| --------------- | --------- | -------- | -------------------------------------------------------------------------------------------- |
| `rpcUrl`        | `string`  | No       | Arbitrum RPC URL. Defaults to the chain's public RPC.                                        |
| `testnet`       | `boolean` | No       | Use Arbitrum Sepolia. Defaults to `false`.                                                   |
| `subgraphUrl`   | `string`  | No       | Override the subgraph endpoint.                                                              |
| `builderApiUrl` | `string`  | No       | Override the builder API base URL.                                                           |
| `alchemyApiKey` | `string`  | No       | Alchemy API key for [`streamAccountUpdates()`](/developer/reference/stream-account-updates). |

Read-only clients do not accept `slippageBps` or `builder` — those only apply to write modes that submit or build trades.

## Notes

* All factories are `async` — `await` them.
* Mode is inferred from the fields you pass; you don't set `mode` directly.
* Builder fee defaults (`builder` at client creation) can be overridden per `openTrade()` call via `builder.address` / `builder.feeBps`.
* On `testnet: true`, omitted `pimlicoUrl`, `subgraphUrl`, and `builderApiUrl` resolve to their Sepolia defaults — you can still override any of them.