# SpeculativeClient

The `SpeculativeClient` allows dry-running transactions against the current chain state without submitting them on-chain.

## Import

```ts
import { SpeculativeClient, HttpHandler, IHandler } from 'casper-js-sdk';
```

## Usage

```ts
// Speculative execution uses port 7778
const handler = new HttpHandler('http://<Node Address>:7778/rpc');
const speculativeClient = SpeculativeClient.newSpeculativeClient(handler);

const result = await speculativeClient.speculativeExec('1', deploy);
console.log('Execution effect:', result.executionResult);
```

## Constructor

```ts
new SpeculativeClient(handler: IHandler)
```

The constructor takes any `IHandler` implementation. Use the static factory for convenience:

```ts
SpeculativeClient.newSpeculativeClient(handler: IHandler): SpeculativeClient
```

### Parameters

#### handler

- **Type:** `IHandler`

The HTTP transport pointing to port `7778` on the node.

## Methods

### speculativeExec

```ts
speculativeClient.speculativeExec(
  reqID: string,
  deploy: Deploy,
  identifier?: BlockIdentifier
): Promise<SpeculativeExecResult>
```

Executes a deploy speculatively. The transaction is **not** written to the chain.

### Parameters

#### reqID

- **Type:** `string`

A unique request ID string for this speculative execution call.

#### deploy

- **Type:** `Deploy`

The legacy deploy to execute speculatively.

#### identifier

- **Type:** `BlockIdentifier` (optional)

The block to execute against. Defaults to the latest block.

### Return Value

`SpeculativeExecResult`

Contains the execution result and effects that would have occurred.

## Notes

- Not all nodes expose port 7778 - check with your node operator.
- The speculative execution state is based on the current latest block.
- Use this to estimate gas costs or verify contract logic before submitting.