# Evm.setExecutionConfig

Replaces the specification and its version overrides.

The block environment stays as it was. Overrides are applied whole rather than merged, so what the new set omits returns to the specification's own value.

## Imports

:::code-group
```ts [Named]
import { Evm } from 'ox/evm'
```

```ts [Entrypoint]
import * as Evm from 'ox/evm/Evm'
```
:::

## Examples

```ts twoslash
// @noErrors
import { Evm } from 'ox/evm'

// Simulate without charging fees or checking balances.
Evm.setExecutionConfig(evm, {
  version: {
    features: { balanceCheck: false, feeCharge: false }
  }
})
```

## Definition

```ts
function setExecutionConfig<asynchronous>(
  evm: Evm<asynchronous>,
  options: setExecutionConfig.Options,
): Awaitable<asynchronous, void>
```

**Source:** [src/evm/Evm.ts](https://github.com/wevm/ox/blob/main/src/evm/Evm.ts#L694)

## Parameters

### evm

* **Type:** `Evm<asynchronous>`

EVM to reconfigure.

#### evm.'~async'

* **Type:** `asynchronous`

#### evm.'~chainId'

* **Type:** `bigint`

#### evm.'~config'

* **Type:** `{ block: Block; specId: "frontier" | "homestead" | "tangerine" | "spuriousDragon" | "byzantium" | "petersburg" | "istanbul" | "berlin" | "london" | "merge" | "shanghai" | "cancun" | "prague" | "osaka" | "amsterdam"; version?: Version; }`

The engine's current execution config.

Held so a setter can replace one half without discarding the other, since
the adapter's operation carries both.

#### evm.'~driver'

* **Type:** `asynchronous extends true ? Driver : undefined`

Drives the asynchronous source, when there is one.

#### evm.'~engine'

* **Type:** `Engine`

#### evm.block

* **Type:** `Block`

#### evm.specId

* **Type:** `"frontier" | "homestead" | "tangerine" | "spuriousDragon" | "byzantium" | "petersburg" | "istanbul" | "berlin" | "london" | "merge" | "shanghai" | "cancun" | "prague" | "osaka" | "amsterdam"`

#### evm.version

* **Type:** `Version`
* **Optional**

### options

* **Type:** `setExecutionConfig.Options`

Specification and version to apply.

#### options.specId

* **Type:** `"frontier" | "homestead" | "tangerine" | "spuriousDragon" | "byzantium" | "petersburg" | "istanbul" | "berlin" | "london" | "merge" | "shanghai" | "cancun" | "prague" | "osaka" | "amsterdam"`
* **Optional**

Specification whose rules apply. Unchanged when omitted.

#### options.version

* **Type:** `Version`
* **Optional**

Overrides applied on top of that specification.

## Return Type

`Awaitable<asynchronous, void>`