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

# Isthmus: System Config

> SystemConfig changes in the Isthmus upgrade, adding operatorFeeScalar and operatorFeeConstant configuration variables.

## Operator Fee Parameter Configuration

Isthmus adds configuration variables `operatorFeeScalar` (`uint32`)
and `operatorFeeConstant` (`uint64`) to `SystemConfig` to control the operator fee parameters.

### `ConfigUpdate`

The following `ConfigUpdate` event is defined where the `CONFIG_VERSION` is `uint256(0)`:

| Name                  | Value      | Definition                                                                        | Usage                                                                |
| --------------------- | ---------- | --------------------------------------------------------------------------------- | -------------------------------------------------------------------- |
| `BATCHER`             | `uint8(0)` | `abi.encode(address)`                                                             | Modifies the account that is authorized to progress the safe chain   |
| `FEE_SCALARS`         | `uint8(1)` | `(uint256(0x01) << 248) \| (uint256(_blobbasefeeScalar) << 32) \| _basefeeScalar` | Modifies the fee scalars                                             |
| `GAS_LIMIT`           | `uint8(2)` | `abi.encode(uint64 _gasLimit)`                                                    | Modifies the L2 gas limit                                            |
| `UNSAFE_BLOCK_SIGNER` | `uint8(3)` | `abi.encode(address)`                                                             | Modifies the account that is authorized to progress the unsafe chain |
| `EIP_1559_PARAMS`     | `uint8(4)` | `uint256(uint64(uint32(_denominator))) << 32 \| uint64(uint32(_elasticity))`      | Modifies the EIP-1559 denominator and elasticity                     |
| `OPERATOR_FEE_PARAMS` | `uint8(5)` | `uint256(_operatorFeeScalar) << 64 \| _operatorFeeConstant`                       | Modifies the operator fee scalar and constant                        |

### Initialization

The following actions should happen during the initialization of the `SystemConfig`:

* `emit ConfigUpdate.BATCHER`
* `emit ConfigUpdate.FEE_SCALARS`
* `emit ConfigUpdate.GAS_LIMIT`
* `emit ConfigUpdate.UNSAFE_BLOCK_SIGNER`
* `emit ConfigUpdate.EIP_1559_PARAMS`

These actions MAY only be triggered if there is a diff to the value.

The `operatorFeeScalar` and `operatorFeeConstant` are initialized to 0.

### Modifying Operator Fee Parameters

A new `SystemConfig` `UpdateType` is introduced that enables the modification of
the `operatorFeeScalar` and `operatorFeeConstant` by the `SystemConfig` owner.

### Interface

#### Operator fee parameters

##### `operatorFeeScalar`

This function returns the currently configured operator fee scalar.

```solidity theme={null}
function operatorFeeScalar()(uint32)
```

##### `operatorFeeConstant`

This function returns the currently configured operator fee constant.

```solidity theme={null}
function operatorFeeConstant()(uint64)
```

##### `setOperatorFeeScalars`

This function sets the `operatorFeeScalar` and `operatorFeeConstant`.

This function MUST only be callable by the `SystemConfig` owner.

```solidity theme={null}
function setOperatorFeeScalar(uint32 _operatorFeeScalar, uint64 _operatorFeeConstant)
```