# API Upgrade

We are announcing a change to our API behavior for the `eth_estimateUserOperationGas` method. Previously, our system provided a default ETH balance override when estimating gas for User Operations. This is an optional upgrade to make sure your users have enough ETH to cover the operation’s cost.

## What’s Changing?

### No More Default ETH Balance Override

After the change goes into effect, we will not add an ETH balance override by default when you call `eth_estimateUserOperationGas`.

### Possible AA21 Error

If a User Operation is not sponsored by a paymaster and the sender does not have enough ETH to cover the operation’s cost, you will encounter an AA21 error.

### If Users Have Sufficient Balance

If you already expect users to hold enough ETH for non-sponsored transactions, no changes are required on your end. You should be able to upgrade without any issues. Click [here](https://dashboard.pimlico.io/apikeys/upgrade) to upgrade.

## How to upgrade?

If you signed up after 17/12/2024, your API is already on the upgraded version.

If you signed up before 17/12/2024, you can manually opt-in to the upgrade through the Pimlico dashboard by clicking [here](https://dashboard.pimlico.io/apikeys/upgrade).

## Estimating Without a User’s Balance

If you need to estimate a User Operation for a sender without sufficient balance, you can add state overrides to the `eth_estimateUserOperationGas` method.

#### Upgrade with permissionless

:::code-group
```ts [upgrade.ts]
import { parseEther, zeroAddress } from "viem"
import { smartAccountClient } from "./createSmartAccountClient"

const userOperation = await smartAccountClient.prepareUserOperation({
	calls: [
		{
			to: zeroAddress,
			value: 0n,
			data: "0x",
		},
	],
	stateOverride: [
		{
			// Adding 100 ETH to the smart account during estimation to prevent AA21 errors while estimating
			balance: parseEther("100"),
			address: smartAccountClient.account.address,
		},
	],
})

const userOperationHash = await smartAccountClient.sendUserOperation(userOperation)

const receipt = await smartAccountClient.waitForUserOperationReceipt({
	hash: userOperationHash,
})

console.log(receipt)
```

```ts [createSmartAccountClient.ts]
import { toSimpleSmartAccount } from "permissionless/accounts"
import { createSmartAccountClient } from "permissionless/clients"
import { createPimlicoClient } from "permissionless/clients/pimlico"
import { createPublicClient, http } from "viem"
import { entryPoint07Address } from "viem/account-abstraction"
import { generatePrivateKey, privateKeyToAccount } from "viem/accounts"
import { base } from "viem/chains"

const publicClient = createPublicClient({
	chain: base,
	transport: http("https://mainnet.base.org"),
})

const owner = privateKeyToAccount(generatePrivateKey())

const simpleSmartAccount = await toSimpleSmartAccount({
	owner,
	client: publicClient,
	entryPoint: {
		address: entryPoint07Address,
		version: "0.7",
	},
})

const pimlicoUrl = "https://api.pimlico.io/v2/sepolia/rpc?apikey=API_KEY"

const pimlicoClient = createPimlicoClient({
	chain: base,
	transport: http(pimlicoUrl),
})

export const smartAccountClient = createSmartAccountClient({
	chain: base,
	account: simpleSmartAccount,
	bundlerTransport: http(pimlicoUrl),
	userOperation: {
		estimateFeesPerGas: async () => {
			return (await pimlicoClient.getUserOperationGasPrice()).fast
		},
	},
})
```
:::

#### Upgrade to the raw API

You can use state overrides to simulate the user operation with a different
state the same way you would with
[`eth_call`](https://geth.ethereum.org/docs/interacting-with-geth/rpc/ns-eth#eth-call)
by including an optional third parameter. This is supported for both EntryPoint
v0.6 and v0.7.

```json
{
  "jsonrpc": "2.0",
  "method": "eth_estimateUserOperationGas",
  "params": [
    {
      "sender": "0xa203fDb8bC335F86016F635b85389B62B189E417",
      "nonce": "0x35bf2a054f92f3730b87582ef223c8d663f9eb01158154750000000000000000",
      "initCode": "0x",
      "callData": "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",
      "callGasLimit": "0x115b5c0",
      "verificationGasLimit": "0x249f0",
      "preVerificationGas": "0xeb11",
      "maxPriorityFeePerGas": "0x12a05f200",
      "maxFeePerGas": "0x5b08082fa",
      "paymasterAndData": "0x",
      "signature": "0xa6cc6589c8bd561cfd68d7b6b0757ef6f208e7438782939938498eee7d703260137856c840c491b3d415956265e81bf5c2184a725be2abfc365f7536b6af525e1c"
    },
    "0x5FF137D4b0FDCD49DcA30c7CF57E578a026d2789",
    {
      "0xd9c9cd5f6779558b6e0ed4e6acf6b1947e7fa1f3": {
        // Adding 100 ETH to the smart account during estimation to prevent AA21 errors while estimating
        "balance": "0x56BC75E2D63100000"
      },
      "0xebe8efa441b9302a0d7eaecc277c09d20d684540": {
        "stateDiff": {
          "0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80": "0x21"
        }
      }
    }
  ],
  "id": 1
}
```