simulateZerodevUserOperation

Preview a ZeroDev user operation’s effects before sending it

Simulates a ZeroDev user operation and returns a breakdown of expected asset changes, security validation results, and optionally an estimated gas fee — before the operation is submitted to the network.

Returns the same result shape as simulateEvmTransaction, since user operations are ultimately EVM transactions. Powered by Blockaid for security validation.

Installation

npm install @dynamic-labs-sdk/zerodev

Usage

import { simulateZerodevUserOperation } from '@dynamic-labs-sdk/zerodev';
import { isEvmWalletAccount } from '@dynamic-labs-sdk/evm';
import { getPrimaryWalletAccount } from '@dynamic-labs-sdk/client';
import { parseEther, encodeFunctionData } from 'viem';

const walletAccount = getPrimaryWalletAccount();

if (walletAccount && isEvmWalletAccount(walletAccount)) {
  const result = await simulateZerodevUserOperation({
    walletAccount,
    userOperation: {
      sender: walletAccount.address,
      callData: encodeFunctionData({
        abi: erc20Abi,
        functionName: 'transfer',
        args: [recipientAddress, parseUnits('100', 18)],
      }),
    },
    networkId: '1',
    entryPoint: ENTRY_POINT_ADDRESS,
  });

  console.log('Assets going out:', result.outAssets);
  console.log('Security check:', result.validation?.result);
}

Parameters

Parameter	Type	Description
walletAccount	EvmWalletAccount	The ZeroDev-enabled wallet account
userOperation	Partial<UserOperation>	The user operation to simulate
networkId	string	The chain ID (e.g., '1' for Ethereum, '137' for Polygon)
entryPoint	string	The EntryPoint contract address
includeFees	boolean (optional)	Whether to include a gas fee estimate. Default: false
client	DynamicClient (optional)	Only required when using multiple clients

Returns

Promise<EvmSimulationResult> — an object with the following fields:

Field	Type	Description
inAssets	AssetDiff[]	Assets the wallet will receive
outAssets	AssetDiff[]	Assets the wallet will send
validation	BlockaidValidation (optional)	Security assessment from Blockaid
validation.result	'benign' | 'warning' | 'malicious'	Overall security verdict
validation.description	string (optional)	Human-readable description
validation.reason	string (optional)	Reason for the verdict
feeData	EvmTransactionFeeData (optional)	Present only when includeFees: true
feeData.humanReadableAmount	string	Fee in ETH, formatted for display
feeData.nativeAmount	bigint	Fee in wei (0n if the operation is sponsored)
feeData.usdAmount	string (optional)	Fee in USD if price data is available
feeData.gasEstimate	bigint	Estimated gas units
priceData	PriceData	Price information for the assets involved
counterparties	string[] (optional)	Other addresses involved in the operation

When the operation is eligible for gas sponsorship, feeData.nativeAmount is 0n — indicating the user will not pay gas. Use canSponsorUserOperation to check sponsorship eligibility before simulating.

Examples

Token transfer

import { encodeFunctionData, parseUnits } from 'viem';

const result = await simulateZerodevUserOperation({
  walletAccount,
  userOperation: {
    sender: walletAccount.address,
    callData: encodeFunctionData({
      abi: erc20Abi,
      functionName: 'transfer',
      args: [recipientAddress, parseUnits('50', 18)],
    }),
  },
  networkId: '137',
  entryPoint: ENTRY_POINT_ADDRESS,
});

console.log('Tokens out:', result.outAssets);
console.log('Tokens in:', result.inAssets);

With gas fee estimation

const result = await simulateZerodevUserOperation({
  walletAccount,
  userOperation: {
    sender: walletAccount.address,
    callData,
  },
  networkId: '1',
  entryPoint: ENTRY_POINT_ADDRESS,
  includeFees: true,
});

if (result.feeData) {
  if (result.feeData.nativeAmount === 0n) {
    console.log('Operation is sponsored — no gas cost');
  } else {
    console.log(`Estimated gas fee: ${result.feeData.humanReadableAmount} ETH`);
  }
}

Security validation

const result = await simulateZerodevUserOperation({
  walletAccount,
  userOperation: { sender: walletAccount.address, callData },
  networkId: '1',
  entryPoint: ENTRY_POINT_ADDRESS,
});

if (result.validation?.result === 'malicious') {
  console.warn('Operation flagged as malicious. Blocking.');
  return;
}

Error handling

import { SimulationFailedError, FeeEstimationFailedError } from '@dynamic-labs-sdk/client';

try {
  const result = await simulateZerodevUserOperation({
    walletAccount,
    userOperation,
    networkId,
    entryPoint,
    includeFees: true,
  });
} catch (error) {
  if (error instanceof SimulationFailedError) {
    console.error('Simulation failed:', error.message);
  } else if (error instanceof FeeEstimationFailedError) {
    console.error('Fee estimation failed:', error.message);
  }
}

Related functions

• simulateEvmTransaction - Simulate a standard EVM transaction
• simulateSolanaTransaction - Simulate a Solana transaction
• sendUserOperation - Send a user operation (single or batch)
• canSponsorUserOperation - Check if a user operation can be sponsored
• estimateUserOperationGas - Estimate gas for a user operation