Sign a user operation

The eth_signUserOperation method allows you to sign an ERC-4337 UserOperation using your client’s MPC key without broadcasting it to the network. The signed UserOperation can then be submitted through a separate backend such as Pimlico or a custom bundler endpoint.

This method requires your client to be created with Account Abstraction enabled (isAccountAbstracted: true). Non-AA clients will receive a METHOD_UNSUPPORTED error.

Prerequisites

Before using eth_signUserOperation, ensure that:

Your organization has Account Abstraction enabled. See the Account Abstraction guide for setup instructions.
Your client was created with isAccountAbstracted: true via the Create a new client endpoint.
Your client has a wallet created and backed up.

Signing a UserOperation

Use the request method with the eth_signUserOperation RPC method. The params array takes a single object with standard Ethereum transaction fields.

import 'package:portal_flutter/portal_flutter.dart';

final portal = Portal();

// Sign a UserOperation on Sepolia testnet
final result = await portal.request(
  chainId: 'eip155:11155111',
  method: 'eth_signUserOperation',
  params: [
    {
      'to': '0xRecipientAddress',
      'value': '0x0',
      'data': '0x',
    }
  ],
);

if (result.error != null) {
  print('Error: ${result.error}');
} else {
  print('Signed UserOp: ${result.result}');
  // result.result contains a hex-encoded signed UserOperation JSON
}

The chainId must be a CAIP-2 compliant Chain ID for a supported Account Abstraction network.

Transaction Parameters

The params object supports the following fields:

Parameter	Type	Required	Description
`to`	`String`	Yes	The recipient or contract address
`value`	`String`	No	Value in wei (hex-encoded)
`data`	`String`	No	Calldata (hex-encoded)
`gas`	`String`	No	Gas limit (hex-encoded)
`maxFeePerGas`	`String`	No	Max fee per gas for EIP-1559 (hex-encoded)
`maxPriorityFeePerGas`	`String`	No	Max priority fee for EIP-1559 (hex-encoded)
`nonce`	`String`	No	Transaction nonce (hex-encoded)

Response

The method returns a PortalProviderResponse where result is a hex-encoded JSON string containing the signed UserOperation. You can decode this result and submit it to a bundler of your choice.

import 'package:portal_flutter/portal_flutter.dart';

final portal = Portal();

final result = await portal.request(
  chainId: 'eip155:11155111',
  method: 'eth_signUserOperation',
  params: [
    {
      'to': '0xRecipientAddress',
      'value': '0xDE0B6B3A7640000', // 1 ETH in wei
      'data': '0x',
    }
  ],
);

if (result.error != null) {
  throw Exception('Failed to sign UserOp: ${result.error}');
}

// The signed UserOperation is a hex-encoded JSON string
final signedUserOp = result.result;
print('Signed UserOperation: $signedUserOp');

// Decode the hex string and submit to your bundler
// e.g., send signedUserOp to Pimlico or your custom bundler endpoint

EIP-1559 Gas Parameters

You can specify EIP-1559 gas parameters for finer control over fees:

final result = await portal.request(
  chainId: 'eip155:11155111',
  method: 'eth_signUserOperation',
  params: [
    {
      'to': '0xRecipientAddress',
      'value': '0x0',
      'data': '0x',
      'maxFeePerGas': '0x3B9ACA00',        // 1 Gwei
      'maxPriorityFeePerGas': '0x3B9ACA00', // 1 Gwei
    }
  ],
);

Error Handling

Error	Description
`METHOD_UNSUPPORTED`	The client does not have Account Abstraction enabled
`NOT_INITIALIZED`	Portal was not initialized
`RPC_ERROR`	The RPC call returned an error

try {
  final result = await portal.request(
    chainId: 'eip155:11155111',
    method: 'eth_signUserOperation',
    params: [
      {
        'to': '0xRecipientAddress',
        'value': '0x0',
        'data': '0x',
      }
    ],
  );

  if (result.error != null) {
    print('Provider error: ${result.error}');
    return;
  }

  print('Signed UserOp: ${result.result}');
} on PortalException catch (e) {
  print('Portal error: ${e.message}');
}

Related Documentation

Getting Started

SDKs

APIs

Integrations

Resources

Sign a user operation

Prerequisites

Signing a UserOperation

Transaction Parameters

Response

EIP-1559 Gas Parameters

Error Handling

​Prerequisites

​Signing a UserOperation

​Transaction Parameters

​Response

​EIP-1559 Gas Parameters

​Error Handling

Prerequisites

Signing a UserOperation

Transaction Parameters

Response

EIP-1559 Gas Parameters

Error Handling