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The Governor Bravo client enables interaction with governance systems built on Compound’s Governor Bravo protocol. It supports both gasless voting through signatures and direct transaction-based voting.

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Installation

npm install @snapshot-labs/sx

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Overview

Governor Bravo is a widely-used on-chain governance protocol originally developed by Compound. Many DAOs use Governor Bravo or its variants for on-chain governance.
The Governor Bravo client currently supports voting only. Proposal creation and execution must be done through direct contract interaction or other tools.

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Client Types

The Governor Bravo client comes in two implementations:
  • GovernorBravoEthereumSig: Signature-based voting (gasless)
  • GovernorBravoEthereumTx: Transaction-based voting (direct)

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GovernorBravoEthereumSig (Signature-based)

The signature-based client allows users to vote using EIP-712 signatures, which can be submitted by relayers for gasless voting.

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Initialization

import { clients } from '@snapshot-labs/sx';

const client = new clients.GovernorBravoEthereumSig({
  chainId: 1 // Ethereum mainnet
});

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Configuration

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chainId
number
required
Chain ID for the network (1 for Ethereum mainnet, 11155111 for Sepolia)

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Methods

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vote()

Create a signed vote message that can be submitted to the Governor Bravo contract. 
import { Wallet } from '@ethersproject/wallet';

const signer = new Wallet(privateKey);

const envelope = await client.vote({
  signer,
  authenticatorType: 'GovernorBravoAuthenticatorSignature',
  data: {
    spaceId: '0x...', // Governor contract address
    proposalId: 42,   // Proposal ID
    choice: 1         // 1 = For
  }
});

// The envelope contains signature data that can be submitted
// to the Governor contract's castVoteBySig function
console.log('Signature:', envelope.signatureData.signature);
​
signer
Signer & TypedDataSigner
required
Ethers.js signer with EIP-712 signing capabilities
​
authenticatorType
'GovernorBravoAuthenticatorSignature'
required
Must be set to ‘GovernorBravoAuthenticatorSignature’
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data
Vote
required
Vote data object
​
envelope
Envelope<Vote>
Returns an envelope containing the signature data and vote data

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Submitting Signed Votes

After creating a signed vote, it must be submitted to the Governor Bravo contract: 
import { Contract } from '@ethersproject/contracts';

const governorAbi = [
  'function castVoteBySig(uint256 proposalId, uint8 support, uint8 v, bytes32 r, bytes32 s)'
];

const governor = new Contract(
  envelope.data.spaceId,
  governorAbi,
  provider
);

// Extract signature components
const sig = envelope.signatureData.signature;
const r = sig.slice(0, 66);
const s = '0x' + sig.slice(66, 130);
const v = parseInt(sig.slice(130, 132), 16);

// Submit the vote
const tx = await governor.castVoteBySig(
  envelope.data.proposalId,
  envelope.data.choice,
  v,
  r,
  s
);

await tx.wait();
console.log('Vote submitted:', tx.hash);

​
GovernorBravoEthereumTx (Transaction-based)

The transaction-based client allows direct voting through contract transactions.

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Initialization

import { clients } from '@snapshot-labs/sx';
import { JsonRpcProvider } from '@ethersproject/providers';

const provider = new JsonRpcProvider('https://eth.llamarpc.com');

const client = new clients.GovernorBravoEthereumTx({
  provider
});

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Methods

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vote()

Submit a vote transaction directly to the Governor Bravo contract. 
import { Wallet } from '@ethersproject/wallet';

const signer = new Wallet(privateKey, provider);

const tx = await client.vote({
  signer,
  data: {
    spaceId: '0x...', // Governor contract address
    proposalId: 42,
    choice: 1 // 1 = For
  }
});

await tx.wait();
console.log('Vote cast:', tx.hash);
​
signer
Signer
required
Ethers.js signer connected to a provider
​
data
Vote
required
Vote data object (same structure as signature-based client)
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transaction
TransactionResponse
Returns an ethers.js transaction response that can be awaited

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Type Definitions

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Vote

type Vote = {
  spaceId: string;      // Governor Bravo contract address
  proposalId: number;   // Proposal ID
  choice: 0 | 1 | 2;    // 0=Against, 1=For, 2=Abstain
  reason?: string;      // Optional vote reason
};

​
EIP712Ballot

type EIP712Ballot = {
  proposalId: number;
  support: number; // Same as choice
};

type EIP712BallotWithReason = {
  proposalId: number;
  support: number;
  reason: string;
};

​
SignatureData

type SignatureData = {
  authenticatorType: 'GovernorBravoAuthenticatorSignature';
  address: string;
  signature: string;
  domain: TypedDataDomain;
  types: Record<string, TypedDataField[]>;
  message: Record<string, any>;
};

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Governor Contract Compatibility

The client automatically detects the governor contract name for EIP-712 signing: 
// The client queries the governor contract's name() function
const name = await governorContract.name();
// e.g., "Compound Governor Bravo"

// Used in EIP-712 domain:
const domain = {
  name: name,
  chainId: 1,
  verifyingContract: '0x...'
};
For contracts without a name() function, custom names can be configured in the client source code.

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Complete Example

Here’s a full example of voting on a Governor Bravo proposal: 
import { clients } from '@snapshot-labs/sx';
import { Wallet } from '@ethersproject/wallet';
import { JsonRpcProvider } from '@ethersproject/providers';
import { Contract } from '@ethersproject/contracts';

// 1. Initialize client
const client = new clients.GovernorBravoEthereumSig({
  chainId: 1
});

// 2. Create signer
const provider = new JsonRpcProvider('https://eth.llamarpc.com');
const signer = new Wallet(process.env.PRIVATE_KEY, provider);

// 3. Generate signed vote
const envelope = await client.vote({
  signer,
  authenticatorType: 'GovernorBravoAuthenticatorSignature',
  data: {
    spaceId: '0x...', // Governor address
    proposalId: 42,
    choice: 1,
    reason: 'Fully support this initiative'
  }
});

// 4. Submit vote to Governor contract
const governorAbi = [
  'function castVoteWithReasonBySig(uint256 proposalId, uint8 support, string reason, uint8 v, bytes32 r, bytes32 s)'
];

const governor = new Contract(
  envelope.data.spaceId,
  governorAbi,
  provider
);

const sig = envelope.signatureData.signature;
const r = sig.slice(0, 66);
const s = '0x' + sig.slice(66, 130);
const v = parseInt(sig.slice(130, 132), 16);

const tx = await governor.castVoteWithReasonBySig(
  envelope.data.proposalId,
  envelope.data.choice,
  envelope.data.reason || '',
  v,
  r,
  s
);

await tx.wait();
console.log('Vote successfully cast:', tx.hash);

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Source Code

View the complete implementation:

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