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Creating a new prediction market on Proteus is simple and only costs gas fees. Markets are created on-chain via the PredictionMarketV2 contract deployed on BASE Sepolia.

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Overview

When you create a market, you specify:
  • Actor Handle: The X.com (Twitter) handle to track
  • Duration: How long until the market closes (1-720 hours)
Market creation is free — you only pay gas fees. Players stake ETH when submitting predictions.

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Prerequisites

1

Connect Your Wallet

You need a connected wallet (MetaMask or Coinbase Embedded Wallet) with BASE Sepolia ETH for gas fees.Get testnet ETH from the BASE Sepolia Faucet.
2

Navigate to Create Market

Go to the market creation page in the Proteus app.

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Creating a Market

1

Enter Actor Handle

Specify the X.com handle to track (e.g., elonmusk, sama, zuck).
  • Do not include the @ symbol
  • Only letters, numbers, and underscores allowed
  • Must be a valid X.com handle
2

Set Market Duration

Choose how long the market will accept predictions:
  • Minimum: 1 hour
  • Maximum: 720 hours (30 days)
  • Default: 24 hours
Markets have a 1-hour betting cutoff before the end time. Submissions stop 1 hour before endTime to prevent last-second manipulation.
3

Submit Transaction

Click Create Market on BASE and confirm the transaction in your wallet.The createMarket function is called:
function createMarket(
    string calldata _actorHandle,
    uint256 _duration
) external whenNotPaused returns (uint256)
You’ll receive a marketId in the transaction receipt.

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Contract Interaction

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Using Web3.js (Frontend)

Here’s how the frontend creates markets: 
class BettingContract {
    async createMarket(actorHandle, durationHours) {
        const durationSeconds = durationHours * 3600;
        
        // Call contract (NOT payable in V2)
        const tx = await this.contract.methods
            .createMarket(actorHandle, durationSeconds)
            .send({ 
                from: this.account,
                gas: 200000
            });
        
        console.log('Market created:', tx.transactionHash);
        
        // Extract market ID from event
        const marketId = tx.events.MarketCreated.returnValues.marketId;
        return { marketId, transactionHash: tx.transactionHash };
    }
}

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Using Python (Backend)

Creating markets via the Python backend: 
from web3 import Web3

# Initialize Web3
w3 = Web3(Web3.HTTPProvider('https://sepolia.base.org'))

# Load contract
contract_address = '0x5174Da96BCA87c78591038DEe9DB1811288c9286'
contract = w3.eth.contract(address=contract_address, abi=contract_abi)

# Create market
actor_handle = 'elonmusk'
duration = 24 * 3600  # 24 hours in seconds

tx_hash = contract.functions.createMarket(
    actor_handle,
    duration
).transact({
    'from': creator_address,
    'gas': 200000
})

# Wait for receipt
receipt = w3.eth.wait_for_transaction_receipt(tx_hash)
print(f'Market created: {receipt.transactionHash.hex()}')

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Market Lifecycle

Once created, markets go through these phases:

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Smart Contract Details

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Contract Address

PredictionMarketV2: 0x5174Da96BCA87c78591038DEe9DB1811288c9286 (BASE Sepolia)

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Market Struct

struct Market {
    string actorHandle;        // Social media handle
    uint256 endTime;           // When betting closes
    uint256 totalPool;         // Total ETH in market
    bool resolved;             // Has winner been determined
    uint256 winningSubmissionId; // Winning submission ID
    address creator;           // Market creator
}

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Events Emitted

event MarketCreated(
    uint256 indexed marketId,
    string actorHandle,
    uint256 endTime,
    address creator
);

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Validation Rules

The contract enforces these validation rules:
  • Duration: Must be between 1 hour and 30 days
  • Contract State: Contract must not be paused
  • Gas: Requires ~200,000 gas for market creation
if (_duration < 1 hours || _duration > 30 days) 
    revert InvalidDuration();

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Example Transaction

Here’s a complete example creating a market for Elon Musk: 
const marketCreator = new MarketCreator();

try {
    const result = await marketCreator.createMarket('elonmusk', 24);
    
    console.log(`Market #${result.marketId} created successfully!`);
    console.log(`Transaction: ${result.transactionHash}`);
    console.log(`View: https://sepolia.basescan.org/tx/${result.transactionHash}`);
    
    // Redirect to market page
    window.location.href = `/market/${result.marketId}`;
    
} catch (error) {
    console.error('Market creation failed:', error.message);
}

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Querying Markets

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Get Market Details

const marketDetails = await contract.methods
    .getMarketDetails(marketId)
    .call();

const [
    actorHandle,
    endTime,
    totalPool,
    resolved,
    winningSubmissionId,
    creator,
    submissionIds
] = marketDetails;

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Via API

curl https://proteus-production-6213.up.railway.app/api/chain/markets
Response: 
{
  "markets": [
    {
      "id": 0,
      "actor_address": "elonmusk",
      "start_time": 1709740800,
      "end_time": 1709827200,
      "status": "active",
      "total_volume": "5000000000000000000",
      "block_number": 12345678
    }
  ],
  "total": 1,
  "source": "blockchain"
}

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Best Practices

  • Short duration (1-6 hours): For handles that tweet multiple times daily
  • Medium duration (12-48 hours): Most common use case
  • Long duration (7+ days): For infrequent posters or specific events
Factor in when your target handle typically posts. Setting market end time during their active hours increases participation.

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Troubleshooting

Common causes:
  • Insufficient gas
  • Invalid duration (< 1 hour or > 30 days)
  • Contract is paused
  • Invalid character in handle
Solution: Check your wallet has enough BASE Sepolia ETH and retry.

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Next Steps

After creating a market:
  1. Share the market ID with potential participants
  2. Monitor submissions as they come in
  3. Wait for the oracle to resolve after endTime
  4. Check the winning submission

Submit Predictions

Learn how to submit predictions and stake ETH on markets

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