Predexon Trade SDK

Trading SDK for Polymarket (Polygon) and Kalshi (Solana).

Installation

npm install @predexon/trade-sdk

Requirements: Node.js 20.18+.

Quick Start

import { PredexonSDK, createEvmAdapter } from '@predexon/trade-sdk';

// Create SDK instance with wallet signer
const sdk = new PredexonSDK({
  apiKey: 'your-api-key',
  wallet: createEvmAdapter(yourWalletClient),
});

// Enable trading (required before placing orders)
await sdk.enableTrading({
  core: { venue: 'polymarket', wallet: walletAddress },
  approvals: 'auto',
});

// Place a market buy order
const result = await sdk.placeOrder({
  core: {
    venue: 'polymarket',
    wallet: walletAddress,
    side: 'buy',
    amount: '10', // $10 USDC
    type: 'market',
  },
  flags: { tokenId: 'your-token-id' },
});

Supported Venues

| Venue | Chain | Order Types | Features | |-------|-------|-------------|----------| | Polymarket | Polygon | Market, Limit | Full support | | Kalshi | Solana | Market only | Orders + redemption (no open orders or cancels) |

Order Semantics

Polymarket

• Market BUY: amount (USDC) or size (shares), exactly one
• Market SELL: size required
• Limit BUY: size + price required
• Limit SELL: size + price required

Kalshi

• Market BUY: amount (USDC) required
• Market SELL: size (tokens) required
• Limit orders are not supported

Enable Trading

Polymarket

enableTrading() handles CLOB credential registration and contract approvals:

• Signs EIP-712 typed data for CLOB authentication
• Optionally signs and broadcasts approval transactions (via approvals: 'auto')

await sdk.enableTrading({
  core: { venue: 'polymarket', wallet: walletAddress },
  approvals: 'auto', // 'auto' | 'manual' | 'skip'
});

Kalshi

enableTrading() registers the Solana wallet with Predexon's server:

• Signs a challenge message to prove wallet ownership
• Server registers the wallet association with your API key

await sdk.enableTrading({
  core: { venue: 'kalshi', wallet: solanaWalletAddress },
});

Wallet Signing Requirements

Polymarket (Polygon)

Requires a wallet implementing:

• getAddress(): Promise<string>
• signTypedData(typedData): Promise<string> - EIP-712 signing
• signTransaction(tx): Promise<string> - for approval transactions

Kalshi (Solana)

Requires additional methods:

• signSolanaTransaction(base64): Promise<string> - for order transactions
• signSolanaMessage(message): Promise<string> - for wallet registration (enableTrading only)

Order Construction

Polymarket

• Uses canonical @polymarket/clob-client to build and sign orders locally
• Market orders resolve price by walking the live orderbook
• Limit orders validate min_order_size from the orderbook
• prepareOrder() returns { order, signature } (SDK signs using your wallet adapter)

Kalshi

• Server-assisted prepare/submit flow via DFlow
• prepareOrder() returns { transaction, orderParams } (unsigned)
• Your wallet signs the Solana transaction; SDK submits on placeOrder()/submitOrder()

Security Notes

• The SDK is hard-locked to https://trade.predexon.com (no custom base URL).
• Kalshi prepare responses are validated before signing (echo + signer checks).
• Polymarket redemption transactions are constructed locally from server-provided metadata.
• Node 20.18+ is required (per engines).

Redemption

Polymarket

await sdk.redeem({
  core: { venue: 'polymarket', wallet: walletAddress },
  flags: { tokenId: 'resolved-token-id' },
});

Kalshi

await sdk.redeem({
  core: { venue: 'kalshi', wallet: solanaWalletAddress },
  flags: { ticker: 'TICKER', outcome: 'Yes' },
});

API Reference

Core Methods

| Method | Description | |--------|-------------| | enableTrading(request) | Enable trading for a venue (registration + approvals) | | placeOrder(request) | Build, sign, and submit an order (primary API) | | prepareOrder(request) | Build order locally (Polymarket: returns signed order; Kalshi: returns unsigned transaction for wallet to sign) | | submitOrder(request) | Submit a prepared order (advanced) | | cancelOrder(params) | Cancel a specific open order (Polymarket only; Kalshi not supported) | | cancelAllOrders(params) | Cancel all open orders (Polymarket only; Kalshi not supported) | | getOpenOrders(params) | List open orders (returns empty for Kalshi) | | getPositions(params) | Get current positions | | getBalance(params) | Get wallet balance | | redeem(request) | Redeem resolved positions |

Idempotency

Provide an idempotencyKey on placeOrder/submitOrder when you need idempotent order submissions. Use the helper below to generate keys. enableTrading and redeem do not accept user-supplied idempotency keys.

import { generateIdempotencyKey } from '@predexon/trade-sdk';

const key = generateIdempotencyKey();
const customKey = generateIdempotencyKey('my-prefix');

Adapters

EVM Adapters (Polymarket)

import { createEvmAdapter, createPrivyEvmAdapter } from '@predexon/trade-sdk';

// Generic EVM adapter (viem, ethers, etc.)
const evmSigner = createEvmAdapter(yourWalletClient);

// Privy-specific EVM adapter
const privyEvmSigner = createPrivyEvmAdapter(privyEmbeddedWallet);

Solana Adapters (Kalshi)

import { createSolanaAdapter, createPrivySolanaAdapter } from '@predexon/trade-sdk';

// Generic Solana adapter (any wallet with signSolanaTransaction)
const solanaSigner = createSolanaAdapter({
  signSolanaTransaction: async (base64Tx) => signedBase64,
  signSolanaMessage: async (message) => signatureBase64,
});

// Privy-specific Solana adapter (Wallet Standard)
import { useSolanaStandardWallets } from '@privy-io/react-auth/solana';

const { wallets } = useSolanaStandardWallets();
const privyWallet = wallets.find(w => w.name === 'Privy');
const address = privyWallet.accounts[0].address;

const privySolanaSigner = createPrivySolanaAdapter(privyWallet, address);

Combined Wallet (Both Venues)

For apps supporting both Polymarket and Kalshi with Privy:

import { PredexonSDK, createPrivyEvmAdapter, createPrivySolanaAdapter } from '@predexon/trade-sdk';

const sdk = new PredexonSDK({
  apiKey: 'your-api-key',
  wallet: {
    ...createPrivyEvmAdapter(privyEvmWallet),
    ...createPrivySolanaAdapter(privySolanaWallet, solanaAddress),
  },
});

Configuration

const sdk = new PredexonSDK({
  apiKey: 'your-api-key',
  wallet: createEvmAdapter(yourWalletClient),
  timeouts: {
    requestMs: 30000,
  },
});

Note: the SDK is hard-locked to the production API base URL and does not support custom base URLs.