@openpx/sdk

Node.js SDK for OpenPX — a unified interface for prediction markets.

Installation

npm install @openpx/sdk

Quick Start

const { Exchange } = require("@openpx/sdk");

const exchange = new Exchange("kalshi");
const markets = await exchange.fetchMarkets();

for (const market of markets.slice(0, 5)) {
  console.log(`${market.question}: ${JSON.stringify(market.prices)}`);
}

Supported Exchanges

• Kalshi — US-regulated event contracts
• Polymarket — Crypto-native prediction markets

Authentication

Kalshi

const exchange = new Exchange("kalshi", {
  api_key_id: process.env.KALSHI_API_KEY_ID,
  private_key_path: "./kalshi-private-key.pem", // or private_key_pem: "<inline PEM>"
});

Public market-data calls work without credentials.

Polymarket

Pick the credential path that matches your wallet:

| Wallet model | Required keys | | -------------------------------------- | ----------------------------------------------------------- | | MetaMask EOA + Polymarket Safe | private_key (EOA) + funder (Safe) | | Plain EOA (no Safe) | private_key only | | Pre-derived API keys (most reliable) | api_key + api_secret + api_passphrase (+ private_key for order signing) |

const exchange = new Exchange("polymarket", {
  private_key: process.env.POLYMARKET_PRIVATE_KEY,
  funder:      process.env.POLYMARKET_FUNDER, // omit for plain EOA
});

signature_type is auto-detected from funder and almost never needs to be set explicitly. If you set it to "eoa" while a funder is configured, the SDK overrides it to "gnosis_safe" with a warning — that combo is rejected by Polymarket and is a common MetaMask misconfiguration.

If derive-api-key returns a Cloudflare WAF block (datacenter IPs are often blocked), generate keys once via the Polymarket web app and pass them as api_key / api_secret / api_passphrase to skip the derive flow entirely.

Full credential matrix: docs.openpx.io/setup/polymarket-credentials.