Cross-Exchange Arbitrage between Kalshi and Polymarket

This strategy, implemented in the 'Polymarket-Kalshi-Arbitrage-Bot', systematically identifies price discrepancies for event contracts that are listed on both Polymarket and Kalshi, two leading prediction market platforms. The bot continuously compares the bid-ask spreads and last trade prices across both exchanges for the same underlying event (e.g., 'Will the Fed raise rates in July?'). When a significant spread is detected—for example, the YES contract is trading at 60 cents on Polymarket but 55 cents on Kalshi—the bot simultaneously buys the cheaper contract and sells the more expensive one, locking in a risk-free profit of 5 cents per share. Entry is automated via API calls to both exchanges, with the bot calculating required capital, transaction fees, and settlement risks. Exit occurs at contract settlement, where both positions resolve to either $1 or $0, realizing the captured spread. The strategy is market-neutral and independent of the event outcome, but relies on sufficient liquidity and speed to capture fleeting arbitrage opportunities. No specific P&L is published, but the spread sizes are typically small (1-5 cents per share). Implementation is minimal (26KB repo) and likely uses Python or JavaScript with REST APIs for both platforms.