drakkar-softwares/polymarket-kalshi-arbitrage-bot

This is an automated trading bot that watches two prediction market platforms, Polymarket and Kalshi, and looks for moments when they price the same event differently. Prediction markets let people buy shares tied to the outcome of real world events, like elections or economic reports, with prices moving between zero and one hundred cents based on how likely traders think the outcome is. When the same event is priced differently on two platforms at once, there is a chance to buy low on one side and profit if the gap closes. The bot focuses on short fifteen minute markets. It continuously checks Kalshi's YES price against Polymarket's UP price for a matched pair of markets. Its main rule fires when Kalshi is trading between 93 and 96 cents while Polymarket is priced at least 10 cents cheaper for the same outcome, at which point it can automatically place a buy order on Polymarket. A second rule watches for cases where Kalshi has already settled a market while Polymarket still has open orders, which can also present a buying opportunity. The project runs as a small web service built with Express, so it exposes a status endpoint you can check to see current prices and any signals the bot has generated. Without wallet credentials it only monitors and reports, adding real credentials lets it place live orders on Polymarket through their official order client. All thresholds, timing, and market identifiers are set through a configuration file, and it connects to both platforms over their standard HTTP APIs. It is written in TypeScript for Node.js 18 and newer, uses ethers for wallet handling, and axios for network requests. The project includes clear warnings that prediction market trading carries real financial risk and that the bot does not guarantee any profit.