Cross-Platform BTC 15-Minute Arbitrage (Kalshi vs Polymarket)

How It Works This strategy monitors the same underlying event (BTC price direction over 15-minute windows) as listed on both Kalshi and Polymarket simultaneously. When the implied probability of the same outcome differs materially between the two platforms, the bot buys the underpriced side on one platform and sells (or buys the opposite) on the other, creating a hedged position that profits regardless of the actual outcome.

Entry / Exit Conditions Entry is triggered when the sum of the two platforms' prices for opposing outcomes is less than 1.0 (i.e., YES on Kalshi + NO on Polymarket < $1, or vice versa), with the gap exceeding combined fees and slippage. Exit is at market resolution, as both legs resolve simultaneously on the same underlying event.

Verification No verified P&L is available from repository metadata. The structural arbitrage logic is sound — identical underlying events priced differently across venues is a classic cross-venue arb. However, execution risk is real given API latency differences between platforms.

Implementation Notes Implemented in TypeScript. Requires API credentials for both Kalshi and Polymarket. The 15-minute market cadence creates frequent opportunities but also demands low-latency execution. Configurable gap thresholds allow tuning for fee sensitivity.

Risks The primary risk is leg execution failure — if one side fills and the other does not, the position is unhedged. Latency differences between platforms can cause the arb to close before both legs execute. Regulatory differences between Kalshi (CFTC-regulated) and Polymarket (crypto-native) may affect settlement timing. Liquidity on 15-minute markets may be insufficient for meaningful position sizes.