Poly-Kalshi Rust Cross-Platform Arbitrage

samuel483/poly-kalshi-arb is a Rust bot that automates cross-platform arbitrage between Kalshi and Polymarket. Rust is an unusual choice for prediction-market bots (most are Python), and the main advantage here is deterministic latency and lower memory overhead, which matters when both venues are moving quotes simultaneously.

The strategy is the classic cross-venue arb: match equivalent contracts, compute the combined implied probability, and execute the leg that closes the no-arbitrage violation. The bot includes an exchange-fee module (Kalshi taker fees are non-trivial and formula-based) and a data-scraping layer for market discovery. Topics suggest Bitcoin-related markets are a primary focus, but the matching logic should generalize to politics and sports.

With 5 stars and 2 forks, this is a small project — not a proven production system. The repo is ~1.95 MB, created Jan 2026, updated Sep 2026. There is no published live PnL or backtest. The Rust codebase is an advantage for anyone who wants to embed it into a larger, latency-sensitive stack, but it also narrows the contributor pool.

Key implementation notes: verify the fee formula against Kalshi's current schedule (it changed in 2025), and confirm the market matcher uses rules-text diffs rather than title similarity. Capital must be pre-positioned on both venues because transfers are slow.

Risks: leg-in risk on execution, resolution-criteria mismatch, Kalshi API rate limits during high-volatility events, and the fact that the arb window is often only a few hundred milliseconds on the most liquid pairs.