Arbitrage
Prediction market arbitrage bots
Arbitrage bots that trade Kalshi vs Polymarket spreads, reviewed on strategy, fee handling, maintenance and what breaks in live trading.
Checked September 8, 2026 · every price read off the live site
Every arbitrage bot
3 reviewed · alphabetical-
Kairos Cross-venue trading terminal: Kalshi, Polymarket and Predict.fun in one order book, with sub-second data and advanced order types.
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08prediction-market-arbitrage-bot Captured real 1.5 to 4.5% spreads, and the author's writeup is the best free education in the category: risk-free is theory, prices move between your two API calls.
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| Bot | Venues | Pricing | Type |
|---|---|---|---|
| prediction-market-arbitrage-bot | Polymarket, Kalshi | Open source (MIT) | bot |
| polymarket-arbitrage | Polymarket, Kalshi | Open source. | bot |
| BTC hourly arb detector | Polymarket, Kalshi | Open source (MIT) | dashboard |
How these bots work
Arbitrage bots look for two kinds of gap. Inside one venue, YES plus NO asks below $1.00 (bundle arb). Across venues, YES on Polymarket plus NO on Kalshi for the same event below $1.00 (synthetic or cross-platform arb). Both are simple to detect and hard to capture.
The open-source entries are honest about it. realfishsam's README says it ignores fees and slippage; ImMike's says real markets are efficient and its win-rate screenshot is simulated; CarlosIbCu's compares different strikes and calls the result risk-free, which it is not between the strikes.
The unsolved problems are the same in every repo: matching markets that resolve on the same source, paying two spreads to capture a one-cent edge, and price movement between the two API calls.
How to choose
- Fee modeling on both legs, including Kalshi's taker fee and Polymarket's spread, before the opportunity is called positive.
- Strict market matching or a manual pair, not fuzzy text similarity at a 0.6 threshold.
- Execution mode: detection only (you click), market orders on both legs, or resting limits. Each has a different failure when one leg fills.
- Orphaned-leg handling: what happens when leg one fills and leg two does not.
- Push date. The three inventory entries here were last pushed in December 2025, January 2026 and May 2026.
Questions about arbitrage bots
Is Polymarket Kalshi arbitrage still possible?
Gaps appear and the detectors here find them. Every README in the category says they are rare and thin after fees, and none publishes live captured spreads.
What is the best open-source prediction market arbitrage bot?
ImMike's polymarket-arbitrage has the most stars (274) and the fullest structure; it is unmaintained. realfishsam's bot is the smallest readable example, built on PMXT. DRADIS and CloddsBot include arbitrage inside larger engines.
Is prediction market arbitrage risk-free?
Only when both legs resolve on the same question, source and strike, and the two fills both happen at the quoted prices. The BTC hourly detector compares different strikes, and cross-venue pairs settle under different rules.
Bots die in execution. Terminals are execution.
Wanted a bot for speed and cross-venue vision? The free Kairos terminal trades Kalshi, Polymarket and Predict.fun from one book, no keys to manage.