Arbitrage Agent vs Rainmaker

What Arbitrage Agent does

Arbitrage scanner for the same event on Kalshi and Polymarket. It pairs markets that ask the same question in different words — with OpenAI embeddings and a reranker that compares resolution rules — recomputes the spread on every Polymarket price change and a continuous Kalshi poll, and lists the pairs that still pay after both venues' fees, each with a step-by-step guide to placing the two legs yourself. Nothing trades for you yet: automated execution of both legs with a circuit breaker is “in final testing” and promised to the higher plan first. Its public proof page is unusually frank about the size of the edge — a median of 0.79% per opportunity, worth a median $0.25 at the depth the order books allow, with capital locked for a median 88 days. Plans are $29 a month for the feed and $99 for alerts and future automation.

• Cross-venue matching of differently worded markets, by embeddings plus a reranker and a diff of resolution criteria
• Spreads re-evaluated on each Polymarket price change; Kalshi polled continuously
• Every edge shown after both venues' fees, with a guide giving both legs and their prices
• Dry-run P&L and mark-to-market on open positions
• Public proof page with live medians of edge, realisable profit, days to resolution and pair turnover

• Cross-venue arbitrage locks in a small, known return and ties the capital up until the market resolves, and the vendor's own numbers say how small. On the proof page on Oct 31, 2026, 409 opportunities over 24 hours across 15 market pairs had a median net edge of 0.79% and a best of 1.85%; at the depth the thinner order book could absorb, the median opportunity was worth $0.25 and the best $16.04, and the median pair resolves in 88 days. The page works that out to about 3.3% a year for a customer who takes everything, and shows 30 days of dry-run profit of $0.43. The landing page's terminal, with a $48k bankroll and a 100% win rate, is labelled simulated.
• The weak point of any such tool is the match: two markets that look alike can resolve on different rules. The site says every pair is validated before it goes live, but the same proof page reports matcher precision from human review as 0 approved and 0 blocklisted, so treat each pair's resolution wording as yours to check before placing both legs.
• Today it is a paid signal feed: you place both legs by hand, on accounts you hold on both venues, and your money stays there. When automated execution ships it will need API keys with trading rights on both — an RSA key on Kalshi and a signing key on Polymarket — which changes the custody picture; the site says neither can withdraw. A blackjack pop-up offers 20% off for a winning hand and asks for an email to play again.