Concept · liquidity-and-trading

Cross-Platform Arbitrage

Quick definition. Trading the same event across different prediction-market platforms to profit from price discrepancies. In practice it's rarely risk-free because different platforms resolve the "same" event under different rules and oracles, leaving residual basis risk.

Key insights

Lotus: same contract priced at 58–67 cents on different platforms simultaneously. Cross-venue fragmentation is its own asset, and conventional MMing fails partly because of it.
Kunal Doshi (Kalshi vs. FanDuel): in-game prices correlate at 0.99+ with FanDuel; Kalshi monthly volume grew 80× to $14.4B in March 2026 (NCAA March Madness alone = $3.3B). But Kalshi taker fees up to 3.5% at midpoint and 76% in-game depth decline vs. pre-game currently limit institutional execution. Valuation comp: Kalshi $20B as exchange vs. sportsbooks at 2–4× revenue.
Pantera/Sui's NFL dataset (282 games, Sep 2025–Jan 2026) gave concrete numbers to cross-platform arb potential: Kalshi $1.3B notional vs. Polymarket $359M for the same games; Kalshi leads in 80% of large moves with median 7-second lead; but Polymarket has 3-4× more concentrated liquidity by Kyle-λ. The arb opportunity is in the latency gap and the depth differential.
st1ne identifies five MEV-style edges, one of which is cross-platform conditional probability arbitrage across correlated markets. Polymarket is "a hidden MEV playground."
Saguillo et al.: ~$40M extracted from Polymarket via single-market and cross-related-market arbs, identified via blockchain tx analysis. Two distinct types: Market Rebalancing Arbitrage (within a market when YES+NO < $1) and Combinatorial Arbitrage (across topically related markets). Their analysis required heuristic reductions to bring the O(2^(n+m)) comparison down to feasible.
Hall & Paschal's overlap data: only 70 of 131 (53%) resolved US elections appeared on both Kalshi and Polymarket, and overlap drops to 18% among 1,826 active electoral events. Cross-platform arb is structurally constrained because the same event simply isn't listed on both venues most of the time. They explicitly call for an ISDA-equivalent for PM contract definitions.
Sethi ("Information Contagion"): the 15-minute spike in oil/stock futures preceding Trump's March 24, 2026 Iran-negotiations tweet shows arbitrage across PM and traditional venues · quant funds extracted the signal from Polymarket and acted in regulated derivatives, profiting without breaking any law. This is the most consequential form of cross-platform arb because it routes around KYC.
Mike's risk-instruments piece: cross-platform composability is live via Gondor (lending against PM positions) and DFlow (tokenizing Kalshi contracts as SPL tokens). Liquidity fragmentation, execution risk, UX are barriers.
Nekt0 lists cross-platform arb as one of eight strategies, with dollar examples and specific risk factors.
Cryptonomads: most PM terminals fail at execution; the cross-platform layer is exactly where institutional API rails win.
The implicit thesis across these pieces: the same event being available on Kalshi (regulated, KYC) and Polymarket (offshore, pseudonymous) is the largest single source of structural arbitrage in the asset class · and information contagion across this boundary (Sethi) is what regulators are now watching.
michaellwy: each Polymarket↔Kalshi pair is fundamentally non-fungible because of different referee systems. "Identical" contracts on Polymarket (UMA oracle) and Kalshi (CFTC-designated contract market) can resolve differently · eliminating the "risk-free" element of arbitrage in many cases.

In their words

The same contract at 58-67 cents on different platforms.· Lotus

In-game prices correlate at 0.99+ with FanDuel.· Kunal Doshi

Information flows freely across platforms even when regulatory frameworks differ.· Rajiv Sethi

Only 70 of 131 resolved elections appeared on both platforms; among 1,826 active electoral events, overlap drops to 18%.· Hall & Paschal

Where it matters

Cross-platform arbitrage is what makes the multi-venue prediction-market world behave like a single market · without it, Polymarket and Kalshi quotes could drift indefinitely. But the arbitrage is bounded by capital lock-up (positions don't settle until resolution), oracle divergence (Kalshi's CFTC settlement vs. UMA on Polymarket can differ), and KYC frictions (the same trader cannot always access both venues legally). Every "meta-pool" or "unified PM liquidity" proposal in 2026 is effectively an attempt to internalize cross-platform arbitrage on behalf of the network.

Connections

Arbitrage · the parent concept.
Liquidity fragmentation · what creates the cross-platform spread.
Resolution criteria / oracle design · what limits "risk-free."
Time arbitrage / orderflow arbitrage · co-located strategies.
Execution quality · what arbitrageurs sell as a service to slower flow.
Platform competition · the meta-game.

Platforms linked to this concept

Kalshi · affected-by · Kalshi–Polymarket cross-platform arb
Polymarket · affected-by · Polymarket–Kalshi cross-platform arb
DFlow Prediction Markets API · implements · Mentioned in Cross-Platform Arbitrage content as an implementing platform
FanDuel Predicts · implements · Mentioned in Cross-Platform Arbitrage content as an implementing platform

Related concepts

Sources

Why Every Prediction-Market Terminal Will Fail (and the Two That Won't) · cryptonomads · Apr 27, 2026
Market Making In PMs Sucks · Lotus · Apr 21, 2026
From Betting to Trading: How Kalshi Is Reshaping Sports Markets · Kunal Doshi · Apr 16, 2026
Polymarket Is a Hidden MEV Playground. Most Traders Have No Idea. · st1ne · Mar 13, 2026
How Prediction Markets Turn Into Risk Instruments · Mike · Feb 9, 2026
All Types of Arbitrage on Prediction Markets · Nekt0 · Feb 5, 2026
Unravelling the Probabilistic Forest: Arbitrage in Prediction Markets · Saguillo, Ghafouri, Kiffer, Suarez-Tangil · Aug 5, 2025

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