Polymarket vs. Kalshi
Compare markets
See where the two biggest prediction markets disagree. Pick any two markets, or start from the biggest gaps below: prices, volume, history and the resolution rules, side by side.
Will OpenAI have the best AI model at the end of October 2026?
Vol $6.6K today · $414K total
Kalshi is 49 points higher than Polymarket (50% vs 1%). Polymarket trades about 406.9× more volume today, so its price has more money behind it. They resolve on different dates (Dec 31 vs Oct 31), so they may not be exactly the same bet.
History starts when we first saw each market, so a newly added market has a short line.
| Kalshi | Polymarket | |
|---|---|---|
| Probability (Yes) | 50% | 1% |
| Change (24h) | +25.5 pt | +0.0 pt |
| Volume today | $16 | $6.6K |
| Total volume | $415 | $414K |
| Liquidity | — | $53K |
| Open interest | $365 | — |
| Resolves | 39mo | 9d |
| Tracked for | 13 days | 10 days |
Resolution rules: read both before trusting a gap
Kalshi
If Google has the highest-ranked AI model on the applicable index at 10:00 AM ET on Dec 31, 2029, then the market resolves to Yes.
Polymarket
This market will resolve according to the company which owns the model which has the highest arena rank based on the arena.ai Text Arena (Overall) when the table under the "Leaderboard" tab is checked on October 31, 2026, 12:00 PM ET. Results from the "Rank" column under the "Text Arena | Overall" Leaderboard tab at https://arena.ai/leaderboard/text/overall-no-style-control with style control off (Adjustments: None) and filtered for "Models" will be used to resolve this market. Note: Models marked “AutoEval” at the applicable check time will not be considered, regardless of whether they display a rank or score. Models will be ordered primarily by their leaderboard rank at the market’s check time. If two or more models are tied on rank, they will be ordered by their Arena score, including any underlying, unrounded, granular values reflected in the data below the leaderboard. If a tie still remains, alphabetical order of company names as listed in this market group will be used as a final tiebreaker (e.g., if the two models are tied by exact arena score, “Google” would be ranked ahead of “SpaceXAI”). This market will resolve based on the company that occupies first place under this ranking. The resolution source for this market is the arena.ai Text Arena (Overall). If this resolution source is unavailable at check time, this market will remain open until the leaderboard come…
Share this comparison
Informational only — not financial advice. Odds are mirrored from each platform and may lag the live order book.