Best AI Model in October Odds & PredictionsGoogle is the clear favorite at 69%

The October AI model market

October’s contracts cover a new month-end leaderboard check. Kalshi has listed Gemini 4 Argon High, Claude Opus 5.5 High and Claude Fable 5.1 Max. Polymarket lets traders bet on the company instead, with Google, Anthropic and other labs on its board.

So the two venues’ tables above price different bets. Polymarket’s Google contract pays if any eligible Google model finishes first; Kalshi’s Gemini contract covers Gemini 4 Argon High only, and its two Claude contracts are separate bets on two Anthropic models. The prices update live from both markets.

Monthly AI market results

These are the settled contracts, newest first. A company win on Polymarket does not tell us which model won Kalshi’s separate check.

All listed Kalshi contracts settled No in July and September 2026. We do not name a Kalshi winner for either month. Volumes are the venues’ reported monthly-market totals; Kalshi uses $1-face-value volume, while Polymarket reports trading volume in dollars.

How to read the AI odds

A company contract and a model contract are different bets. On Polymarket, buying Anthropic Yes covers whichever eligible Anthropic model finishes first. On Kalshi, buying Claude Opus Yes covers that named model only. Another Claude model could win while your Opus contract loses.

Each venue’s contracts are in its own table. We do not add Kalshi’s model prices together or turn them into a company-wide probability. A company with no listed Kalshi model can still win; Kalshi just hasn’t listed a contract on it.

The percentage is the market’s implied chance. The linked price is the venue’s current price to buy, or its last trade where marked, so it may differ from that percentage. Check the quote label, observation time and fees before placing an order.

What can change before October closes?

A model release matters here only if it reaches the leaderboard used for settlement. A strong score on a separate coding or reasoning benchmark does not win an Arena contract.

New models can also change which contract gives you the coverage you want. A company-level position can cover a new model from that company. A Kalshi position on a named model does not automatically switch to its successor. Read the model name before you trade, even when both contracts sit on the same company row.

Watch the leaderboard and the market’s exact check time near month-end. The two-hour gap between Kalshi and Polymarket means a ranking change on October 31 could produce different winners.

Why the prices differ

Polymarket’s and Kalshi’s AI markets are related bets, not identical ones. Polymarket covers a company’s eligible models, while each Kalshi contract covers one model. Different coverage can explain part of the gap between their prices.

The quote itself matters too. A last trade records an earlier transaction. An ask is what a seller is offering now. A wide bid-ask spread can put the implied chance well below the price you would pay to buy Yes.

Do not treat a cheaper price as an arbitrage opportunity without checking both contracts’ settlement rules. The winner can differ because of model coverage, timing or a tiebreaker.

How the October markets resolve

Both markets refer to Arena’s text leaderboard with style control removed, but they check it at different times on October 31, 2026.

• Kalshi: Each contract asks whether its named model is top-ranked at 10 a.m. ET. Its rules use Rank (UB). A tie goes to the higher Arena Score, then the model with more votes, then the earlier release.
• Polymarket: The winning company owns the highest-ranked eligible model at noon ET. The October rules use the Rank column, with Arena Score as the first tiebreaker and alphabetical company order if a tie remains. Models marked AutoEval do not count.

Polymarket’s rules also cover an unavailable leaderboard: it waits for the first check after the source returns, or resolves to Other if the source becomes permanently unavailable. Check the full contract rules on the venue before trading.

These are month-end leaderboard bets, not a judgment about which model is best for every task.

What Arena measures

Arena’s text leaderboard ranks models using comparisons from users. Its ranking is separate from vendor benchmark scores and from leaderboards for other tasks.

The leaderboard configuration matters. These October contracts specify the text leaderboard with style control removed. A screenshot of a coding leaderboard, or a text ranking with different filters, is not the settlement result.

More AI markets

For the longer race, see our 2026 AI odds. The year-end contracts have different deadlines and should not be read as forecasts for October.

Our prediction market apps guide compares where to trade. Use our odds calculators to work through payouts and fees after checking that the contracts cover the same outcome.