Which company has the best AI model end of September?

Platform comparison

Market context

The Arena.ai Text leaderboard will determine which company owns the highest-ranked model on 30 September 2026, with the current crowd assessment heavily favouring a decisive outcome. The 89% implied probability reflects confidence that a single company's model will maintain clear separation atop the rankings through the settlement window, though the leaderboard remains fluid as developers iterate rapidly on their systems.

Historical precedent suggests such dominance claims require sustained technical advantage rather than momentary leadership. OpenAI held consistent leaderboard superiority throughout 2024 and into 2025, but competitive pressure from Anthropic, Google DeepMind, and others has narrowed gaps on standardised benchmarks. Previous prediction markets on model capability have resolved with the frontrunner holding position when measurement dates arrived, though margin compression has been the trend—suggesting the current 89% may reflect either genuine technical separation or market uncertainty being compressed into a single direction.

Traders should monitor announcement schedules from major labs through Q3 2026, particularly any model releases or capability demonstrations in August and early September that could shift leaderboard rankings in the final weeks. Recent patterns show that new model versions can substantially alter Arena rankings within days of deployment. The specific methodology matters here: the market uses the "Overall" category with style control disabled, which emphasises raw performance over stylistic preferences, potentially favouring models optimised for benchmark performance rather than user experience refinement. Any clarifications from Arena.ai regarding leaderboard calculation methods or methodology changes would warrant reassessment of current probabilities.

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). That keeps the comparison honest — a single canonical probability across the row, with the venue-by-venue trade-offs spelt out in the columns next to it.

Resolution & payout

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

UK Frequently Asked Questions

Where can I trade this market with the lowest fees?

Polymarket is geo-blocked in the US/UK/EU. The easiest 0%-fee broker into the same order book is Prediction Today. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

Is Polymarket legal in the UK?

Polymarket is accessible to UK traders but is not UKGC-licensed. It operates under US CFTC jurisdiction. UK residents face no domestic legal prohibition on using it, but UKGC consumer protections do not apply. For UKGC-regulated alternatives, Betfair Exchange and Smarkets offer similar prediction-style markets.

Do I pay tax on prediction market profits in the UK?

UKGC-licensed platform profits (Betfair, Smarkets) are typically tax-free gambling winnings for UK individuals. Polymarket profits involve USDC crypto transactions, which HMRC treats as Capital Gains Tax events. Keep full transaction records and report via Self Assessment if gains exceed £3,000 per tax year.

How do I deposit on Polymarket from the UK?

UK traders typically fund Polymarket via Coinbase UK, Kraken or Revolut — buying USDC with GBP and transferring to a Polygon-compatible wallet (MetaMask, Coinbase Wallet). Polymarket's onboarding walks you through the bridging process. Typical GBP-to-USDC conversion costs 0.5–1%.