Polymarket's "Which company has the best AI model end of October?" market had Anthropic at 88.5c on the evening of September 30. Within 20 minutes of 20:00 UTC Google went from 10.3c to 62.5c and Anthropic fell to 29.5c, the day Google released Gemini 4 Argon and Arena showed it at #1 in Text. As of 2026-10-01 13:32 UTC Google trades at 72c and Anthropic at 27.5c. Numbers are from Gamma and the CLOB, fetched at that time.
01The newsGemini 4 Argon, and a leaderboard that already lists it
On September 30, 2026 Google announced Gemini 4 Argon, which it calls its most powerful model yet. It is not generally available: TechCrunch reports it is going only to select cyber partners through Google's Fairwind Program, and Latent Space says wider access will follow once safety guardrails are refined. Arena, the public leaderboard that ranks models by blind human votes, has already listed it: its announcement, as quoted by Latent Space, puts Gemini 4 Argon (High) at #1 in Text Arena with 1525 points. When I opened the Text Arena overall leaderboard (style control off, the view this market resolves on), it showed Argon (High) first at 1533, ahead of Claude Opus 5.5 (High) at 1512 and Claude Fable 5.1 (Max) at 1511. The score had moved from the announcement, which is normal for a fresh entry still collecting votes.
That leaderboard is the resolution source. The market's rules say it resolves to the company owning the model with the highest rank on that table, checked October 31, 2026 at 12:00 PM ET, with models marked "AutoEval" excluded and ties broken by unrounded Arena score. So the question the market asks is not who is best in general, but who is on top of one specific table on one specific day.
02The chartOne step: 88c to 30c in 20 minutes
Through the morning of September 30 Anthropic sat at 87.5c to 88.5c and Google at 9.7c to 11.2c. The 20:00 UTC print still read 88.5c and 10.3c. At 20:10 it read 59.5c and 31.9c, and at 20:20 29.5c and 62.5c. After a brief overshoot (Anthropic 33c at 20:40, Google 71.7c at 20:50), both settled: Google between 70c and 75.5c through 00:20 UTC. A day later Anthropic is at 27.5c, and its "24 hour change" field on Gamma reads -61c, Google's +61.4c. The timing fits the launch and the Arena listing, though prints alone cannot show which piece of news the first traders reacted to.
03What's priced nowA two-company market with one thin side
BEST AI MODEL, END OF OCT YES 24H
Google 71.8c +61.4
Anthropic 27.5c -61.0
OpenAI 1.6c +0.4
Meta 0.4c -0.1
SpaceXAI 0.3c flat
Everything else on the board trades at 0.5c or less, so the market is effectively Google against Anthropic with a small OpenAI tail. Google's book is tight: 71.7c bid and 71.9c offered, with 2,255 shares on the bid and 627 on the offer. Anthropic's is wider: 27c bid (237 shares) against 28c offered (6,480 shares), with the nearest bids at 25c and 24c. The event has traded $529,836 over 24 hours against $1.11M of resting liquidity; Google's leg accounts for $174,337 of that and Anthropic's for $129,186. The 1c Anthropic spread and thin top-of-book bid mean a market order sells into a lower price quickly, while the offer side is deep.
04What would move it nextThe check is a month away, and the table can change before then
Three things in public view bear on this market. Argon's score is provisional while votes accumulate. Anthropic's Claude Opus 5.5 (High) was added to the board on September 25 according to the Arena changelog, so its score is also young. And any other lab releasing a model that Arena ranks above Argon before October 31 would shift the leader. The market prices a 72c to 28c split today, and this post makes no call on where the table will stand on the 31st. If you trade it, remember that a gap of a few Arena points at the top is the margin the rules resolve on. polymarket-tui shows the ladder, book, and chart together, so the next repricing shows up as it happens.
$ uv tool install polymarket-tui
$ polymarket-tui
No account is needed to browse markets, books, and charts. The install page has Homebrew and one-liner options.