I gave 7 AI models $10k each and made them bet on the World Cup. The cheapest one is winning. The most expensive is dead last.
Setup: seven frontier models (GPT-5.5, Claude Opus 4.8, Gemini 3.5 Flash, Grok 4.3, Mistral Medium, DeepSeek V4, Kimi K2.6). Each starts with $10k of paper money. Before every match the model goes into agent mode, reads the fixture, looks at the live Polymarket odds, and has to commit. It picks the markets, sizes its own bets, and defends its capital curve. It's a simulation, not betting advice.
Current standings (85 of 94 matches covered):
- Gemini 3.5 Flash - $18,675 (+86.7%) · 112W/61L
- Mistral Medium - $17,779 (+77.8%) · 117W/74L
- Kimi K2.6 - $16,482 (+64.8%) · 83W/50L
- Grok 4.3 - $16,163 (+61.6%) · 57W/28L
- DeepSeek V4 - $15,366 (+53.7%) · 102W/71L
- GPT-5.5 - $10,049 (+0.5%) · 89W/87L
- Claude Opus 4.8 - $8,066 (−19.3%) · 120W/78L
Two things I find interesting for this sub.
First, look at Claude's line. 120 wins, a 60.6% hit rate (the most winning bets of any model in the arena) and it's the only one with negative PNL. Meanwhile Grok has placed the fewest bets by far (85 settled, less than half of Claude's volume) and is up +61.6%.
Hit rate and EV telling opposite stories: Claude keeps taking short-priced favorites where the market is already efficient, wins often, collects scraps, and gives it all back on the misses. Grok bets rarely but apparently only when it sees an actual price discrepancy. Picking the winner is for fans, finding mispriced odds is for smart bettors.
Second, the ranking is completely uncorrelated with AI benchmarks. The two most capable models by any standard leaderboard (GPT-5.5 and Claude Opus) are the only two not beating the market. The cheapest model in the arena has nearly doubled its bankroll. "Decision-making under uncertainty with money on the line" is just a different leaderboard, and almost nobody measures it. That's where I find this experiment interesting.
Caveats: around 200 settled bets per model is not nothing but it's not enough to fully separate skill from variance. Claude was down -41% 3 days ago and has recovered half of that, so these gaps are noisy. Fills are against real Polymarket prices.
Everything is public. Each bet shows the model's full reasoning at time of entry, so you can judge the process independently of the outcome: worldcup.obside.com
Curious what you all think: is Claude's profile (high hit rate, negative EV) so far just favorite-longshot bias showing up in an LLM, or something else? And which model would you have picked before seeing the numbers? I picked Opus...
Happy to answer any question!