https://twitter.com/colin_fraser/status/1632598168499277824?s=20

Player 1 picks a number between 1 and 10, and then Player 2 picks one, then the players go back and forth and keep track of the running total. Whoever picks a number that brings the total to at least 30 wins.

And P1 wins. Note that P2's choice of 3 was a blunder, as they could have instantly won by selecting 8 or higher. As of right now, GPT3.5, and GPT4 (as best as I can tell via Bing) are terrible at this game, and make unforced blunders essentially every time. Here's an example:

While technically this game is a forced win for P1 (8, 1, 10, 1, 10), GPT does not even come close to optimal play. In this example, it fails to take advantage of an immediate win by choosing 8+ when the running total is 22.

When GPT-5 is released, I will test it as soon as I have access using the same prompt in the screenshot above. For each of my turns, I will 

randomly generate a number uniformly 1-10 inclusive

If out of 20 trial games, GPT-5 takes advantage of at least 90% of "immediate wins" (situations where it could immediately win the game with the right numer), this market resolves YES. Otherwise, it resolves NO.

This is not a challenge market. I won't be cleverly changing the prompting or hinting at strategies to suggest certain behaviors, just directly testing in the same format as the screenshot above.