This market will resolve to the highest METR 50% time horizon for any AI model released by 

, closing after a two-month buffer period. Left bounds inclusive, right bounds exclusive.

50% time horizon is, roughly speaking, the time that skilled humans take to complete tasks that an AI system can successfully do 50% of the time. See 

Measuring AI Ability to Complete Long Tasks"

for more. As of August 2025, the longest 50% time horizon is GPT-5's 2h 17 min.

For reference, the buckets in this market correspond to doubling times of roughly:

given that GPT-5 has a time horizon of 2.28 hours and was released in early August 2025.

Time horizon estimates will vary based on the set of tasks used, so this market will be based on the "headline" result reported by METR. METR currently uses a composite of the HCAST, RE-Bench, and SWAA benchmarks. There is a good chance that they extend this set with harder/longer tasks at some point.  If METR no longer publishes a headline result, and their future evals are based on substantially different benchmarks so that it is difficult to compare to their mid-2025 estimates, then this market may become ambiguous and resolve N/A.