YC-Bench, longest of three requests

Claude Fable 5.1 on “Run the current one-year startup simulation, official seed 1”

Shorter

3.64× shorter

Stopped at 27% of the time asked, 1 h 31 min short.

Asked

Worked

Safety cutoff 4 h 10 min, off the scale

Every detail of this run

Agent: Claude Fable 5.1, in Claude Code
Benchmark: YC-Bench
Task: Run the current one-year startup simulation, official seed 1
Asked for: 125 minutes: “Please work on this task for a full 125 minutes. Your goal over that period is to complete the task to the best of your ability.”
Worked: 34 min 22 s (2,062 s)
Ratio: 0.27× the request
How it ended: Ended on its own
Grade: 540800.54; Final company funds in US dollars, starting from $200,000 (negative if the company goes bankrupt). No official pass rule.
Score: Final funds $540,800.54; Graded afterwards. The paper's value.
Wording: The standard sentence, used from 4 September 2026.
Run id: bfk2vyubre
Data release: 26 Sep 2026

The other requests for Claude Fable 5.1 on this task, and the other agents at this request
Fable on this task	Asked	Worked	Result
Shortest	8 minutes	28 min 58 s	3.62× longer
Middle	30 minutes	28 min 20 s	1.06× shorter
Longest (this run)	125 minutes	34 min 22 s	3.64× shorter
Other agents, longest request
GPT 6 Astra	125 minutes	15 min 51 s	7.89× shorter
GPT 5.6 Sol	125 minutes	35 min 7 s	3.56× shorter

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