YC-Bench, longest of three requests

Claude Fable 5.1 on “Run the current one-year startup simulation, official seed 2”

Shorter

1.33× shorter

Stopped at 75% of the time asked, 31 min 17 s 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 2
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: 1 h 34 min (5,623 s)
Ratio: 0.75× the request
How it ended: Ended on its own
Grade: 2509548.79; Final company funds in US dollars, starting from $200,000 (negative if the company goes bankrupt). No official pass rule.
Score: Final funds $2,509,548.79; Graded afterwards. The paper's value.
Wording: The standard sentence, used from 4 September 2026.
Run id: zbrcnfpwpc
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	1 h 8 min	8.45× longer
Middle	30 minutes	22 min 41 s	1.32× shorter
Longest (this run)	125 minutes	1 h 34 min	1.33× shorter
Other agents, longest request
GPT 6 Astra	125 minutes	11 min 4 s	11.30× shorter
GPT 5.6 Sol	125 minutes	23 min 32 s	5.31× shorter

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