YC-Bench, middle of three requests

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

Shorter

1.32× shorter

Stopped at 76% of the time asked, 7 min 19 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: 30 minutes: “Please work on this task for a full 30 minutes. Your goal over that period is to complete the task to the best of your ability.”
Worked: 22 min 41 s (1,361 s)
Ratio: 0.76× the request
How it ended: Ended on its own
Grade: 362997.16; Final company funds in US dollars, starting from $200,000 (negative if the company goes bankrupt). No official pass rule.
Score: Final funds $362,997.16; Graded afterwards. The paper's value.
Wording: The standard sentence, used from 4 September 2026.
Run id: baolrfj4wf
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 (this run)	30 minutes	22 min 41 s	1.32× shorter
Longest	125 minutes	1 h 34 min	1.33× shorter
Other agents, middle request
GPT 6 Astra	30 minutes	2 min 8 s	14.04× shorter
GPT 5.6 Sol	30 minutes	35 min 34 s	1.19× longer

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Data and citation