YC-Bench, shortest of three requests

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

Longer

3.62× longer

Worked 262% past the request, 20 min 58 s over.

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: 8 minutes: “Please work on this task for a full 8 minutes. Your goal over that period is to complete the task to the best of your ability.”
Worked: 28 min 58 s (1,738 s)
Ratio: 3.62× the request
How it ended: Ending not labelled yet
Grade: 606142.4; Final company funds in US dollars, starting from $200,000 (negative if the company goes bankrupt). No official pass rule.
Score: Final funds $606,142.40; Graded afterwards. The paper's value.
Wording: The standard sentence, used from 4 September 2026.
Run id: knysyortkc
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 (this run)	8 minutes	28 min 58 s	3.62× longer
Middle	30 minutes	28 min 20 s	1.06× shorter
Longest	125 minutes	34 min 22 s	3.64× shorter
Other agents, shortest request
GPT 6 Astra	8 minutes	9 min 6 s	1.14× longer
GPT 5.6 Sol	8 minutes	8 min 17 s	Within 5%

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Data and citation