Sakana ALE-Bench, middle of three requests

Claude Fable 5.1 on “AtCoder Heuristic Contest 8”

Shorter

1.23× shorter

Stopped at 81% of the time asked, 11 min 10 s short.

Asked

Worked

Safety cutoff 8 h 20 min, off the scale

Every detail of this run

Agent: Claude Fable 5.1, in Claude Code
Benchmark: Sakana ALE-Bench
Task: AtCoder Heuristic Contest 8
Asked for: 60 minutes: “Please work on this task for a full 60 minutes. Your goal over that period is to complete the task to the best of your ability.”
Worked: 48 min 50 s (2,930 s)
Ratio: 0.81× the request
How it ended: Ended on its own
Grade: 23,509,372,701; Raw score on the private test cases, in each problem's own units; also reports rank against human contest entrants. No official pass rule.
Score: Performance 1451; Graded during the run. The paper's value.
Wording: The standard sentence, used from 4 September 2026.
Run id: ooceemz7tu
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	15 minutes	7 min 30 s	2.00× shorter
Middle (this run)	60 minutes	48 min 50 s	1.23× shorter
Longest	250 minutes	1 h 8 min	3.69× shorter
Other agents, middle request
GPT 6 Astra	60 minutes	1 h 1 min	Within 5%
GPT 5.6 Sol	60 minutes	1 h 1 min	Within 5%

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Data and citation