METR public tasks, longest of three requests

Claude Fable 5.1 on “Build an efficient AI for the novel Cowthello board game”

Shorter

3.56× shorter

Stopped at 28% of the time asked, 21 h 34 min short.

Asked

Worked

Safety cutoff 60 h, off the scale

Every detail of this run

Agent: Claude Fable 5.1, in Claude Code
Benchmark: METR public tasks
Task: Build an efficient AI for the novel Cowthello board game
Asked for: 30 hours: “Please work on this task for a full 30 hours. Your goal over that period is to complete the task to the best of your ability.”
Worked: 8 h 26 min (30,372 s)
Ratio: 0.28× the request
How it ended: Ended on its own
Grade: 1; Cowthello: win rate against 3 bots, divided by a 70% target and capped at 1. Complex Payments: share of held-out feature tests passed. No official pass rule.
Score: 100 of 100; Graded during the run. The paper's value.
Wording: The standard sentence, used from 4 September 2026.
Run id: immdbkvypt
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	2 hours	37 min 28 s	3.20× shorter
Middle	8 hours	3 h 21 min	2.39× shorter
Longest (this run)	30 hours	8 h 26 min	3.56× shorter
Other agents, longest request
GPT 6 Astra	30 hours	30 h 1 min	Within 5%
GPT 5.6 Sol	30 hours	6 h 7 min	4.90× shorter

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