PaperBench, middle of three requests

Claude Fable 5.1 on “FRE”

Shorter

3.16× shorter

Stopped at 32% of the time asked, 27 min 21 s short.

Asked

Worked

Safety cutoff 5 h, off the scale

Every detail of this run

Agent: Claude Fable 5.1, in Claude Code
Benchmark: PaperBench
Task: FRE
Asked for: 40 minutes: “Please work on this task for a full 40 minutes. Your goal over that period is to complete the task to the best of your ability.”
Worked: 12 min 39 s (759 s)
Ratio: 0.32× the request
How it ended: Ending not labelled yet
Grade: 0.353; Replication score: a weighted rubric of pass/fail leaf checks, 0 to 1, after a full reproduction attempt. No official pass rule.
Score: 35.3 of 100; Judged afterwards. The paper's value.
Wording: The standard sentence, used from 4 September 2026.
Run id: cz4bxpw3te
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	10 minutes	5 min 1 s	1.99× shorter
Middle (this run)	40 minutes	12 min 39 s	3.16× shorter
Longest	150 minutes	42 min 3 s	3.57× shorter
Other agents, middle request
GPT 6 Astra	40 minutes	41 min 39 s	Within 5%
GPT 5.6 Sol	40 minutes	27 min 36 s	1.45× shorter

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Data and citation