CORE-Bench v1.1, longest of three requests

Claude Fable 5.1 on “Reproduce a rockshelter chronology and archaeological materials analysis”

Shorter

6.05× shorter

Stopped at 17% of the time asked, 2 h 5 min short.

Asked

Worked

Safety cutoff 5 h, off the scale

Every detail of this run

Agent: Claude Fable 5.1, in Claude Code
Benchmark: CORE-Bench v1.1
Task: Reproduce a rockshelter chronology and archaeological materials analysis
Asked for: 150 minutes: “Please work on this task for a full 150 minutes. Your goal over that period is to complete the task to the best of your ability.”
Worked: 24 min 48 s (1,488 s)
Ratio: 0.17× the request
How it ended: Ended on its own
Grade: Did not pass; It did not get every answer right. The grader returned 0. Pass rule: Every answer correct, with numbers inside a 95% prediction interval.
Score: 0 of 100; Graded during the run. The paper's value.
Wording: The standard sentence, used from 4 September 2026.
Run id: ogyvry6z5s
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	15 min 47 s	1.58× longer
Middle	40 minutes	17 min 27 s	2.29× shorter
Longest (this run)	150 minutes	24 min 48 s	6.05× shorter
Other agents, longest request
GPT 6 Astra	150 minutes	2 h 31 min	Within 5%
GPT 5.6 Sol	150 minutes	15 min 24 s	9.74× shorter

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Data and citation