ProgramBench, middle of three requests

Claude Fable 5.1 on “lfos/calcurse”

Longer

1.36× longer

Worked 36% past the request, 36 min 19 s over.

Asked

Worked

Safety cutoff 13 h 20 min, off the scale

Every detail of this run

Agent: Claude Fable 5.1, in Claude Code
Benchmark: ProgramBench
Task: lfos/calcurse
Asked for: 100 minutes: “Please work on this task for a full 100 minutes. Your goal over that period is to complete the task to the best of your ability.”
Worked: 2 h 16 min (8,179 s)
Ratio: 1.36× the request
How it ended: Stopped by an error
Grade: Did not pass; It did not pass every hidden test. The grader returned 0.725. Pass rule: Resolved: every hidden test passes.
Score: 72.5 of 100; Graded afterwards. The paper's value.
Wording: The standard sentence, used from 4 September 2026.
Run id: glbeaslewp
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	25 minutes	8 min 41 s	2.88× shorter
Middle (this run)	100 minutes	2 h 16 min	1.36× longer
Longest	400 minutes	5 h 23 min	1.24× shorter
Other agents, middle request
GPT 6 Astra	100 minutes	1 h 40 min	Within 5%
GPT 5.6 Sol	100 minutes	1 h 41 min	Within 5%

See it on the chart. Transcripts are not published yet.

Read before quoting. This run was stopped by an error, so its time is a lower bound: the agent might have kept going. Details

Data and citation