PostTrainBench v1.1, longest of three requests

Claude Fable 5.1 on “Post-train Qwen3-1.7B-Base for GSM8K”

Shorter

1.38× shorter

Stopped at 72% of the time asked, 8 h 20 min short.

Asked

Worked

Safety cutoff 60 h, off the scale

Asked for: 30 hours
Worked: 21 h 40 min
Grade: Grading…; The run's output is saved, but grading it needs GPU time for the benchmark's judge or evaluation, which has not run yet.
How it ended: Ending not labelled yet

Every detail of this run

Agent: Claude Fable 5.1, in Claude Code
Benchmark: PostTrainBench v1.1
Task: Post-train Qwen3-1.7B-Base for GSM8K
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: 21 h 40 min (77,982 s)
Ratio: 0.72× the request
How it ended: Ending not labelled yet
Grade: Grading…; The run's output is saved, but grading it needs GPU time for the benchmark's judge or evaluation, which has not run yet.
Wording: The standard sentence, used from 4 September 2026.
Run id: 72hytp57vd
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	13 min 43 s	8.75× shorter
Middle	8 hours	54 min 48 s	8.76× shorter
Longest (this run)	30 hours	21 h 40 min	1.38× shorter
Other agents, longest request
GPT 6 Astra	30 hours	30 h 1 min	Within 5%
GPT 5.6 Sol	30 hours	12 h 55 min	2.32× shorter

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Read before quoting. How this run ended has not been labelled yet. It is timed like every other run and counted in every number. Details

Data and citation