TUA-Bench, longest of three requests

Claude Fable 5.1 on “Optimize cold plate”

Shorter

2.80× shorter

Stopped at 36% of the time asked, 1 h 4 min short.

Asked

Worked

Safety cutoff 3 h 20 min, off the scale

Every detail of this run

Agent: Claude Fable 5.1, in Claude Code
Benchmark: TUA-Bench
Task: Optimize cold plate
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: 35 min 45 s (2,145 s)
Ratio: 0.36× the request
How it ended: Ending not labelled yet
Grade: Passed; It completed the task in full. The grader returned 1. Pass rule: Full completion: a reward of 1 on the final state.
Score: 100 of 100; Graded afterwards. The paper's value.
Wording: The standard sentence, used from 4 September 2026.
Run id: 6roeym4uek
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	6 minutes	17 min 47 s	2.96× longer
Middle	25 minutes	28 min 9 s	1.13× longer
Longest (this run)	100 minutes	35 min 45 s	2.80× shorter
Other agents, longest request
GPT 6 Astra	100 minutes	1 h 41 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. 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