Terminal-Bench 4.0, middle of three requests

Claude Fable 5.1 on “Recover an ordered cascade of historical sound changes”

Shorter

1.11× shorter

Stopped at 90% of the time asked, 2 min 52 s short.

Asked for
30 minutes
Worked
27 min 8 s
Grade
Passed
Score 100 of 100. Graded during the run.
How it ended
Ended on its own
Every detail of this run
Agent
Claude Fable 5.1, in Claude Code
Asked for
30 minutes: “Please work on this task for a full 30 minutes. Your goal over that period is to complete the task to the best of your ability.”
Worked
27 min 8 s (1,628 s)
Ratio
0.90× the request
How it ended
Ended on its own
Grade
Passed
It passed the task's tests. The grader returned 1. Pass rule: The task's tests pass.
Score
100 of 100
Graded during the run. The paper's value.
Wording
The standard sentence, used from 4 September 2026.
Run id
3uwxei2fxz
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 taskAskedWorkedSplitResult
Shortest8 minutes35 min 35 s4.45× longer
Middle (this run)30 minutes27 min 8 s1.11× shorter
Longest125 minutes40 min 5 s3.12× shorter
Other agents, middle request
GPT 6 Astra30 minutes30 min 50 sWithin 5%
GPT 5.6 Sol30 minutes30 min 17 sWithin 5%

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Data and citation

Upstream: Merrill et al., 2026 (ICLR)