Terminal-Bench 4.0, middle of three requests

GPT 5.6 Sol on “Recover an ordered cascade of historical sound changes”

Within 5%

Worked 101% of the time asked, within 5% of it.

Asked

Worked

Safety cutoff 4 h 10 min, off the scale

Every detail of this run

Agent: GPT 5.6 Sol, in Codex
Benchmark: Terminal-Bench 4.0
Task: Recover an ordered cascade of historical sound changes
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: 30 min 17 s (1,817 s)
Ratio: 1.01× the request
How it ended: Ending not labelled yet
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: eml5z6pq5r
Data release: 26 Sep 2026

The other requests for GPT 5.6 Sol on this task, and the other agents at this request
Sol on this task	Asked	Worked	Result
Shortest	8 minutes	33 min 8 s	4.14× longer
Middle (this run)	30 minutes	30 min 17 s	Within 5%
Longest	125 minutes	2 h 6 min	Within 5%
Other agents, middle request
GPT 6 Astra	30 minutes	30 min 50 s	Within 5%
Claude Fable 5.1	30 minutes	27 min 8 s	1.11× shorter

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Data and citation