DeepSWE v1.1, longest of three requests

Claude Fable 5.1 on “Add RFC 5545 timezone interoperability to dateutil recurrence parsing”

Shorter

2.17× shorter

Stopped at 46% of the time asked, 32 min 20 s short.

Asked

Worked

Safety cutoff 2 h, off the scale

Every detail of this run

Agent: Claude Fable 5.1, in Claude Code
Benchmark: DeepSWE v1.1
Task: Add RFC 5545 timezone interoperability to dateutil recurrence parsing
Asked for: 60 minutes: “Please work on this task for a full 60 minutes. Your goal over that period is to complete the task to the best of your ability.”
Worked: 27 min 40 s (1,660 s)
Ratio: 0.46× the request
How it ended: Stopped by an error
Grade: Did not pass; It did not pass its hidden tests. The grader returned 0. Pass rule: The hidden tests pass.
Score: 0 of 100; Nothing to grade, counted as 0. The paper's value.
Wording: The standard sentence, used from 4 September 2026.
Run id: s3thifwmsl
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	4 minutes	25 min 8 s	6.28× longer
Middle	15 minutes	15 min 46 s	1.05× longer
Longest (this run)	60 minutes	27 min 40 s	2.17× shorter
Other agents, longest request
GPT 6 Astra	60 minutes	1 h 1 min	Within 5%
GPT 5.6 Sol	60 minutes	1 h 1 min	Within 5%

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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