Claude Fable 5.1
- Made by
- Anthropic
- Released
- Announced in
- Introducing Claude Fable 5.1 and Claude Mythos 5.1anthropic.com
- Event
- Claude Fable 5.1 and Mythos 5.1
- API record
- /api/v1/models/claude-fable-5-1
Benchmark results
| Benchmark | Score | Source check |
|---|---|---|
| Humanity's Last ExamNo tools | 60.9% | CheckedA person checked this number against its source on 17 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced. |
| Humanity's Last ExamWith tools | 65.0% | CheckedA person checked this number against its source on 17 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced. |
| reported later, in Introducing Claude Opus 5.5 | 65.6% | CheckedA person checked this number against its source on 17 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced.CorroboratedThe same number is printed in 1 other lab document: 1 |
| SWE-bench Proaverage of 5 trials · The source doesn't say whether this is the public or the commercial set | 81.2% | CheckedA person checked this number against its source on 17 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced.CorroboratedThe same number is printed in 1 other lab document: 1 |
| ARC-AGI-2max effort; semi-private set; as reported by the ARC Prize Foundation | 90% | CheckedA person checked this number against its source on 17 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced.CorroboratedThe same number is printed in 1 other lab document: 1 |
| Terminal-Bench 4.0 | 55.8% | CheckedA person checked this number against its source on 17 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced. |
| Terminal-Bench Science 0.1standard error ±3.5 to 4.5 points | 52.6% | CheckedA person checked this number against its source on 19 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced. |
| AutomationBenchZapier leaderboard, private held-out set; max effort; with production safeguards | 31.4% | |
| OSWorld 2.1Full set, partial score · max effort; mean of 5 runs; September 10, 2026 task files; the system card labels it OSWorld 2.0 · reported later, in Introducing Claude Opus 5.5 | 80.7% | CorroboratedThe same number is printed in 1 other lab document: 1 |
| OSWorld 2.0Offline set, partial score · partial score; August 2026 task release, not comparable to earlier OSWorld 2.0 scores; tasks where safeguards intervened scored zero | 77.9% | CheckedA person checked this number against its source on 18 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced. |
| FrontierCode 1.1Main set · medium effort | 50.9% | CheckedA person checked this number against its source on 19 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced. |
| run by Cognition in Claude Code · reported later, in Introducing Claude Opus 5.5 | 50.3% | CorroboratedThe same number is printed in 1 other lab document: 1 |
| best effort level; run by Cognition in Claude Code · reported later, in Claude Opus 5.5 System Card | 52.8% | CheckedA person checked this number against its source on 20 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced. |
| FrontierCode 1.1Extended set · medium effort | 63.6% | CheckedA person checked this number against its source on 19 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced. |
| DeepSWE v1.1average of 5 trials | 67.4% | CheckedA person checked this number against its source on 17 Oct 2026. This confirms the number matches what the lab published, not that the score was reproduced. |
Sources
Reported by Anthropic
- Claude Fable 5.1 and Claude Mythos 5.1 System Cardanthropic.com · 1 Sep 2026
Our capture of page 197 - Introducing Claude Fable 5.1 and Claude Mythos 5.1anthropic.com · 1 Sep 2026
Our capture of the source - Introducing Claude Opus 5.5anthropic.com · 22 Sep 2026
Our capture of the source - Claude Opus 5.5 System Cardanthropic.com · 22 Sep 2026