Time series forecasting task (Anthropic)
Claude Mythos Preview 4.55 leads since Apr 2026 Only in system cards
Agents solve a regression and time-series forecasting problem with known state-of-the-art results, in six variants.
In-house Anthropic evaluation. The tasks are not public.
Made by Anthropic Released May 2025 Machine learning engineering Tasks kept private Last in a system card Jul 2026
Last model added Jul 2026
- Level
- Expert Specialists with years of training, often over hours of work
- Scored
- Checked automatically A program checks the result against an answer key, unit tests or the expected final state.
- Answers
- Agent task Many steps in a terminal, browser, desktop, app, game or robot.
9
Models scored in lab cards
11
System cards report it, from 1 lab
Claude Mythos Preview leads with 4.55 among models released by Jul 2026
Best score per model as labs report them in their own cards. Labs pick their own settings, so these compare less cleanly than independent runs.
The newest model with a score here came out in Jul 2026, and nobody has reported a newer one. Among the 20 highest-ranked models on the capability index, these have no score yet:
- GPT-6 Astra
- Claude Opus 5.5
- GPT-6.1 Terra
- GPT-6.1 Sol
- and 15 more
- 1 Claude Mythos Preview 4.55
- 2 Claude Opus 4.7 4.78
- 3 Claude Sonnet 4.5 5.30
- 4 Claude Opus 5 5.68
- 5 Claude Sonnet 4.6 5.70
- 6 Claude Sonnet 4 5.80
- 7 Claude Sonnet 5 5.80
- 8 Claude Opus 4 6.15
- 9 Claude Opus 4.1 6.54
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | Claude Mythos Preview | 4.55 | Apr 2026 | Model card | |
| 2 | Claude Opus 4.7 | 4.78 | Apr 2026 | Model card | |
| 3 | Claude Sonnet 4.5 | 5.30 | Sep 2025 | Model card | |
| 4 | Claude Opus 5 | 5.68 | Jul 2026 | Model card | |
| 5 | Claude Sonnet 4.6 | 5.70 | Feb 2026 | Model card | |
| 6 | Claude Sonnet 4 | 5.80 | May 2025 | Model card | |
| 7 | Claude Sonnet 5 | 5.80 | Jun 2026 | Model card | |
| 8 | Claude Opus 4 | 6.15 | May 2025 | Model card | |
| 9 | Claude Opus 4.1 | 6.54 | Aug 2025 | Model card |
3 models have held number one since its release in May 2025
Lab claims count from the day the card came out, independent runs from the model’s release.
Anthropic
Scores over time
All the scores we have, one dot each, so a model tested at several settings appears more than once.
Reported by the lab in its model card
Labs report it only in system cards
We read the headline results of 479 launch posts from 51 labs, and none of them list this benchmark. Some system cards do, below.
11 system cards report it, from 1 lab
Besides launch posts, we read the system cards, model cards and technical reports labs publish with a release. They report far more, including safety and frontier-risk tests.
| Date | Document | Score | As the document writes it | Section |
|---|---|---|---|---|
| 24 Jul 2026 | Claude Opus 5 system card | 5.68 | Time Series Forecasting, MSE on the hard variant, lower is better (Table 2.3.5.A) | AI R&D risk |
| 30 Jun 2026 | Claude Sonnet 5 system card | 5.8 | Time Series Forecasting, MSE on hard variant 5.80, lower is better (Table 2.3.3.A) | AI R&D risk |
| 16 Apr 2026 | Claude Opus 4.7 system card | 4.78 | Time Series Forecasting, MSE on hard variant 4.78, lower is better (Table 2.3.4.A) | AI R&D risk |
| 7 Apr 2026 | Claude Mythos Preview system card | 4.55 | Time Series Forecasting, MSE on hard variant 4.55, lower is better (Table 2.3.3.A) | AI R&D risk |
| 17 Feb 2026 | Claude Sonnet 4.6 system card | 5.7 | Time series forecasting, hard variant, minimum MSE 5.70, lower is better (6.3.3.2) | AI R&D risk |
| 5 Feb 2026 | Claude Opus 4.6 system card | Time series forecasting, two variants with no overall: minimum MSE 5.86 hard (human 5.3) and 5.76 medium (human 5.8), lower is better (8.3.3.2) | AI R&D risk | |
| 24 Nov 2025 | Claude Opus 4.5 system card | Time series forecasting, two variants with no overall: minimum MSE 5.66 easy (human 5.8) and 5.71 hard (human 5.3), lower is better (7.3.2.2) | AI R&D risk | |
| 29 Sep 2025 | Claude Sonnet 4.5 system card | 5.3 | Time series forecasting, minimum MSE 5.30 on the hard variant, lower is better. Easy variant MSE 5.91 (9.3.3.2) | AI R&D risk |
| 5 Aug 2025 | Claude Opus 4.1 system card addendum | 6.54 | Time series forecasting, minimum MSE 6.541 on the hard variant, lower is better (6.4.1) | AI R&D risk |
| 22 May 2025 | Claude Sonnet 4 system card | 5.8 | Time series forecasting, minimum MSE 5.8 on the hard variant (normalized score 0.824), lower is better. Easy variant MSE 6 (7.3.3.2) | AI R&D risk |
| 22 May 2025 | Claude Opus 4 system card | 6.15 | Time series forecasting, minimum MSE 6.15 on the hard variant (normalized score 0.815), lower is better. Easy variant MSE 6.02 (7.3.3.2) | AI R&D risk |
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