Time series forecasting task (Anthropic)
Claude Mythos Preview 4.55 leads since April 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
- Kind
- Machine learning engineering
- Level
- Expert
- Scored
- Checked automatically
- Answers
- Agent task
- Tasks
- Kept private
- Strongest model tested
- Claude Opus 5 #10 on the capability index
- Last in a system card
- July 2026
- Last model added
- July 2026
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 July 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 July 2026, and nobody has reported a newer one. Among the 20 highest-ranked models on the capability index, these have no score yet:
- Claude Fable 5.2
-
Gemini 4 Carbon - GPT-6 Astra
- Claude Opus 5.5
- 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
Source: Labs’ model cards
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | Claude Mythos Preview | 4.55 | Apr 2026 | Lab model card | |
| 2 | Claude Opus 4.7 | 4.78 | Apr 2026 | Lab model card | |
| 3 | Claude Sonnet 4.5 | 5.30 | Sep 2025 | Lab model card | |
| 4 | Claude Opus 5 | 5.68 | Jul 2026 | Lab model card | |
| 5 | Claude Sonnet 4.6 | 5.70 | Feb 2026 | Lab model card | |
| 6 | Claude Sonnet 4 | 5.80 | May 2025 | Lab model card | |
| 7 | Claude Sonnet 5 | 5.80 | Jun 2026 | Lab model card | |
| 8 | Claude Opus 4 | 6.15 | May 2025 | Lab model card | |
| 9 | Claude Opus 4.1 | 6.54 | Aug 2025 | Lab model card |
3 models have held number one in labs’ own numbers since its release in May 2025
Lab claims count from the day the card came out, independent runs from the model’s release.
Anthropic
Source: Labs’ model cards
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
Source: Labs’ model cards
Labs report it only in system cards
We read the headline results of 522 launch posts from 52 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 |
|---|---|---|---|---|
| Jul 24, 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 |
| Jun 30, 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 |
| Apr 16, 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 |
| Apr 7, 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 |
| Feb 17, 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 |
| Feb 5, 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 | |
| Nov 24, 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 | |
| Sep 29, 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 |
| Aug 5, 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 |
| May 22, 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 |
| May 22, 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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