Riemann-bench
25 private research-mathematics problems from professors and IMO medalists. Agents with tools, 100 runs per problem.
In the authors’ words
Recent AI systems have achieved gold-medal-level performance on the International Mathematical Olympiad, demonstrating remarkable proficiency at competition-style problem solving. However, competition mathematics represents only a narrow slice of mathematical reasoning: problems are drawn from limited domains, require minimal advanced machinery, and can often reward insightful tricks over deep theoretical knowledge. We introduce Riemann-Bench, a private benchmark of expert-curated problems designed to evaluate AI systems on research-level mathematics that goes far beyond the olympiad frontier. Problems are authored by Ivy League mathematics professors, graduate students, and PhD-holding IMO medalists, and routinely took their authors weeks to solve independently. Each problem undergoes double-blind verification by two independent domain experts who must solve the problem from scratch, and yields a unique, closed-form solution assessed by programmatic verifiers. We evaluate frontier models as unconstrained research agents, with full access to coding tools, search, and open-ended reasoning, using an unbiased statistical estimator computed over 100 independent runs per problem. Our results reveal that all frontier models currently score below 10%, exposing a substantial gap between olympiad-level problem solving and genuine research-level mathematical reasoning. By keeping the benchmark fully private, we ensure that measured performance reflects authentic mathematical capability rather than memorization of training data.
- Level
- Research frontier Researchers, on open problems or tasks that take days
- Scored
- Checked automatically A program checks the result against an answer key, unit tests or the expected final state.
- Answers
- Short answer A number, word or short string matched to a key.
Gemini 4 Carbon leads with 80%
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.
- 1
Gemini 4 Carbon 80%
- 2
Gemini 4 Argon 76%
- 3 Claude Opus 5 60%
- 4 Claude Fable 5 55%
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | | 80% | Oct 2026 | Model card | |
| 2 | | 76% | Oct 2026 | Model card | |
| 3 | Claude Opus 5 | 60% | Jul 2026 | Model card | |
| 4 | Claude Fable 5 | 55% | Jun 2026 | Model card |
4 models have held number one since its release in Apr 2026
Lab claims count from the day the card came out, independent runs from the model’s release.
Scores over time
All the scores we have, one dot each, so a model tested at several settings appears more than once.
2 labs put it in a launch post in the last six months
Launch posts from every lab that has listed it, one tick per post. Tall colored ticks include it, and short gray ones leave it out.
| Date | Launch post | Score | As the post writes it |
|---|---|---|---|
| 28 Oct 2026 | 80 | RiemannBench | |
| 13 Oct 2026 | 76 | RiemannBench | |
| 9 Jun 2026 | Claude Fable 5 | 55 | RiemannBench |
2 system cards report it, from 2 labs
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 |
|---|---|---|---|---|
| 13 Oct 2026 | | 76 | RiemannBench (results table, p.5) | Capabilities |
| 24 Jul 2026 | Claude Opus 5 system card | 60 | RiemannBench, max effort without tools, mean of 4 attempts (79% with tools), printed on chart (8.7, Figure 8.7.A) | Capabilities |
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