HLE Calibration
Models give a confidence score with each HLE answer. The benchmark reports RMS calibration error and AUROC between confidence and correctness.
Calibration evaluation layered on the public Humanity's Last Exam. RMS error is on a 0-100 scale.
- Made by
- Center for AI Safety + Scale AI
- Released
- January 2025
- Kind
- Hallucination rates
- Level
- Expert
- Scored
- Checked automatically
- Answers
- Short answer
- Tasks
- All public
- Strongest model tested
-
Muse Spark 1.3 #26 on the capability index
- Last in a launch post
- March 2026, dropped before it saturated
- Last model added
- October 2026
- Scores refreshed
- November 12th, 2026
In the authors’ words
Benchmarks are important tools for tracking the rapid advancements in large language model (LLM) capabilities. However, benchmarks are not keeping pace in difficulty: LLMs now achieve over 90% accuracy on popular benchmarks like MMLU, limiting informed measurement of state-of-the-art LLM capabilities. In response, we introduce Humanity's Last Exam (HLE), a multi-modal benchmark at the frontier of human knowledge, designed to be the final closed-ended academic benchmark of its kind with broad subject coverage. HLE consists of 2,500 questions across dozens of subjects, including mathematics, humanities, and the natural sciences. HLE is developed globally by subject-matter experts and consists of multiple-choice and short-answer questions suitable for automated grading. Each question has a known solution that is unambiguous and easily verifiable, but cannot be quickly answered via internet retrieval. State-of-the-art LLMs demonstrate low accuracy and calibration on HLE, highlighting a significant gap between current LLM capabilities and the expert human frontier on closed-ended academic questions. To inform research and policymaking upon a clear understanding of model capabilities, we publicly release HLE at https://lastexam.ai.
Muse Spark 1.1 leads with 23.4 among models released by September 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.
o3 leads with 34.0 across all independent runs
Best score per model across the official leaderboard, Epoch AI’s own runs and any board Epoch AI copied. Each bar and row names its source.
Muse Spark 1.1 leads with 23.4, claims included
Best score per model from every source, including labs’ own numbers and claims Epoch AI collected from reports and papers. Labs pick their own settings, so a claim can beat an independent run of the same model.
The newest model with a score here came out in September 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 16 more
- 1
Muse Spark 1.1 23.4
- 2
Muse Spark 1.3 35.3
- 3
Muse Spark 50.3
Source: Labs’ model cards
- 1 o3 high 34.0
- 2 o4-mini high 57.0
- 3 o3-mini text only; high 80.0
- 4 o1 83.0
Source: Official HLE Calibration leaderboard
- 1
Muse Spark 1.1 23.4
- 2 o3 high 34.0
- 3
Muse Spark 1.3 35.3
- 4
Muse Spark 50.3
- 5 o4-mini high 57.0
- 6 o3-mini text only; high 80.0
- 7 o1 83.0
Sources: Labs’ model cards and official HLE Calibration leaderboard
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | | 23.4 | Jul 2026 | Lab model card | |
| 2 | | 35.3 | Oct 2026 | Lab model card | |
| 3 | | 50.3 | Jun 2026 | Lab model card |
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | o3 | 34.0 | high | Apr 2025 | Official leaderboard |
| 2 | o4-mini | 57.0 | high | Apr 2025 | Official leaderboard |
| 3 | o3-mini | 80.0 | text only; high | Jan 2025 | Official leaderboard |
| 4 | o1 | 83.0 | Dec 2024 | Official leaderboard |
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | | 23.4 | Jul 2026 | Lab model card | |
| 2 | o3 | 34.0 | high | Apr 2025 | Official leaderboard |
| 3 | | 35.3 | Oct 2026 | Lab model card | |
| 4 | | 50.3 | Jun 2026 | Lab model card | |
| 5 | o4-mini | 57.0 | high | Apr 2025 | Official leaderboard |
| 6 | o3-mini | 80.0 | text only; high | Jan 2025 | Official leaderboard |
| 7 | o1 | 83.0 | Dec 2024 | Official leaderboard |
The benchmark's own leaderboard has 4 models. Switch the scores above to rank them together.
2 models have held number one in labs’ own numbers since its release in January 2025 3 models have held number one across all independent runs since its release in January 2025 4 models have held number one with claims included since its release in January 2025
Lab claims count from the day the card came out, independent runs from the model’s release. We draw one row each for the benchmark’s own leaderboard and what labs claim in their cards.
Sources: Official HLE Calibration leaderboard and 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.
Sources: Official HLE Calibration leaderboard and labs’ model cards
Labs headline it less often now, last in March 2026
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 |
|---|---|---|---|
| Mar 9, 2026 | Grok 4.20 | 19 | Humanity’s Last Exam, RMS calibration error 0.19, Grok 4.2 SA, Table 2 |
4 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 |
|---|---|---|---|---|
| Oct 23, 2026 | | 35.3 | Humanity's Last Exam calibration, RMS calibration error 0-100 with browser and search tools, Muse Spark 1.3 (API) (Table 2, Table 13). AUROC 72.22 | Hallucination |
| Jul 9, 2026 | | 23.4 | Humanity's Last Exam RMS calibration error (Table 2, Table 11). AUROC 70.2 | Hallucination |
| Jun 12, 2026 | | 50.3 | HLE Calibration RMS calibration error (Table 2, Table 20) | Hallucination |
| Apr 7, 2026 | Grok 4.20 model card | 19 | Humanity’s Last Exam, RMS calibration error 0.19, Grok 4.2 SA, Table 2 | Hallucination |
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