Origin · news · prior work

A shared idea, built into a benchmark.

Patrick Heusser and Markus Tuor came up with Deep20Bench while playing Twenty Questions with the kids. Patrick then designed and built the benchmark.

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Updates

What’s new.

New models, releases, and articles. A score is the average number of questions per round, with a fixed penalty for failed rounds. Lower is better.

Claude Haiku 5.5 (high) joins the leaderboard.

It averaged 20.00 questions per round in edition 1.1, 15th of 21 models, with 5 failed rounds out of 30. Compared with GPT-6 Luna (high) at 21.17, it needed fewer questions on seven of the ten subjects, with clear leads on Garfield and Achilles. Spider web was its weak spot: 30, 38, and 21 questions, against Luna’s 16, 22, and 15.

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Gemini 4 Argon (high) matches the lowest average score.

It averaged 13.67 questions per round in edition 1.1, the same as GPT-6 Astra (high): both used 410 questions over 30 rounds and solved every round. Astra ranks first because its 95% confidence interval is narrower. Argon was the best of 20 models on Door handle and second on Albert Schweitzer and Bike pump, but 19th on Moon, which took it 11, 12, and 14 questions.

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Muse Wonder (high) joins the leaderboard.

It averaged 19.63 questions per round in edition 1.1, 13th of 19 models at the time. Some subjects were much harder for it than others: it was 9th best on Albert Schweitzer but 18th on Garfield, which took it 10, 22, and 30 questions. Achilles took 8 questions every time.

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Claude Sonnet 5.5 (high) joins the leaderboard.

It averaged 17.83 questions per round in edition 1.1, with 3 failed rounds out of 30.

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Older updates (13)

GPT-6.1 Sol (high) joins the leaderboard.

It averaged 15.23 questions per round in edition 1.1, with 1 failed round out of 30.

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Claude Opus 5.5 (high) joins the leaderboard.

It averaged 15.00 questions per round in edition 1.1, with 1 failed round out of 30.

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GPT-6 Sol (high) joins the leaderboard.

It averaged 18.03 questions per round in edition 1.1, with no failed rounds.

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GPT-6 Luna (high) joins the leaderboard.

It averaged 21.17 questions per round in edition 1.1, with 6 failed rounds out of 30.

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Grok 4.7 (high) joins the leaderboard.

It averaged 22.23 questions per round in edition 1.1, with 8 failed rounds out of 30.

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GPT-6 Astra (high) joins the leaderboard.

It averaged 15.09 questions per round in edition 1.0, with 2 failed rounds out of 35.

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Gemini 3.8 Flash (high) joins the leaderboard.

It averaged 13.14 questions per round in edition 1.0, with no failed rounds.

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Claude Fable 5.1 (high) joins the leaderboard.

It averaged 12.11 questions per round in edition 1.0, with 1 failed round out of 35.

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Behind Deep20Bench: the hard part wasn’t the game.

Patrick writes about what it took to build Deep20Bench: wrong answers from the answering model, the blind second check, format errors, and the design choices along the way.

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We tried Ox Alpha (high) from OpenRouter.

An anonymous stealth model on OpenRouter. It averaged 17.60 questions per round in edition 1.0, 12th of 15 models at the time.

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Gemini 3.7 Flash (high) joins the leaderboard.

It averaged 14.03 questions per round in edition 1.0, with 1 failed round out of 35.

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Grok 4.6 (high) joins the leaderboard.

It averaged 14.29 questions per round in edition 1.0, with no failed rounds.

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Claude Fable 5 (high) joins the leaderboard.

It averaged 12.06 questions per round in edition 1.0, with no failed rounds.

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Prior work

Related research.

Deep20Bench was developed independently. These projects work on related problems.

Research related to Deep20Bench
YearFocusPublicationSource
2018Question strategy

Learning-to-Ask: Knowledge Acquisition via 20 Questions

Yihong Chen et al. · KDD

Learns which questions to ask to identify a subject and gather knowledge.

Microsoft Research ↗
2022World knowledge

20Q: Overlap-Free World Knowledge Benchmark for Language Models

Maxime De Bruyn et al. · GEM

Uses Twenty Questions to test world knowledge with separate training and test subjects.

ACL Anthology ↗
2024Planning benchmark

The Entity-Deduction Arena

Yizhe Zhang, Jiarui Lu & Navdeep Jaitly · Apple · ACL

Tests how language models plan questions and use earlier answers to find a hidden subject.

Apple Machine Learning Research ↗
2025Choosing useful questions

Adaptive Elicitation of Latent Information Using Natural Language

Jimmy Wang et al. · ICML

Chooses the questions that most reduce uncertainty about the answer.

OpenReview ↗
2025Information gain

BED-LLM: Intelligent Information Gathering with LLMs

Deepro Choudhury et al. · Apple · ICLR

Chooses questions by how much information each answer is expected to give.

Apple Machine Learning Research ↗

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Method and results.

Read the rules or inspect the current model runs.