Benchmark Almanac

LegalReasonBench

Gemini 4 Argon 50.8% leads since Oct 2026 Not in model cards

Models work long-horizon legal matters built by practicing lawyers, writing memoranda and court filings across dependent assignments, in closed-record and open-research settings.

Rule and application scores drop 11 to 38 points when models must find the law themselves. Gemini 4 Argon led at 50.8% at launch.

Made by micro1 Released Oct 2026 Law All tasks public Last model added Sep 2026 Scores refreshed 2 Nov 2026
Level
Expert Specialists with years of training, often over hours of work
Scored
Graded by a model A language model scores each response, usually against a rubric.
Answers
Open-ended Free-form text, documents, designs or media judged as a whole.
Paper Dataset Leaderboard
8
Models scored on its own leaderboard

Gemini 4 Argon leads with 50.8%

Best score per model from the benchmark's own leaderboard, read on 2 Nov 2026. Where a model ran with several settings or harnesses, we keep its best.

  1. 50.8 Gemini 4 Argon
  2. 50.6 Claude Fable 5.1
  3. 46.5 Claude Opus 5.5
  4. 40.4 Muse Spark 1.3
  5. 40.4 Grok 4.7
  6. 39.6 Gemini 3.8 Flash
  7. 39.5 GPT-6 Astra
  8. 31.9 GPT-6 Sol
  1. 1 Gemini 4 Argon 50.8%
  2. 2 Claude Fable 5.1 50.6%
  3. 3 Claude Opus 5.5 46.5%
  4. 4 Muse Spark 1.3 40.4%
  5. 5 Grok 4.7 40.4%
  6. 6 Gemini 3.8 Flash 39.6%
  7. 7 GPT-6 Astra 39.5%
  8. 8 GPT-6 Sol 31.9%
#ModelScoreSettingDateSource
1 Gemini 4 Argon 50.8% Sep 2026 Official leaderboard
2 Claude Fable 5.1 50.6% Sep 2026 Official leaderboard
3 Claude Opus 5.5 46.5% Sep 2026 Official leaderboard
4 Muse Spark 1.3 40.4% Sep 2026 Official leaderboard
5 Grok 4.7 40.4% Sep 2026 Official leaderboard
6 Gemini 3.8 Flash 39.6% Sep 2026 Official leaderboard
7 GPT-6 Astra 39.5% Sep 2026 Official leaderboard
8 GPT-6 Sol 31.9% Sep 2026 Official leaderboard

Number one over time

Lab claims count from the day the card came out, independent runs from the model’s release.

Google DeepMind
Own leaderboard 1 leader
Gemini 4 Argon 50.8%

Scores over time

All the scores we have, one dot each, so a model tested at several settings appears more than once.

On the benchmark’s own leaderboard Best so far
0% 20% 40% 60% 80% 100% Near the ceiling (85%) Gemini 4 Argon 0% 20% 40% 60% 80% 100% Near the ceiling (85%) Gemini 4 Argon

No lab model card reports it yet

We read the headline results of 479 launch posts from 51 labs, and none of them list this benchmark.

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