Benchmark Almanac

FrontierCS 1.1

Claude Opus 5.5 56.5 leads since September 2026
Not in model cards

Agents solve 179 algorithmic tasks under revised scoring that rewards solutions beyond the reference. The score is the official average task score.

Version 1.1 changes the task set and scoring. It is separate from 1.0 and the research-focused FrontierCS 2.

Released
December 2025
Kind
Competitive programming
Level
Research frontier
Scored
Checked automatically
Answers
Code
Tasks
All public
Strongest model tested
GPT-6 Astra #3 on the capability index
Last model added
September 2026
Scores refreshed
November 12th, 2026

In the authors’ words

We introduce FrontierCS, a benchmark of 156 open-ended problems across diverse areas of computer science, designed and reviewed by experts, including CS PhDs and top-tier competitive programming participants and problem setters. Unlike existing benchmarks that focus on tasks with known optimal solutions, FrontierCS targets problems where the optimal solution is unknown, but the quality of a solution can be objectively evaluated. Models solve these tasks by implementing executable programs rather than outputting a direct answer. FrontierCS includes algorithmic problems, which are often NP-hard variants of competitive programming problems with objective partial scoring, and research problems with the same property. For each problem we provide an expert reference solution and an automatic evaluator. Combining open-ended design, measurable progress, and expert curation, FrontierCS provides a benchmark at the frontier of computer-science difficulty. Empirically, we find that frontier reasoning models still lag far behind human experts on both the algorithmic and research tracks, that increasing reasoning budgets alone does not close this gap, and that models often over-optimize for generating merely workable code instead of discovering high-quality algorithms and system designs.

Abstract of FrontierCS: Evolving Challenges for Evolving Intelligence (arXiv:2512.15699, CC0)
6
Models scored on its own leaderboard

Claude Opus 5.5 leads with 56.5 among models released by September 2026

Best score per model from the benchmark's own leaderboard, read on November 12th, 2026. Where a model ran with several settings or harnesses, we keep its best.

The newest model with a score here came out in September 2026, and nobody has tested a newer one. Among the 20 highest-ranked models on the capability index, these have no score yet:

  1. 1 Claude Opus 5.5 High 56.5
  2. 2 GPT-6 Astra Low 54.0
  3. 3 Claude Sonnet 5.5 Max 53.9
  4. 4 GPT-6 Sol High 52.4
  5. 5 Gemini 3.7 Flash Medium 48.0
  6. 6 Gemini 3.8 Flash Medium 47.8

Source: Official FrontierCS 1.1 leaderboard

#ModelScoreSettingDateSource
1 Claude Opus 5.5 56.5 High, Claude Code Sep 2026 Official leaderboard
2 GPT-6 Astra 54.0 Low, Codex CLI Sep 2026 Official leaderboard
3 Claude Sonnet 5.5 53.9 Max, Claude Code Sep 2026 Official leaderboard
4 GPT-6 Sol 52.4 High, Codex CLI Sep 2026 Official leaderboard
5 Gemini 3.7 Flash 48.0 Medium, Gemini CLI Aug 2026 Official leaderboard
6 Gemini 3.8 Flash 47.8 Medium, Gemini CLI Sep 2026 Official leaderboard

3 models have held number one on the official leaderboard since its release in December 2025

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

Google DeepMind OpenAI Anthropic
Own leaderboard Replaced by 2, Oct 2026

Source: Official FrontierCS 1.1 leaderboard

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
47.5 50.0 52.5 55.0 57.5 47.5 50.0 52.5 55.0 57.5

Source: Official FrontierCS 1.1 leaderboard

No lab model card reports it yet

We read the headline results of 522 launch posts from 52 labs, and none of them list this benchmark.

Versions

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