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arxiv:2611.11995

Infrathon: Benchmarking Language Agents for Real-World, Long-Horizon AI Infra Optimization

Published on Nov 9
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TengXiao
on Nov 10
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Abstract

In this work, we study whether frontier agent can continually improve real-world AI infrastructure over long horizons. We introduce Infrathon, a benchmark of diverse, long-horizon AI infrastructure optimization tasks across different levels. We evaluate six models across 150 runs with 24-hour budgets, totaling over 10,000 GPU-hours. Our results show that model rankings vary with the evaluation horizon, while 135 of the 150 runs achieve further improvements during the second half of their budgets. These findings indicate that shorter evaluations can overlook both optimization gains and changes in relative model performance. We also find agents can discover solutions that outperform human-designed baselines: Claude Opus 5.5 increases the mean KV-cache compression ratio from 6.82% with the human-designed Quant-VideoGen codec to 19.86%. Analysis of agent trajectories identifies task violations, unreliable testing, and premature completion as barriers to sustained improvement. Together, Our Infrathon framework provide resources for constructing long-horizon tasks, evaluating frontier agents, and discovering good infrastructure solutions.

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edited about 1 hour ago

Infrathon: Benchmarking Language Agents for Real-World, Long-Horizon AI Infra Optimization

Zhengyu Hu1    Zheyuan Xiao1    Yike Wang1,2    Hamish Ivison1    Haoyu Wang3    Yige Yuan1    Rulin Shao1    Yuetai Li1    Niqi Lyu4    Yicheng Ding4*    Shu Yang5    Zhichen Zeng1,6    Banghua Zhu1,6    Jiaxin Pei5,7    Kaize Ding8    Pradeep Dasigi2    Dan Roth3    Hannaneh Hajishirzi1    Noah A. Smith1,2    Teng Xiao1,2*†    Radha Poovendran1*

1University of Washington   2Allen Institute for AI   3University of Pennsylvania   4Pyromind Dynamics   5Stanford University   6RadixArk   7The University of Texas at Austin   8Northwestern University
†Project leader   *Corresponding authors

Can frontier agents keep improving real AI infrastructure for 24 hours? Infrathon gives an agent an H100 workstation, a real ML system and a 12–24 hour budget: 25 tasks from GPU operators to full training and serving systems, scored by an independent Judge on held-out workloads. We evaluate 6 models over 150 runs and 10,000+ GPU-hours; 135 of the 150 runs still improve in the second half of their budget.

🏠 Homepage · 📝 Blog · 💻 Code · 🛠️ Infrathon-build · 🤗 Dataset · 🐳 Docker Hub

How a run works: the agent edits and tests in its Work container; the Controller reviews each submission; the Judge scores it on held-out workloads; the run keeps its best valid score.

1️⃣ Claude Opus 5.5 leads all six models with a mean rank score of 91.2, winning 17 of 25 tasks.
ModelMean rank score ↑Tasks won
Claude Opus 5.591.217
GPT-6 Astra75.26
GPT-6.1 Sol54.41
Qwen 3.8 Flash40.81
DeepSeek V4.1 Flash30.40
GLM 5.3 Flash8.00

Mean rank scores range from 0 to 100; 100 means first place on every task.

2️⃣ Agents can beat human designs. On the Quant-VideoGen KV codec, Claude raises mean KV-cache compression from 6.82× to 19.86× while improving video quality.
Dataset / video modelCompression (×) ↑PSNR (dB) ↑SSIM ↑LPIPS ↓
WorldScore
HY-WorldPlay
6.75 → 20.8931.15 → 36.330.923 → 0.9750.059 → 0.023
MovieGen
LongCat-Video
6.88 → 18.8323.67 → 26.950.836 → 0.8840.126 → 0.085

Mean values: human codec → Claude's codec. Quality metrics use the uncompressed BF16 reference.

Quant-VideoGen KV codec, 24 hours: best valid score for six agents. Claude Opus 5.5 reaches 28.45, about four times the human codec's 6.82; the other five agents end between 5.82 and 11.34.

3️⃣ Long horizons matter for bigger systems. At equal GPU-hours, one long run wins 9 of 12 comparisons against best-of-2/4 short runs, including all four on system-level tasks; short runs stay competitive on operators.
Task levelBest of two / one long runBest of four / one long run
Operator101.3%102.6%
Module96.5%96.9%
System79.4%77.3%

Geometric means of task–model score ratios; 100% means equal performance at equal GPU-hours.

Everything is open: the tasks, the Work/Controller/Judge images, the held-out data, and 🛠️ Infrathon-build for turning an expert's task definition into a new Infrathon task.

📄 If you find Infrathon useful, please cite:

@inproceedings{Hu2026InfrathonBL,
  title={Infrathon: Benchmarking Language Agents for Real-World, Long-Horizon AI Infra Optimization},
  author={Zhengyu Hu and Zhe-Yuan Xiao and Yike Wang and Hamish Ivison and Hao-Yu Wang and Yi-Ge Yuan and Ru-Lin Shao and Yue-Tai Li and Niqi Lyu and Yi-Cheng Ding and Shu Yang and Zhi-Chen Zeng and Bang-Hua Zhu and Jia-Xin Pei and Kai-Ze Ding and Pradeep Dasigi and Dan Roth and Hanna Hajishirzi and Noah A. Smith and Teng Xiao and Radha Poovendran},
  year={2026},
  url={https://api.semanticscholar.org/CorpusID:295731967}
}

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Rankings changing with the evaluation horizon is the finding I keep thinking about: a model that looks fine after an hour may not after twenty-four. 135 of 150 runs still improving in the second half is striking too. Did the task violations and premature completion cluster in particular models, or show up everywhere?

·
Paper author

We saw both behaviors across multiple models, including the top performers. Our task-violation examples involve Claude, DeepSeek, and GLM submitting solutions that broke task instructions. For premature completion, selected runs with GPT-6 Astra, DeepSeek, and GLM improved by another 7.3%, 14.0%, and 24.8%, respectively, after our stop hook prompted them to continue, all within the original budget.

We’ll follow up with more detailed, systematic statistics on how often these behaviors occur in each model.

What stood out was that agents could declare completion while substantial improvements were still possible, even with time remaining.

Thank you for raising this question!

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