New Benchmark Challenges AI Agents with Long, Complex Tasks.

Zongxia Li, Zhongzhi Li, Yucheng Shi, Ruhan Wang, Junyao Yang, Zhichao Liu, Xiyang Wu, Anhao Li, Yue Yu, Ninghao Liu, Lichao Sun, Haotao Mi, LeoweiLiang· July 13, 2026 View original

Summary

Long-Horizon-Terminal-Bench is a new benchmark featuring 46 long-horizon tasks across nine categories, designed to test AI agents on complex, multi-step problems. It introduces dense intermediate rewards and partial credit grading, providing a more comprehensive evaluation of agent capabilities beyond just final outcomes.

Researchers have introduced Long-Horizon-Terminal-Bench, a novel benchmark designed to rigorously test the capabilities of AI agents on tasks that are significantly more complex and time-consuming than those in existing benchmarks. Comprising 46 long-horizon tasks across diverse categories like software engineering, scientific computing, and interactive games, this benchmark moves beyond simple, short-duration problems. A key innovation of Long-Horizon-Terminal-Bench is its detailed grading system. Unlike previous benchmarks that only assess final outcomes, this new system decomposes tasks into fine-grained subtasks, enabling dense intermediate rewards and partial credit. This allows for a more nuanced evaluation, capturing an agent's progress and partial solutions in open-ended workflows, rather than just a binary pass/fail. Initial evaluations of 15 frontier models revealed that even the strongest agents struggled, achieving only a 15.2% pass rate at a 0.95 partial-reward threshold. Agents consumed millions of tokens and hours of execution time per task, highlighting the significant headroom for improvement in long-horizon planning, context management, and iterative debugging for current AI agents.

Why it matters

This benchmark provides a crucial tool for evaluating and driving progress in AI agent development, pushing towards more capable and robust agents that can handle real-world, multi-step problems.

How to implement this in your domain

  1. 1Utilize Long-Horizon-Terminal-Bench to rigorously evaluate the performance of internal AI agents on complex, multi-step tasks.
  2. 2Adopt dense reward signals and partial credit grading in internal agent development to better understand and optimize intermediate progress.
  3. 3Focus agent development efforts on improving long-horizon planning, long-context management, and iterative debugging capabilities.
  4. 4Collaborate with research institutions to contribute to and leverage advanced benchmarks for AI agent development.

Who benefits

Software DevelopmentRoboticsResearch & DevelopmentGamingEducation

Key takeaways

  • Existing AI benchmarks often overlook intermediate progress and partial solutions.
  • Long-Horizon-Terminal-Bench offers 46 complex, multi-step tasks with dense reward grading.
  • It stresses long-horizon planning, context management, and iterative debugging.
  • Current frontier models show significant room for improvement on these challenging tasks.

Original post by Zongxia Li, Zhongzhi Li, Yucheng Shi, Ruhan Wang, Junyao Yang, Zhichao Liu, Xiyang Wu, Anhao Li, Yue Yu, Ninghao Liu, Lichao Sun, Haotao Mi, LeoweiLiang

"arXiv:2607.08964v1 Announce Type: new Abstract: AI agents have become capable of autonomously completing short, well-specified tasks. However, existing terminal benchmarks largely focus on simple problems that finish within minutes and are evaluated only by their final outcome. T…"

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Originally posted by Zongxia Li, Zhongzhi Li, Yucheng Shi, Ruhan Wang, Junyao Yang, Zhichao Liu, Xiyang Wu, Anhao Li, Yue Yu, Ninghao Liu, Lichao Sun, Haotao Mi, LeoweiLiang on X · view source

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