OS-Marathon: Benchmarking Computer-Use Agents on Vast-Horizon, Repetitive Tasks

Jing Wu, Wenjie Ai, Daphne Barretto, Yiye Chen, Qingyu Chen, Yuhang He, Pranit Chawla, Nicholas Gydé, Yanan Jian, Vibhav Vineet


Abstract
Vast-horizon, repetitive workflows are common in daily routines, e.g., processing expense reports from a stack of receipts, organising a collection of PDF annotations into structured notes, and are tedious for humans, with execution length scaling with the volume of data to process. They are, however, well-suited to autonomous agents, since their structured, recurring sub-workflows follow a logic that can be systematically learned. Yet no existing benchmark evaluates agents specifically on vast-horizon repetitive capabilities, leaving the problem largely underexplored. To bridge this gap, we establish OS-Marathon, comprising 100 vast-horizon repetitive tasks across 5 scenarios and 10 domains, on which our evaluation reveals that leading state-of-the-art (SOTA) CUAs struggle substantially. We further find that introducing a task orchestrator to decompose the workflow into per-instance subtasks fails to mitigate the difficulty: errors accumulate and propagate across solver agents, indicating that naive decomposition is insufficient for these tasks. We then explore a cost-effective personalisation strategy, i.e. GraphDemo, that adapts general agents to such tasks from a single human demonstration of the recurring sub-workflow logic. Extensive experiments show both the real-world challenge of vast-horizon repetitive tasks and the improvement provided by human demonstration in this setting.
Anthology ID:
2026.emnlp-main.2493
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
56604–56622
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2493/
DOI:
Bibkey:
Cite (ACL):
Jing Wu, Wenjie Ai, Daphne Barretto, Yiye Chen, Qingyu Chen, Yuhang He, Pranit Chawla, Nicholas Gydé, Yanan Jian, and Vibhav Vineet. 2026. OS-Marathon: Benchmarking Computer-Use Agents on Vast-Horizon, Repetitive Tasks. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 56604–56622, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
OS-Marathon: Benchmarking Computer-Use Agents on Vast-Horizon, Repetitive Tasks (Wu et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2493.pdf