Haystack Engineering: Context Engineering for Heterogeneous and Agentic Long-Context Evaluation

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Hauptverfasser: Li, Mufei, Fu, Dongqi, Wang, Limei, Zhang, Si, Zeng, Hanqing, Sancak, Kaan, Qiu, Ruizhong, Wang, Haoyu, He, Xiaoxin, Bresson, Xavier, Xia, Yinglong, Sun, Chonglin, Li, Pan
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Veröffentlicht: 2025
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author Li, Mufei
Fu, Dongqi
Wang, Limei
Zhang, Si
Zeng, Hanqing
Sancak, Kaan
Qiu, Ruizhong
Wang, Haoyu
He, Xiaoxin
Bresson, Xavier
Xia, Yinglong
Sun, Chonglin
Li, Pan
author_facet Li, Mufei
Fu, Dongqi
Wang, Limei
Zhang, Si
Zeng, Hanqing
Sancak, Kaan
Qiu, Ruizhong
Wang, Haoyu
He, Xiaoxin
Bresson, Xavier
Xia, Yinglong
Sun, Chonglin
Li, Pan
contents Modern long-context large language models (LLMs) perform well on synthetic "needle-in-a-haystack" (NIAH) benchmarks, but such tests overlook how noisy contexts arise from biased retrieval and agentic workflows. We argue that haystack engineering is necessary to construct noisy long contexts that faithfully capture key real-world factors -- distraction from heterogeneous biased retrievers and cascading errors in agentic workflows -- to test models' long-context robustness. We instantiate it through HaystackCraft, a new NIAH benchmark built on the full English Wikipedia hyperlink network with multi-hop questions. HaystackCraft evaluates how heterogeneous retrieval strategies (e.g., sparse, dense, hybrid, and graph-based) affect distractor composition, haystack ordering, and downstream LLM performance. HaystackCraft further extends NIAH to dynamic, LLM-dependent settings that simulate agentic operations, where models refine queries, reflect on their past reasonings, and decide when to stop. Experiments with 15 long-context models show that (1) while stronger dense retrievers can introduce more challenging distractors, graph-based reranking simultaneously improves retrieval effectiveness and mitigates more harmful distractors; (2) in agentic tests, even advanced models like Gemini 2.5 Pro and GPT-5 suffer cascading failures from self-generated distractors or struggle to perform early stops. These results highlight persistent challenges in agentic long-context reasoning and establish HaystackCraft as a valuable testbed for future progress.
format Preprint
id arxiv_https___arxiv_org_abs_2510_07414
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Haystack Engineering: Context Engineering for Heterogeneous and Agentic Long-Context Evaluation
Li, Mufei
Fu, Dongqi
Wang, Limei
Zhang, Si
Zeng, Hanqing
Sancak, Kaan
Qiu, Ruizhong
Wang, Haoyu
He, Xiaoxin
Bresson, Xavier
Xia, Yinglong
Sun, Chonglin
Li, Pan
Computation and Language
Artificial Intelligence
Information Retrieval
Modern long-context large language models (LLMs) perform well on synthetic "needle-in-a-haystack" (NIAH) benchmarks, but such tests overlook how noisy contexts arise from biased retrieval and agentic workflows. We argue that haystack engineering is necessary to construct noisy long contexts that faithfully capture key real-world factors -- distraction from heterogeneous biased retrievers and cascading errors in agentic workflows -- to test models' long-context robustness. We instantiate it through HaystackCraft, a new NIAH benchmark built on the full English Wikipedia hyperlink network with multi-hop questions. HaystackCraft evaluates how heterogeneous retrieval strategies (e.g., sparse, dense, hybrid, and graph-based) affect distractor composition, haystack ordering, and downstream LLM performance. HaystackCraft further extends NIAH to dynamic, LLM-dependent settings that simulate agentic operations, where models refine queries, reflect on their past reasonings, and decide when to stop. Experiments with 15 long-context models show that (1) while stronger dense retrievers can introduce more challenging distractors, graph-based reranking simultaneously improves retrieval effectiveness and mitigates more harmful distractors; (2) in agentic tests, even advanced models like Gemini 2.5 Pro and GPT-5 suffer cascading failures from self-generated distractors or struggle to perform early stops. These results highlight persistent challenges in agentic long-context reasoning and establish HaystackCraft as a valuable testbed for future progress.
title Haystack Engineering: Context Engineering for Heterogeneous and Agentic Long-Context Evaluation
topic Computation and Language
Artificial Intelligence
Information Retrieval
url https://arxiv.org/abs/2510.07414