@inproceedings{zhang-etal-2026-prism,
title = "Prism: Persistent Faceted File Memory for Cost-Efficient Coding Agents",
author = "Zhang, Ziyun and
Liu, Yihao and
Zhang, Yuzhe and
Cai, Huaqian",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Findings of the {A}ssociation for {C}omputational {L}inguistics: {EMNLP} 2026",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.findings-emnlp.1301/",
pages = "27518--27531",
ISBN = "979-8-89176-462-0",
abstract = "Coding agents working on sequential maintenance tasks re-read the same files across related tasks, wasting more than a third of their input tokens on redundant context. The natural fix, caching file summaries, fails to reliably reduce cost: tool-use traces are consistent with agents over-relying on generic descriptions, skipping re-reads, and offsetting token savings with less effective downstream decisions, leaving net cost roughly unchanged. We introduce Prism, a content-hash-keyed file memory that augments summaries with bounded facets: identifier-grounded facts distilled from the agent{'}s own prior reasoning. On 12 SWE-Chain dependency-upgrade chains, Prism reduces cost by 24.9{\%} on GPT-5 and 9.9{\%} on GPT-5.4-mini, while maintaining comparable aggregate Build+Fix F1. Against no memory, a summary-only ablation yields only a nominal 2.4{\%} cost decrease that falls within run-to-run variability, while a static Aider-style repo-map baseline costs substantially more at 13{\%} over no memory. Two controlled ablations isolate the causal contributions: wiping the persistent store before every task raises cost by 37{\%} over no memory, and replacing facets with a 3{\texttimes} larger unstructured summary raises it by 41{\%}. Code: https://github.com/WhiteFlamesCN/Prism-Opencode."
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<abstract>Coding agents working on sequential maintenance tasks re-read the same files across related tasks, wasting more than a third of their input tokens on redundant context. The natural fix, caching file summaries, fails to reliably reduce cost: tool-use traces are consistent with agents over-relying on generic descriptions, skipping re-reads, and offsetting token savings with less effective downstream decisions, leaving net cost roughly unchanged. We introduce Prism, a content-hash-keyed file memory that augments summaries with bounded facets: identifier-grounded facts distilled from the agent’s own prior reasoning. On 12 SWE-Chain dependency-upgrade chains, Prism reduces cost by 24.9% on GPT-5 and 9.9% on GPT-5.4-mini, while maintaining comparable aggregate Build+Fix F1. Against no memory, a summary-only ablation yields only a nominal 2.4% cost decrease that falls within run-to-run variability, while a static Aider-style repo-map baseline costs substantially more at 13% over no memory. Two controlled ablations isolate the causal contributions: wiping the persistent store before every task raises cost by 37% over no memory, and replacing facets with a 3× larger unstructured summary raises it by 41%. Code: https://github.com/WhiteFlamesCN/Prism-Opencode.</abstract>
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%0 Conference Proceedings
%T Prism: Persistent Faceted File Memory for Cost-Efficient Coding Agents
%A Zhang, Ziyun
%A Liu, Yihao
%A Zhang, Yuzhe
%A Cai, Huaqian
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Findings of the Association for Computational Linguistics: EMNLP 2026
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-462-0
%F zhang-etal-2026-prism
%X Coding agents working on sequential maintenance tasks re-read the same files across related tasks, wasting more than a third of their input tokens on redundant context. The natural fix, caching file summaries, fails to reliably reduce cost: tool-use traces are consistent with agents over-relying on generic descriptions, skipping re-reads, and offsetting token savings with less effective downstream decisions, leaving net cost roughly unchanged. We introduce Prism, a content-hash-keyed file memory that augments summaries with bounded facets: identifier-grounded facts distilled from the agent’s own prior reasoning. On 12 SWE-Chain dependency-upgrade chains, Prism reduces cost by 24.9% on GPT-5 and 9.9% on GPT-5.4-mini, while maintaining comparable aggregate Build+Fix F1. Against no memory, a summary-only ablation yields only a nominal 2.4% cost decrease that falls within run-to-run variability, while a static Aider-style repo-map baseline costs substantially more at 13% over no memory. Two controlled ablations isolate the causal contributions: wiping the persistent store before every task raises cost by 37% over no memory, and replacing facets with a 3× larger unstructured summary raises it by 41%. Code: https://github.com/WhiteFlamesCN/Prism-Opencode.
%U https://aclanthology.org/2026.findings-emnlp.1301/
%P 27518-27531
Markdown (Informal)
[Prism: Persistent Faceted File Memory for Cost-Efficient Coding Agents](https://aclanthology.org/2026.findings-emnlp.1301/) (Zhang et al., Findings 2026)
ACL