@inproceedings{joshi-etal-2026-cap,
title = "Re:{CAP} - Auditing Retrieval Coverage in Production {RAG} Pipelines",
author = "Joshi, Aviral and
Bhathena, Hanoz and
Nelson, Max and
Sharma, Saket",
editor = "Atanasova, Pepa and
Haffari, Gholamreza and
Wang, Minghan",
booktitle = "Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.emnlp-industry.150/",
pages = "2532--2565",
ISBN = "979-8-89176-460-6",
abstract = "Retrieval-augmented generation (RAG) is hard to monitor in production: exhaustive relevance labels do not exist for non-stationary multi-million-passage corpora that re-index in real time. As a result, retrieval quality is generally understudied and often deprioritised in favour of generation-oriented metrics. In this work, we propose auditing retrieval coverage by probing for evidence of missing documents rather than enumerating every relevant one. Our method Re:CAP (REtrieval Coverage Audit by iterative Probing) is a reference-free audit loop applied to a deployed RAG pipeline{'}s initial answer and retrieved context: it identifies the topics already covered, generates probing questions for plausibly missing topics, retrieves candidate documents, and applies an LLM-as-judge to retain only those that introduce previously-unretrieved information. On four public benchmarks, Re:CAP recovers 9{--}29{\%} of gold labels that flat BM25 top-500 cannot reach, rising to 48{\%} on TREC-COVID. On MuSiQue Re:CAP beats flat hybrid top-500 by +12.9 pp on recall at less than half the document budget. An ensemble BM25, dense, and hybrid baseline (top-500 each) still leaves out 21.2{\%} of gold docs on TREC-COVID that Re:CAP recovers; human annotators judge that 78.9{\%} of those structurally distinct documents add new information to the baseline answer (Fleiss {\ensuremath{\kappa}} = 0.79, n = 123), and 73.9{\%} on live production traffic (n = 180). End-to-end recall is reproducible to within {\ensuremath{\pm}}1{\%} across three independent runs, making Re:CAP a stable instrument for periodic retrieval audits."
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<abstract>Retrieval-augmented generation (RAG) is hard to monitor in production: exhaustive relevance labels do not exist for non-stationary multi-million-passage corpora that re-index in real time. As a result, retrieval quality is generally understudied and often deprioritised in favour of generation-oriented metrics. In this work, we propose auditing retrieval coverage by probing for evidence of missing documents rather than enumerating every relevant one. Our method Re:CAP (REtrieval Coverage Audit by iterative Probing) is a reference-free audit loop applied to a deployed RAG pipeline’s initial answer and retrieved context: it identifies the topics already covered, generates probing questions for plausibly missing topics, retrieves candidate documents, and applies an LLM-as-judge to retain only those that introduce previously-unretrieved information. On four public benchmarks, Re:CAP recovers 9–29% of gold labels that flat BM25 top-500 cannot reach, rising to 48% on TREC-COVID. On MuSiQue Re:CAP beats flat hybrid top-500 by +12.9 pp on recall at less than half the document budget. An ensemble BM25, dense, and hybrid baseline (top-500 each) still leaves out 21.2% of gold docs on TREC-COVID that Re:CAP recovers; human annotators judge that 78.9% of those structurally distinct documents add new information to the baseline answer (Fleiss \ensuremathąppa = 0.79, n = 123), and 73.9% on live production traffic (n = 180). End-to-end recall is reproducible to within \ensuremath\pm1% across three independent runs, making Re:CAP a stable instrument for periodic retrieval audits.</abstract>
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%0 Conference Proceedings
%T Re:CAP - Auditing Retrieval Coverage in Production RAG Pipelines
%A Joshi, Aviral
%A Bhathena, Hanoz
%A Nelson, Max
%A Sharma, Saket
%Y Atanasova, Pepa
%Y Haffari, Gholamreza
%Y Wang, Minghan
%S Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-460-6
%F joshi-etal-2026-cap
%X Retrieval-augmented generation (RAG) is hard to monitor in production: exhaustive relevance labels do not exist for non-stationary multi-million-passage corpora that re-index in real time. As a result, retrieval quality is generally understudied and often deprioritised in favour of generation-oriented metrics. In this work, we propose auditing retrieval coverage by probing for evidence of missing documents rather than enumerating every relevant one. Our method Re:CAP (REtrieval Coverage Audit by iterative Probing) is a reference-free audit loop applied to a deployed RAG pipeline’s initial answer and retrieved context: it identifies the topics already covered, generates probing questions for plausibly missing topics, retrieves candidate documents, and applies an LLM-as-judge to retain only those that introduce previously-unretrieved information. On four public benchmarks, Re:CAP recovers 9–29% of gold labels that flat BM25 top-500 cannot reach, rising to 48% on TREC-COVID. On MuSiQue Re:CAP beats flat hybrid top-500 by +12.9 pp on recall at less than half the document budget. An ensemble BM25, dense, and hybrid baseline (top-500 each) still leaves out 21.2% of gold docs on TREC-COVID that Re:CAP recovers; human annotators judge that 78.9% of those structurally distinct documents add new information to the baseline answer (Fleiss \ensuremathąppa = 0.79, n = 123), and 73.9% on live production traffic (n = 180). End-to-end recall is reproducible to within \ensuremath\pm1% across three independent runs, making Re:CAP a stable instrument for periodic retrieval audits.
%U https://aclanthology.org/2026.emnlp-industry.150/
%P 2532-2565
Markdown (Informal)
[Re:CAP - Auditing Retrieval Coverage in Production RAG Pipelines](https://aclanthology.org/2026.emnlp-industry.150/) (Joshi et al., EMNLP 2026)
ACL