@inproceedings{tint-2025-prood,
title = "{PROOD}: A Simple {LLM} Out-of-Distribution Guardrail Leveraging Response Semantics",
author = "Tint, Joshua",
editor = "Christodoulopoulos, Christos and
Chakraborty, Tanmoy and
Rose, Carolyn and
Peng, Violet",
booktitle = "Findings of the Association for Computational Linguistics: EMNLP 2025",
month = nov,
year = "2025",
address = "Suzhou, China",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2025.findings-emnlp.1272/",
doi = "10.18653/v1/2025.findings-emnlp.1272",
pages = "23428--23438",
ISBN = "979-8-89176-335-7",
abstract = "Out-of-distribution (OOD) detection is a key safeguard for large language models, especially when they{'}re deployed in real-world applications. However, existing OOD methods often struggle with prompts that are deliberately obfuscated, context-dependent, or superficially benign{---}making it hard to distinguish between harmless queries and adversarial or dangerous ones. These methods typically assess prompts in isolation, missing important semantic cues from the model{'}s response. We introduce PROOD, prompt-response OOD detection, a framework that jointly analyzes LLM prompts \textit{and their corresponding outputs} to improve semantic understanding. PROOD supports zero-shot multiclass detection using synthetic data generation and it offers a tunable probabilistic classification output. We validate PROOD on three challenging benchmarks{---}TrustLLM, OR-Bench, and AdvBench{---}where consistently outperforms prior OOD techniques, improving F1 scores by up to 6.3 points, from 0.871 to 0.934. Our results show that incorporating model responses enables more accurate, context-aware OOD detection in complex and adversarial prompt environments."
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<abstract>Out-of-distribution (OOD) detection is a key safeguard for large language models, especially when they’re deployed in real-world applications. However, existing OOD methods often struggle with prompts that are deliberately obfuscated, context-dependent, or superficially benign—making it hard to distinguish between harmless queries and adversarial or dangerous ones. These methods typically assess prompts in isolation, missing important semantic cues from the model’s response. We introduce PROOD, prompt-response OOD detection, a framework that jointly analyzes LLM prompts and their corresponding outputs to improve semantic understanding. PROOD supports zero-shot multiclass detection using synthetic data generation and it offers a tunable probabilistic classification output. We validate PROOD on three challenging benchmarks—TrustLLM, OR-Bench, and AdvBench—where consistently outperforms prior OOD techniques, improving F1 scores by up to 6.3 points, from 0.871 to 0.934. Our results show that incorporating model responses enables more accurate, context-aware OOD detection in complex and adversarial prompt environments.</abstract>
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%0 Conference Proceedings
%T PROOD: A Simple LLM Out-of-Distribution Guardrail Leveraging Response Semantics
%A Tint, Joshua
%Y Christodoulopoulos, Christos
%Y Chakraborty, Tanmoy
%Y Rose, Carolyn
%Y Peng, Violet
%S Findings of the Association for Computational Linguistics: EMNLP 2025
%D 2025
%8 November
%I Association for Computational Linguistics
%C Suzhou, China
%@ 979-8-89176-335-7
%F tint-2025-prood
%X Out-of-distribution (OOD) detection is a key safeguard for large language models, especially when they’re deployed in real-world applications. However, existing OOD methods often struggle with prompts that are deliberately obfuscated, context-dependent, or superficially benign—making it hard to distinguish between harmless queries and adversarial or dangerous ones. These methods typically assess prompts in isolation, missing important semantic cues from the model’s response. We introduce PROOD, prompt-response OOD detection, a framework that jointly analyzes LLM prompts and their corresponding outputs to improve semantic understanding. PROOD supports zero-shot multiclass detection using synthetic data generation and it offers a tunable probabilistic classification output. We validate PROOD on three challenging benchmarks—TrustLLM, OR-Bench, and AdvBench—where consistently outperforms prior OOD techniques, improving F1 scores by up to 6.3 points, from 0.871 to 0.934. Our results show that incorporating model responses enables more accurate, context-aware OOD detection in complex and adversarial prompt environments.
%R 10.18653/v1/2025.findings-emnlp.1272
%U https://aclanthology.org/2025.findings-emnlp.1272/
%U https://doi.org/10.18653/v1/2025.findings-emnlp.1272
%P 23428-23438
Markdown (Informal)
[PROOD: A Simple LLM Out-of-Distribution Guardrail Leveraging Response Semantics](https://aclanthology.org/2025.findings-emnlp.1272/) (Tint, Findings 2025)
ACL