@inproceedings{zhang-etal-2026-stars,
title = "{STARS}: Skill Triage via Activation Risk Scoring for {LLM} Agents",
author = "Zhang, Guijia and
Yang, Shu and
Gong, Xilin and
Wang, Di",
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.891/",
doi = "10.18653/2026.findings-emnlp.891",
pages = "18874--18890",
ISBN = "979-8-89176-462-0",
abstract = "The risk of an agent skill call depends not on the skill alone but on the invocation context: the same file-reading skill is benign when listing logs, yet dangerous when tainted content steers the agent toward secret exfiltration. We formalize invocation-time auditing: intercept a proposed skill call before execution and score its risk from the user request, the candidate skill, and the runtime context. STARS implements this as a three-stage pipeline that fuses a static capability prior with a request-conditioned invocation scorer. The primary configuration, STARS-LLM, uses an LLM judge; STARS-Rules is a deterministic, API-free alternative. On SIA-Bench, a 3,000-record synthetic benchmark with a 180-record human check at Fleiss {\ensuremath{\kappa}} = 0.709, request-conditioned scoring improves high-risk retrieval on held-out indirect prompt injection, where static metadata cannot see the attack. On a frozen 500/100 scoring subset, STARS-LLM raises rules-only HR-AUPRC from 0.297 to 0.728 in-distribution and from 0.504 to 0.757 on held-out IPI. That gain is in ranking: under frozen thresholds, held-out classification accuracy does not improve. SIA-Bench is a ranking stress test, not an estimate of real-world prevalence."
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<abstract>The risk of an agent skill call depends not on the skill alone but on the invocation context: the same file-reading skill is benign when listing logs, yet dangerous when tainted content steers the agent toward secret exfiltration. We formalize invocation-time auditing: intercept a proposed skill call before execution and score its risk from the user request, the candidate skill, and the runtime context. STARS implements this as a three-stage pipeline that fuses a static capability prior with a request-conditioned invocation scorer. The primary configuration, STARS-LLM, uses an LLM judge; STARS-Rules is a deterministic, API-free alternative. On SIA-Bench, a 3,000-record synthetic benchmark with a 180-record human check at Fleiss \ensuremathąppa = 0.709, request-conditioned scoring improves high-risk retrieval on held-out indirect prompt injection, where static metadata cannot see the attack. On a frozen 500/100 scoring subset, STARS-LLM raises rules-only HR-AUPRC from 0.297 to 0.728 in-distribution and from 0.504 to 0.757 on held-out IPI. That gain is in ranking: under frozen thresholds, held-out classification accuracy does not improve. SIA-Bench is a ranking stress test, not an estimate of real-world prevalence.</abstract>
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%0 Conference Proceedings
%T STARS: Skill Triage via Activation Risk Scoring for LLM Agents
%A Zhang, Guijia
%A Yang, Shu
%A Gong, Xilin
%A Wang, Di
%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-stars
%X The risk of an agent skill call depends not on the skill alone but on the invocation context: the same file-reading skill is benign when listing logs, yet dangerous when tainted content steers the agent toward secret exfiltration. We formalize invocation-time auditing: intercept a proposed skill call before execution and score its risk from the user request, the candidate skill, and the runtime context. STARS implements this as a three-stage pipeline that fuses a static capability prior with a request-conditioned invocation scorer. The primary configuration, STARS-LLM, uses an LLM judge; STARS-Rules is a deterministic, API-free alternative. On SIA-Bench, a 3,000-record synthetic benchmark with a 180-record human check at Fleiss \ensuremathąppa = 0.709, request-conditioned scoring improves high-risk retrieval on held-out indirect prompt injection, where static metadata cannot see the attack. On a frozen 500/100 scoring subset, STARS-LLM raises rules-only HR-AUPRC from 0.297 to 0.728 in-distribution and from 0.504 to 0.757 on held-out IPI. That gain is in ranking: under frozen thresholds, held-out classification accuracy does not improve. SIA-Bench is a ranking stress test, not an estimate of real-world prevalence.
%R 10.18653/2026.findings-emnlp.891
%U https://aclanthology.org/2026.findings-emnlp.891/
%U https://doi.org/10.18653/2026.findings-emnlp.891
%P 18874-18890
Markdown (Informal)
[STARS: Skill Triage via Activation Risk Scoring for LLM Agents](https://aclanthology.org/2026.findings-emnlp.891/) (Zhang et al., Findings 2026)
ACL