Large language models (LLMs) often answer ambiguous inputs as if they had a single intended meaning. This is problematic because input ambiguity is an upstream source of uncertainty: when a prompt admits multiple valid interpretations, the key question is whether the model should answer directly at all. Existing input uncertainty methods often rely on LLM-generated statements or clarifications, but such transformations may already disambiguate the input before the ambiguity is measured. We propose a label-preserving perturbation framework for input ambiguity detection in which perturbations remain close to the original input while preserving its label. We instantiate this principle with two detectors: a black-box rule-based perturbation library and a white-box importance-guided method using model-internal signals. Experiments across four datasets in open-domain, conversational, and visual QA show that our methods outperform output-side uncertainty baselines and LLM-paraphrase-based perturbation baselines. Our results highlight the importance of detecting ambiguity before attempting to disambiguate it. Our code is available here.

The increasing complexity of modern driving systems demands efficient collection and analysis of specific driving scenarios that are crucial for system development and validation. Current approaches either rely on massive data collection followed by manual filtering, or rigid threshold-based recording systems that often miss important edge cases. In this paper, we present Distributed Adaptive Scene Recognition (DASR), a novel multi-agent cloud-edge framework for language-guided scene detection in connected vehicles. Our system leverages the complementary strengths of cloud-based large language models and edge-deployed vision language models to intelligently identify and preserve relevant driving scenarios while optimizing limited on-vehicle buffer storage. The cloud-based LLM serves as an intelligent coordinator that analyzes developer prompts to determine which specialized tools and sensor data streams should be incorporated, while the edge-deployed VLM efficiently processes video streams in real time to make relevant decisions. Extensive experiments across multiple driving datasets demonstrate that our framework achieves superior performance compared to larger baseline models, with exceptional performance on complex driving tasks requiring sophisticated reasoning. DASR also shows strong generalization capabilities on out-of-distribution datasets and significantly reduces storage requirements (28.73 %) compared to baseline methods.