Multi-Agent Systems (MAS) are commonly used to improve reasoning diversity and robustness by simulating interactions among agents with distinct roles. However, prior work often entangles the contribution of the multi-agent architecture with that of prompt conditioning, making the source of observed diversity gains unclear. We address this confound with a controlled study on divergent thinking tasks, using identical prompt conditioning for MAS and single agent baseline. Under these matched conditions, single agent setups consistently outperform multi-agent systems in semantic diversity. We attribute this gap to information visibility: parallel agents often converge on overlapping ideas, whereas a single agent model can condition on its own generation to avoid redundancy. We further find that a Multi-Output strategy, which prompts a single agent to produce multiple responses within a single inference pass, achieves the highest diversity without degrading logical validity. Together, these results point to a more efficient and effective way to expand diversity, with implications for the design of more efficient agentic frameworks.

Counterfactual data augmentation (CDA) is a promising strategy for improving hate speech classification, but automating counterfactual text generation remains a challenge. Strong attribute control can distort meaning, while prioritizing semantic preservation may weaken attribute alignment. We propose **Gradient-assisted Energy-based Sampling (GENES)** for counterfactual text generation, which restricts accepted samples to text meeting a minimum BERTScore threshold and applies gradient-assisted proposal generation to improve attribute alignment. Compared to other methods that solely rely on either prompting, gradient-based steering, or energy-based sampling, GENES is more likely to jointly satisfy attribute alignment and semantic preservation under the same base model. When applied to data augmentation, GENES achieved the best macro F1-score in two of three test sets, and it improved robustness in detecting targeted abusive language. In some cases, GENES exceeded the performance of prompt-based methods using a GPT-4o-mini, despite relying on a smaller model (Flan-T5-Large). Based on our cross-dataset evaluation, the average performance of models aided by GENES is the best among those methods that rely on a smaller model (Flan-T5-L). These results position GENES as a possible lightweight and open-source alternative.

Social media has emerged as a valueable source for early pandemic detection, as repeated mentions of symptoms by users may signal the onset of an outbreak. However, to be a reliable system, validation through fact-checking and verification against official health records is essential. Without this step, systems risk spreading misinformation to the public. The effectiveness of these systems also depend on their ability to process data in multiple languages, given the multilingual nature of social media data.Yet, many NLP datasets and disease surveillance system remain heavily English-centric, leading to significant performance gaps for low-resource languages.This issue is especially critical in Southeast Asia, where symptom expression may vary culturally and linguistically.Therefore, this study evaluates the symptom detection capabilities of LLMs in social media posts across multiple languages, models, and symptoms to enhance health-related fact-checking. Our results reveal significant language-based discrepancies, with European languages outperforming under-resourced Southeast Asian languages. Furthermore, we identify symptom-specific challenges, particularly in detecting respiratory illnesses such as influenza, which LLMs tend to overpredict.The overestimation or misclassification of symptom mentions can lead to false alarms or public misinformation when deployed in real-world settings. This underscores the importance of symptom detection as a critical first step in medical fact-checking within early outbreak detection systems.