Joachim Baumann
Author directory2026
WildSEEK: Evaluating Language Models for Information-Seeking
Tanise Ceron | Joachim Baumann | Elisa Bassignana | Berat Cabuk | Dirk Hovy | Debora Nozza
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Tanise Ceron | Joachim Baumann | Elisa Bassignana | Berat Cabuk | Dirk Hovy | Debora Nozza
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Language models are increasingly mediating information access to end users, urging a systematic evaluation of their responses for a fair and reliable information ecosystem. Existing evaluations, however, are often topic-specific or synthetic, limiting their ability to capture the complexity of "in the wild" information-seeking queries and the risks present in model responses. To address this gap, we introduce WildSEEK, a manually annotated dataset of 3k information-seeking queries from real user interactions, and an evaluation framework for LLM-generated responses. WildSEEK includes annotations for risk-sensitive domains (e.g. health and financial information), and distinguishes factoid queries from analytical queries which seek responses beyond facts. We train classifiers on WildSEEK to analyze more than 1.8M realistic user queries. We find that over a third of information-seeking queries are high-risk and more often analytical. Our findings show that LLM responses fail more often in four criteria: sycophantic behavior, overreliance, a default US-centric perspective, and poor handling of vulnerable populations — with failure rates being mostly higher for analytical queries. By providing methods to monitor the reliability, safety, and fairness of LLM behavior, our dataset and evaluation framework offer an empirical foundation for the broader question of how these systems should behave as they take on a growing role in information access.
API Benchmark Scores Do Not Reliably Transfer to Chatbot Interfaces
Jennifer Wang | Joachim Baumann | Daniel E. Ho | Sanmi Koyejo
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Jennifer Wang | Joachim Baumann | Daniel E. Ho | Sanmi Koyejo
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Benchmark scores are a central currency in model releases: they inform purchasing decisions, shape public trust, and influence policy. Yet, a key assumption underlying benchmark scores is that the model performance measured through APIs faithfully reflects the behavior of deployed systems.
We challenge this assumption by auditing ChatGPT, Claude, and Gemini across seven systems and nine benchmarks spanning general capability, social bias, and sycophancy. We find systematic API–interface differences in both accuracy and consistency. On average, API evaluations score 3.4 percentage points higher in accuracy and 2.1 percentage points higher in test–retest agreement than corresponding interface evaluations. For ChatGPT, the performance difference between API and interface access rivals the API-only difference between GPT 5.3 and GPT 5.4. Put differently, switching access surfaces can degrade performance as much as downgrading a full model generation.
We further test whether exposed API controls can reproduce interface behavior by varying system prompts, sampling parameters, and reasoning settings. These controls shift behavior in some cases but do not reliably eliminate the gap. Our findings document a context-validity gap: measurements obtained through APIs do not necessarily generalize to corresponding deployed interfaces, complicating the use of API evaluations as proxies for deployed systems.
We challenge this assumption by auditing ChatGPT, Claude, and Gemini across seven systems and nine benchmarks spanning general capability, social bias, and sycophancy. We find systematic API–interface differences in both accuracy and consistency. On average, API evaluations score 3.4 percentage points higher in accuracy and 2.1 percentage points higher in test–retest agreement than corresponding interface evaluations. For ChatGPT, the performance difference between API and interface access rivals the API-only difference between GPT 5.3 and GPT 5.4. Put differently, switching access surfaces can degrade performance as much as downgrading a full model generation.
We further test whether exposed API controls can reproduce interface behavior by varying system prompts, sampling parameters, and reasoning settings. These controls shift behavior in some cases but do not reliably eliminate the gap. Our findings document a context-validity gap: measurements obtained through APIs do not necessarily generalize to corresponding deployed interfaces, complicating the use of API evaluations as proxies for deployed systems.
Prompt Revision as a Source of Cultural Bias in Text-to-Image Systems
Aleksandra Urman | Elsa Lichtenegger | Salima Jaoua | Azza Bouleimen | Robin Forsberg | Corinna Hertweck | Stefania Ionescu | Nicolò Pagan | Ancsa Hannak | Joachim Baumann
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Aleksandra Urman | Elsa Lichtenegger | Salima Jaoua | Azza Bouleimen | Robin Forsberg | Corinna Hertweck | Stefania Ionescu | Nicolò Pagan | Ancsa Hannak | Joachim Baumann
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Commercial text-to-image systems silently revise user prompts before generating images, a step users typically cannot disable or even see. Existing audits of cultural bias examine only the final images and treat generation as a single pipeline, so they cannot tell where the bias originates. We introduce WORLDVIEW, a multilingual benchmark of 8,960 prompts across 15 languages and 31 language–context pairings. Using it, we audit the revision layer in three systems (DALL-E-3, Imagen-4, GPT-Image-1.5) through a three-step analysis of how heavily it marks each cultural context, whether it flattens that context into a narrow vocabulary, and whether that vocabulary is stereotypical. Relative to a no-context English baseline, the US is the least-marked context, while non-Western and non-Anglophone contexts are marked far more heavily, flattened into narrow vocabularies applied across topically diverse prompts, and reduced to recognizable cultural stereotypes. Comparing images from original versus revised prompts on models without a revision layer, we identify the layer itself as a previously undocumented, causal source of this stereotyping. To locate cultural bias, and fix it, we must audit the system as deployed, not the model alone.