Generative retrieval (GR) maps queries directly to document identifiers (docids) using parametric knowledge. However, this design makes corpus expansion costly: adding new documents requires updating model parameters to encode new document-docid associations incurs repeated training and catastrophic forgetting of previously indexed documents. In this work, we revisit incremental GR as an in-context retrieval problem, where newly added documents are supplied as inference-time document-docid evidence. We propose ICICLE, an in-context indexing framework that performs source-aware docid generation over both parametric memory and context-provided document-docid pairs. ICICLE combines a ‘[COPY]‘-based routing mechanism, preference-based calibration, and large context adaptation to distinguish context-grounded retrieval from parametric retrieval. Experiments on MS MARCO and NQ320K show that ICICLE improves retrieval of newly introduced documents while preserving seen-document retention without corpus-specific retraining. Our analysis further shows that high-shot degradation is mainly caused by routing failure, highlighting source-selection calibration as a key bottleneck for scaling in-context generative retrieval.

Vision-Language Models (VLMs) often struggle in Taiwanese Mandarin environments due to region-specific orthographic and cultural context. We introduce VisTW, a comprehensive benchmark featuring (i) multiple-choice questions (3,795 academic questions) and (ii) free-form generation evaluation (141 Taiwanese-context free-form pairs). Beyond standard accuracy, we investigate character mixing— the unintended production of Simplified Chinese characters under Taiwanese-Mandarin-style prompts—and propose a human-grounded purity penalty derived from perceptual thresholds measured from users. Our evaluation reveals substantial character contamination (3%–19%) across state-of-the-art VLMs. We find that Gemini-3-Pro significantly outperforms the strongest open-weight baseline, Qwen3 235B MoE, by up to 22 percentage points on dialogue tasks once the purity penalty is applied. These results highlight orthographic consistency as a vital, yet overlooked, dimension for localized multimodal evaluation and deployment.