Recent OCR models achieve strong results on document benchmarks, with several 1–2B OCR-specialized models surpassing much larger general multimodal LLMs (MLLMs). However, complex real-world documents often contain blur, cropping, curved text, handwriting, and unfamiliar structures, which remain challenging for current OCR systems. We trace this gap to a shift in the error source: errors on canonical benchmarks mainly arise from layout analysis, including localization, element classification, and reading order, while errors under these challenging conditions mainly arise from content recognition. To this end, we propose CL-OCR, a two-stage framework that first fuses semantic structure from an MLLM-based detector with geometric candidates from a vision detector to obtain calibrated layouts, then enhances recognition via a shared LoRA adapter gated by a lightweight router. We further construct OCRWildBench and a companion training split to study these conditions. Experiments show that CL-OCR remains competitive on canonical benchmarks and achieves the strongest overall performance among OCR-specialized models on OCRWildBench.

Large vision language models (LVLMs) have improved the document understanding capabilities remarkably, enabling the handling of complex document elements, longer contexts, and a wider range of tasks. However, existing document understanding benchmarks have been limited to handling only a small number of pages and fail to provide a comprehensive analysis of layout elements locating. In this paper, we first define three primary task categories: Long Document Understanding, numerical Reasoning, and cross-element Locating, and then propose a comprehensive benchmark—LongDocURL—integrating above three primary tasks and comprising 20 sub-tasks categorized based on different primary tasks and answer evidences. Furthermore, we develop a semi-automated construction pipeline and collect 2,325 high-quality question-answering pairs, covering more than 33,000 pages of documents, significantly outperforming existing benchmarks. Subsequently, we conduct comprehensive evaluation experiments on both open-source and closed- source models across 26 different configurations, revealing critical performance gaps in this field. The code and data: https://github.com/dengc2023/LongDocURL.