Multimodal Large Language Models (MLLMs) show strong potential for cross-modal understanding by integrating powerful language models with multimodal encoders. However, extending MLLMs to handle a diverse range of modalities introduces two critical and intertwined challenges: (1) the reliance on fully paired multimodal data, often scarce or costly to acquire across all modalities, and (2) the computational inefficiency from processing numerous modality tokens and requiring substantial model updates for each new modality. To address these challenges, we enable MLLMs to handle missing modalities by generating representations for absent inputs. Furthermore, recognizing that an increasing number of modalities leads to linearly scaling token counts and that lengthy generated sequences can hinder performance, we employ a dual-stage compression mechanism. It first reduces the number of tokens per modality and then condenses information from multiple modalities into a single, compact token sequence. This culminates in Flex-M³, a novel MLLM framework designed for flexible and efficient learning across arbitrary combinations of modalities. Experiments across diverse multimodal benchmarks and backbones demonstrate that Flex-M³ robustly handles varied modality inputs and scales efficiently. Notably, Flex-M outperforms its counterpart trained on only full-modality data, with consistent improvements of 2.29%, 3.15%, 11.01% on multimodal reasoning tasks NExT-QA, MUSIC-AVQA, SQA3D. Moreover, Flex-M³ demonstrates superior robustness during inference, even when a high proportion of modalities are missing from the input samples, showcasing its capacity for complex, data-scarce multimodal applications.

Translating natural language into SQL (Text2SQL) is a longstanding challenge at the intersection of natural language understanding and structured data access. While large language models (LLMs) have significantly improved fluency in SQL generation, producing correct and executable SQL, particularly for complex queries, remains a bottleneck. We present Arctic-Text2SQL-R1, a reinforcement learning (RL) framework and model family designed to generate accurate, executable SQL using a lightweight reward signal based solely on execution correctness. Our approach avoids brittle intermediate supervision and complex reward shaping, promoting stable training and alignment with the end task. Combined with carefully curated data, strong supervised initialization, and effective training practices, Arctic-Text2SQL-R1 achieves state-of-the-art execution accuracy across six diverse Text2SQL benchmarks and ranks among the leading entries on the BIRD leaderboard. Notably, our 7B model outperforms prior 70B-class systems, highlighting the framework’s scalability and efficiency. We further demonstrate inference-time robustness through simple extensions like value retrieval and majority voting. Extensive experiments and ablation studies offer both positive and negative insights, providing practical guidance for future Text2SQL research.

Recent work has shown that directly fine-tuning large language models (LLMs) for dense retrieval yields strong performance, but their substantial parameter counts make them computationally inefficient. While prior studies have revealed significant layer redundancy in LLMs for generative tasks, it remains unclear whether similar redundancy exists when these models are adapted for retrieval tasks, which require encoding entire sequences into fixed representations rather than generating tokens iteratively. To this end, we conduct a comprehensive analysis of layer redundancy in LLM-based dense retrievers. We find that, in contrast to generative settings, MLP layers are substantially more prunable, while attention layers remain critical for semantic aggregation. Building on this insight, we propose EffiR, a framework for developing efficient retrievers that performs large-scale MLP compression through a coarse-to-fine strategy (coarse-grained depth reduction followed by fine-grained width reduction), combined with retrieval-specific fine-tuning. Across diverse BEIR datasets and LLM backbones, EffiR achieves substantial reductions in model size and inference cost while preserving the performance of full-size models.

Mixture-of-Experts (MoE) has emerged as a promising approach for scaling large language models efficiently. However, how to design a desired MoE architecture given performance, efficiency, or safety goals remains absent. Existing benchmarks often focus on isolated aspects (e.g., reasoning, efficiency, safety), and there is a lack of consensus on optimal design choices, such as the number and size of experts, the type of routers, and the regularization during pre-training, or strategies like freezing, learning rate adjustments, and limiting expert collaboration during fine-tuning, with prior works often yielding conflicting conclusions. Motivated by this research gap, we introduce MoEBench, the first comprehensive assessment of MoE designs across the three dimensions of reasoning ability, efficiency, and safety. Our benchmark systematically evaluates optimal architectural choices during both pre-training and fine-tuning phases. We evaluate two popular MoE backbones across four dimensions of design choices on over eight metrics. Our empirical findings uncover hidden underlying correlations among MoE design choices. Specifically, we observe that (1) token-level routing and z-loss regularization improve reasoning performance; (2) shared experts enhance training stability but reduce specialization; and (3) collaboration-constrained routing and freezing strategies significantly influence load balance, specialization, and safety alignment. Furthermore, we propose three “sweet point” combinations of optimal strategies tailored to different scenarios. We hope this study provides actionable insights for building more robust, efficient, and secure MoE models. Code, checkpoints, and raw data will be released upon acceptance of the paper.