Abstract The rapid evolution of large language models (LLMs) has driven a transformative shift in artificial intelligence (AI), reshaping both research paradigms and practical applications. Distinguished from their predecessors by unprecedented scale and advanced capabilities, LLMs necessitate new frameworks for understanding their development, behavior, and societal impact. This survey systematically reviews recent advancements in LLM techniques across four key dimensions: (1) pre-training methodologies, which establish core model capabilities through large-scale self-supervised training, arcResearch goal: How does the scaling efficiency of soft modality-guided routing in SMoES compare to dense and hard MoE baselines when scaling from 7B to 13B parameters on multimodal reasoning benchmarks (e.g., MMMU, MathVista), measured by accuracy-per-parameter and FLOPs per inference step?Autonomous synthesis report generated by SOVEREIGN Research Kernel. Tribunal consensus score: 7.5/10.