arXiv:2610.23064v1 Announce Type: new Abstract: Fine-grained Mixture-of-Experts (MoE) is the de facto architecture for scaling large language models. However, dynamic expert load imbalance causes severe memory fluctuations that degrade training efficiency. Existing systems rely on static memory provisioning: they either over-provision, leaving GPU memory idle during normal execution, or under- provision, inviting out-of-memory crashes and costly manual rollbacks when load spikes occur. To address these challenges, we propose BaGuaLu-2, a large-scale MoE training system that eliminates this dilemma through flexible provisioning. By transforming memory allocation from a static, one-time tuning choice into a continuous and fine-grained control. BaGuaLu-2 grants exact activation memory on demand for each training batch. Furthermore, it offsets any dynamic management overhead through system optimizations. BaGuaLu-2 demonstrates exceptional scalability, training a model with 1040 billion parameters across 12,288 GPUs while sustaining over 2 EFlops at 35% MFU. Compared with state-of-the-art systems, BaGuaLu-2 delivers 1.14x and 1.13x average throughput improvements over Megatron-Kuai and AdaPipe, respectively.