Fudan & Shanghai AI Lab map PEFT recipes for MoE LLMs: tune experts alone, LoRA/DoRA win

kalyan_kpl · x · 2026-10-20

A large-scale empirical study from Fudan University, Shanghai AI Laboratory and collaborators systematically establishes PEFT design recipes for MoE LLMs across three backbones. Key findings: adapting MoE experts alone gives the highest downstream performance with competitive general-capability retention at equal parameter budgets; native expert-weight updates beat adapters that bypass experts; LoRA and DoRA define the strongest operating region; no nonzero load-balancing coefficient Pareto-dominates the zero baseline. A weight-level redesign of MoE²-LoRA on Qwen3 moves the module-level bypass pool into native expert weights, improving four upstream endpoints by 2.4–17.9 points with 17% fewer trainable params at 3.2-point average downstream cost.

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