FLAME-MoE: A Transparent End-to-End Research Platform for
  Mixture-of-Experts Language Models
Authors: name: Hao Kang, name: Zichun Yu, name: Chenyan Xiong

Recent large language models such as Gemini-1.5, DeepSeek-V3, and Llama-4
increasingly adopt Mixture-of-Experts (MoE) architectures, which offer strong
efficiency-performance trade-offs by activating only a fraction of the model
per token. Yet academic researchers still lack a fully open, end-to-end MoE
platform for investigating scaling, routing, and expert behavior. We release
FLAME-MoE, a completely open-source research suite composed of seven
decoder-only models, ranging from 38M to 1.7B active parameters, whose
architecture--64 experts with top-8 gating and 2 shared experts--closely
reflects modern production LLMs. All training data pipelines, scripts, logs,
and checkpoints are publicly available to enable reproducible experimentation.
Across six evaluation tasks, FLAME-MoE improves average accuracy by up to 3.4
points over dense baselines trained with identical FLOPs. Leveraging full
training trace transparency, we present initial analyses showing that (i)
experts increasingly specialize on distinct token subsets, (ii) co-activation
matrices remain sparse, reflecting diverse expert usage, and (iii) routing
behavior stabilizes early in training. All code, training logs, and model
checkpoints are available at https://github.com/cmu-flame/FLAME-MoE.