Marin 535B-A23B Architecture Postmortem: MoE, XSA, MuonH and 18T-Token Curves

StasBekman · x · 2026-11-13

Marin published detailed training notes on the architecture decisions behind 535B-A23B, pretrained on 18T tokens — packed with plots and decision notes for practitioners. Highlights: Latent MoE (8 of 384 experts, 2 shared, SwiGLU); 3:1 sliding-window/global attention with GQA and gated attention; partial RoPE on local and NoPE on global layers; MuonH/AdamH Hyperball optimizers; exclusive self-attention (XSA); kernel-4 short convolutions; top-k quantile balancing routing; a wide-shallow 6144-hidden/48-layer design (128 width:depth); no leading dense layers. Full per-step loss curves mark the ragged all-to-all EP switch, data-mix updates, and 4k→16k→65k context extensions.

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