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MoE Routing Design

A cluster of 2026 papers questioning the rigid inductive biases of the standard Mixture-of-Experts routing pipeline — external router, TopK, Softmax, hard-coded per-layer expert counts, fixed attention/FFN FLOPs split, auxiliary load-balancing loss with a tuned coefficient. Each contribution removes or replaces one (or more) of these design axes: the architecture-side end ranges from share router weights across layers (PathMoE) to eliminate the router entirely (Routing-Free MoE, STEM); the training-side end ranges from unify token-balancing and expert-balancing to make the load-balancing coefficient adaptive to give an explicit scaling law for attention vs. expert FLOPs allocation. Common thread: the empirical token-path distribution is highly non-uniform, and constraints that fight that non-uniformity (uniform per-layer sparsity, fixed TopK, equal-FLOPs-per-token) leave loss on the table.

  • [2026-07-19] RynnBrain 1.1 — Open Embodied Foundation Models (Alibaba DAMO Academy): RynnBrain 1.1-122B-A10B is the first embodied-VLM at 122B-scale sparse MoE on this page: 122B total / ~10B activated, built on Qwen3.5-122B-A10B, released alongside dense 2B and 9B siblings under a shared training recipe to enable systematic scaling comparisons of embodied cognition, spatial reasoning, grounding, and planning.
  • [2026-07-16] Kimi K3 — Open Frontier Intelligence (2.8T MoE with KDA + AttnRes): Kimi K3 scales Quantile Balancing (Su, 2026-02) to 16-of-896 expert activation inside “Stable LatentMoE” at 2.8T parameters — the deepest sparsity ratio yet in the cluster to run in a shipping frontier model.
  • [2026-07-16] RxBrain: Embodied Cognition Foundation Model with Joint Language-Visual Reasoning and Imagination: RxBrain routes visual-understanding vs visual-generation tokens to separate FFN experts within a shared vision transformer (shared QKV), with the generation expert widened 2× (6,144→12,288 intermediate dim).
  • [2026-07-15] Introducing Inkling — Thinking Machines' open-weights 975B/41B MoE multimodal reasoning model: Inkling adopts the DeepSeek-V3 routing recipe verbatim at 975B-total / 41B-active scale: 256 routed experts + 2 shared, top-6 routed active per token, sigmoid router with auxiliary-loss-free load-balancing bias, and joint normalization of routed + shared expert scores before combining outputs. Concrete datapoint that the DeepSeek-V3 MoE recipe transfers to a from-scratch frontier training run by an independent lab.
  • [2026-07-14] Inside TPU and GPU Clusters: The Anatomy of Collective Communication: Grounds MoE Expert Parallelism in the underlying All-to-All primitive that dispatches tokens to expert-hosting devices: derives All-to-All as a “sharded transpose” on ring/path topologies (TPU) and shows that inside an NVSwitch node balanced All-to-All is ~2× faster than a bidirectional 1D torus ring at equal bandwidth. Complements DeepEP + NVSHMEM (which optimize the irregular per-token dispatch inside NCCL’s blind spot) by explaining what the balanced baseline looks like.
  • [2026-07-10] LingBot-VA 2.0: Native Video-Action Pretraining for Generalizable Robot Control: First filed instance of a DeepSeek-V3-style routed MoE (128 experts / top-8 / group-limited routing / auxfree Loss-Free-Balancing bias correction) inside a video-generation stream used as a policy backbone, rather than in an LLM or T2I model. Reports MoE-13B-A1.9B matching a Dense-5B baseline at both step-aligned training loss (dense slightly lower) and wall-clock-aligned final loss, and pairs it with a dense action expert under the Mixture-of-Transformers pattern — capacity added on the modeling-heavy modality only. Concrete datapoint that the LLM-side MoE recipe transfers cleanly to causal video-action pretraining without an optimization tax.
  • [2026-07-08] LingBot-Video: Scaling Mixture-of-Experts Video Pretraining for Embodied Intelligence: LingBot-Video is the first from-scratch MoE video-DiT datapoint in the cluster: imports DeepSeekMoE’s fine-grained-experts + shared-expert-isolation + auxiliary-loss-free bias + group-limited sigmoid routing directly into a video DiT (E=128, top-8), adds a sequence-wise Lseq to catch per-video routing imbalance that batch-level stats hide, and reports from-scratch scaling laws from 13B/A1.4B up to 120B/A11B — with fine-grained top-8-of-128 beating coarse top-4-of-64 under matched 13B total budget despite lower active FLOPs.
  • [2026-06-30] Agents-A1: A 35B MoE Agentic Foundation Model: Agents-A1 — another ~35B-total MoE entry in the open agentic-foundation cluster (alongside Qwen-AgentWorld-35B-A3B, Ornith-1.0-35B-MoE, Qwen3.6-35B-A3B), TP=1 serving config implies active-params fit a single GPU.
  • [2026-06-29] Demystifying NVSHMEM: A System-Level Analysis on Symmetric Memory and Device-Initiated Operations in GPU Communication: Uses DeepEP — the dispatch/combine library under every recent large MoE training/serving stack — as a case study for NVSHMEM’s device-side symmetric-memory model; explains why standard NCCL all-to-all is the wrong primitive for irregular per-token MoE dispatch and what NVSHMEM provides instead.
  • [2026-06-23] PithTrain: A Compact and Agent-Native MoE Training System: PithTrain provides a compact (11K-LoC) production-quality MoE training framework targeting Qwen3-MoE, GPT-OSS, and DeepSeek-V2-Lite on H100/B200 with EP-dispatch deduplication, FP8 weight cache across micro-batches, and DualPipeV-based EP all-to-all overlap on a separate communication stream. Matches Megatron-LM throughput on 4 of 5 configurations while shipping pure-Python self-contained per-model files under models/ (no shared layer skeleton or plugin registry) — a deliberate trade of cross-model reuse for local readability and agent-traceability.
  • [2026-05-28] Paris 2.0 — decentralized trained video generation model from Bagel Labs (bidhan announcement): Paris 2.0 announcement extends the router-over-independently-trained-experts design (no load balancing, no joint training) from image diffusion to video generation, claiming ~2× FVD over a monolithic iso-compute baseline.
  • [2026-05-24] ERNIE 4.5 Technical Report: ERNIE 4.5 Technical Report (Baidu, June 2025). Heterogeneous fine-grained MoE with text experts, vision experts (1/3 the intermediate dim of text experts, removed in the final layer), and a tier of shared experts; routing is modality-isolated — each token only sees experts of its own modality, plus the always-on shared experts; self-attention parameters are shared. Author claim is that text and vision expert activation patterns are intrinsically different (heatmap evidence: concentrated for text, dispersed for vision) so a single router collapses under multimodal continuation training. Adds two loss-side ingredients: a router-orthogonality auxiliary loss and a token-balanced multimodal LBL that compensates for the text-vs-visual token-count imbalance. Engineering: intra-node Expert Parallelism, FP8 mixed precision, hits 47% MFU on 2,016 H800s pretraining the largest (300B-A47B) language model. Three new axes for this page: modality-conditioned routing, router-direction orthogonalization, token-count-aware LBL.
  • [2026-05-24] MegaScale-MoE: Large-Scale Communication-Efficient Training of Mixture-of-Experts Models in Production: ByteDance Seed’s production MoE training system. Pairs Ulysses-style Sequence Parallelism for attention with Expert Parallelism for FFN, drops Tensor Parallelism entirely, and rejects Context Parallelism on causal-mask-imbalance grounds. Reports 1.88× MFU over Megatron-LM on a 352B MoE / 1,440 Hopper GPUs. Algorithmic-systems counterpart to Scalable Training of Mixture-of-Experts Models with Megatron Core‘s Parallel Folding (same TP-vs-MoE mismatch problem, opposite resolution) and sibling to veScale-FSDP: Flexible and High-Performance FSDP at Scale (same ByteDance team, different layer of the stack). Per-GPU-group auxiliary balance loss adopts DeepSeek-V2’s recipe and sits between the micro-batch and global-batch LBL scopes in the Demons in the Detail: On Implementing Load Balancing Loss for Training Specialized Mixture-of-Expert Models axis.
  • [2026-05-24] Slicing and Dicing MoEs — Margaret Li announcing a >2000-MoE-LM design-space study: Margaret Li announces “Slicing and Dicing MoEs”, a study that reports training >2000 MoE LMs across five design axes (total vs active experts, expert size, shared experts, routing, token dropping) and summarizes the sweep with a one-line ranking: expert size and count dominate. First artifact in the cluster to claim a multi-axis head-to-head; arxiv link not yet visible. Candidate empirical answer to the “multi-axis Pareto frontier is unmapped” open question below.
  • [2026-05-24] Raven Part 1 — Memory as a Set of Slots: Raven exports the MoE-routing vocabulary from FFN-experts to state-slots. Unifies SSMs (dense router rt=1r_t = \mathbf{1}) and SWA (one-hot cyclic router rt=etr_t = e_t) under a single state-update equation; Raven uses a learned sparse rtr_t to decide per-token which slots get the SSM decay-and-write and which are preserved verbatim. Imports the same questions the FFN-MoE thread is wrestling with (router sparsity, load balancing, top-k vs soft) into recurrent-state design.
  • [2026-05-24] Demons in the Detail: On Implementing Load Balancing Loss for Training Specialized Mixture-of-Expert Models: shows that the canonical LBL implementation is computed at micro-batch (≈ sequence-level) scope and silently forbids domain-specialized routing; a one-line all-reduce on fif_i to make balance corpus-level beats both micro-batch LBL and DeepSeek’s loss-free bias-update on both PPL and downstream accuracy up to 42.8B params, and produces visibly domain-specialized expert heatmaps.
  • [2026-05-24] Routing-Free Mixture-of-Experts: composes AoE (expert-internal scoring) with ReMoE (ReLU gating, no TopK/Softmax) and adds a per-expert bias to give a fully decentralized self-activation rule; pairs this with a unified β\beta-interpolated token+expert balancing loss and adaptive auxiliary coefficient; reports scaling gains at 0.8B and wider LR tolerance.
  • [2026-05-23] Path-Constrained Mixture-of-Experts: PathMoE shares router parameters across blocks of consecutive layers, sitting between independent-per-layer (standard MoE) and one-shared-router (Omni-Router ASR) on the constraint spectrum; analytically demonstrates that this amplifies natural path concentration.
  • [2026-05-23] Optimal Expert-Attention Allocation in Mixture-of-Experts: A Scalable Law for Dynamic Model Design: fits a closed-form scaling law for rr^* = fraction of per-token FLOPs spent in experts as a function of CC and sparsity SS; rr^* rises with compute.
  • [2026-05-23] Scalable Training of Mixture-of-Experts Models with Megatron Core: Megatron-Core MoE systems report — names the attention-vs-experts compute mismatch as the systems wall and provides Parallel Folding to resolve it.
  • [2026-05-23] DynaMoE: Dynamic Token-Level Expert Activation with Layer-Wise Adaptive Capacity for Mixture-of-Experts Neural Networks: percentile-threshold gate replaces TopK and sweeps six closed-form per-layer expert-count schedules at toy scale (<6M params); finds optimal schedule is task- and scale-dependent.
  • [2026-05-23] Quantile Balancing: A Hyperparameter-Free MoE Load Balancing Method: removes the auxiliary-loss / bias-update tuning axis via quantile balancing at 32B-A5B production scale.
  • [2026-05-22] STEM: Scaling Transformers with Embedding Modules: replaces the FFN with a static per-token embedding lookup, eliminating routing entirely — adjacent / opposite-direction alternative to the router-redesign thread.
  • Does eliminating routing transfer past 1B? Routing-Free MoE’s most aggressive design (no router, no TopK, no Softmax, no per-layer sparsity) reports gains widening at 0.8B but no run exists at frontier scale (>10B). PathMoE, the Su quantile recipe, and Demons-in-the-Detail’s global-batch LBL each have at least one 30B+-class datapoint; Routing-Free MoE does not.
  • Pretrained-MoE conversion. Every paper in the cluster trains from scratch. Adapting a pretrained Mixtral/DeepSeek MoE into router-free, path-constrained, global-batch-balanced, or quantile-balanced form via continued pretraining is explicitly future work everywhere — and the cost calculus changes radically if such conversion is cheap.
  • Composition. PathMoE constrains the router parameters, Routing-Free MoE removes the router, Optimal Expert-Attention Allocation in Mixture-of-Experts: A Scalable Law for Dynamic Model Design prescribes rr^*, Quantile Balancing removes the LB knob, and Demons-in-the-Detail rescopes the LB. The papers do not run head-to-head against each other or in combination; the multi-axis Pareto frontier is unmapped. Slicing and Dicing MoEs — Margaret Li announcing a >2000-MoE-LM design-space study claims a >2000-run multi-axis sweep with size + count as the dominant levers — once the underlying paper surfaces, it may close (or refine) this question.
  • Per-layer vs. global density: Routing-Free MoE’s 11-point PPL swing from global density enforcement is the cluster’s biggest single result, but only one paper measured it. Does the per-layer-uniform-sparsity bias hurt standard MoE / AoE / ReMoE by similar amounts? Demons-in-the-Detail’s temporal analogue — global vs. per-step balance scope — suggests the same answer holds along the time axis.
  • Path-distribution concentration as a diagnostic. PathMoE introduces path-occupancy and path-stability as metrics for routing quality; Demons-in-the-Detail’s expert-frequency-per-domain heatmaps are a related diagnostic. Could a path-concentration or domain-specialization metric replace the validation-perplexity proxy as the primary signal for routing design?
  • MoE-over-state vs. MoE-over-FFN. Raven applies the same routing primitives to the recurrent state. Open question: do the lessons from the FFN-side thread (global-batch LBL, soft-gate-not-TopK, per-layer-uniform-sparsity hurts, rr^* scaling law) transfer to slot routing in SSMs/Raven, or does the temporal structure of state updates change the answer?
  • Drop-TP vs Parallel-Folding for the attention/MoE parallelism mismatch. MegaScale-MoE (MegaScale-MoE: Large-Scale Communication-Efficient Training of Mixture-of-Experts Models in Production) and Megatron-Core MoE (Scalable Training of Mixture-of-Experts Models with Megatron Core) resolve the same problem with opposite recipes — drop TP for attention vs. keep TP/CP for attention but decouple parallelism groups. Both ship to production. No head-to-head comparison exists; the right answer likely depends on context length (CP / ring attention is argued necessary at ultra-long contexts, but rejected by MegaScale-MoE on causal-mask-imbalance grounds at production-typical lengths) and on intra-node topology (NVL8 vs NVL72).
  • Modality-conditioned routing vs single-router multimodal MoE. ERNIE 4.5 (ERNIE 4.5 Technical Report) argues for separate text-expert and vision-expert pools on the basis that text and vision activation patterns differ (concentrated vs dispersed) and a single router collapses. Open: at what model scale does single-router multimodal MoE collapse, vs when is the routing capacity sufficient to handle both modalities? No filed head-to-head comparison exists. Adjacent open question: is modality isolation a capacity fix (more routers per modality) or a gradient-interference fix (separate expert pools so that modality-specific FFN weights don’t get overwritten)?