Qwen3.8-Flash-Next-REAM-288

Qwen3.8-Flash-Next with 288 of 512 experts per MoE layer, merged not pruned (REAM), in native bf16 for transformers. 251GB vs 360GB stock. MTP block included (its experts merged 512->288 as well) — vLLM-style qwen4_exp speculative decoding keeps working.

Method

REAM (arXiv 2604.04356, Samsung SAIL Montréal: Merging Improves Pruning of Experts in LLMs), offline adaptation: instead of dropping the 224 non-kept experts per layer (REAP), each is merged into its most-similar kept expert with saliency-proportional coefficients.

  • Kept set / slot order: exactly the per-layer REAP-288 manifest published by sh0wie (saliency calibrated on ~686K tokens of agentic-coding traffic) — full credit to that work; this build is a direct A/B against it.
  • Similarity (offline, no calibration run): cosine of router gate rows.
  • Merge coefficients: measured saliency from sh0wie's saliency_full_505.npz (its argsort reproduces his pinned manifest bit-for-bit), tempered and shrunk: w_i = (S_i/S_c)^2 * router_cos * count_confidence, with the centroid keeping at least 90% of itself. Raw proportional weights are catastrophic here (KL 1.397) because the real kept/dropped saliency gap is only ~1.6x — the merge dissolves the expert REAP chose to keep. Hungarian permutation alignment of intermediate channels before averaging (fp32 accumulate, bf16 out).
  • Trajectory flat_tsg_tsD: flat one-shot groups (canonical REAM)
  • Router: absorbed rows deleted; kept rows byte-identical to stock.
  • MTP block: same machinery, k-center centroids on its own gate rows.
  • A six-point ladder (see campaign/reports/truesal_ladder.md) locates the optimum: KL is minimised when kept experts give away ~9% of their mass — both heavier blending and near-pruning are worse.

Evaluation (A/B vs REAP prune, same harness, same hardware)

model KL vs stock (mean) rare-name probe (10 names) HumanEval subset (25 tasks)
stock 512e 0 0.97 90.0% (full 50)
REAP-288 recon (prune) 1.3066 0.91 92.0% (stock on same 25: 92.0%)
REAM-288 flat_tsg_tsD (this) 1.2564 0.94 not re-run for tsD; flat_sim (previous main, same pipeline) scored 88.0% vs stock 88.0% on its slice

KL: teacher-forced top-256 KL vs the stock model over a fixed mixed corpus (en/ru/code/rare-entities/agentic, ~10K positions). Probe: rare entities x 10 seeded sampled generations, pass = name reproduced intact; aggregates recomputed on the name subset common to all rows (a monitoring bug killed the winner's third probe batch mid-run). HumanEval: 25-task slices of a frozen 50-task subset, no-thinking, greedy; the two 288e models landed on different slices (2-task overlap), so each is paired with the stock score on its own slice. Single-run evals; ±1-2 point differences are noise. RU slice of the probe (3 Cyrillic names, 30 gens): stock 27, prune 21, merge 24.

Files

Standard HF sharding. experts-layerNN shards carry the merged expert stacks; backbone tensors are byte-identical to stock (verified by streaming sha256).

Limitations

  • Merge coefficients use the author's measured saliency, tempered (see Method).
  • Calibration-free similarity (router-row cosine): no activation statistics.
  • MTP merged without measured saliency (k-center on gate rows).
  • Vision tower untouched but untested after merging.

Credits

  • sh0wie / HamsterResearch — REAP-288 saliency calibration, kept-expert manifests, MLX conversion conventions.
  • Samsung SAIL Montréal — the REAM method.
  • Qwen team — the base model. License inherited (Qwen Community License 1.0).
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Paper for WaveCut/Qwen3.8-Flash-Next-REAM-288