Qwen3.8-Flash-Next-MLX-BEAM-4bit

Experimental — work in progress. Text generation works (smoke-tested, see below). Images do not work yet: the vision tower is shipped, but no runtime uses it from here. Quality was not measured by us - the weights are bit-identical to the source build, whose card carries the numbers.

MLX build of Qwen3.8-Flash-Next (125B-A6B hybrid Gated-DeltaNet / sparse-attention MoE with a 51B hashed n-gram embedding) for Apple Silicon. The weights are those of pipenetwork/Qwen3.8-Flash-Next-MLX-mixed-4_8bit - 4-bit routed experts, 8-bit everything else - repackaged in the B.E.A.M. layout: the bf16 vision tower moved out of the first shard into extras/, a hardened chat template, and a manifest that records the bit allocation. 106 GB on disk. No multi-token-prediction head (the source ships none).

The architecture (qwen4_exp) is not in a released mlx-lm; the package ships qwen4_exp.py (the source build's runtime file, unchanged) and declares it via model_file, hence --trust-remote-code.

What is in the package

This is a B.E.A.M. package: a standard MLX checkpoint plus everything the base model ships beyond the language model, kept as separate, index-listed parts under extras/. Any loader that follows model.safetensors.index.json finds them; nothing here depends on a particular runtime. (B.E.A.M. is the engine this layout is built for; it is not published yet — the package works without it.)

Part	File	Note
Chat template	chat_template.jinja	10 KiB — hardened chat template (Unsloth pattern): leading system/developer messages merged into one system block, reasoning_effort 'high' mapped to 'xhigh', no exception for a conversation without a user turn
Vision tower (bf16)	extras/vision.safetensors	333 tensors, 856 MiB — split out of model-00001.safetensors; patch_embed.proj.weight transposed from the PyTorch conv layout to MLX (out, T, H, W, in)
Allocation	extras/allocation.json	bits per module, schema v1
Manifest	extras/manifest.json	sizes and SHA-256 of every part

extras/manifest.json lists every part with its size and SHA-256, and extras/allocation.json records which module got how many bits.

Quantization

Affine MLX quantization, group size 64 unless noted - taken over unchanged from the source build. This package repackages, it does not re-quantize; nothing about the allocation was measured by us.

Group	Bits
routed experts (switch_mlp, 96.6 % of the parameters)	4
hashed n-gram embedding tables (128 shards)	4, group size 32 (row width 160 is not a multiple of 64)
attention, DeltaNet, hyper-connection mixers, shared experts, PLE projections, embed_tokens, lm_head	8
MoE routers, gates, DeltaNet in_proj_a/b, indexer projection	bf16
vision tower	bf16

extras/allocation.json lists every quantized module with its bits (module names as in the quantization map of config.json; a quantized module not listed there takes the default of 4 bit). The source card explains why this split was chosen and gives paired per-window NLL results against bf16 and against the uniform 4-bit, 6-bit and 8-bit builds - they apply here unchanged.

Use

Text, with mlx-lm:

pip install -U mlx-lm
mlx_lm.generate --model p4ik/Qwen3.8-Flash-Next-MLX-BEAM-4bit --trust-remote-code --prompt "Explain the difference between a list and a tuple in Python." --max-tokens 200

from mlx_lm import load, generate

model, tokenizer = load("p4ik/Qwen3.8-Flash-Next-MLX-BEAM-4bit", trust_remote_code=True)
prompt = tokenizer.apply_chat_template(
    [{"role": "user", "content": "Explain the difference between a list and a tuple in Python."}],
    add_generation_prompt=True)
print(generate(model, tokenizer, prompt=prompt, max_tokens=200))

Images: the vision tower is in the package (extras/vision.safetensors, listed in the index), but no runtime uses it from here yet. mlx-lm is text-only. mlx-vlm would run the tower with its own qwen4_exp implementation, but a model_file in config.json takes precedence there, and qwen4_exp.py is an mlx-lm text model (no ModelConfig, no tower) - so mlx-vlm does not load this package at all. Text via mlx-lm only, for now.

What has been checked

Mac mini M4 Pro, 64 GB unified memory, 2026-09-14, mlx 0.32.2 / mlx-lm 0.31.3:

• Layout - every part matches extras/manifest.json (bytes, SHA-256, tensor count); the index is complete and names all 333 vision tensors in extras/vision.safetensors; the 432 routed-expert tensors are byte-identical to the source's uniform 4-bit build (the mixed build differs from it only in the 8-bit groups).
• Text - the package is larger than that machine's memory, so it ran under our own expert-streaming loader (routed experts and n-gram tables read from SSD on demand, 5.4 GB resident): greedy output on two short prompts and a 3.7k-token prompt is coherent; 3.9 tokens/s decode and about 120 tokens/s prompt processing there. A smoke test, not a benchmark, and not a stock-mlx-lm run.
• Not checked - loading with stock mlx-lm on a machine with enough memory (128 GB or more); the hardened chat template with tool calls on this model; the vision tower (no runtime, see above); quality (bit-identical weights, see the source card).

License

Qwen Community License 1.0, as the base model. qwen4_exp.py is the runtime file of the source build (port code: https://github.com/PipeNetwork/qwen38-flash-next-mlx).