Qwen3.8-Flash-Next-NanoSeedLM-P4

Qwen3.8-Flash-Next with SeedLM seed experts, for oMLX on a 128 GB Mac. Its 120.8 B routed expert weights are seeds of a linear feedback shift register: 68.0 GB, at 4.5 bits each. It runs in mlx-vlm and oMLX as well as in the NanoSeedLM engines. As shipped, its KL against BF16 is 0.169, and its 4-bit dense weights cause most of it. Its experts are on Unsloth's quality curve: 0.0408 at 4.5 bits, 2% below it. For the lowest KL, use TCQ4.

Research preview. It runs in the NanoSeedLM engines, in mlx-vlm with Trust Remote Code, and in oMLX with the fix in jundot/omlx#5112.

Which pack

The five packs are the same model, Qwen3.8-Flash-Next. They differ in three things: how they store the 120.8 B routed expert weights, their dense weights, and the runtimes that load them.

Your machine	Pack	Why
PC: a GPU of 24 GB or more, 96 to 128 GB of RAM	TCQ4	The lowest KL
PC: a 16 GB GPU, 96 to 128 GB of RAM	TCQ3-D4	The middle KL, 10 GB smaller
PC: a 12 or 16 GB GPU, 64 GB of RAM	TCQ3	The only pack for 64 GB of RAM
Mac: 128 GB	TCQ4	The lowest KL
Mac: 128 GB, for speed	P3	About 20% faster, 4 times the KL
Mac: 96 GB	TCQ3-D4	Room for long contexts
Research on seeds	P4, P3	SeedLM seeds
Less than 64 GB of RAM	None	The experts must fit in RAM

• On a PC, the experts stay in RAM, and the GPU caches the experts in use. A smaller pack lets the GPU cache more of its experts.
• A 12 GB GPU caches fewer experts than a 16 GB GPU. On an RTX 4080 limited to 12 GB, TCQ3 decodes at 27 tokens per second, against 44 with all 16 GB. We did not test a PC with 64 GB of RAM yet.
• P3 is faster on a Mac because its dense weights are 4-bit. They are also why its KL is 4 times that of TCQ4.
• The start script of the NanoSeedLM engine release checks the machine and picks a TCQ pack.

The family

Pack	Experts	Bits	Memory GB	KL as shipped
TCQ4	Trellis K4	4.125	70	0.0415
TCQ3-D4	Trellis K3, down K4	3.458	60	0.0638
TCQ3	Trellis K3	3.125	55	0.0778
P4	Seeds P4	4.500	74	0.169
P3	Seeds P3	4.000	66	0.182

Pack	Expert GB	Dense weights	Download GB	Runtimes
TCQ4	62.3	8-bit	127.5	Engines, mlx-vlm, oMLX
TCQ3-D4	52.2	8-bit	117.2	Engines, mlx-vlm, oMLX
TCQ3	47.2	8-bit	112.1	Engines, mlx-vlm, oMLX
P4	68.0	4-bit	131.3	Engines, mlx-vlm, oMLX
P3	60.4	4-bit	123.8	Engines, mlx-vlm, oMLX

• Bits are the bits for each expert weight. Memory counts the weights that stay resident, about. The PLE n-gram table stays on the disk, and the page cache holds the rows that a session reads.
• KL as shipped is against BF16 in llama.cpp, on 64 windows of 2,048 tokens of wikitext-2, with Unsloth's Q8_0 PLE table. Lower is closer to the original model.
• Engines are the NanoSeedLM engines: CUDA on Linux and Windows, Metal on macOS. oMLX needs the fix in jundot/omlx#5112. We tested TCQ4 and P3 in oMLX with the 8-bit PLE table, and each pack with the earlier 4-bit table.

The trade-offs.

• Trellis or seeds. Both compute each expert weight from a few stored bits with integer arithmetic, and neither stores a codebook. On this model the trellis code (TCQ) is closer to BF16 for its bits. Compare the experts with the same 8-bit dense weights: TCQ4 gives 0.0398 at 4.125 bits, P4 0.0408 at 4.5 bits and P3 0.0600 at 4.0 bits.
• 8-bit or 4-bit dense weights. The dense weights are a small part of the bytes, but in P3 and P4 they cause most of the KL. With 8-bit dense weights, P3 gives 0.0600 and P4 0.0408. With the 4-bit ones that they ship, P3 gives 0.182 and P4 0.169. So the TCQ packs ship 8-bit dense weights. The cost is speed: they read 1.84 GB more for each token. On the M4 Max, TCQ4 decodes about 15% slower than P3.
• Runtimes. Each pack carries its MLX model files, so mlx-vlm runs it with Trust Remote Code. oMLX runs it with the fix in jundot/omlx#5112. The NanoSeedLM engines run each pack too. The start scripts of the engine release prepare the TCQ packs.
• The PLE table. Each pack carries the PLE n-gram table at 8 bits (57.6 GB, MLX's form, group 32), made from Qwen's BF16 table. Every runtime reads it. Its row error against BF16 is 0.88 times that of Unsloth's Q8_0 table (the encoding). A 4-bit table would add about 0.006 to the KL.

Decode in tokens per second: nslm-serve --ctx 32768 with Unsloth's Q8_0 PLE table, 4,096 tokens, thinking on, temperature 0, without MTP drafts, the mean of two runs. The machines are an M4 Max with 128 GB and an RTX 4080 (16 GB) with 128 GB of RAM. Read the runs on the M4 Max and the RTX 4080. The 12 GB GPU is the RTX 4080 with 4 GB kept free.

Pack	M4 Max, Metal	RTX 4080, CUDA
TCQ4	39.0	31.4
TCQ3-D4	not measured	38.0
TCQ3	not measured	44.0
P4	not measured	not measured
P3	46.9	not measured

MTP drafts (engine v0.1.1). Set Q4E_DRAFTS=2 and Q4E_DRAFT_MIN_P=0.3. Then the M4 Max decodes TCQ4 32% faster at temperature 0 and 16% faster at 1.0. At temperature 0 the text does not change. On the RTX 4080, drafts break even, so they stay off there. The start script turns them on for a Mac. Read the gates on the M4 Max and the RTX 4080.

Why NanoSeedLM

NanoSeedLM began when Matt Barnson heard about SeedLM (Shafipour et al., 2024) at Apple's machine learning summit in the spring of 2025. SeedLM stores each block of 8 weights as the seed of a linear feedback shift register (LFSR), plus a few small coefficients. An LFSR is the cheapest pseudo-random generator in hardware. The paper rebuilt the weights on an FPGA, where an LFSR is a few flip-flops.

The idea: a chip that can calculate a weight from a few bits does not have to store the weight or wait for it. Decode on home hardware waits mostly for memory. A gaming PC keeps most experts in system RAM, behind PCIe, and a Mac waits for its memory bandwidth. Cheap arithmetic on the GPU, the CPU or an FPGA can take the place of some memory reads. Then a model that was state of the art a year ago can run on that hardware at a usable speed.

The first NanoSeedLM model was K2-Horizon-MoVA-36B-A4B in 22.76 GB, for a 32 GB Mac. This family takes the idea to Qwen3.8-Flash-Next. On this model, the trellis code of QTIP gives the best quality for its bits. QTIP is the closest working relative of SeedLM: its weights also come from cheap integer arithmetic, on a bit stream in place of a seed. So the TCQ packs are the ones to use, and P3 and P4 keep the SeedLM seeds. A planned next step is a CPU kernel for the trellis experts. Then the CPU of a PC can compute the experts that are not in VRAM. Read the story: NanoSeedLM: LLM inference using pseudo-random numbers.

How it works

Each block of 8 expert weights is a 16-bit LFSR seed, 4 int4 coefficients and a 4-bit exponent code (SeedLM). The GPU runs the register inside the matrix multiply and rebuilds the weights there, so the pack stores no expert weight. The seed search tried all 65,535 seeds for each block. It weighted the error of each weight by the mean square of its input activation, from Unsloth's imatrix. The PLE table is 8-bit, from Qwen's BF16 table. All other weights come unchanged from mlx-community/Qwen3.8-Flash-Next-4bit-mtp (4-bit affine, group size 32), with its MTP head.

Part	P4	mlx-community 4-bit
Routed experts	Seeds P4, 4.5 bits	4-bit affine, 5.0 bits
The PLE table	8-bit affine, from BF16	4-bit affine
All other weights	The same tensors	4-bit affine, 8-bit routers
Size	131.3 GB	113.3 GB

The routed experts are 120.8 B weights (48 layers of 512 experts). The other weights are attention, DeltaNet, the shared experts and the routers. They also include the embedding, the LM head, the vision tower and the MTP head. The 4-bit affine weights use groups of 32 and the routers groups of 64.

Quality

P4	Mean KLD against BF16
The experts, with 8-bit dense weights	0.0408
As shipped, with 4-bit dense weights	0.169

The 8-bit dense weights of the first row are Unsloth's Q8_0, in llama.cpp.

With the same dense weights, Unsloth's packs give 0.0416 at 4.5 bits: the straight line between their two packs nearest in bits. This pack's experts are 2% below that line. Read KL against BF16 and packs as shipped.

Speed

We did not measure this pack over long runs yet.

How to run

NanoSeedLM engines

Download the engine (releases, or build it) and this folder. Then chat, or serve an OpenAI-compatible API. On macOS, use out/bin in place of build/bin.

hf download txgsync/Qwen3.8-Flash-Next-NanoSeedLM-P4 --local-dir Qwen3.8-Flash-Next-NanoSeedLM-P4
build/bin/nslm-chat --model Qwen3.8-Flash-Next-NanoSeedLM-P4 "Why do tide pools matter?"
build/bin/nslm-serve --model Qwen3.8-Flash-Next-NanoSeedLM-P4 --ctx 32768 --port 8080

The engines memory-map the pack's 8-bit PLE table, so it stays on the disk. Q4E_DRAFTS=2 turns on the MTP drafts. Read Run and serve.

mlx-vlm

python -m mlx_vlm.generate --model txgsync/Qwen3.8-Flash-Next-NanoSeedLM-P4 --trust-remote-code \
    --prompt "Why do tide pools matter?" --max-tokens 256

mlx-vlm loads the whole pack, 131.3 GB, and macOS gives the GPU about three quarters of its memory. So mlx-vlm needs a Mac with about 175 GB. On a 128 GB Mac, use oMLX with SSD PLE (below) or the NanoSeedLM engines: both keep the PLE table on the SSD.

oMLX

Stock oMLX removes model_file from each qwen4_exp configuration, so it does not load this pack's model files. The fix in jundot/omlx#5112 keeps model_file when it is not the stock qwen4_exp.py. Until it merges, use the branch fix/qwen4-exp-custom-model-file. Then enable Trust Remote Code for this model. Its PLE table is the same file as TCQ4's and P3's, which we tested in oMLX with SSD PLE.

Limits

• This is a research preview. Its output is not identical to the output of the original model.
• mlx-vlm and oMLX need Trust Remote Code. The NanoSeedLM engines do not.
• On Apple Silicon, seed experts decode slower than affine experts of the same size.
• We did not test image or video input.

Files

• model-*.safetensors: the weights. NAME.seeds, NAME.nibbles and NAME.exp_bias hold the routed experts. model-ple8-*.safetensors: the PLE table (8-bit MLX, group 32, from Qwen's BF16).
• nanoseedlm_qwen4.py, nanoseedlm_seeds.py: the MLX model files.
• config.json: the configuration of the 4-bit MLX model, with model_file.
• LICENSE: the Qwen Community License 1.0.

Credits

Base model: Qwen, Qwen3.8-Flash-Next (Qwen Community License 1.0). MLX conversion: mlx-community/Qwen3.8-Flash-Next-4bit-mtp. PLE table: Qwen's BF16, in 8 bits by tools/hf_ple8.py. Activation statistics: Unsloth imatrix. Method: SeedLM (arXiv:2410.10714). Code: NanoSeedLM.