MTPLX: the fastest way to run Qwen 3.8 on a Mac. Native multi-token-prediction speculative decoding on Apple Silicon, two to three times the speed of plain decoding, exact at any temperature.
Qwen 3.8 Flash-Next Optimized Quality
8-bit body and MTP head, BF16 structural tensors, and a 4-bit n-gram table. Higher-fidelity Flash-Next build.
Qwen's 125B-A6B Flash-Next preview, the Qwen4-generation architecture with GDN hybrid MoE, Qwen Sparse Attention and the 51B-parameter n-gram memory, at 8 bits: the highest-fidelity way to run it on a Mac, with its native multi-token-prediction head drafting through MTPLX's speculative path. It is built for Mac Studio with 256 GB or 512 GB. On a 128 GB Mac, pick Optimized Speed, the recommended build.
The 32 GB n-gram table streams from SSD, so only the weights stay in memory: about 128.5 GiB, which leaves about 59.5 GiB for context and the session cache on a 256 GB Mac.
How it is built
- The experts, attention and the multi-token-prediction head at 8 bits with 64-weight groups, twice the precision of Optimized Speed.
- The structural weights stay in BF16.
- The n-gram table at 4 bits, as a separate sidecar that MTPLX streams from SSD. The vision tower is preserved in the weights.
| Download | 170 GB (includes the 32 GB n-gram table) |
| Weights in memory (n-gram on SSD) | about 128.5 GiB |
| Recommended Macs | 256 GB and 512 GB (on 128 GB, use Optimized Speed) |
| Context window | 262,144 tokens |
| MTP depth | adaptive, ceiling 3 |
| Sampling | temperature 1.0, top-p 0.95, top-k 20 (the official Qwen 3.8 contract) |
Speed on 256 GB and 512 GB Macs has not been measured yet. The 8-bit weights move twice the bytes per token of Optimized Speed, so it decodes slower.
The serving contract ships inside mtplx_runtime.json. MTPLX reads it on
load. Drafts are accepted with the probability-ratio rule plus residual
resampling, so the output follows the model's own distribution at any
temperature.
Use it
Mac app (MTPLX 2.12.0 or later): download at mtplx.com, pick "Qwen 3.8 Flash-Next Optimized Quality". On Macs with 256 GB or more it is listed second, after Optimized Speed.
Command line (MTPLX 2.12.0 or later):
pip install mtplx
mtplx serve --model Youssofal/Qwen3.8-Flash-Next-MTPLX-Optimized-Quality --model-id mtplx-flash-next-optimized-quality
Siblings: Optimized Speed (the recommended build) and Bare Speed (flat 4-bit, the quickest build).
Base model: Qwen/Qwen3.8-Flash-Next
(Qwen Community License; the upstream model card is preserved in this repo as
README-upstream-qwen.md).