AX Qwen3.5 9B MLX OptiQ 4-bit MTP

Parameter count: approximately 9.41B logical target parameters (9B class). 4-bit is the target quantization precision, not a 4B model-size claim. The separately packaged MTP sidecar is not included in the target count.

This is a self-contained MLX package for Apple Silicon. It combines the pinned upstream OptiQ mixed-precision target with an AX Engine-compatible multi-token-prediction (MTP) sidecar.

Try this model locally with AX Engine.

Attribution and changes

AutomatosX did not train Qwen3.5-9B or create its OptiQ quantization. The target model comes from mlx-community/Qwen3.5-9B-OptiQ-4bit at revision 890b4c43f99ff392819d83605f7b1e59fa9688aa.

AutomatosX used AX Engine's prepare_mtp_sidecar.py flow to extract the MTP head from Qwen/Qwen3.5-9B at revision c202236235762e1c871ad0ccb60c8ee5ba337b9a, apply the required RMSNorm-delta normalization, quantize projections to 4-bit with group size 64, patch the runtime config, and generate the AX manifests. The upstream OptiQ card is preserved as UPSTREAM_README.md.

No new training or benchmark results are claimed by AutomatosX.

Package details

The package retains the upstream optiq/mtp.safetensors file and adds the AX-prepared root mtp.safetensors. AX Engine uses the root sidecar through the mlx_lm_extra_tensors config entry.

Download and serve

hf download AutomatosX/AX-Qwen3.5-9B-MLX-OptiQ-4bit-MTP \
  --local-dir ./AX-Qwen3.5-9B-MLX-OptiQ-4bit-MTP

ax-engine doctor \
  --mlx-model-artifacts-dir ./AX-Qwen3.5-9B-MLX-OptiQ-4bit-MTP

ax-engine serve ./AX-Qwen3.5-9B-MLX-OptiQ-4bit-MTP --port 31418

The download is approximately 7.8 GB. The server exposes an OpenAI-compatible API. Consult the AX Engine repository for installation and API examples.

AX-specific files

• mtp.safetensors: AX-prepared MTP sidecar
• mtplx_runtime.json: draft-depth and sampler guidance
• ax_mtp_sidecar_manifest.json: sanitized, revision-pinned provenance
• model-manifest.json: AX native target manifest
• config.json: upstream target config with the AX sidecar registration

Validation

Validated on macOS arm64 with AX Engine 6.9.0 on 2026-07-20:

• AX artifact doctor: ready, with no model issues
• Safetensors headers, data bounds, and index mappings: passed
• MTP tensor-layout exactness baseline: maximum absolute difference 0.0 at context length 2,048
• Source and destination revisions are immutable and recorded in the provenance manifest

Quantization can change model quality, and speculative-decoding acceptance depends on the workload. Evaluate this package on your own tasks.

License

Apache License 2.0. See LICENSE, the original Qwen model card, and the pinned upstream OptiQ card for limitations and responsible-use guidance.