An AXQuant (AXQ) mixed-precision MLX checkpoint for Apple Silicon, converted directly from the BF16 source model. The language path is quantized under AXQuant protection floors (embeddings, norms, and other protected tensors remain higher precision).

Development evidence — not a certified AXQuant release. This package has conversion and artifact-integrity records, but it does not publish measured quality, long-context, kernel-speed, or MTP-speed evidence. Do not interpret the AXQ product label as a benchmark claim.

Model details

Property	Value
Base model	openai/gpt-oss-20b
Source revision	`6cee5e81ee83917806bbde320786a8fb61efebee`
Product family	`gpt-oss`
Source architecture	`GptOssForCausalLM` (mixture of experts (MoE)); text path optimized
Main-model parameters	20.91B logical parameters
Quantizer	AXQuant `1.6.2`
Hub budget class	`6bit`
AXQuant base precision class	`6bit`
Planned storage-adjusted BPW	6.0000
Measured main-model BPW	6.0000
Measured total BPW	6.0000
Safetensors weight size	15.69 GB
Approximate complete download	15.71 GB
Configured maximum context	131,072 tokens; practical limits depend on unified memory
Primary MLX runtime	MLX-LM
AX Engine native execution	Native manifest included; execution still requires a runtime check
MTP present	`False`
Vision present	`False`
Audio present	`False`

This repository contains MLX Safetensors. It does not contain PyTorch or GGUF weights.

Choosing an AXQ pack

AXQ names describe a storage-budget product class, not one uniform precision applied to every tensor. Protected tensors remain at higher precision, so the exact measured BPW is authoritative. In particular, a 6bit-named mixed plan may retain 4bit as its base precision while selecting 6-bit, 8-bit, or BF16 for other tensors to meet an approximately 6-BPW total budget. Protection floors can also raise a 4bit-named pack close to (or above) a 6bit budget on small or heavily protected models. When that collapse happens, AutomatosX does not publish a separate misleading 4bit sibling for that base.

Sibling	Intended trade-off
4bit sibling	Lower-storage AXQ budget; check its exact BPW
6bit sibling	Higher average precision near the 6-BPW budget

See the AutomatosX MLX model catalog for related MLX and OptiQ alternatives.

Download

bash

python -m pip install -U huggingface_hub
hf download AutomatosX/AX-gpt-oss-20b-MLX-AXQ-6bit --local-dir ./AX-gpt-oss-20b-MLX-AXQ-6bit

Allow at least 15.71 GB of free disk space. Pin the resulting Hub commit in reproducible deployments rather than relying indefinitely on main.

Run with MLX-LM

bash

python -m pip install -U mlx-lm
mlx_lm.generate \
  --model AutomatosX/AX-gpt-oss-20b-MLX-AXQ-6bit \
  --prompt "Explain mixed-precision quantization in three sentences." \
  --max-tokens 128 \
  --temp 0.0

MLX-LM compatibility covers standard text/backbone inference. It may ignore AXQuant runtime metadata and optional sidecars (vision.safetensors, mtp.safetensors); this command therefore does not establish MTP acceleration or vision-language quality. The artifact records MLX 0.32.0 and MLX-LM 0.31.3 from conversion.

Serve with AX Engine

After installing AX Engine, download the complete repository (see AXQuant for conversion, certificates, and model-card tooling) and serve the local directory:

ax-engine serve ./AX-gpt-oss-20b-MLX-AXQ-6bit --port 31418

AX Engine is the authority for the AXQ runtime contract. This development package does not claim runtime speedups until identical-checkpoint benchmarks are published. The artifact records AX Engine version 6.11.1. Native model-manifest.json status: included as model-manifest.json.

Quantization layout

Main-weight precision	Parameters	Share
`4bit`	11.68B	55.84%
`6bit`	8.06B	38.54%
`8bit`	588.72M	2.81%
`bf16`	586.10M	2.80%

Quantization methods: affine, bf16.
Group sizes used by quantized assignments: 32, 64.
MTP sidecar: not included.
Vision sidecar: not included.
Optimization scope: text-path.
Support tier: convertible.

BF16 sidecars, when present, are included in total download size. Their presence does not by itself establish MTP acceleration or vision-language quality.

Evidence and validation status

Check	Status
Planning evidence	`architecture_prior`
Calibration	none; the allocation is based on architecture priors
Quantizer execution	169/169 recorded module conversions succeeded; 0 fallbacks
AX Engine native manifest	included as `model-manifest.json`
Quality versus BF16 or uniform baselines	Not published; no quality-retention claim
MTP acceptance and speed	not measured; no MTP speedup claim
AX Engine kernel evidence	`unmeasured`
Vision-language quality	Not applicable (no vision tower in this package)
Speech-recognition quality	Not applicable
Long-context quality	131,072-token capacity is config metadata, not a validated claim
Release certification	Not certified; formal AXQuant M0-M8 gates are not closed

Modalities (capability-gated)

Text checkpoint Tier 1 does not imply vision or audio quality. Vision present=true on a pack is not a quality pass.

Modality	Claim	Supported	Reason
Vision	`not-applicable`	`false`	vision not supported (no tower config and no sidecar weights)
Audio	`not-applicable`	`false`	audio not supported (no tower config and no sidecar weights)

Intended use and limitations

Intended for local development and evaluation on Apple Silicon with MLX-compatible runtimes.
No minimum unified-memory figure is claimed; loadability depends on model size, context length, KV-cache policy, runtime buffers, and other processes using unified memory.
Architecture-prior allocation is not measured sensitivity. It must not be presented as measured model quality.
The configured context window can require substantially more memory as the KV cache grows.
Upstream capabilities, limitations, biases, and responsible-use guidance still apply.

Provenance and audit files

axquant_manifest.json: package identity, byte accounting, runtime contract, software versions, and file checksums.
axquant_plan.json: per-tensor precision decisions and planning evidence.
axquant_quantizer_execution.json: conversion coverage and fallback records.
axquant_runtime.json: declared AX Engine and MLX compatibility metadata; runtime checks remain separate evidence.
model-manifest.json: AX Engine native tensor manifest.

All published provenance uses repository-relative paths. Local source paths are stripped before publication. The checkpoint was converted from BF16 rather than re-quantized from an OptiQ artifact. If an OptiQ repository is published separately, it uses a different quantizer and should not be assumed to have identical BPW or quality.

License

The checkpoint follows the upstream model license where applicable (often Apache License 2.0). See the openai/gpt-oss-20b model card for license terms, model limitations, and responsible-use guidance.

OpenAI-native remake (2026-08-11/12)

Convert source: openai/gpt-oss-20b@6cee5e81ee83917806bbde320786a8fb61efebee (native MXFP4 experts + BF16 non-experts)
Path: --allow-quantized dequant → affine re-pack (not community MXFP4-Q4 double-quant)
Quality measured vs OpenAI native on development suites (seed 20260728, max_tokens 64)
Size still reported vs mlx-community/gpt-oss-20b-MXFP4-Q4 for packaging continuity