GLM-5.3-Flash-MLX

An MLX build of the official GLM-5.3-Flash — 2bit-lite / 2 / 3 / 4 / 6-bit OrcaSAQ quant for Apple Silicon & MLX

▶ Run GLM-5.3-Flash instantly on the OrcaRouter API — no download, full precision.

One Gateway. Every Model. — Route Smarter · Ship Safer · Spend Less.
GLM-5.3-Flash on OrcaRouter →

Website · Model Catalog · Model API · GitHub · OrcaCode Review · Discord · X

---

An MLX build of the official zai-org/GLM-5.3-Flash — a 320B-total / 18B-active MoE, the first natively multimodal model in the GLM-5 series, built on the new glm5_next hybrid architecture (sparse + linear attention with Manifold-Constrained Hyper-Connections) — quantized to MLX for Apple Silicon and the MLX CUDA backend. Five builds (2bit-lite / 2 / 3 / 4 / 6-bit) ship as subfolders, with the 4-bit build mirrored at the repo root, produced with OrcaSAQ (Sensitivity-Aware Quantization) — calibration-free and architecture-aware: sensitive tensors get more bits (shared experts +2, down_proj +1), and every tensor that was not FP8 in the base release — the 34 linear-attention layers, the sparse indexer, hyper-connections, norms, embed_tokens, lm_head, and the entire vision tower — is carried through in BF16. The four projections of the sparse-attention blocks were FP8 upstream and are quantized at the base width. Browse all models in the OrcaRouter Model Catalog; deployed as API here. Put this model to work reviewing your pull requests with OrcaCode Review.

---

Available quantizations

Folder	Base bits	Group size	Size	Min RAM	Quality vs FP8
6-bit/	6	64	~296 GB	320 GB	Near-lossless — best quality
4-bit/	4	64	~204 GB	224 GB	Very good — recommended default
3-bit/	3	32	~184 GB	200 GB	Good — aggressive but usable
2-bit/	2	32	~145 GB	160 GB	Aggressive — best-effort
2bit-lite/	2	128	~102 GB	112 GB	Smallest — fits 128 GB Macs & a single H200

The repository root is a mirror of 4-bit/, so orcarouter/GLM-5.3-Flash-MLX resolves to the recommended default with no subfolder needed.

Quantized from the official FP8 release. Bit-widths above are the base precision; the OrcaSAQ policy below raises sensitive tensors above the base. Group size is 64 for 4/6-bit, 32 for 2/3-bit (shared experts always use 64), and 128 throughout 2bit-lite.

No 8-bit build was produced. 2bit-lite follows a separate, memory-first recipe — see below.

---

OrcaSAQ — Sensitivity-Aware Quantization

OrcaSAQ is a calibration-free, architecture-aware mixed-precision quantization method designed to preserve model quality while aggressively reducing memory footprint.

Instead of running expensive calibration datasets or per-layer sensitivity searches, OrcaSAQ uses architectural and tensor-role priors to determine which weights are most sensitive to quantization. Critical components receive higher precision, while more quantization-tolerant tensors remain at the target base precision.

For MoE architectures, for example, OrcaSAQ can preserve shared experts at base +2 bits, down_proj at base +1 bit, keep gate_proj and up_proj at the base precision, and retain sensitive non-quantized components in BF16.
The result is a fast, deterministic, zero-calibration quantization pipeline that can be applied to new architectures without costly dataset-driven optimization.

Architecture-aware. Calibration-free. Quality-preserving.

Bit allocation for GLM-5.3-Flash

Component	Count	2-bit	3-bit	4-bit	6-bit	Policy
Expert gate_proj / up_proj	24 768	2	3	4	6	base
Expert down_proj	12 384	3	4	5	8	base +1
Dense-MLP gate_proj / up_proj (layers 0–2)	6	2	3	4	6	base
Dense-MLP down_proj (layers 0–2)	3	3	4	5	8	base +1
Shared expert gate_proj / up_proj / down_proj	129	4	5	6	8	base +2
Sparse-attn q_a_proj / q_b_proj / kv_a_proj_with_mqa / o_proj	48	2	3	4	6	base
Linear-attn layers, sparse indexer, mHC, norms, embed_tokens, lm_head, vision tower	—	BF16	BF16	BF16	BF16	never quantized

Bits are rounded up to the nearest MLX-supported width ({2,3,4,5,6,8}). The architectural prior that selects the quantizable set is mechanical and needs no data: a tensor is re-quantized iff the FP8 release shipped it with a _scale_inv companion. For GLM-5.3-Flash that set is the MoE and dense-MLP linears plus the four projections of every deepseek_sparse_attention block — the 11 sparse layers at depth 3, 7, 11 … 43, and the MTP block, hence 12 × 4 = 48 tensors. The 34 linear_attention layers, the sparse indexer, and the vision tower were never FP8 and stay BF16.

37 338 tensors are quantized in total. The assignment is recorded in config.json → quantization, as per-module {group_size, bits} overrides keyed by MLX module path — e.g. model.layers.3.mlp.switch_mlp.down_proj. MLX fuses a layer's routed experts into one switch_mlp, so 173 entries cover all 37 338 tensors. This is what the loader reads at load time and it is required: the top-level bits/group_size alone would mis-shape every raised-precision tensor.

The MTP (multi-token prediction) layer — layer 45 — is included inside the quantized weights rather than exported as a separate mtp/ module.

---

Quality vs FP8

All three tables compare each build against the full FP8 reference (dequantized to BF16 and run through the identical glm5_next forward, so the only variable is the quantization). Sizes are decimal GB, matching the file sizes in this repo.

Perplexity

Build	Size	PPL	ΔPPL
FP8 (ref)	328 GB	2.7797	—
6-bit	296 GB	2.7864	+0.24 %
4-bit	204 GB	2.8620	+2.96 %
3-bit	184 GB	3.0566	+9.96 %
2-bit	145 GB	4.3622	+56.9 %
2bit-lite	102 GB	6.7018	+141 %

KL divergence & Top-1 token agreement — lower KLD and higher Top-1 = closer to the original.

Build	Size	Mean KLD	KLD p95	Top-1 agreement
FP8 (ref)	328 GB	—	—	100 %
6-bit	296 GB	0.0063	0.0142	97.76 %
4-bit	204 GB	0.0131	0.0477	96.13 %
3-bit	184 GB	0.0421	0.1332	92.06 %
2-bit	145 GB	0.1647	0.6528	86.56 %
2bit-lite	102 GB	0.3456	1.2617	77.19 %

Weight-space fidelity (mean over sampled MoE/MLP tensors, quantized vs FP8):

Build	Size	Cosine sim	SNR (dB)	Rel. error
6-bit	296 GB	0.9998	37.3	1.6 %
4-bit	204 GB	0.9969	22.9	7.6 %
3-bit	184 GB	0.9892	17.6	14.0 %
2-bit	145 GB	0.9518	11.1	29.7 %
2bit-lite	102 GB	0.9135	7.5	42.4 %

The three measurements agree on the ordering, and they agree on where the cliff is: everything down to 3-bit degrades gently, 2-bit costs a lot, and 2bit-lite costs a lot more. Pick it for fit, not for quality.

---

2bit-lite/ — smallest build, for 128 GB Macs and a single H200

A memory-first build that trades quality for the smallest footprint that still loads and runs on mlx-vlm. It exists to fit machines where the regular 2-bit build (145 GB) is just too big:

• 128 GB MacBook Pro (M4 / M5 Max) — regular 2-bit does not fit; this does, with a raised wired-memory limit.
• A single H200 (141 GB) — regular 2-bit overflows one card; 2bit-lite fits with ~39 GB left for the KV cache.

Recipe (group_size 128 throughout):

Component	Bits
Routed experts (gate_proj / up_proj / down_proj)	2
Attention MLA + dense MLP	2
Shared expert (fires on every token)	3
embed_tokens / lm_head / linear-attention path	BF16

Size: ~102 GB (≈2.25 bpw on the experts). That is the floor for this architecture: MLX's affine quantizer cannot go below 2 bits, and the fused MoE experts — ~97 % of the weights — cannot use the 1-bit path.

Field notes — what 2bit-lite is actually good for

Verified on a single H200: it deploys cleanly, multi-turn conversation is stable at ~10 tok/s, and everyday Q&A and short-form text come out fine.

Long code generation is not reliable at this precision. Three failure modes reproduce consistently:

• Repetition loops — the model gets stuck emitting the same block over and over.
• Missing glue code — the overall structure is right, but load-bearing lines (imports, wiring, error handling) are silently dropped.
• Rewrite churn — it keeps restarting the answer and never commits to a final version.

So: reach for 2bit-lite when the hardware cannot hold anything larger, and keep it to chat, Q&A and short generations. For coding and long-horizon agentic work use 2-bit or higher — the quality tables above show why the gap shows up in practice, and the API option needs no local memory at all.

---

Usage

Hosted API — no download

The full-precision model is live on OrcaRouter as z-ai/glm-5.3-flash, so you can call it without pulling 100–300 GB of weights — endpoint, keys and pricing are on the model page:

https://www.orcarouter.ai/models/z-ai/glm-5.3-flash

Run it locally (mlx-vlm)

GLM-5.3-Flash is a vision-language model, so it runs under mlx-vlm — not mlx-lm.

pip install -U "mlx-vlm>=0.6.17"

The repo root is the 4-bit build, so the recommended default needs no subfolder — the excludes are what stop hf download from also pulling all five variant folders:

hf download orcarouter/GLM-5.3-Flash-MLX --local-dir ./GLM-5.3-Flash-MLX \
    --exclude "2bit-lite/*" "2-bit/*" "3-bit/*" "4-bit/*" "6-bit/*"

python -m mlx_vlm.generate --model ./GLM-5.3-Flash-MLX \
    --prompt "Explain quantum entanglement in one sentence." --max-tokens 256

To pick a different precision, download just that subfolder and load it from the local path:

hf download orcarouter/GLM-5.3-Flash-MLX --include "6-bit/*" --local-dir ./GLM-5.3-Flash-MLX

python -m mlx_vlm.generate --model ./GLM-5.3-Flash-MLX/6-bit \
    --prompt "Explain quantum entanglement in one sentence." --max-tokens 256

With an image or a video frame:

python -m mlx_vlm.generate --model ./GLM-5.3-Flash-MLX \
    --image photo.jpg --prompt "Describe this image." --max-tokens 256

Python API:

from mlx_vlm import load, generate
from mlx_vlm.prompt_utils import apply_chat_template

model, processor = load("./GLM-5.3-Flash-MLX")          # repo root == 4-bit
prompt = apply_chat_template(processor, model.config, "Describe this image.", num_images=1)

print(generate(model, processor, prompt, ["photo.jpg"], max_tokens=256, verbose=True))

glm5_next runtime required. This is a brand-new architecture (hybrid sparse + linear attention, mHC, MoE). Use an mlx-vlm build that has landed glm5_next support. On Apple Silicon the Metal backend is used automatically. On the Linux CUDA backend install mlx[cuda] and set MLX_CUDA_USE_CUDNN_SDPA=0.

---

🐳 Run it with OrcaCode Review

Models are only half the system.

OrcaCode Review turns every model listed on OrcaRouter into a production code-review agent:

• reviews every PR
• finds security + correctness issues
• posts inline findings
• P0/P1 can block merges
• swap models anytime

Open model. Open harness. Open bill.

• Website — https://www.orcarouter.ai
• GitHub — https://github.com/Continuum-AI-Corp/Orca-Code-Review

---

GLM-5.3-Flash

Available full-precision on the OrcaRouter API as z-ai/glm-5.3-flash — https://www.orcarouter.ai/models/z-ai/glm-5.3-flash

GLM-5.3-Flash is the first natively multimodal model in the GLM-5 series. With 320B total parameters and just 18B active parameters, it outperforms GLM-5.2 across benchmarks and real-world workloads at one-tenth the price, while approaching Claude Opus 4.8 on coding and agentic benchmarks.

For the first time in the GLM series, GLM-5.3-Flash introduces a hybrid architecture combining sparse and linear attention, sharply reducing long-context serving costs while preserving precise long-context capabilities. It also adopts Manifold-Constrained Hyper-Connections (mHC) to improve scaling efficiency, and is trained on a 30T-token multimodal corpus.

Model Overview

• Type: Mixture-of-Experts multimodal Causal LM (glm5_next) with vision encoder
• Parameters: 320B total · 18B active per token
• Experts: 288 routed + 1 shared, top-8 routing
• Layers: 45 (3 dense + 42 MoE) · 11 deepseek_sparse_attention + 34 linear_attention, plus 1 MTP layer (also MoE, with its own sparse attention)
• Attention: hybrid sparse + linear attention with a learned sparse indexer, plus Manifold-Constrained Hyper-Connections (mHC)
• Precision (base release): FP8 (block-wise e4m3, 128×128), dynamic activation scheme
• Modalities: text, image, video

Best Practices

• Sampling: follow the official GLM-5.3-Flash guidance; long-horizon agentic and coding tasks benefit from generous max-tokens headroom.
• Long context: the hybrid sparse/linear attention is designed for low-cost long-context serving; give the runtime enough KV budget for your target length.
• Pick a precision: 6-bit for near-lossless, 4-bit (repo root) as the everyday default, 3-bit and 2-bit when memory is the binding constraint, 2bit-lite only when nothing else fits (see the quality tables above — the drop from 2-bit to 2bit-lite is steep).
• Or skip the download: the unquantized model is served at full precision on the OrcaRouter API as z-ai/glm-5.3-flash.

---

Citation

@misc{glm5team2026glm5vibecodingagentic,
      title={GLM-5: from Vibe Coding to Agentic Engineering},
      author={GLM-5-Team and Aohan Zeng and Xin Lv and Zhenyu Hou and Zhengxiao Du and others},
      year={2026},
      eprint={2602.15763},
      archivePrefix={arXiv},
      primaryClass={cs.LG},
      url={https://arxiv.org/abs/2602.15763},
}

License

MIT, inherited from zai-org/GLM-5.3-Flash. Quantization does not change the underlying license obligations.