Table | |
|---|
| Source checkpoint | zai-org/GLM-5.3-BF16, revision 304b8051cfb2b260b61ce0cbe330e02a98e73639 |
| Method | ModelOpt NVFP4, routed expert gate/up/down weights only, block size 16, two-level scaling, max algorithm, no calibration |
| Precision retained | BF16 attention, indexer, router, dense and shared experts, embeddings, LM head, layer 0, and the layer 78 MTP/nextn block |
| KV cache | FP8 declared in hf_quant_config.json (runtime BF16 recommended, see below) |
| Size | 465 GB tensor bytes (433 GiB on disk), down from 1506.7 GB BF16, about 69% smaller |
| Export layout | 163 safetensors shards, 232,385 indexed tensors, 19,200 quantized expert bundles (layers 3-77) |
| Conversion | 292 seconds with 3 GPU workers, streamed shard by shard on 3x RTX PRO 6000 Blackwell 96 GB |
| Context length | 1,048,576 tokens (unchanged from the source config) |
| ModelOpt revision | 0.46.0.dev65+g977d34dc3 (NVFP4QTensor) |
| Serving validation | Not yet performed on this export. The identical architecture is proven in production on 7x RTX PRO 6000 Blackwell with nvidia/GLM-5.2-NVFP4 (see below) |
Quantization recipe
The conversion streams every source shard and quantizes all 57,600 routed-expert projection
tensors (75 MoE layers, 256 experts each, gate/up/down). It uses ModelOpt's NVFP4QTensor max
quantizer with 16-value blocks. gate_proj and up_proj share the second-level FP32 global
scale (fused gate/up runtime layout), down_proj gets its own. The exported weights use packed
U8 data, FP8 E4M3 block scales, and FP32 global scales. No calibration dataset was used; the
quantization is weight-only max scaling, which matches the layout served by SGLang and vLLM as
modelopt_fp4.
Everything else stays BF16: attention (including the DSA indexer), the router, dense layers 0-2,
shared experts, embeddings, the LM head, and the complete layer 78 MTP/nextn draft block.
The exclude-module list in hf_quant_config.json mirrors the official nvidia/GLM-5.2-NVFP4
release (158 entries).
Run it with SGLang
The proven recipe for this architecture on 7x RTX PRO 6000 Blackwell 96 GB (SM120), taken from
the live nvidia/GLM-5.2-NVFP4 deployment:
python3 -m sglang.launch_server \ --model-path GLM-5.3-NVFP4 \ --served-model-name GLM-5.3-NVFP4 \ --host 0.0.0.0 --port 30000 \ --tp-size 1 --pp-size 7 \ --quantization modelopt_fp4 \ --trust-remote-code --dtype auto \ --context-length 1048576 \ --kv-cache-dtype bf16 \ --mem-fraction-static 0.90 \ --chunked-prefill-size 12288 \ --attention-backend flashinfer \ --moe-runner-backend flashinfer_cutlass \ --fp4-gemm-backend flashinfer_cutlass \ --disable-flashinfer-autotune \ --disable-custom-all-reduce \ --tool-call-parser glm47 --reasoning-parser glm45 \ --sleep-on-idle
Pipeline-parallel partition on 7 GPUs: 10,12,12,12,12,12,8 (required by the DSA
index_topk_freq=4 / index_skip_topk_offset=3 layer pattern). BF16 KV cache is strongly
recommended for this architecture: the FP8-KV path lacks per-model scaling factors and measured
75% lower decode throughput on the GLM-5.2 sibling deployment.
This exact export has not yet been smoke-tested in SGLang; the command above is the validated
GLM-5.2-NVFP4 production profile and is expected to carry over unchanged.
Run it with vLLM
vllm serve GLM-5.3-NVFP4 \ --quantization modelopt \ --kv-cache-dtype auto \ --max-model-len 131072 \ --tool-call-parser glm45
Not yet validated on this export. Start with a reduced context before scaling up.
Quality and limitations
- No benchmark run has been performed on this export yet. The GLM-5.2 evidence base (same
architecture, official NVFP4 quant of the same base) showed NVFP4 experts-only quantization at
or under 1% on common benchmarks; treat that as the expectation, not a measurement.
hf_quant_config.json declares kv_cache_quant_algo: FP8 for loader compatibility with the
official NVIDIA GLM-5.2 release, but serve with BF16 KV cache (see the SGLang note above).
- MTP speculative decoding weights (layer 78) are preserved in BF16 but the SGLang MTP path for
this architecture requires a patched fork; serve without speculative decoding on stock builds.
- NVFP4 requires Hopper/Blackwell-class GPUs (compute capability 9.0+, SM120 validated).
Ampere and older cannot run this checkpoint.
Provenance and reproducibility
Converted on 2026-08-29 from zai-org/GLM-5.3-BF16 revision
304b8051cfb2b260b61ce0cbe330e02a98e73639 with a streaming experts-only ModelOpt NVFP4
conversion (recipe streaming/nvfp4_experts_only_input_scale1-kv_fp8-glm_moe_dsa):
NVFP4QTensor.get_weights_scaling_factor / quantize, block size 16, input scale 1.0,
shared gate/up global scale, max algorithm, zero calibration samples. Full run metadata is in
run-manifest.json inside the repo.
License and credits
GLM-5.3 License (Copyright (c) 2026 Z.AI), inherited from
zai-org/GLM-5.3. Quantization and validation by
Robert Ressl
(Hugging Face · Website · LinkedIn · Patreon).
Built with the NVIDIA TensorRT Model Optimizer and SGLang.
❤️ Support this work: if these models are useful to you, consider supporting on
Patreon, more at ressl.ch.