GLM-5.3 Int4-Int8Mix (743B) — the quant that fits 4x NVIDIA DGX Spark

✅ Live — all 282 shards uploaded, fully open (2026-08-29)

The complete model is here: 282 safetensors shards + config + tokenizer, ~378 GB, public and ungated. Everything below is verified on our own hardware. Recipe + launchers + benchmarks: github.com/tonyd2wild/GLM-5.3-Int4-Int8Mix-TP4-4x-DGX-Spark.

An Int4-Int8 mixed-precision quantization of the full zai-org/GLM-5.3 (743B total / ~40B active MoE, glm5_next, 78 layers, 1M context), in the compressed-tensors format for vLLM. Produced with the QuantTrio-style recipe (data-free, mixed W4A16 / W8A16), it is, as far as we can tell, the first quant of the big GLM-5.3 that actually serves on four DGX Spark (GB10) nodes with real KV-cache headroom.

Why this one fits when the NVFP4s do not

The existing full-GLM-5.3 NVFP4 quants are all ~465 GB because they keep the entire attention stack at bf16. Across 4 Sparks that is ~116 GB/rank, leaving only ~12 GB/rank, which is not enough for the KV pool plus framework, so they OOM in practice.

This quant takes the attention to Int8 instead of bf16. That single change drops the footprint to ~378 GB (~94.5 GB/rank at TP4), leaving ~33 GB/rank for a real KV pool. It is the difference between "loads on paper" and "serves under real traffic."

The recipe (data-free, mixed precision)

Static, symmetric, weight-only, compressed-tensors / pack-quantized, group size 128. No calibration data. Per-layer map:

• MoE experts (layers 3-77): W4A16, group 128 — the bulk of the weights, where the size savings come from.
• Dense + attention (layers 1-77): W8A16, group 128 — self_attn.*, mlp.gate_up/gate/up/down, shared_experts.*.
• MTP block (layer 78): W8A16, channelwise.
• Kept at full precision (this is what protects accuracy): layer 0 entirely, every mlp.gate (the MoE router), self_attn.indexer / indexers_proj (the DSA sparse-attention selector), the MTP eh_proj/enorm/hnorm, and shared_head.norm / shared_head.head (the LM head).

The trick in one line: Int4 only the bulky experts, Int8 the dense and attention, and leave the routing, indexer, and head alone.

Serving (vLLM, 4x DGX Spark GB10, TP4)

vllm serve <path-to-this-model> \
  --quantization compressed-tensors \
  --kv-cache-dtype fp8 \
  --tensor-parallel-size 4 --enable-expert-parallel \
  --served-model-name glm-5.3 \
  --max-model-len 131072   # raise per your KV pool

• ⚠️ GB10 / sm121 needs the sm12x kernel overlays (the sparse-MLA + fp8-KV path is not in stock vLLM for this arch). Get them from the sibling recipe repo: tonyd2wild/GLM-5.2-QuantTrio-200K-4x-DGX-Spark. On standard CUDA (H100/A100 etc.), --quantization compressed-tensors is all you need.
• kv_cache_scheme: None in the config — KV precision is a serve-time choice (--kv-cache-dtype), not baked into the weights.
• Speculative decode: pairs with incoai/GLM-5.3-DFlash2 (a 4.9 GB DFlash2 drafter) at ~zero extra KV pool — the flagship stack. Native MTP (layer 78) is preserved as a fallback.
• Long context: add Decode Context Parallel (--decode-context-parallel-size 4) to split the KV across all four nodes for a ~600K single-request context (the tradeoff is a small cross-node cost per decode step).

Verification (what's proven, and what isn't)

Produced by a shard-streaming RTN quantizer (reads one BF16 shard at a time, quantizes with compressed_tensors' own calculate_qparams / quantize / pack_to_int32, writes a 1:1 output shard; peak RAM ~10 GiB, runtime 28.2 min). NOT llmcompressor.oneshot — accelerate disk-offload would need ~1.4 TB of scratch this fleet doesn't have.

Proven:

• Structural (fail-closed): 59,585 source tensors → 58,992 quantized modules → 177,569 output tensors (exact). Group counts 57,600 / 616 / 776 match the pre-quant dry-run exactly (75 layers × 256 experts × 3 = 57,600 ✓). Sacred modules (layer 0, mlp.gate, indexer, lm_head, MTP norms) all plain BF16, zero packed leaks. 282 shards, none missing.
• Layout matches QuantTrio byte-for-byte (verified via HTTP range-reads of their published safetensors headers): expert down_proj.weight_packed I32 [6144,256], weight_scale BF16 [6144,16], MTP scale BF16 [6144,1] — all identical.
• Numerical round-trip: int8 group/128 ≈ 0.70% rel error, int4 ≈ 12% (normal for 16 levels), full range used.
• Serves live: TP4 across 4× DGX Spark (GB10/sm121), vLLM 0.23.1rc1, weights 95.53 GiB/rank, fp8_ds_mla KV, 202,944-token KV pool @ 200K ctx, health 200. Passed the bat-and-ball coherence trap ($0.05 with correct algebra) — a mis-quantized router or indexer cannot do that.

Performance (measured — TP4, 200K ctx, fp8_ds_mla KV, MTP k=4, thinking off, all four ranks clocking correctly):

Single-stream is ~12 tok/s; 46 is the peak at 6 concurrent streams. For reference, the GLM-5.2 QuantTrio recipe on the same four nodes reports 32.5 mean / 36 peak.

NOT yet done (honest):

• No 69-scenario eval. Coherence is proven; quality-vs-fp8 parity is NOT measured. Do not assume parity.
• DFlash2 speculative decode is not yet enabled (native MTP is). It is one flag away (fp8_e4m3 KV, method dflash, num_speculative_tokens 7) and is the next speed step.

Credits (what's whose)

We stand on a lot of other people's work here, so to be precise about who did what:

• Base model: zai-org / Z.ai — GLM-5.3 (743B / ~40B active MoE). Everything starts here.
• Quantization format + tooling: the compressed-tensors format and llm-compressor are by Neural Magic (now Red Hat). Mixed-precision weight quantization (some layers 4-bit, some 8-bit) is a general, well-established technique, not any one group's invention.
• The GLM recipe (the layer map): curated by QuantTrio (e.g. GLM-5.2-Int4-Int8Mix) — specifically the choice of which layers stay Int4 vs Int8 vs full-precision so GLM MoE routing and accuracy hold up. We reproduced that map for GLM-5.3 and verified its coverage before quantizing.
• Speculative drafter: IncoAI — the DFlash2 drafter used in the serving stack.
• This artifact — the first Int4-Int8Mix of the big GLM-5.3, and the first one that serves on 4x NVIDIA DGX Spark with the DFlash2 + DCP4 stack: @tonyd2wild.

License

Inherits the GLM-5.3 license from the base model. Quantization changes weights only, not the license terms.