---
language: en
license: apache-2.0
base_model: Zyphra/Zamba2-7B-instruct
tags:
  - zamba2
  - mamba
  - hybrid
  - compressed
  - hxq
  - helix-substrate
  - vector-quantization
  - helixcode
library_name: transformers
pipeline_tag: text-generation
model-index:
  - name: zamba2-7b-instruct-hxq
    results: []
---

# Zamba2-7B-Instruct-HXQ

> **2.0x smaller from BF16. 81-layer hybrid Mamba2+Transformer. Largest HXQ hybrid model.**
>
> Zamba2-7B-Instruct compressed from 14.7 GB (BF16) to 7.5 GB. 213 linear layers compressed, 573 exact tensors preserved. No calibration data. Just `pip install` and `from_pretrained()`.

## Install and Run

```bash
pip install "helix-substrate[hf]"
```

```python
import helix_substrate  # registers the HXQ quantizer with HuggingFace
from transformers import AutoModelForCausalLM, AutoTokenizer

model = AutoModelForCausalLM.from_pretrained("EchoLabs33/zamba2-7b-instruct-hxq")
tokenizer = AutoTokenizer.from_pretrained("EchoLabs33/zamba2-7b-instruct-hxq")

inputs = tokenizer("Explain the theory of relativity in simple terms:", return_tensors="pt")
outputs = model.generate(**inputs, max_new_tokens=128)
print(tokenizer.decode(outputs[0], skip_special_tokens=True))
```

That's it. `import helix_substrate` registers the quantizer. `from_pretrained()` handles the rest automatically.

## Benchmark

| | Dense (BF16) | HXQ |
|---|---|---|
| **Size** | 14.7 GB | **7.5 GB** |
| **Perplexity** (WikiText-2) | pending | pending |
| **Compression ratio** | — | **2.0x** |
| **Compressed modules** | — | 213 HelixLinear layers |
| **Architecture** | Zamba2 (81 layers, Mamba2 + shared Transformer) | unchanged |

## Good to Know

- **GPU recommended** — 7.5 GB requires 10+ GB VRAM. Use `device_map="auto"` for multi-GPU.
- **Fine-tunable via LoRA** — compressed weights remain frozen, but LoRA adapters attach to each `HelixLinear` layer via `HelixLinearSTE`. See `helix-substrate` for training infrastructure.
- **Requires `helix-substrate`** — the quantizer is not built into transformers. You need `pip install "helix-substrate[hf]"`.
- **Requires `transformers >= 4.45`** — for Zamba2 architecture support.
- **`mamba-ssm` recommended** — without it, falls back to a slower sequential code path.
- **PPL pending** — requires cloud GPU eval (model doesn't fit on 4 GB T2000).

## What is HelixCode?

HelixCode is a universal weight compression codec based on vector quantization:

- Each weight matrix is replaced by a **256-entry codebook** (float32) + **uint8 index matrix** + optional **sidecar corrections** for outlier values
- The compressed form *is* the executable — `HelixLinear` performs `codebook[indices] @ x` directly, no decompression step
- Works on any `nn.Linear` regardless of architecture (Transformer, Mamba, MLP, CNN)
- **No calibration data required** — unlike GPTQ/AWQ, codebooks are fit from the weights alone

## How It Works

1. `import helix_substrate` registers the `hxq` quantizer with HuggingFace
2. `from_pretrained()` reads `quantization_config.quant_method = "hxq"` from `config.json`
3. The quantizer replaces 213 `nn.Linear` modules with `HelixLinear` shells before weight loading
4. Safetensors populates the codebook, indices, and sidecar buffers directly
5. The model runs in compressed form — no decompression needed

## Architecture Details

Zamba2-7B-Instruct is a hybrid architecture with:
- **81 total layers** (Mamba2 + shared Transformer hybrid)
- **hidden_size=3584**, **attention_hidden_size=7168**, **32 attention heads**
- **mamba_d_state=64**, **mamba_d_conv=4**
- **vocab_size=32000**

213 linear layers compressed (162 Mamba projections, 38 attention/MLP, 26 LoRA adapters). Normalization layers, embeddings, conv1d, and Mamba-specific parameters (A_log, D, dt_bias) are stored at full precision.

## Compression Receipt

```
Compressed modules:  213
Exact tensors:       573  (norms, embeddings, conv1d, A_log, D, dt_bias, LoRA)
Skip tensors:        243  (from original model)
Total keys:          1425
Dense size:          14.7 GB (BF16)
Compressed size:     7.5 GB
Compression ratio:   2.0x
PPL delta:           pending (cloud GPU eval)
Gate 1:              PASS (structural validation + SHA256)
```

## Companion Models

Same codec, same `pip install`, multiple architectures:

| Model | Architecture | Ratio | PPL Delta |
|-------|-------------|-------|-----------|
| [qwen2.5-14b-instruct-helix](https://huggingface.co/EchoLabs33/qwen2.5-14b-instruct-helix) | Transformer | 3.4x | pending |
| [qwen2.5-7b-instruct-helix](https://huggingface.co/EchoLabs33/qwen2.5-7b-instruct-helix) | Transformer | 2.2x | +6.34% |
| [qwen2.5-3b-instruct-helix](https://huggingface.co/EchoLabs33/qwen2.5-3b-instruct-helix) | Transformer | 1.6x | +0.69% |
| [qwen2.5-coder-3b-helix](https://huggingface.co/EchoLabs33/qwen2.5-coder-3b-helix) | Transformer (code) | 1.6x | +1.92% |
| [qwen2.5-coder-1.5b-instruct-helix](https://huggingface.co/EchoLabs33/qwen2.5-coder-1.5b-instruct-helix) | Transformer (code) | 2.4x | +1.63% |
| [tinyllama-1.1b-helix](https://huggingface.co/EchoLabs33/tinyllama-1.1b-helix) | Transformer | 4.0x | +0.78% |
| [zamba2-2.7b-instruct-helix](https://huggingface.co/EchoLabs33/zamba2-2.7b-instruct-helix) | Hybrid (Mamba2+Transformer) | 1.8x | +6.59% |
| [zamba2-1.2b-helix](https://huggingface.co/EchoLabs33/zamba2-1.2b-helix) | Hybrid (Mamba2+Transformer) | 1.7x | +2.90% |
| [mamba2-1.3b-helix](https://huggingface.co/EchoLabs33/mamba2-1.3b-helix) | Pure SSM (Mamba2) | 2.1x | +8.0% |
| [mamba-130m-helix](https://huggingface.co/EchoLabs33/mamba-130m-helix) | Pure SSM | 3.8x | +18.4% |

## Citation

```bibtex
@software{helix_substrate_2026,
  title={Helix Substrate: Universal Weight Compression via HelixCode},
  author={EchoLabs},
  year={2026},
  url={https://github.com/echo313unfolding/helix-substrate}
}
```

## License

Apache 2.0 (inherited from [Zyphra/Zamba2-7B-instruct](https://huggingface.co/Zyphra/Zamba2-7B-instruct)).