How to use from
Pi
Start the llama.cpp server
# Install llama.cpp:
brew install llama.cpp
# Start a local OpenAI-compatible server:
llama-server -hf localweights/Qwen3.5-4B-MTP-BF16-GGUF:BF16
Configure the model in Pi
# Install Pi:
npm install -g @mariozechner/pi-coding-agent
# Add to ~/.pi/agent/models.json:
{
  "providers": {
    "llama-cpp": {
      "baseUrl": "http://localhost:8080/v1",
      "api": "openai-completions",
      "apiKey": "none",
      "models": [
        {
          "id": "localweights/Qwen3.5-4B-MTP-BF16-GGUF:BF16"
        }
      ]
    }
  }
}
Run Pi
# Start Pi in your project directory:
pi
Quick Links

Qwen3.5-4B-MTP-BF16-GGUF

Qwen3.5-4B (qwen35 dense+ssm hybrid arch) with NextN/MTP head preserved, full bf16 precision (~8.3 GB). Source for further quantization. Built via the patched convert_hf_to_gguf.py from patched llama.cpp build with Qwen3.5/3.6 MTP support.

Files

File Size Purpose
Qwen3.5-4B-MTP-bf16.gguf 8.3 GB Full-precision source. NextN tensors at blk.32.

Note on outlier weights

This model contains 3 tensors with extreme magnitudes (1e19 to 1e36):

  • blk.9.ssm_out.weight
  • blk.15.attn_output.weight
  • blk.24.ffn_gate.weight

These are genuine learned weights (forward pass numerically OK). They overflow the fp16 scale-block storage of certain k-quants (e.g. Q4_K_M). When quantizing downstream, keep them at bf16 via:

llama-quantize \
  --tensor-type "blk\.9\.ssm_out\.weight=bf16" \
  --tensor-type "blk\.15\.attn_output\.weight=bf16" \
  --tensor-type "blk\.24\.ffn_gate\.weight=bf16" \
  Qwen3.5-4B-MTP-bf16.gguf \
  Qwen3.5-4B-MTP-Q4_K_M.gguf \
  Q4_K_M

IQ4_XS does not need overrides โ€” its imatrix-aware path masks the outliers.

Build pipeline

python convert_hf_to_gguf.py /path/to/Qwen3.5-4B \
    --outfile Qwen3.5-4B-MTP-bf16.gguf

Required adding the qwen35 pre-tokenizer chkhsh entry to convert_hf_to_gguf.py:1531 (vendored in the fork).

Sibling repos

Tokenizer

qwen35 pre-tokenizer, 151,936 vocab. Standard chat template.

License

Apache 2.0.

Provenance

Built on Crucible: 9950X / 96 GB DDR5 / RTX 3090 Ti.

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GGUF
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