How to use from
Pi
Start the MLX server
# Install MLX LM:
uv tool install mlx-lm
# Start a local OpenAI-compatible server:
mlx_lm.server --model "Youssofal/Qwen3.5-4B-MTPLX-Optimized-Speed"
Configure the model in Pi
# Install Pi:
npm install -g @mariozechner/pi-coding-agent
# Add to ~/.pi/agent/models.json:
{
  "providers": {
    "mlx-lm": {
      "baseUrl": "http://localhost:8080/v1",
      "api": "openai-completions",
      "apiKey": "none",
      "models": [
        {
          "id": "Youssofal/Qwen3.5-4B-MTPLX-Optimized-Speed"
        }
      ]
    }
  }
}
Run Pi
# Start Pi in your project directory:
pi
Quick Links

Qwen3.5-4B MTPLX Optimized Speed

4-bit (group 64) Qwen3.5-4B with a calibrated native-MTP draft head, built for MTPLX on Apple Silicon. 2.47 GB on disk, ~2.9 GiB peak at load. The fastest model MTPLX ships.

Measured on an M5 Max (max fans, MTPLX 2.2.0, deterministic suite):

  • AR baseline: 133.6 tok/s
  • MTP depth 3: 227.8 tok/s (1.71x), first-position acceptance 0.95

The engine reads the tuned depth from mtplx_runtime.json; no manual configuration needed. Runs on any Apple Silicon Mac with 8 GB+ of unified memory.

July 2026 rebuild (important)

Earlier revisions of this repo shipped a defective MTP sidecar: the RMSNorm weights were stored in the raw zero-centered convention and never restored, so the draft head proposed garbage and MTP made the model slower than plain decoding (reported as #176, thanks lBroth). This revision is rebuilt from source with the fixed forge. MTPLX 2.2.0+ also detects and heals the old sidecar at load, so existing downloads recover without re-downloading.

Usage

Pick "Qwen 3.5 4B Optimized Speed" in the MTPLX app, or:

mtplx serve --model Youssofal/Qwen3.5-4B-MTPLX-Optimized-Speed
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