Ornith-1.5-9B-MLX-distil-oQ4

Ornith-1.5-9B-MLX-distil-oQ4

A 4.9 GB model that outscores the 8.9 GB one it's based on — and matches a 17 GB model on MMLU.

Distilled from two teachers, then quantized with the same mixed-bit oQ4 scheme as the stock release. Runs on any Apple Silicon Mac with ~8 GB of free memory.

+5.5 MMLU, +3.0 HumanEval over the oQ4 it replaces — same size, same bit width. It also beats the 1.8× larger oQ8 on both, and edges out the 3.5× larger bf16 base on MMLU while landing 0.7 points behind it on HumanEval.

It got faster too: HumanEval −33%, MMLU −15% wall clock versus the stock oQ4, because it stops reasoning when it's done instead of rambling into the token limit.

⚠️ TruthfulQA is 1.7 points worse than the stock oQ4 (79.0% vs 80.7%), reproduced on two independent harnesses. See Limitations.

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Quick start

pip install mlx-lm

from mlx_lm import load, generate

model, tokenizer = load("adityak74/Ornith-1.5-9B-MLX-distil-oQ4")

prompt = tokenizer.apply_chat_template(
    [{"role": "user", "content": "Write a Python function to check if a string is a palindrome."}],
    add_generation_prompt=True,
    tokenize=False,
)
print(generate(model, tokenizer, prompt=prompt, max_tokens=1024))

Or from the command line:

mlx_lm.generate --model adityak74/Ornith-1.5-9B-MLX-distil-oQ4 \
  --prompt "Explain the difference between a process and a thread." --max-tokens 1024

This is a reasoning model — it thinks before answering, and the chat template opens a <think> block for it. Give it room: 4096 max tokens for coding problems, 2048+ for everything else. Truncating mid-reasoning throws away the answer entirely.

Which variant should I use?

How it was made

Two teachers, split by what each is measurably good at:

• Qwen3.6-35B-A3B-4bit → knowledge and truthfulness (89.3% MMLU)
• Ornith-1.5-35B-A3B-4bit → code (93.3% HumanEval, and 4.6× faster to sample from)

Rejection sampling did the heavy lifting. 3,974 teacher traces were generated and only verifiably correct ones kept — multiple-choice answers matched against the gold letter, open questions against gold aliases, and generated code executed against its source dataset's real tests. 1,672 survived. Anything sharing a 13-gram with MMLU test, TruthfulQA or HumanEval was dropped before training.

Training was rank-32 LoRA over the top 16 layers of the bf16 base (3,200 steps, 1.76M tokens on one M4 Pro), fused back to full precision, and only then quantized — so the quantizer starts from an improved checkpoint instead of compounding two lossy steps. The oQ4 map (4-bit affine, group size 64, with 120 modules promoted to 5/6/8 bits) was replicated exactly from the stock release, so the comparison above is like-for-like.

Why it works: termination, not knowledge

The interesting part. On a strict harness that scores unfinished output as wrong, the stock oQ4 fails to reach an answer on 24% of HumanEval problems — it reasons past the token budget. This model cuts that to 12%, and 22 of the 28 problems it gains are ones where the stock model simply ran out of road.

Quantization appears to damage a model's ability to stop reasoning more than its ability to reason. Training on teacher traces that terminate cleanly repairs much of it. That also explains the flat multiple-choice results: a truncated multiple-choice answer is often still recoverable, a truncated program never is.

Limitations

• TruthfulQA regressed 1.7 points. The truthfulness training data came from TriviaQA and SciQ, which reward confident factual recall — close to the opposite of what TruthfulQA measures, which is resisting a plausible-sounding falsehood. This is a known defect with a known fix, not a mystery.
• MMLU and HumanEval gains are measured, TruthfulQA aside. Both numbers above come from the same harness across every row, but a single harness is a single harness. Independent evaluation is welcome.
• It is a 9B model. It does not match the 35B teachers on truthfulness (−7.4 points against Ornith-35B), and it is slower than those MoE models on Apple Silicon despite being smaller, because it is dense and they activate ~3B parameters per token. It wins on memory, not latency.
• Reasoning length means it wants a generous token budget. Small max_tokens will hurt it more than a non-reasoning model.

Reproducing this

The full pipeline is open source, including the decisions log with every measurement, dead end and hardware limit hit along the way:

github.com/adityak74/ornith-1.5-9b-distil

odistil prompts    # build the prompt pool
odistil teach      # generate teacher traces
odistil dataset    # verify, decontaminate, mix
odistil train      # LoRA distillation
odistil fuse       # fuse to bf16
odistil quantize --variant oq4
odistil eval --model runs/v1/quant/oq4

License and attribution

Derived from ornith-ai/Ornith-1.5-9B-MLX, which per its own model card was built on Qwen3.5 and Gemma4. The base model card states no license, so the terms governing this derivative are whatever govern that model and its upstreams — including the Gemma terms, which flow downstream. Please check those before redistribution or commercial use. This repository claims no rights beyond the distillation recipe itself.

Teachers: Qwen3.6-35B-A3B (Alibaba / Qwen team) and Ornith-1.5-35B-A3B (ornith.ai). Built with mlx-lm.