Qwen3.5-9B backbone · 8.95B parameters · BF16 · Thinking Mode · Apache 2.0
The first NEG-enabled model — self-regulating reasoning with no extra library.
Abstract
Darwin-9B-NEG is the first model in the Darwin series to feature Native Entropy Gating (NEG) — a proprietary Darwin architectural innovation that embeds a sense of self-confidence directly into the model weights. Unlike external multi-turn iteration (MTI) techniques that require 3×–8× extra inference, NEG operates inside the single decoding loop and activates in fewer than 5 % of generation steps, lifting reasoning accuracy by more than 12 percentage points at 1× inference cost.
On the GPQA Diamond PhD-level reasoning benchmark (198 questions), Darwin-9B-NEG scores 84.34 % with the full 3-stage ensemble protocol — surpassing even the published Qwen3.5-9B leaderboard result (81.7 %).
What Makes Darwin-9B-NEG Different
🧬 Darwin Series — Evolutionary Model Merging
The Darwin family is produced by Darwin V7, an evolutionary breeding engine that recombines two parent LLMs into a single descendant, preserving hybrid vigour across reasoning and knowledge capabilities. Darwin-9B-Opus — this model's base — is the Qwen3.5-family member of the Darwin series, previously published as a stand-alone reasoning model.
⚡ NEG — Native Entropy Gating (Darwin V8)
NEG is a proprietary Darwin technology that gives the language model an architecturally-internalised self-confidence sense. Two tiny learnable modules ride alongside the transformer:
NEG-Head (≈ 4 M params, ~ 0.05 % of total weights) predicts, at each step, the entropy of the next-token distribution from the last hidden state.
NEG-Gate (1 learnable threshold) decides, on a per-token basis, whether the model is "confident enough" to commit to its top choice, or whether it should restrict its choice to a narrow top-k subset.
Because NEG is carried inside the model weights themselves, there is nothing extra to ship or to install: standard transformers loading with trust_remote_code=True attaches the modules automatically. The model file is the feature.
Why it matters
1× inference cost — no multi-sample voting, no multi-turn loops
< 5 % gate activation — negligible latency overhead versus the base model
+12.63 %p on GPQA Diamond vs. the NEG-free Darwin-9B-Opus baseline (same greedy decoding, same prompt, same tokens)
Single-file deployment — drop in to vLLM / SGLang / TGI / transformers, no new engine required
No trade-secret leaks — the merge recipe is kept internal; only the final model weights are released under Apache 2.0
🏗️ Architecture Overview
Input Text
↓
[Darwin-9B-Opus backbone (frozen during NEG training)]
↓
Transformer Layers × 32
↓
last hidden state ──┐
│ │
▼ ▼
LM Head NEG-Head
│ │
base logits predicted entropy
│ │
└──▶ NEG-Gate ◀─┘
│
▼
guided logits
│
▼
next token
Mode 1 (Pure NEG): default do_sample=False, NEG is always on.
Mode 2 (Permutation): shuffle the option order 4 times, greedy each, majority-vote.
Mode 3 (Ensemble): production protocol combining permutation, temperature sampling and second-opinion re-query (internal; reproduction scripts are released separately).
🧬 Model Lineage
Qwen/Qwen3.5-9B + (Opus-distilled sibling)
╲ ╱
Darwin V7 evolutionary merge
▼
Darwin-9B-Opus ── stand-alone reasoning model (Apache 2.0)
▼
NEG-Head / NEG-Gate training (Darwin V8)
▼
Darwin-9B-NEG ── THIS MODEL
Complex chain-of-thought tasks where a small reasoning model with a big boost is desired
⚠️ Limitations
Optimised for English first, with secondary support for Korean / Chinese / Japanese.
At 8.95 B parameters, knowledge coverage is smaller than the larger Darwin models (27B / 31B / 36B) — for pure world-knowledge tasks consider Darwin-36B-Opus.
The Ensemble mode (84.34 %) uses ≈ 20× inference; choose Pure NEG (mode 1) for cost-sensitive deployments.
📚 Citation
bibtex
1@misc{darwin9b_neg_2026,
2 title = {Darwin-9B-NEG: Native Entropy Gating for Self-Regulated Reasoning at 1x Inference Cost},
3 author = {FINAL-Bench / Darwin Research Team},
4 year = {2026},
5 howpublished = {\url{https://huggingface.co/FINAL-Bench/Darwin-9B-NEG}},
6 note = {Darwin V8 — Native Entropy Gating technology generation}
7}