Known issues
Reasoning loop under stacked output-format constraints. Reported by
zxbc2023 (full writeup, discussion #1).
Combining "no prose" with a second output-format constraint (e.g.
or
"no comments") can send this model into a non-converging
self-verification reasoning loop -- it burns the entire token budget with
zero visible output. Fully deterministic and reproducible at temp=0.
Root cause: traced to part of the training data being sourced from
reconstructed (not verbatim) Opus reasoning traces, not a capability gap.
Fixed in barozp/Qwen3.8-27B-Opus-Distill-v2
-- retrained on a rebuilt dataset where every row is traced to a verified
genuine source. If you're hitting this, switch to v2.
Workaround if staying on this version: avoid combining "no prose" with
another format constraint, or raise the generation token budget to >=4096
for constrained code-gen tasks.
Model overview
- Base model: Qwen/Qwen3.8-27B — dense 27B, native vision-language, native MTP.
- Method: LoRA (
r=64, alpha=64, dropout=0.05), merged into the base weights.
- LoRA targets: attention
q/k/v/o_proj on the 16 full-attention layers only; FFN gate/up/down_proj on all 64 layers. Gated-DeltaNet (linear-attention) projections are left untouched, matching the Qwen3.6 recipe.
- Training data:
barozp/opus-reasoning-distill-train (14,250 examples) + -validation (750, held out).
- Training run: 1 epoch (891 steps),
lr=1e-4 cosine with 3% warmup, effective batch 16 (micro-batch 1 × grad-accum 16), MAX_SEQ=4096, bf16, ~5h52m on an A100 80GB.
- Final validation loss:
0.4647 (step 891/891).
- Vision + MTP: carried over from base, never trained.
Highlights
- Reasoning improves, nothing else degrades. ARC-Challenge and GPQA-Diamond
both rise while MMLU (general knowledge) and wikitext (language modeling)
stay flat within noise.
- Reflex-level reasoning gets the biggest boost. GPQA is measured in
loglikelihood mode with thinking disabled — the model has no chance to
deliberate. Distillation more than doubles that "reflex" score, meaning the
model internalized step-by-step reasoning rather than just learning to
generate
<think> blocks.
- Vision and MTP are fully intact. This is a complete multimodal model with
self-speculative decoding, not a text-only strip-down.
Benchmark results
Measured with lm-evaluation-harness, 0-shot, loglikelihood (multiple-choice),
chat template OFF, QUICK mode (--limit 500). Base and distill were run with
the identical harness, so the Δ column is the meaningful signal — not the
absolute values.
Table with columns: Task, Metric, Base, Distill, Δ| Task | Metric | Base | Distill | Δ |
|---|
| wikitext | word perplexity ↓ | 8.434 | 8.344 | −0.09 |
| mmlu | acc | 0.849 | 0.849 | −0.001 |
| hellaswag | acc_norm | 0.742 | 0.740 | −0.002 |
| arc_challenge |
Important caveats
- GPQA is not comparable to Qwen's published 89.2. Qwen reports GPQA with
thinking mode ON and their own harness. Here GPQA is measured in
loglikelihood mode with thinking OFF — the base model scores near random
(25%) precisely because it gets no chance to reason. The +26pt Δ is a valid
same-protocol comparison (base vs distill), but do not place 0.495 next
to Qwen's 89.2 as if they were the same measurement.
- ARC-Challenge is saturated for modern models. The +4.2pt Δ is real and
consistent with the Qwen3.6 release, but ARC (2018, middle-school science) is
not a headline reasoning benchmark anymore. GPQA is the stronger signal here.
- QUICK mode limits each task to 500 samples; hellaswag and arc_challenge
are noisy at that size. Treat small Δ values (±0.01) on those as noise.
Quick start
from transformers import AutoModelForImageTextToText, AutoProcessor
import torch
model = AutoModelForImageTextToText.from_pretrained(
"barozp/Qwen3.8-27B-Opus-Distill", dtype=torch.bfloat16, device_map="auto",
)
processor = AutoProcessor.from_pretrained("barozp/Qwen3.8-27B-Opus-Distill")
Text-only inference also works via AutoModelForCausalLM (vision is ignored,
which is the expected/standard behavior for that class).