Why Qwen3.8-27B overthinks? Here the reason.

#38
by LuffyTheFox - opened

I checked the official GGUF BF16 weights directly from Unsloth.

What I found is not a “reasoning style” issue. It is a structural defect in the temporal processing layers.

Tensor QType C2 α S_b S_a
blk.52.ssm_conv1d.weight F32 0.59005 0.0016 0.0006
blk.53.ssm_conv1d.weight F32 0.55484 0.0015 0.0005
blk.56.ssm_conv1d.weight F32 0.54486 0.0015 0.0004
blk.57.ssm_conv1d.weight F32 0.53574 0.0015 0.0004
blk.58.ssm_conv1d.weight F32 0.60972 0.0012 0.0005
blk.60.ssm_conv1d.weight F32 0.48136 0.0017 0.0004
blk.61.ssm_conv1d.weight F32 0.65327 0.0010 0.0004
blk.62.ssm_conv1d.weight F32 0.61856 0.0013 0.0005

Column meaning:

  • C2 = scale misalignment detected
  • α = optimal scale correction factor
  • S_b = saturation before correction
  • S_a = saturation after correction

In plain terms:

  • these layers should prepare the signal for SSM recurrence
  • instead, their scale is shifted far from the peer distribution
  • α ≈ 0.48–0.65

That means the model does not receive a clean temporal signal. It receives a distorted one.

The result is exactly what users see:

  • reasoning does not stop at the right time
  • simple questions take 100+ seconds
  • token consumption is ~5× higher than it should be

Here is a real example from the released model.

User asked:

I need to wash my car, the car wash is 100m away. Do I go by car or by foot?

The model spent 137 tokens in xhigh reasoning mode before answering:

By car - you need the car at the car wash to wash it.

That is not “too smart” or “thinking hard”. That is broken ssm_conv1d signal conditioning.

That is also why I will not make Genesis for 27B.
You cannot fix this by patching a few tensors or doing SVD to fix noise gate.
The SSM input pathway is damaged across too many layers.

A healthy model should answer:

By car - you need the car at the car wash.

Not spend 137 tokens explaining the obvious.

LuffyTheFox pinned discussion

I really appreciate your attitude towards model tuning keep on,sir

What are the changes you made in the V8 (Hermes3.6-35B-A3B-Uncensored-Genesis-V8-APEX-Compact.gguf uploaded 1 hour ago) ? It would be cool to have a change list somewhere.

What are the changes you made in the V8 (Hermes3.6-35B-A3B-Uncensored-Genesis-V8-APEX-Compact.gguf uploaded 1 hour ago) ? It would be cool to have a change list somewhere.

Here info: https://huggingface.co/LuffyTheFox/Qwen3.6-35B-A3B-Uncensored-Genesis-Hermes-V7-GGUF/discussions/39

Independent verification of your conv1d diagnosis — full benchmark results

Thank you for this write-up — it prompted us to run an independent, controlled verification, and your diagnosis holds up. We are the hermes-nova team (org redashes), working with official Qwen/Qwen3.8-27B BF16 weights.

1. Diagnosis confirmed by independent measurement

We measured linear_attn.conv1d.weight std across the 48 GatedDeltaNet layers on the official BF16 weights, and flagged the same 8 layers using a std/median > 1.6 rule:

Layer our α your α match
52 0.59005 0.59005
53 0.55484 0.55484
56 0.54486 0.54486
57 0.53574 0.53574
58 0.60972 0.60972
60 0.48136 0.48136
61 0.65327 0.65327
62 0.61856 0.61856

Layer set and α values are identical — two independent implementations, convergent diagnosis. α ≈ 0.48–0.65, exactly your range.

2. What a strict per-layer α fix does — measured, not asserted

We applied your strict per-layer α (not median normalization), kept everything else bit-exact, and ran a full controlled battery on the exact same stack (vLLM 0.27.1, same harness, same hardware: single RTX PRO 6000).

Metric official BF16 +SSMFIX (per-layer α) Δ
MT-Bench avg (DeepSeek-V4-Flash judge) 7.05 7.47 +0.42
IFEval inst-level strict 0.6247 0.6343 +0.96pp
GSM8K strict (5-shot) 0.9606 0.9644 +0.38pp
TruthfulQA gen rouge1 0.2840 0.3452 +6.1pp
TruthfulQA gen rouge2 0.1616 0.2460 +8.4pp
TruthfulQA gen rougeL 0.2803 0.3452 +6.5pp
TruthfulQA gen bleu 0.1775 0.2558 +7.8pp
TruthfulQA mc1 / mc2 0.3647/0.5418 0.3758/0.5513 +0.0111 / +0.0095
CMMLU (68 subtasks) 0.7179 0.6996 −1.8pp

9 of 11 metrics ≥ official. Generation quality and truthfulness improve substantially (TruthfulQA-gen +6~8pp, MT-Bench +0.42), and the "overthinking" pattern you documented is visibly reduced. The single notable cost: CMMLU −1.8pp (knowledge-heavy closed-book recall).

3. On "you cannot fix this by patching a few tensors"

Partial refutation, with nuance. A small tensor patch does move the model meaningfully — our data shows it is not a free lunch, but it is also not a write-off:

  • Generative metrics moved large (TruthfulQA-gen +6~8pp) — the drift was real and the fix effective.
  • But CMMLU −1.8pp confirms your broader point that the repair trades knowledge capacity for generation quality; the pathway damage is not simply reversible.

So: your diagnosis is confirmed, your pessimism is partially justified, and the measured verdict is "worth it for generative use, not for knowledge-max use".

4. Release (public, weights + full eval + method)

redashes/Qwen3.8-27B-BF16-SSMFIX — now public on Hugging Face, with bilingual README, full eval tables, fix report, and method credit to you and FGDumitru (qwen-ssm-repair, who independently re-implemented this and got overlapping α 0.61–0.70):

https://huggingface.co/redashes/Qwen3.8-27B-BF16-SSMFIX

Thanks again for the original investigation — it was the right lead.

Independent verification of your conv1d diagnosis — full benchmark results

Thank you for this write-up — it prompted us to run an independent, controlled verification, and your diagnosis holds up. We are the hermes-nova team (org redashes), working with official Qwen/Qwen3.8-27B BF16 weights.

1. Diagnosis confirmed by independent measurement

We measured linear_attn.conv1d.weight std across the 48 GatedDeltaNet layers on the official BF16 weights, and flagged the same 8 layers using a std/median > 1.6 rule:

Layer our α your α match
52 0.59005 0.59005
53 0.55484 0.55484
56 0.54486 0.54486
57 0.53574 0.53574
58 0.60972 0.60972
60 0.48136 0.48136
61 0.65327 0.65327
62 0.61856 0.61856

Layer set and α values are identical — two independent implementations, convergent diagnosis. α ≈ 0.48–0.65, exactly your range.

2. What a strict per-layer α fix does — measured, not asserted

We applied your strict per-layer α (not median normalization), kept everything else bit-exact, and ran a full controlled battery on the exact same stack (vLLM 0.27.1, same harness, same hardware: single RTX PRO 6000).

Metric official BF16 +SSMFIX (per-layer α) Δ
MT-Bench avg (DeepSeek-V4-Flash judge) 7.05 7.47 +0.42
IFEval inst-level strict 0.6247 0.6343 +0.96pp
GSM8K strict (5-shot) 0.9606 0.9644 +0.38pp
TruthfulQA gen rouge1 0.2840 0.3452 +6.1pp
TruthfulQA gen rouge2 0.1616 0.2460 +8.4pp
TruthfulQA gen rougeL 0.2803 0.3452 +6.5pp
TruthfulQA gen bleu 0.1775 0.2558 +7.8pp
TruthfulQA mc1 / mc2 0.3647/0.5418 0.3758/0.5513 +0.0111 / +0.0095
CMMLU (68 subtasks) 0.7179 0.6996 −1.8pp

9 of 11 metrics ≥ official. Generation quality and truthfulness improve substantially (TruthfulQA-gen +6~8pp, MT-Bench +0.42), and the "overthinking" pattern you documented is visibly reduced. The single notable cost: CMMLU −1.8pp (knowledge-heavy closed-book recall).

3. On "you cannot fix this by patching a few tensors"

Partial refutation, with nuance. A small tensor patch does move the model meaningfully — our data shows it is not a free lunch, but it is also not a write-off:

  • Generative metrics moved large (TruthfulQA-gen +6~8pp) — the drift was real and the fix effective.
  • But CMMLU −1.8pp confirms your broader point that the repair trades knowledge capacity for generation quality; the pathway damage is not simply reversible.

So: your diagnosis is confirmed, your pessimism is partially justified, and the measured verdict is "worth it for generative use, not for knowledge-max use".

4. Release (public, weights + full eval + method)

redashes/Qwen3.8-27B-BF16-SSMFIX — now public on Hugging Face, with bilingual README, full eval tables, fix report, and method credit to you and FGDumitru (qwen-ssm-repair, who independently re-implemented this and got overlapping α 0.61–0.70):

https://huggingface.co/redashes/Qwen3.8-27B-BF16-SSMFIX

Thanks again for the original investigation — it was the right lead.

Thank you very much for sharing testing results with SSM fix. This is the right path to take open source. We should not blindly use models shared by companies. A neural network is not a black box; it is a statistical machine governed by fundamental mathematical laws. Let's hope Alibaba Group will fix this issue in Qwen4.0 during training process.

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