Ornith-1.5-35B-A3B-abliterated-NVFP4
NVFP4 (W4A16) quantization of an abliterated (refusal-direction removed) build of
ornith-ai/Ornith-1.5-35B-A3B.
The per-layer quantization recipe is matched exactly to the official
ornith-ai/Ornith-1.5-35B-A3B-NVFP4;
the only difference is the underlying weights, which come from the abliterated model.
20 GB, runs on 2×16 GB consumer GPUs (tested on 2× RTX 5070 Ti, TP2).
⚠️ Text-only. The abliteration was performed on a language-model-only export, so this
checkpoint contains no vision tower and no MTP head (the official NVFP4 release keeps both).
--language-model-only is therefore unnecessary — there is nothing to skip.
⚠️ Uncensored. Safety refusal behaviour has been deliberately removed. You are responsible
for how you use it.
1. How the abliteration was done
Classic refusal-direction ablation (orthogonalization), single direction:
This projects the refusal direction out of the output space of the attention- and MLP-output
projections. Tooling derived from
remove-refusals-with-transformers.
The BF16 abliterated weights are published separately at
pottokao/Ornith-1.5-35B-A3B-abliterated.
2. How the quantization was done
NVIDIA TensorRT Model Optimizer 0.45.0 (same version as the official release),
RTN for weights, max calibration for activations.
Calibration: 64 samples × 512 tokens from abisee/cnn_dailymail (3.0.0).
Only the 130 FP8 (W8A8) projections need calibration; all NVFP4 parts are weight-only.
Verification against the official release
Tensor-level audit vs ornith-ai/Ornith-1.5-35B-A3B-NVFP4:
(The only differing patterns are visual.* and mtp.*, which this text-only build does not contain.)
3. Serving with vLLM + DFlash speculative decoding
The draft model used for all benchmarks below is
z-lab/Qwen3.6-35B-A3B-DFlash
(0.72 GB, 6 layers, hidden 2048). A copy is included under dflash_draft/ for convenience —
original weights and license belong to z-lab.
Memory / KV budget on 2× 16 GB
The KV pool is shared, so --max-model-len 131072 and --max-num-seqs 4 coexist fine —
but 4 concurrent requests cannot each hold a full 128 K context
(vLLM reports Maximum concurrency for 131,072 tokens per request: 2.26x).
The pool is this large because only 10 of 40 layers use full attention; the other 30 are
linear-attention (Mamba-style) layers that keep a fixed-size state instead of a growing KV cache.
Do not push --gpu-memory-utilization to 0.95. Startup fails with a CUDA OOM inside the
sampler warm-up: the top-k/top-p Triton buffer needs batch × vocab(248320) × 4B ≈ 62 MiB,
which vLLM's memory profiler does not reserve. 0.93 leaves enough headroom.
Kernels actually selected: attention TRITON_ATTN, MoE humming, linear layers Marlin
(the only NVFP4 W4A16 path on sm120), sampling FlashInfer.
4. Benchmarks
Hardware: 2× RTX 5070 Ti (16 GB, 250 W), TP2, PCIe Gen5.
Config: 128 K context, max-num-seqs 4, DFlash K=8, FP8 KV, util 0.93.
4.1 Spec-Bench style suite (vllm bench serve, 8 prompts/category, concurrency 1, 8 warm-ups)
4.2 Single-stream by prompt type (end-to-end, temperature 0.6)
Acceptance depends heavily on the prompt type — anywhere from 1.65 to 5.73 accept_len on the
same model and config. Structured output (math, code, JSON) drafts very well; free-form Chinese
prose drafts poorly. Always report the prompt mix alongside an acceptance number.
5. AIME 2026 — sanity check only
This is not a capability benchmark. It exists solely to check that abliteration +
NVFP4 quantization did not cause catastrophic degradation (looping, gibberish, broken
arithmetic). There is no external baseline to compare against — neither the base model card nor
the official NVFP4 release reports AIME 2026 — so these numbers can only rule out loud failure
modes. They say nothing about how this model ranks against the original, unquantized LLM.
Setup: serial, concurrency 1 (hard-reasoning benchmarks must not be run concurrently),
thinking enabled, max_tokens=96000, top_p=0.95, top_k=20, answer parsed from \boxed{N}.
A question was retried when it was wrong or hit the token limit.
39 attempts across 30 questions, ~1.41 M generated tokens.
The three that did not pass first time
Every failure was non-termination — the model burned the full 96 K budget without converging.
Not a single question was failed by producing a wrong answer. That distinction matters for a
sanity check: the failure mode is "kept thinking", not "computed garbage", which is what a badly
damaged quantization would look like.
Q15 converged exactly once (high temperature, 1194 tokens) and answered 3766 — outside AIME's
valid 0–999 range — after misidentifying the problem as USAMO 2017 P6. That is a "doesn't know how
to solve it" failure, not a degradation artifact.
Retrying non-termination: temperature, not tokens
Q30 was retried three times at the same temperature and truncated all three times, then solved
on the second attempt at temperature 0.9. Q29 followed the same pattern. Raising max_tokens
does not help this failure mode either. If you hit finish_reason: length on a reasoning task,
change the sampling temperature rather than re-running identical parameters or adding tokens.
6. Provenance