Cerebellum

Gemma 4 E4B Heretic — Cerebellum GGUF

Sensitivity-guided mixed-precision quantization of coder3101/gemma-4-E4B-it-heretic, which is itself a decensored variant of google/gemma-4-E4B-it produced by coder3101 using Heretic v1.2.0.

All future Heretic versions of this build will live in this repository. Version identifiers appear only in filenames, not in the repo name.

Files

File Size Description
Gemma-4-E4B-it-Heretic-Cerebellum-v1-Q3_K_M.gguf 4.2 GiB (~4.51 GB, 4,498,725,440 bytes) Cerebellum v2 recipe — recommended

No vision mmproj is included. Stock Cerebellum v2 ships none either — Gemma 4 E4B's vision projector is not publicly available in a distributable form.

Provenance

  1. Base architecture: google/gemma-4-E4B-it — Google DeepMind (Apache-2.0)
  2. Heretic variant: coder3101/gemma-4-E4B-it-heretic — coder3101. The safetensors from that repository were converted to F16 GGUF and used as the direct quantization source (single quantization step from F16). coder3101 applied Heretic v1.2.0 with the Arbitrary-Rank Ablation (ARA) method (with row-norm preservation), targeting layers 21–42. Their reported result: 0.0058 KL divergence from base, 3/100 refusals vs 99/100 on the original model.
  3. Quantization: Cerebellum v2 recipe transferred verbatim from the stock deucebucket/Gemma-4-E4B-it-Cerebellum-v2-GGUF build — same 179-entry tensor-type override file, same imatrix. The heretic build lands within 384 bytes of the stock v2 file (4,498,725,440 vs 4,498,725,056 bytes) — byte-class identical.

Benchmarks

Benchmarks run on these GGUF files directly using llama.cpp on RTX 3090. All numbers are audited; every failed answer was manually verified as a genuine model error — audit reports are in benchmark_results/AUDIT_e4b.md. Full per-question detail (summary JSON, samples JSONL, EvalPlus eval JSON, adversarial audit reports) is in benchmark_results/ in this repository.

Heretic Cerebellum v1 (4.2 GiB) vs baselines

Benchmark Heretic Cerebellum v1 (4.2 GiB) Stock Cerebellum v2 (4.2 GiB) Notes
Wiki PPL (ctx 2048, 32 chunks) 50.61 ± 1.23 51.35 ± 1.26 RTX 3090, identical invocation — see note
ARC-Challenge 87.37% (1172 q) 85.7% 25-shot
HellaSwag 74.98% (10042 q) 75.3% 10-shot
MMLU-Redux 58.63% (2400 q) 58.4% 5-shot — see footnote
HumanEval base (chat, no-think) 70.12% (164 q) 68.3% pass@1, patched evalplus harness
HumanEval+ (chat, no-think) 65.24% not published pass@1, patched evalplus harness

Stock Cerebellum v2 is the same tensor allocation applied to the non-heretic base.

Perplexity measurement note

Stock v2's published card number of 52.20 was measured under a different protocol. The 51.35 figure above is a same-night, same-invocation pair run alongside the heretic build (ctx 2048, 32 chunks, RTX 3090) and is the directly comparable baseline. The heretic build's 50.61 ± 1.23 is 0.74 points lower than that paired measurement; error bars overlap at the edges, making this a marginal improvement consistent with the abliteration applying a slight distributional shift rather than introducing noise.

MMLU-Redux footnote

The audit (BE-16) identified 12 truly identical duplicate entries in the MMLU-Redux dataset resulting from a subject-boundary edge case in the benchmark runner. These entries inflate the reported score by ≤0.04pp (58.6654% → 58.6250% without duplicates), which is below the 0.1pp non-blocking threshold. The reported 58.63% is rounded from 58.625% and is trustworthy within standard rounding tolerance.

HumanEval methodology note

Zero fabricated completions. One model-authored stub (HumanEval/79, decimal_to_binary) — a literal pass placeholder — was correctly scored as fail and does not inflate pass@1. Stock v2's published 68.3% base was measured with the upstream evalplus harness; HumanEval+ was not published for stock v2. The heretic numbers above use the patched no-think chat harness (same harness used for all Cerebellum builds since the harness audit, May 2026).

Heretic Abliteration Details (from coder3101)

The following parameters are as reported in coder3101's model card and are reproduced here for downstream reference.

Parameter Value
Method Arbitrary-Rank Ablation (ARA) with row-norm preservation
Targeted layers 21–42
preserve_good_behavior_weight 0.3873
steer_bad_behavior_weight 0.0003
overcorrect_relative_weight 0.8555
neighbor_count 14

Tool: Heretic v1.2.0, method: Arbitrary-Rank Ablation (ARA) with row-norm preservation.

Cerebellum v2 Tensor Allocation

Same allocation as the stock build. Listed here for reference. 179 overrides over a Q3_K_M base: 174 PLE tensors pinned to Q5_K, 2 sacred promotions to Q6_K, 3 demotions to Q2_K.

Group Precision Rationale
Per-layer embedding (PLE) tensors × 174 Q5_K Without PLE protection: PPL ~104 at Q3_K_M; with PLE@Q5_K: PPL ~55. Q4_K→Q3_K cliff is catastrophic for this architecture
2 sacred attention tensors Q6_K Highest per-tensor PPL sensitivity per ablation
3 ffn tensors Q2_K Reverse ablation confirmed Q2_K neutral or beneficial at these positions
Norm tensors F32 Protected; standard practice
Bulk ffn / remaining attention Q3_K_M Base precision, imatrix-guided

The PLE protection is the load-bearing element of this recipe. Gemma 4's per-layer embedding tensors degrade catastrophically at Q3_K_M — the Q4_K→Q3_K transition produces a PPL cliff rather than a gradual slope, going from ~55 to ~104 without PLE pins. This finding is documented in the stock v2 ablation logs.

Measured launch (RTX 3090, llama.cpp)

Measured 2026-06-13 on a single RTX 3090 (24 GB), one llama-server, KV cache q8_0:

metric measured
decode speed 116 tok/s
peak VRAM (4-slot serving) 5.3 GB
max measured context (q8_0 KV) 65,536
llama-server -m Gemma-4-E4B-it-Heretic-Cerebellum-v1-Q3_K_M.gguf \
  -ngl 99 --parallel 4 -c 24576 --jinja --reasoning-budget 0

This rig's measurements; no quality claims beyond them.

Runtime — Casual Deployment

llama-server \
  --model Gemma-4-E4B-it-Heretic-Cerebellum-v1-Q3_K_M.gguf \
  --n-gpu-layers 99 \
  --ctx-size 8192

Fits comfortably in 6 GB VRAM at 8K context on an RTX 3060/3070/3080 class card.

Reproduction

Standard Cerebellum recipe. The tensor-type override file and ablation logs from the stock v2 build apply directly.

# 1. imatrix (constant ~300 MB RAM)
python -m osmosis.imatrix_stream \
    --model gemma-4-E4B-it-heretic-f16.gguf \
    --output imatrix.dat

# 2. quantize with stock llama-quantize
llama-quantize \
    --imatrix imatrix.dat \
    --tensor-type-file cerebellum_v2_overrides.txt \
    gemma-4-E4B-it-heretic-f16.gguf \
    Gemma-4-E4B-it-Heretic-Cerebellum-v1-Q3_K_M.gguf \
    Q3_K_M

The 179-entry tensor override file (cerebellum_v2_overrides.txt) is included in this repository alongside the ablation logs.

Benchmark Artifacts

Summary JSONs, per-question JSONL samples, EvalPlus eval JSON files, and adversarial audit reports (AUDIT_e4b.md) are in benchmark_results/ in this repository per project policy.

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