Known-issues sheets for local language models Rev 0.1.0 · reviewed every 7 days

Model datasheet · Gemma 4

Gemma 4 12B

The 'Unified' one: an encoder-free architecture that takes image and audio straight into the embedding space, at a size that leaves room to breathe on a 16GB machine. Punches near the 26B MoE on reasoning while being the only model here that hears.

Vendor
Google
Architecture
Dense · 11.95B
Context
262,144 tokens
License
Apache-2.0
Released
2026-07-02
Vision
Yes

→ GGUF (llama.cpp / LM Studio / Ollama) → MLX (Apple Silicon)

§1 Characteristics by quantization band

Q2–Q3 — 2–3 bit

6GB weights · e.g. Q3_K_M + KV: 832MB at 8K · 2.3GB at 32K · 8.3GB at 128K

— Not yet rated · contributions welcome —

Q4–Q5 — 4–5 bit

7GB weights · e.g. Q4_0 , Q4_K_M , mlx-4bit + KV: 832MB at 8K · 2.3GB at 32K · 8.3GB at 128K
Math & reasoning 6/10
data checked Aug 2026
  • quant-degradation-community — community consensus @ Q4_0 · aggregated · 2026-08-30

    Editorial derivation: QAT Q4_0 is the intended local build; one point for quant loss, consistent with the family.

Coding 6/10
data checked Aug 2026
Tool calling / agentic 6/10
data checked Aug 2026
  • quant-degradation-community — community consensus @ Q4_0 · aggregated · 2026-08-30

    Editorial derivation: carried from the full band.

Q6–Q8 — 6–8 bit

10GB weights · e.g. Q6_K + KV: 832MB at 8K · 2.3GB at 32K · 8.3GB at 128K

— Not yet rated · contributions welcome —

FP16 — full precision (fp16/bf16)

24GB weights · e.g. bf16 + KV: 832MB at 8K · 2.3GB at 32K · 8.3GB at 128K
Math & reasoning 7/10
data checked Aug 2026
  • vendor-model-cardAIME 2026 (no tools) = 77.5 @ bf16 · vendor-reported · 2026-08-30

    GPQA Diamond: 78.8, MMLU-Pro: 77.2. A 12B scoring 77.5 on AIME 2026 is the headline of this release.

Coding 7/10
data checked Aug 2026
Tool calling / agentic 7/10
data checked Aug 2026
Long context 4/10
data checked Aug 2026

§2 Known issues & what fixes them

ISSUE-01 moderate Q2–Q3 / Q4–Q5 / Q6–Q8 · instruction-following

The 12B ships a Multi-Token-Prediction drafter for speculative decoding, and that path has its own bug reports in llama.cpp — enabling it (`-fit on`) can break generation on this size specifically. The speed feature is the risk, not the model.

Fix
Update your runtime [strong]

Run without MTP/speculative decoding until the issue closes, or track a llama.cpp build that has the Gemma4 MTP fix. Plain Q4_0 decoding is unaffected.

Evidence · 2 sources · community-consensus
ISSUE-02 severe Q2–Q3 / Q4–Q5 / Q6–Q8 · instruction-following, coding

Shares the family's rocky local-runtime history: Google's refreshed official GGUFs (2026-07-15) failed to load in LM Studio 0.4.19, and the family produces gibberish past ~230 tokens when KV offload (-nkvo) is on.

Fix
Update your runtime [strong]

Take a re-cut community quant and a current llama.cpp; don't run Gemma 4 with -nkvo.

Evidence · 2 sources · community-consensus
ISSUE-03 moderate Q2–Q3 / Q4–Q5 / Q6–Q8 / FP16 · long-context

The 256K window oversells it: retrieval accuracy at 128K is 43.4% (vendor's own MRCR v2 number), essentially the same as the 26B-A4B. Don't stuff the window and expect recall.

Fix
RAG (retrieval) [strong]

Retrieve and paste the relevant chunk rather than the whole corpus.

Evidence · 1 source · anecdotal