๐Ÿ’ป Gemma4-12B-Coder (GGUF) โ€” Composer 2.5 ร— Fable 5 โœจ

๐Ÿฃ Tiny footprint, big brain โ€” a local coding model for everyone

No matter your GPU. No matter your RAM. If you've got ~4.5 GB of VRAM or unified memory free, you can run your own private, offline coding assistant right now. ๐Ÿš€ This is the v1 / code edition โ€” distilled from real chain-of-thought so it thinks through a problem before writing the solution. ๐Ÿง ๐Ÿ’ป All local, all yours, no API, no cloud.

๐ŸŽฏ What it is

A focused fine-tune of Gemma 4 12B on verifiable Python coding data โ€” every training example's reasoning leads to code that actually passed its tests. The result reasons in the open (edge cases, complexity, approach) and then emits a clean, runnable solution. ๐Ÿ’š


๐Ÿ“š Training data (the interesting part ๐Ÿณ)

This is a distillation of two complementary chain-of-thought sources, both over verifiable Python coding tasks (algorithmic / function-level problems that come with deterministic tests):

  • ๐Ÿฅ‡ Main set โ€” Composer 2.5 real CoT. Genuine, model-authored reasoning traces. The teacher solved each problem, its code was run against the task's tests, and only the passing solutions were kept. So the reasoning you're learning from leads to code that actually works.
  • ๐Ÿฅˆ Aux set โ€” Fable 5 (released today! ๐ŸŽ‰). A clever twist: we took the problems where Composer 2.5 got it wrong and handed them to Fable 5 to redo โ€” re-deriving a fresh, self-consistent chain-of-thought and a correct solution, again gated on passing the tests. This recovers the hard cases the main teacher missed. These traces are synthetic (rationalized CoT), and are tagged separately so the two sources stay distinguishable.

The recipe: real CoT for the bulk of solid coverage, plus synthetic "second-attempt" CoT to patch the failures โ€” both verified by execution before anything entered training. โœ…


๐Ÿ—บ๏ธ Roadmap โ€” v2 (if there's interest! ๐Ÿ’š)

This is v1. If the likes / downloads add up, I'll ship a v2 that pushes for the benchmarks ๐Ÿ.

๐Ÿ“ข Update on v2 & the Fable 5 situation (2026-06-14)

Quick heads-up for everyone waiting on v2:

Fable 5 access has been pulled. The Fable 5 CoT data I managed to save beforehand is honestly a pretty small set โ€” not enough on its own to act as the primary signal for v2 without risking overfitting. So the plan is shifting:

  • v2 will lean more heavily on Composer 2.5 verifiable CoT as the backbone (the main, execution-verified source), and use the limited Fable 5 data carefully as a supplement rather than the core.
  • If Fable 5 access doesn't come back within ~a week, I'm considering bringing in GLM-5.2 as an additional teacher. I just went through the benchmarks: per BridgeMind's eval posted on X, GLM-5.2 actually edges out Fable 5 on both the BS and reasoning leaderboards. I haven't tested it hands-on myself yet โ€” my gut says it'll land slightly below Fable 5 in practice, but likely very close.

Bottom line: v2 is still coming. I'd just rather take a little longer and ship something that generalizes than rush out an overfit model. Thanks for the patience and support ๐Ÿ’š

โญ Like & download if you'd like to see v2 โ€” that's the signal I'm watching!


๐Ÿ“ฆ Pick your size (GGUF quants)

Quant Size Vibe
๐ŸŸข Q2_K 4.5 GB tiniest โ€” runs almost anywhere
๐Ÿ”ต Q4_K_M 6.87 GB the sweet spot ๐Ÿ‘Œ (recommended)
๐ŸŸฃ Q6_K 9.11 GB near-lossless
โšช Q8_0 11.8 GB basically full quality

๐Ÿงฎ "Will it fit?" โ€” context length cheat-sheet

Rough estimates ๐Ÿค“ (assumes q8_0 KV cache + ~1.5 GB overhead; use q4_0 KV cache for โ‰ˆ2ร— more context!). Max context is 131K. "โ€”" = won't fit, pick a smaller quant. โœ‚๏ธ

Your VRAM / unified mem ๐ŸŸข Q2_K (4.5G) ๐Ÿ”ต Q4_K_M (6.87G) ๐ŸŸฃ Q6_K (9.11G) โšช Q8_0 (11.8G)
8 GB ~16K ctx tight (~2โ€“4K) โ€” โ€”
12 GB ~48K ~30K ~12K โ€”
16 GB ~80K ~64K ~44K ~22K
24 GB 131K (max) ๐ŸŽ‰ ~128K ~110K ~88K
32 GB 131K 131K 131K 131K

๐Ÿ’ก Apple Silicon / integrated GPUs with unified memory count too โ€” same numbers, just slower than a dGPU. ๐Ÿ’ก Low on room? Drop a quant or switch KV cache to q4_0 and your context roughly doubles.


๐Ÿš€ How to run it (super easy)

Option A โ€” llama.cpp (recommended) ๐Ÿฆ™

  1. Grab a quant above (e.g. โ€ฆ-Q4_K_M.gguf) and llama-server from llama.cpp.

    โš ๏ธ Needs a recent llama.cpp (this is the gemma4_unified architecture โ€” older builds won't load it).

  2. Run a server (Windows .bat shown โ€” tweak --port, --ctx-size to taste):
@echo off
cd /d C:\llama.cpp
llama-server.exe ^
  -m C:\models\gemma4-coding-Q4_K_M.gguf ^
  --ctx-size 16384 ^
  --n-gpu-layers 99 ^
  --no-mmap ^
  -fa on ^
  --cache-type-k q8_0 --cache-type-v q8_0 ^
  --temp 1.0 --top-p 0.95 --top-k 64 ^
  --host 0.0.0.0 --port 18080
pause
  1. Open http://localhost:18080 and chat. ๐ŸŽ‰ (Tip: bump --ctx-size per the table; use q4_0 KV for more.)

Option B โ€” one-click apps ๐Ÿ–ฑ๏ธ

Works in LM Studio, Jan, Ollama, etc. โ€” just import the GGUF, pick your quant, go. ๐Ÿพ

๐Ÿง  Thinking mode

This model thinks in Gemma's native thought channel before answering โ€” exactly how it was trained. Keep enable_thinking=true (the default chat template handles it). Recommended sampling: temp 1.0, top_p 0.95, top_k 64. For coding you can also go greedy (temp 0) for more deterministic solutions.


โš ๏ธ Good to know

  • Reduced refusals: the training data is task-focused with no safety hedging, so this refuses less than the base model. It is not safety-aligned โ€” add your own guardrails for production. Use responsibly. ๐Ÿ™
  • Specialized for Python / algorithmic coding. Reasoning quality is strongest in that domain; general-knowledge facts/numbers should still be double-checked.
  • English-centric.

๐Ÿ“š Base & License

  • Base model: google/gemma-4-12B-it. Subject to the Gemma Terms of Use (derivatives must comply).
  • Personal/hobby project โ€” shared as-is, no warranty. Have fun, and happy hacking! ๐Ÿพโœจ
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