Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add google-gemma/gemma-skills --skill gemma-trainergit clone --depth 1 https://github.com/google-gemma/gemma-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/google-gemma/gemma-skills/gemma-trainer)<a href="https://agentmods.dev/skills/google-gemma/gemma-skills/gemma-trainer"><img src="https://agentmods.dev/badge/skills/google-gemma/gemma-skills/gemma-trainer/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/google-gemma/gemma-skills/gemma-trainer"><img src="https://agentmods.dev/badge/skills/google-gemma/gemma-skills/gemma-trainer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00065 | $0.01981 |
| Opus 5 | $0.00032 | $0.00991 |
| Sonnet 5 | $0.00013 | $0.00396 |
| Haiku 4.5 | $0.00006 | $0.00198 |
Grade A, and why
gemma-trainer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 168 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Gemma Training and Fine-Tuning Skill
1. Core Principles: Local Fine-Tuning Setup
When training locally, memory efficiency and execution speed are huge. Always guide the user to follow these best practices:
- Prioritize Unsloth: For local single-GPU training, always recommend Unsloth. It supports Gemma 4 natively, uses up to 70% less memory, and is up to 2x faster than standard Hugging Face PEFT training.
- Fall Back to TRL: For multi-GPU environments (using DDP/FSDP) or when Unsloth is unavailable, use Hugging Face TRL (
SFTTrainer,DPOTrainer) coupled with PEFT and bitsandbytes (for QLoRA). - Always use QLoRA (4-bit Quantization): Crucial for fitting Gemma models (like Gemma 4 12B/31B) into consumer VRAM.
- Manage Context Window & Max Length: Although Gemma 4 supports up to a 256K context window, recommend training with a context window of 2048 to 8192 tokens locally to prevent Out-Of-Memory (OOM) errors.
2. Choosing the Right Training Method
Help the user choose the correct workflow based on their goal:
- Supervised Fine-Tuning (SFT): Teaching new domains, specialized task instructions, or custom output structures.
- Prerequisites: Raw text, instruction pairs, or chat logs.
- Output: Adaptor trained on prompt/completion pairs.
- Direct Preference Optimization (DPO): Aligning model style, behavior, tone, or safety with human preferences.
- Prerequisites: A previously SFT-trained Gemma model and preferred pairwise datasets.
- Output: Aligning model weights directly without a separate reward head.
- Reward Modeling (RM): Training a scoring system to evaluate response quality.
- Prerequisites: Binary preference pairwise datasets.
- Output: A classification-style reward head on top of Gemma.
3. Dataset Preparation & Validation
Formatting issues are the #1 cause of poor training runs. Ensure you validate files using the utility script [assets/dataset_prep.py].
Gemma Chat Prompt Format
What ships with it
5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 10d ago First seen · 168 lines · 65 tokens per session scan A fa063ee07e9a
gemma-trainer is a skill published in the GitHub repository google-gemma/gemma-skills (985 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 65 tokens to every session and 1,981 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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