workshop-build-an-agent: Skill for Claude Code

.agents/skills/module-4/SKILL.md

module-4 is a skill for Claude Code from brevdev/workshop-build-an-agent. It costs 265 tokens per session (3,420 once invoked), scanned A, original, Apache-2.0.

A learning guide for Module 4 of the Build-an-Agent workshop, which teaches how to customize a command-line agent and train it with examples, rewards, and reinforcement learning. It also covers the GPU and service requirements for the training process.

In plain words
What is it for?
It helps explain prompting versus training, supervised fine-tuning, GRPO reinforcement learning, the training pipeline, GPU memory needs, and how to run the resulting agent.
Why use it?
It helps learners understand the workshop's most complex module without doing the work for them, including why training may be slow or fail when the required GPU or reward server is missing.

Skill for Claude Code

Written for Claude Code: disable-model-invocation in frontmatter. Also seen: installed under .agents/ (shared by several agents); mentions Codex; $skill-name invocation.

This is brevdev/workshop-build-an-agent's own configuration. It tells Claude Code how to work on workshop-build-an-agent itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything workshop-build-an-agent configures →

Reuse

Borrowing it

Nothing to install: this file belongs to brevdev/workshop-build-an-agent. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/brevdev/workshop-build-an-agent/main/.agents/skills/module-4/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/brevdev/workshop-build-an-agent

Made for: Claude Code.

Wrote 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.

agentmods badge for module-4

README.md
[![agentmods](https://agentmods.dev/badge/skills/brevdev/workshop-build-an-agent/module-4/github.svg)](https://agentmods.dev/skills/brevdev/workshop-build-an-agent/module-4)
Your own site
<a href="https://agentmods.dev/skills/brevdev/workshop-build-an-agent/module-4"><img src="https://agentmods.dev/badge/skills/brevdev/workshop-build-an-agent/module-4/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.

agentmods 80×15 button for module-4

Your own site · 80×15
<a href="https://agentmods.dev/skills/brevdev/workshop-build-an-agent/module-4"><img src="https://agentmods.dev/badge/skills/brevdev/workshop-build-an-agent/module-4.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 265 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,420 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Privilege Escalation · line 76
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00265 $0.03420
Opus 5.5 $0.00106 $0.01368
Sonnet 5.5 $0.00053 $0.00684
Haiku 4.5 $0.00026 $0.00342

Measured 17d ago against content hash 555daf3a9b44, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

module-4 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 17d 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.

.agents/skills/module-4/SKILL.md · 161 lines

How it starts

The opening of the file, as written. The whole thing — 161 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Module 4 — "Agent Customization": Learning Assistant

Act as a patient, Socratic learning assistant for a developer working through Module 4 of the Build-an-Agent workshop. Deepen the learner's own understanding — never do the work for them. The learner may be in the DevX-Lab (JupyterLab) UI or in Codex / their editor against a clone; reference files by path so help works in either setting.

Module 4 is the workshop's most complex and most GPU-intensive module. It customizes a bash agent into a LangGraph CLI expert with a full training pipeline: synthetic data → verifiable rewards → GRPO reinforcement learning → run the result.

The learner asked: $ARGUMENTS

Module 4 reality — read this first

  • Training requires substantial free GPU memory. Runtime depends on hardware and completion length; a DGX Spark (GB10) requires sufficient free memory and a validated training stack — recommend A100/H100 for the GRPO step. Base model is nvidia/NVIDIA-Nemotron-Nano-9B-v2 (Mamba2, LoRA, bf16 — load_in_4bit=False), so it's VRAM-hungry (A100-80GB+).
  • Multi-stage pipeline with an out-of-notebook dependency: the NeMo Gym reward server must be running (uvicorn app:app --port 8001) before GRPO training works.
  • One shortcut exists (offer it when a learner is blocked on time/quota): a provided reviewed dataset (data/langgraph_cli/train.jsonl = 155, val.jsonl = 50) lets them skip SDG — the GRPO notebook trains on it by default. No trained checkpoint or adapter ships: a customized model exists only after the learner's own GRPO run, which writes outputs/grpo_langgraph_cli/merged_model/.

Your role

  • Explain customization concepts (train vs prompt vs tools, SFT vs GRPO, SDG, RLVR, reward engineering, HITL) in the workshop's framing.
  • Give graduated hints on the code blanks, never finished code.
  • Help interpret training behavior (reward curves, OOM, garbage outputs) — diagnostically, not by doing it.
  • Troubleshoot SDG, the reward server, GRPO/unsloth, and GPU memory.
  • Keep the learner in the driver's seat — and keep their GPU time/cost in mind.

Read the full file on GitHub · 161 lines

Files

What ships with it

6 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.

Changes

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.

  1. 17d ago Changed · +3 lines 555daf3a9b44
  2. 21d ago Changed · -4 lines cd9716d0e3d1
  3. 1mo ago First seen · 162 lines · 265 tokens per session scan A de6c53b7d749

Subscribe to this mod's changes

module-4 is a skill published in the GitHub repository brevdev/workshop-build-an-agent (151 stars, last pushed 16d ago), licensed Apache-2.0. It adds 265 tokens to every session and 3,420 once invoked, about $0.0011 per session on Opus 5.5. 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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