skill

skill is a skill for Claude Code, Codex from nidhish28guhan-netizen/hachiman-agent. It costs 0 tokens per session (946 once invoked), scanned A, original, MIT.

An authorized security-testing workflow that examines a target like an attacker, confirms weaknesses, explains them, and checks fixes again. It requires written permission and limits testing to the approved scope.

In plain words
What is it for?
Use it to test an authorized application or system, document confirmed security findings, create repair guidance, and retest fixes for unresolved issues or regressions.
Why use it?
It avoids treating unverified scanner warnings as real problems and provides evidence that a vulnerability can be reproduced and whether a fix worked.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions Claude Code; mentions Codex.

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is node bin/hachiman.js pentest examples/engagement.vuln-notes.json.

Good fit Use it to test an authorized application or system, document confirmed security findings, create repair guidance, and retest fixes for unresolved issues or regressions.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/nidhish28guhan-netizen/hachiman-agent
agentmods
npx agentmods add skills/nidhish28guhan-netizen/hachiman-agent/skill

Made for: Claude Code, Codex.

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 skill

README.md
[![agentmods](https://agentmods.dev/badge/skills/nidhish28guhan-netizen/hachiman-agent/skill/github.svg)](https://agentmods.dev/skills/nidhish28guhan-netizen/hachiman-agent/skill)
Your own site
<a href="https://agentmods.dev/skills/nidhish28guhan-netizen/hachiman-agent/skill"><img src="https://agentmods.dev/badge/skills/nidhish28guhan-netizen/hachiman-agent/skill/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 skill

Your own site · 80×15
<a href="https://agentmods.dev/skills/nidhish28guhan-netizen/hachiman-agent/skill"><img src="https://agentmods.dev/badge/skills/nidhish28guhan-netizen/hachiman-agent/skill.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 946 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.
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 $0.00000 $0.00946
Opus 5 $0.00000 $0.00473
Sonnet 5 $0.00000 $0.00189
Haiku 4.5 $0.00000 $0.00095

Measured 12d ago against content hash 76a665dcbd9c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

skill 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 12d 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.

skill/SKILL.md · 81 lines

How it starts

The opening of the file, as written. The whole thing — 81 lines — stays where its author put it; the contents beside it link to each section on GitHub.

HACHIMAN — Offensive Security Skill (AI-builder instructions)

Layer 1 of the Master Security Skill Architecture: this is what an AI coding agent (Claude Code, Codex, Cursor, Hermes, DeepSeek Harness, Qoder, …) must know to operate Hachiman's offensive loop against an authorized target. Keep this file next to the repository.

What this skill does

Hachiman is a watchman that thinks like an attacker. On an authorized target it runs:

DISCOVER → MAP → HYPOTHESIZE → ATTACK → ADAPT → CHAIN → VALIDATE → EXPLAIN → FIX → RETEST

Signature loop: ATTACK → PROVE → UNDERSTAND → FIX → REATTACK → VERIFY.

It is not a scanner that emits warnings. It produces confirmed, reproduced findings, an AI Repair Contract per finding, and an independent retest verdict (VERIFIED, UNRESOLVED, REGRESSION) for every fix.

Non-negotiable rules of engagement (hard-coded)

  1. Authorization first. Every run needs an engagement file with authorized_by set. No authorization → Hachiman refuses to run. This is enforced in code, not convention.
  2. Scope is a wall. Tools outside scope.allowed_tools are never touched; violations abort the run and are audit-logged.
  3. No persistence. No real exfiltration. No destructive testing. (doc-06 §46 defaults.) Exfil demonstrations are allowed only against the local canary sink when explicitly enabled.
  4. Budgets are enforced: requests, duration, concurrency. Exhausting a budget stops the run and reports partial results honestly.

Operating commands (run from the repository root)

# 1. Authorize + scope the target (write an engagement JSON — see examples/)
node bin/hachiman.js pentest examples/engagement.vuln-notes.json

# 2. Recon only (no attacks)
node bin/hachiman.js recon examples/engagement.vuln-notes.json

# 3. Inspect results
node bin/hachiman.js findings
node bin/hachiman.js explain <finding-id>       # root-cause developer card
node bin/hachiman.js fix <finding-id>           # AI Repair Contract (yaml + json)
node bin/hachiman.js chain --eng <engagement>   # attack graph + chained impact
node bin/hachiman.js report pentest <engagement>

# 4. After YOUR fix: prove it
node bin/hachiman.js retest <finding-id> --fixed <fixture|url>

Read the full file on GitHub · 81 lines

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. 12d ago First seen · 81 lines · 0 tokens per session scan A 76a665dcbd9c

Subscribe to this mod's changes

skill is a skill published in the GitHub repository nidhish28guhan-netizen/hachiman-agent (1 stars, last pushed 19d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 946 tokens. 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 2026-08-31.