Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add AppsVortex/arness/plugin install arn-codeWrote 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/appsvortex/arness/arn-code-init)<a href="https://agentmods.dev/skills/appsvortex/arness/arn-code-init"><img src="https://agentmods.dev/badge/skills/appsvortex/arness/arn-code-init/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/appsvortex/arness/arn-code-init"><img src="https://agentmods.dev/badge/skills/appsvortex/arness/arn-code-init.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00170 | $0.08876 |
| Opus 5.5 | $0.00068 | $0.03550 |
| Sonnet 5.5 | $0.00034 | $0.01775 |
| Haiku 4.5 | $0.00017 | $0.00888 |
Grade A, and why
arn-code-init 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 1mo 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 — 643 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Arness Init
Set up Arness for a project by analyzing or defining code patterns, choosing configuration options, and persisting everything to CLAUDE.md. This is optional — Arness auto-configures with sensible defaults on first skill invocation. Use this to customize directories, add integrations, update templates, or review your current settings.
Workflow
Step 1: Check Existing Configuration
Read the project's CLAUDE.md and look for a ## Arness section. If no CLAUDE.md exists, create one at the project root before proceeding.
If the section does not exist:
- Proceed to Step 2 (fresh init)
If the section exists:
- Parse all config fields from the existing
## Arnessblock - Read the current plugin version from
${CLAUDE_PLUGIN_ROOT}/.claude-plugin/plugin.json - Show the user their current configuration and version comparison:
- Config template version vs current plugin version
- Number of config fields present vs expected
- Ask via
AskUserQuestion:- Review — Show current configuration summary, no changes
- Upgrade (recommended) — Check for gaps and update only what's needed. Best after a plugin update.
- Reconfigure — Re-run the full setup flow from scratch (change directories, regenerate patterns, etc.)
- Keep — No changes
- If Review → display a clean summary of all
## Arnessfields, then exit the skill - If Keep → done, exit the skill
- If Reconfigure → continue to Step 2, pre-filling known values as defaults
- If Upgrade → proceed to the Upgrade Flow section
Step 2: Detect Project State
Determine whether this is an existing codebase or a greenfield project.
Look for indicators of an existing codebase:
- Package manifests:
package.json,pyproject.toml,Cargo.toml,go.mod,pom.xml,build.gradle,Gemfile,composer.json - Source directories:
src/,app/,lib/,cmd/,pkg/ - Framework markers:
manage.py,next.config.*,angular.json,vite.config.*,main.go,main.rs - Meaningful source files (not just README, LICENSE, .gitignore)
What ships with it
8 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.
- references/agent-models-presets/all-opus.md 626 B
- references/agent-models-presets/balanced.md 642 B
- references/bkt-setup.md 1.7 KB
- references/greenfield-questions.md 5.0 KB
- references/jira-mcp-setup.md 2.6 KB
- references/pattern-schema.md 18 KB
- references/platform-labels.md 5.5 KB
- references/template-setup.md 1.9 KB
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.
- 1mo ago First seen · 643 lines · 170 tokens per session scan A aa307bb9abeb
arn-code-init is a skill published in the GitHub repository AppsVortex/arness (33 stars, last pushed 2mo ago), licensed MIT. It adds 170 tokens to every session and 8,876 once invoked, about $0.0007 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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