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-save-plan)<a href="https://agentmods.dev/skills/appsvortex/arness/arn-code-save-plan"><img src="https://agentmods.dev/badge/skills/appsvortex/arness/arn-code-save-plan/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-save-plan"><img src="https://agentmods.dev/badge/skills/appsvortex/arness/arn-code-save-plan.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 | $0.00098 | $0.03037 |
| Opus 5.5 | $0.00039 | $0.01215 |
| Sonnet 5.5 | $0.00020 | $0.00607 |
| Haiku 4.5 | $0.00010 | $0.00304 |
Grade A, and why
arn-code-save-plan 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 — 231 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Arness Save Plan
Convert a planning conversation into a structured, executable project with phased implementation plans, testing plans, task lists, and progress tracking.
This skill requires Arness to be configured in the target project. If Arness configuration is not found in the project's CLAUDE.md, the user should run /arn-planning to get started.
Workflow
Step 1: Check Arness Configuration
Read the project's CLAUDE.md and look for a ## Arness section. Also check for a legacy ## Arness Save Plan section (from earlier versions of this skill).
If ## Arness is found, extract:
- Plans directory -- base path where project plans are saved
- Specs directory -- path to the directory containing specification files
- Report templates --
defaultorcustom - Template path -- path to the report template set (JSON templates)
- Template version -- plugin version the templates were copied from (if present)
- Template updates -- user preference:
ask,auto, ormanual(if present) - Code patterns -- path to the directory containing stored pattern documentation
Validate that all paths exist on disk. If any path is missing, warn the user before proceeding.
Template Version Check
If the ## Arness section contains Template version and Template updates fields, compare the project's template version against the plugin version. If they differ, check for user modifications via checksums and either auto-update, prompt the user, or skip based on the configured preference. If ## Arness does NOT contain these fields, treat as legacy and skip.
Read
${CLAUDE_PLUGIN_ROOT}/skills/arn-code-save-plan/references/template-versioning.mdfor the full template version check procedure.
If legacy ## Arness Save Plan is found but no ## Arness, offer to migrate:
- Inform the user: "I found a legacy
## Arness Save Plansection. Arness now uses a unified## Arnessconfiguration section." - Ask (using
AskUserQuestion):
What ships with it
15 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/template-versioning.md 3.7 KB
- references/templates.md 8.5 KB
- report-templates/default/BATCH_SIMPLIFICATION_REPORT_TEMPLATE.json 1.9 KB
- report-templates/default/BUGFIX_REPORT_TEMPLATE.json 1.7 KB
- report-templates/default/CATCHUP_REPORT_TEMPLATE.json 886 B
- report-templates/default/CHANGE_RECORD_TEMPLATE.json 580 B
- report-templates/default/IMPLEMENTATION_REPORT_TEMPLATE.json 999 B
- report-templates/default/PROJECT_PROGRESS_REPORT_TEMPLATE.json 890 B
- report-templates/default/REVIEW_REPORT_TEMPLATE.json 1.5 KB
- report-templates/default/SIMPLIFICATION_REPORT_TEMPLATE.json 1.7 KB
- report-templates/default/STANDARD_REPORT_TEMPLATE.json 1.5 KB
- report-templates/default/SWIFT_REPORT_TEMPLATE.json 1.2 KB
- report-templates/default/TASK_REVIEW_REPORT_TEMPLATE.json 1.3 KB
- report-templates/default/TESTING_REPORT_TEMPLATE.json 1.3 KB
- scripts/save_plan.sh 3.4 KB runs code
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 · 231 lines · 98 tokens per session scan A ad76ab64cd8f
arn-code-save-plan is a skill published in the GitHub repository AppsVortex/arness (33 stars, last pushed 2mo ago), licensed MIT. It adds 98 tokens to every session and 3,037 once invoked, about $0.0004 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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