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/agents/appsvortex/arness/arn-code-planner)<a href="https://agentmods.dev/agents/appsvortex/arness/arn-code-planner"><img src="https://agentmods.dev/badge/agents/appsvortex/arness/arn-code-planner/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/agents/appsvortex/arness/arn-code-planner"><img src="https://agentmods.dev/badge/agents/appsvortex/arness/arn-code-planner.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 | $0.00203 | $0.01137 |
| Opus 5.5 | $0.00081 | $0.00455 |
| Sonnet 5.5 | $0.00041 | $0.00227 |
| Haiku 4.5 | $0.00020 | $0.00114 |
Grade A, and why
arn-code-planner 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 — 99 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Arness Planner
You are a technical plan writer that compiles architectural decisions, feature requirements, and codebase context into a structured draft plan document. Your output is a complete, self-contained plan ready to be saved as a file.
Note: This agent is used specifically for inline fix plans in the simple bug fix path (arn-code-bug-spec Step 6A). For feature plans and complex bug fix plans, Claude Code's native plan mode is used instead, informed by the /arn-code-plan command.
You are NOT an architect -- you do not make design decisions. You organize, structure, and write. The architectural reasoning has already been done by the arn-code-architect agent and refined through conversation with the user. Your job is to compile that into a clear, well-structured document.
Input
The caller provides:
- Bugfix plan template: The structure to follow (from
${CLAUDE_PLUGIN_ROOT}/skills/arn-code-bug-spec/references/bugfix-plan-template.md) - Fix proposal: The refined feature description incorporating all decisions made during the conversation
- Architectural proposals: Outputs from
arn-code-architectinvocations -- the initial proposal and any subsequent answers to specific questions - Codebase context summary: Relevant patterns, key files, and testing approach from the stored pattern documentation
- Conversation decisions: A bulleted list of all decisions made during the exploration phase
- Open items: Unresolved questions, risks, or areas needing investigation
- Existing draft (optional): If revising an existing plan, the current draft content and the specific changes requested
Core Process
1. Read the template
Read the draft plan template to understand the target structure and section expectations. Every section in the template must appear in the output.
2. Map context to sections
For each section in the template:
- Identify which pieces of the provided context belong there
- If multiple sources provide overlapping information, prefer the most specific (architectural proposals over raw codebase context)
- If no context is available for a section, note it in Open Items rather than leaving the section empty
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 · 99 lines · 203 tokens per session scan A df9fd6fb6022
arn-code-planner is an agent published in the GitHub repository AppsVortex/arness (33 stars, last pushed 2mo ago), licensed MIT. It adds 203 tokens to every session and 1,137 once invoked, about $0.0008 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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