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-sparkWrote 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-spark-scaffold)<a href="https://agentmods.dev/skills/appsvortex/arness/arn-spark-scaffold"><img src="https://agentmods.dev/badge/skills/appsvortex/arness/arn-spark-scaffold/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-spark-scaffold"><img src="https://agentmods.dev/badge/skills/appsvortex/arness/arn-spark-scaffold.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 | $0.00082 | $0.02988 |
| Opus 5.5 | $0.00033 | $0.01195 |
| Sonnet 5.5 | $0.00016 | $0.00598 |
| Haiku 4.5 | $0.00008 | $0.00299 |
Grade A, and why
arn-spark-scaffold 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 today.
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 — 240 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Arness Scaffold
Set up a working project skeleton from architecture vision decisions through guided conversation, aided by the arn-spark-scaffolder agent for project creation and optionally the arn-spark-tech-evaluator agent for UI toolkit comparisons. This is a conversational skill that runs in normal conversation (NOT plan mode). The primary artifact is a buildable project with all dependencies installed and configured.
This skill covers the initial project setup: framework scaffolding, dependency installation, build configuration, linting, and UI toolkit setup. It does not implement features, create screens, or write application logic -- those are handled by subsequent skills (/arn-spark-spike, /arn-spark-style-explore, /arn-spark-static-prototype, /arn-spark-clickable-prototype).
Prerequisites
An architecture vision document must exist. Check in order:
- Read the project's
CLAUDE.mdfor a## Arnesssection. If found, check the configured Vision directory forarchitecture-vision.md - If no
## Arnesssection exists or Arness Spark fields are missing, inform the user: "Arness Spark is not configured for this project yet. Run/arn-brainstormingto get started — it will set everything up automatically." Do not proceed without it. - If
## Arnessexists but no architecture vision found, check.arness/vision/architecture-vision.mdat the project root
If an architecture vision is found: Read it and proceed to Step 1.
If no architecture vision is found: Inform the user:
"No architecture vision document found. I recommend running /arn-spark-arch-vision first to define your technology stack. The scaffold needs to know which frameworks, build tools, and libraries to set up."
Do not proceed without an architecture vision or explicit technology stack from the user.
Determine the project root:
- The project root is the working directory unless the user specifies otherwise
- If the project root already contains a
package.json,Cargo.toml, or similar, warn the user: "This directory already has a project manifest. Do you want to extend the existing project or start fresh in a subdirectory?"
What ships with it
2 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.
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.
- today First seen · 240 lines · 82 tokens per session scan A 648d9b15e357
arn-spark-scaffold is a skill published in the GitHub repository AppsVortex/arness (33 stars, last pushed today), licensed MIT. It adds 82 tokens to every session and 2,988 once invoked, about $0.0003 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 2026-10-25.
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