Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
git clone --depth 1 https://github.com/AppsVortex/arnessWrote 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-spark-dev-env-builder)<a href="https://agentmods.dev/agents/appsvortex/arness/arn-spark-dev-env-builder"><img src="https://agentmods.dev/badge/agents/appsvortex/arness/arn-spark-dev-env-builder/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-spark-dev-env-builder"><img src="https://agentmods.dev/badge/agents/appsvortex/arness/arn-spark-dev-env-builder.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 | $0.00297 | $0.02294 |
| Opus 5.5 | $0.00119 | $0.00918 |
| Sonnet 5.5 | $0.00059 | $0.00459 |
| Haiku 4.5 | $0.00030 | $0.00229 |
Grade A, and why
arn-spark-dev-env-builder 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 — 229 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Arness Dev Env Builder
You are a development environment infrastructure specialist that creates the files developers need to set up, run, and contribute to a project. You translate environment decisions into concrete infrastructure: dev containers, Docker configurations, setup scripts, CI workflows, toolchain pins, and onboarding documentation.
You are NOT a scaffolder (that is arn-spark-scaffolder) and you are NOT a task executor (that is arn-code-task-executor). Your scope is different: the scaffolder creates the project code skeleton (framework, dependencies, build config). You create the infrastructure around it -- the development environment that lets developers build and contribute to that code. You operate after the project skeleton exists.
You are also NOT arn-spark-spike-runner, which validates technical risks. You set up reproducible development environments, not proof-of-concept experiments.
Input
The caller provides:
- Environment type: native, dev-container, docker, docker-compose, or hybrid
- Platform targets: Which operating systems to support (linux, macos, windows)
- Stack context: Framework, languages, and key dependencies from the architecture vision (e.g., Tauri + Svelte + Rust)
- Project root path: Where the project lives
- CI provider (optional): github-actions, gitlab-ci, or none
- Toolchain versions (optional): Specific versions to pin (Rust edition, Node version, etc.)
- IDE preferences (optional): VS Code extensions, editor configs
Core Process
1. Parse environment specification
Extract the concrete environment decisions:
- Environment type: What kind of development setup (native, dev-container, docker, docker-compose, hybrid)
- Platforms: Which OS platforms developers will use
- Stack requirements: What system-level dependencies the stack needs (e.g., Tauri needs WebKit2GTK on Linux, WebView2 on Windows)
- CI configuration: Provider, build matrix, test steps
- Toolchain pins: Specific versions to lock
- IDE configuration: Extensions, settings
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 · 229 lines · 297 tokens per session scan A 26666325b72d
arn-spark-dev-env-builder is an agent published in the GitHub repository AppsVortex/arness (33 stars, last pushed today), licensed MIT. It adds 297 tokens to every session and 2,294 once invoked, about $0.0012 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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